US20230416323A1

US20230416323A1 - Erythropoietin and analogs for veterinary use

Info

Publication number: US20230416323A1
Application number: US18/203,184
Authority: US
Inventors: Hangjun Zhan; Lam Nguyen; Yongzhong Li; Qingyi Chu; Estela Garcia-Murillo; Victoria Leitman; Stephen Sundlof; Richard Chin; Shyr Jiann Li
Original assignee: Elanco US Inc
Current assignee: Elanco US Inc
Priority date: 2017-06-06
Filing date: 2023-05-30
Publication date: 2023-12-28
Also published as: RU2019143664A3; RU2019143664A; EP3634988A4; US20210032305A1; CA3065540A1; EP3634988A1; AU2022228088A1; JP2024012296A; WO2018226747A1; JP2020522263A; US11667686B2; AU2018281334A1; BR112019025563A2; CN110997707A

Abstract

Provided are various embodiments relating to feline erythropoietin (EPO) polypeptide analogs with one or more additional glycosylation sites and methods of producing and using the same to treat anemia in companion animals. Also provided are various embodiments relating to EPO polypeptides having a mutation in the second binding site, polypeptides comprising an extracellular domain of EPO receptor, and methods of using the same for treating polycythemia in mammals.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to US Provisional Application Nos. 62/516,092, filed Jun. 6, 2017; 62/516,642, filed Jun. 7, 2017; and 62/559,104, filed Sep. 15, 2017, each of which is incorporated by reference herein in its entirety for any purpose.

SEQUENCE LISTING

The Application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on May 27, 2023, is named 78045-387293_SL.xml and is 51,835 bytes in size.

FIELD

This present disclosure relates to erythropoietin (EPO) polypeptide analogs having enhanced pharmacokinetics and methods of producing and using the same, for example, for treating anemia in companion animals, such as canines, felines, and equines. The present disclosure also relates to EPO polypeptides having a mutation in the second binding site and methods of using the same, for example, for treating over production of EPO in a mammal, including humans and companion animals. The present disclosure relates to nucleic acids, vectors, and expression systems encoding EPO polypeptides and methods of using the same (e.g., gene therapy methods), for example for controlled or induced expression of EPO polypeptides. This present disclosure further relates to formulations for EPO polypeptides, including the EPO polypeptides described herein. The present disclosure also relates to polypeptides comprising an extracellular domain of EPO receptor and methods of using the same, for example, for treating overproduction of EPO in any mammal, including humans and companion animals.

BACKGROUND

Erythropoietin (EPO), also known as hematopoeitin or hemopoietin, is a glycoprotein hormone that can stimulate erythropoiesis (i.e., red blood cell production). EPO is used for treating anemia resulting from chronic kidney disease, inflammatory bowel disease (Crohn's disease and ulcer colitis) and myelodysplasia resulting from chemotherapy and radiation therapy. These human disorders are sometimes treated with a recombinant EPO molecule (e.g., Darbepoetin (Aranesp™ and Epogen™, Amgen) and Dynepo™, Shire).
Companion animals suffer from many diseases that are similar to human diseases, including autoimmune diseases and cancer. While human proteins have been used to treat companion animal diseases, it is understood that proteins having significant human-derived amino acid sequence content can be immunogenic to the treated animals. If a human drug elicits an immune response in a companion animal, it may not be effective. See Mauldin et al., August 2010, 21(4):373-382.
Anemia in cats is currently treated by administering human erythropoietin drugs, such as Epogen™ or Aranesp™. However, it is likely that human EPO drugs could illicit an immunogenic response when administered to cats. In addition, human EPO drugs may not bind companion animal EPO receptor in a manner that provides an equally beneficial therapeutic effect in the companion animal as it does in humans.
There remains an unmet need, therefore, for methods and compounds that can be used to treat anemia (e.g., non-refractory anemia) in companion animals, including cats, dogs, and horses. Ideally, the compounds would bind specifically to EPO receptor and have a half-life in plasma sufficiently long to be practicable for therapy, but would be species specific and not be highly immunogenic. EPO polypeptides, including feline EPO polypeptides, having enhanced pharmacokinetics and methods of administering those EPO polypeptides or nucleic acids encoding those EPO polypeptides for the treatment of anemia in companion animals are described herein.
Overproduction of EPO is also an issue. For example, polycythemia may be caused by overproduction and/or secretion of EPO from a tumor (e.g., a kidney tumor), by non-activating mutations in JAK2, or by a genetically-inherited dysregulation resulting in overproduction of EPO. EPO polypeptides having a mutation in the second binding site and methods of administering those EPO polypeptides or nucleic acids encoding those EPO polypeptides for the treatment of polycythemia in mammals are also described herein. Also, described herein are polypeptides comprising an extracellular domain of feline EPO receptor and methods of administering those polypeptides or nucleic acids encoding those EPOR polypeptides for the treatment of polycythemia in mammals.

SUMMARY

Embodiment 1. An erythropoietin (EPO) polypeptide comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 13 except for the presence of at least one N-linked glycosylation site not present in SEQ ID NO: 2 or SEQ ID NO: 13, wherein the N-linked glycosylation site comprises the sequence asparagine-xaa-serine or asparagine-xaa-threonine, wherein xaa is any amino acid except proline, and wherein one N-linked glycosylation site does not overlap with another N-linked glycosylation site.
Embodiment 2. The EPO polypeptide of embodiment 1, wherein each of the at least one N-linked glycosylation site is present at:

- a) a position selected from position 47-49, 55-57, 56-58, 60-62, 61-63, 79-81, 82-84, 91-93, 92-94, 97-99, 98-100, 99-101, 112-114, 113-115, 114-116, 115-117, 116-118, 137-139, 140-142, 141-143, 142-144, 143-145, 144-146, 145-147, 146-148, 147-149, 148-150, 149-151, 150-152, 161-163, 162-164, 184-186, and 186-188 of SEQ ID NO: 2; or
- b) a position selected from position 21-23, 29-31, 30-32, 34-36, 35-37, 53-55, 56-58, 65-67, 66-68, 71-73, 72-74, 73-75, 86-88, 87-89, 88-90, 89-91, 90-92, 111-113, 114-116, 115-117, 116-118, 117-119, 118-120, 119-121, 120-122, 121-123, 122-124, 123-125, 124-126, 135-137, 136-138, 158-160, and 162-164 of SEQ ID NO: 13.

Embodiment 3. The EPO polypeptide of embodiment 1 or embodiment 2 comprising valine at a position corresponding to position 113 of SEQ ID NO: 4.
Embodiment 4. The EPO polypeptide of any one of embodiments 1 to 4 comprising:

- a) asparagine at a position corresponding to position 47 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 48 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 49 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 21 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 22 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 23 of SEQ ID NO: 13.

Embodiment 5. The EPO polypeptide of any one of embodiments 1 to 5 comprising:

- a) asparagine at a position corresponding to position 55 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 56 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 57 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 29 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 30 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 31 of SEQ ID NO: 13.

Embodiment 6. The EPO polypeptide of any one of embodiments 1 to 5 comprising:

- a) asparagine at a position corresponding to position 56 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 57 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 58 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 30 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 31 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 32 of SEQ ID NO: 13.

Embodiment 7. The EPO polypeptide of any one of embodiments 1 to 6 comprising:

- a) asparagine at a position corresponding to position 60 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 61 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 62 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 34 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 35 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 36 of SEQ ID NO: 13.

Embodiment 8. The EPO polypeptide of any one of embodiments 1 to 7 comprising:

- a) asparagine at a position corresponding to position 61 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 62 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 63 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 35 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 36 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 37 of SEQ ID NO: 13.

Embodiment 9. The EPO polypeptide of any one of embodiments 1 to 8 comprising:

- a) asparagine at a position corresponding to position 79 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 80 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 81 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 53 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 54 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 55 of SEQ ID NO: 13.

Embodiment 10. The EPO polypeptide of any one of embodiments 1 to 9 comprising:

- a) asparagine at a position corresponding to position 82 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 83 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 84 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 56 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 57 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 58 of SEQ ID NO: 13.

Embodiment 11. The EPO polypeptide of any one of embodiments 1 to 10 comprising:

- a) asparagine at a position corresponding to position 91 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 92 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 93 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 65 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 66 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 67 of SEQ ID NO: 13.

Embodiment 12. The EPO polypeptide of any one of embodiments 1 to 11 comprising:

- a) asparagine at a position corresponding to position 92 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 93 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 94 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 66 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 67 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 68 of SEQ ID NO: 13.

Embodiment 13. The EPO polypeptide of any one of embodiments 1 to 12 comprising:

- a) asparagine at a position corresponding to position 97 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 98 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 99 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 71 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 92 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 73 of SEQ ID NO: 13.

Embodiment 14. The EPO polypeptide of any one of embodiments 1 to 13 comprising:

- a) asparagine at a position corresponding to position 98 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 99 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 100 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 72 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 73 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 74 of SEQ ID NO: 13.

Embodiment 15. The EPO polypeptide of any one of embodiments 1 to 14 comprising:

- a) asparagine at a position corresponding to position 99 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 100 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 101 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 73 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 74 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 75 of SEQ ID NO: 13.

Embodiment 16. The EPO polypeptide of any one of embodiments 1 to 15 comprising:

- a) asparagine at a position corresponding to position 112 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 113 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 114 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 86 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 87 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 88 of SEQ ID NO: 13.

Embodiment 17. The EPO polypeptide of any one of embodiments 1 to 16 comprising:

- a) asparagine at a position corresponding to position 113 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 114 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 115 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 87 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 88 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 89 of SEQ ID NO: 13.

Embodiment 18. The EPO polypeptide of any one of embodiments 1 to 17 comprising:

- a) asparagine at a position corresponding to position 114 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 115 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 116 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 88 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 89 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 90 of SEQ ID NO: 13.

Embodiment 19. The EPO polypeptide of any one of embodiments 1 to 18 comprising:

- a) asparagine at a position corresponding to position 115 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 116 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 117 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 89 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 90 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 91 of SEQ ID NO: 13.

Embodiment 20. The EPO polypeptide of any one of embodiments 1 to 19 comprising:

Embodiment 21. The EPO polypeptide of any one of embodiments 1 to 20 comprising:

- a) asparagine at a position corresponding to position 116 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 117 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 118 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 90 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 91 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 92 of SEQ ID NO: 13.

Embodiment 22. The EPO polypeptide of any one of embodiments 1 to 21 comprising:

- a) asparagine at a position corresponding to position 137 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 138 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 139 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 111 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 112 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 113 of SEQ ID NO: 13.

Embodiment 23. The EPO polypeptide of any one of embodiments 1 to 22 comprising:

- a) asparagine at a position corresponding to position 140 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 141 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 142 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 114 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 115 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 116 of SEQ ID NO: 13.

Embodiment 24. The EPO polypeptide of any one of embodiments 1 to 23 comprising:

- a) asparagine at a position corresponding to position 141 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 142 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 143 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 115 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 116 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 117 of SEQ ID NO: 13.

Embodiment 25. The EPO polypeptide of any one of embodiments 1 to 24 comprising:

- a) asparagine at a position corresponding to position 142 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 143 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 144 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 116 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 117 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 118 of SEQ ID NO: 13.

Embodiment 26. The EPO polypeptide of any one of embodiments 1 to 25 comprising:

- a) asparagine at a position corresponding to position 143 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 144 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 145 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 117 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 118 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 119 of SEQ ID NO: 13.

Embodiment 27. The EPO polypeptide of any one of embodiments 1 to 26 comprising:

- a) asparagine at a position corresponding to position 144 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 145 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 146 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 118 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 119 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 120 of SEQ ID NO: 13.

Embodiment 28. The EPO polypeptide of any one of embodiments 1 to 27 comprising:

- a) asparagine at a position corresponding to position 145 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 146 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 147 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 119 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 120 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 121 of SEQ ID NO: 13.

Embodiment 29. The EPO polypeptide of any one of embodiments 1 to 28 comprising:

- a) asparagine at a position corresponding to position 146 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 147 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 148 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 120 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 121 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 122 of SEQ ID NO: 13.

Embodiment 30. The EPO polypeptide of any one of embodiments 1 to 29 comprising:

- a) asparagine at a position corresponding to position 147 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 148 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 149 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 121 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 122 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 123 of SEQ ID NO: 13.

Embodiment 31. The EPO polypeptide of any one of embodiments 1 to 30 comprising:

- a) asparagine at a position corresponding to position 148 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 149 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 150 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 122 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 123 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 124 of SEQ ID NO: 13.

Embodiment 32. The EPO polypeptide of any one of embodiments 1 to 31 comprising:

- a) asparagine at a position corresponding to position 149 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 150 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 151 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 123 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 124 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 125 of SEQ ID NO: 13.

Embodiment 33. The EPO polypeptide of any one of embodiments 1 to 32 comprising:

- a) asparagine at a position corresponding to position 150 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 151 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 152 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 124 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 125 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 126 of SEQ ID NO: 13.

Embodiment 34. The EPO polypeptide of any one of embodiments 1 to 33 comprising:

- a) asparagine at a position corresponding to position 161 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 162 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 163 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 135 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 136 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 137 of SEQ ID NO: 13.

Embodiment 35. The EPO polypeptide of any one of embodiments 1 to 34 comprising:

- a) asparagine at a position corresponding to position 162 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 163 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 164 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 136 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 137 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 138 of SEQ ID NO: 13.

Embodiment 36. The EPO polypeptide of any one of embodiments 1 to 35 comprising:

Embodiment 37. The EPO polypeptide of any one of embodiments 1 to 36 comprising:

- a) asparagine at a position corresponding to position 184 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 185 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 186 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 158 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 159 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 160 of SEQ ID NO: 13.

Embodiment 38. The EPO polypeptide of any one of embodiments 1 to 37 comprising:

- a) asparagine at a position corresponding to position 186 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 187 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 188 of SEQ ID NO: 2; or
- b) asparagine at a position corresponding to position 162 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 163 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 164 of SEQ ID NO: 13.

Embodiment 39. The EPO polypeptide of any one of embodiments 1 to 38 comprising the amino acid sequence of SEQ ID NO: 4.
Embodiment 40. The EPO polypeptide of any one of embodiments 1 to 39, wherein the N-linked glycosylation site comprises an amino acid derivative.
Embodiment 41. The EPO polypeptide of embodiment 40, wherein the amino acid derivative is an asparagine derivative, a serine derivative, or a threonine derivative.
Embodiment 42. The EPO polypeptide of any one of embodiments 1 to 41, wherein the EPO polypeptide is glycosylated.
Embodiment 43. The EPO polypeptide of any one of embodiments 1 to 42 comprising at least one glycan moiety attached to the N-linked glycosylation site.
Embodiment 44. The EPO polypeptide of any one of embodiments 1 to 43, wherein the EPO polypeptide is PEGylated.
Embodiment 45. The EPO polypeptide of any one of embodiments 1 to 44, wherein the EPO polypeptide is PEGylated at a glycan.
Embodiment 46. The EPO polypeptide of any one of embodiments 1 to 45, wherein the EPO polypeptide is PEGylated at a primary amine.
Embodiment 47. The EPO polypeptide of any one of embodiments 1 to 46, wherein the EPO polypeptide is PEGylated at the N-terminal alpha-amine.
Embodiment 48. A composition comprising a plurality of EPO polypeptides of any one of embodiments 1 to 47 having a range of isoelectric points of from about 1 to about 3.5, of from about 1.5 to about 3.5, of from about 2 to about 3.5, of from about 2.5 to about 3.5, of from about 3 to about 3.5, of about 3.5 or less, or of about 3 or less, as determined by isoelectric focusing.
Embodiment 49. A composition comprising a plurality of EPO polypeptides of any one of embodiments 1 to 47 having a range of isoelectric points of from about 3.5 to about 6, of from about 4 to about 6, of from about 4.5 to about 6, of from about 5 to about 6, of from about 5.5 to about 6, of from about 3.5 to about 5, of from about 4 to about 5, of from about 4.5 to about 5, of about 3.5 or greater, of about 4 or greater, or of about 4.5 or greater, as determined by isoelectric focusing.
Embodiment 50. A combination comprising the composition of embodiment 48 and the composition of embodiment 49.
Embodiment 51. An isolated nucleic acid encoding the EPO polypeptide of any one of embodiments 1 to 41.
Embodiment 52. The nucleic acid of embodiment 51, wherein the nucleic acid comprises a regulatory sequence.
Embodiment 53. The nucleic acid of embodiment 52, wherein the regulatory sequence is a constitutive promoter; an inducible regulatory sequence, such as a tetracycline response element or a hypoxia-inducible promoter; a tissue specific promoter; an enhancer; a silencer; or encodes a micro RNA or transcription factor.
Embodiment 54. An isolated nucleic acid encoding an EPO polypeptide comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 13; and a heterologous regulatory sequence, wherein the heterologous regulatory sequence is not a constitutive promoter.
Embodiment 55. The nucleic acid of embodiment 54, wherein the heterologous regulatory sequence is an inducible regulatory sequence, such as a tetracycline response element or a hypoxia-inducible promoter; a tissue specific promoter; an enhancer; a silencer; or encodes a micro RNA or transcription factor.
Embodiment 56. A vector comprising the nucleic acid of any one of embodiments 51 to 55.
Embodiment 57. The vector of embodiment 56, wherein the vector is a viral vector or a bacterial vector.
Embodiment 58. The vector of embodiment 56 or embodiment 57, wherein the vector is a retroviral vector, a herpesviral vector, an adenoviral vector, an adeno-associated viral vector, or a pox viral vector.
Embodiment 59. An expression system comprising a first vector comprising a nucleic acid encoding the EPO polypeptide of any one of embodiment 1 to 41; and a second vector comprising a regulatory sequence.
Embodiment 60. An expression system comprising a first vector comprising a nucleic acid encoding an EPO polypeptide comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 13; and a second vector comprising a regulatory sequence.
Embodiment 61. The expression system of embodiment 59 or embodiment 60, wherein the regulatory sequence encodes a micro RNA or transcription factor.
Embodiment 62. The expression system of embodiment 60 or embodiment 61, wherein the first vector and/or second vector is a viral vector or a bacterial vector.
Embodiment 63. The expression system of any one of embodiments 60 to 62, wherein the first vector and/or second vector is a retroviral vector, a herpesviral vector, an adenoviral vector, an adeno-associated viral vector, or a pox viral vector.
Embodiment 64. A host cell comprising the nucleic acid of any one of embodiments 51 to 55, the vector of any one of embodiments 56 to 58, or the expression system of any one of embodiments 59 to 63.
Embodiment 65. A method of producing a composition comprising EPO polypeptides comprising culturing the host cell of embodiment 64 and isolating the EPO polypeptides.
Embodiment 66. The method of embodiment 65, wherein the EPO polypeptides are isolated by column chromatography.
Embodiment 67. The method of embodiment 65 or embodiment 66, wherein the EPO polypeptides are isolated by ion exchange column chromatography.
Embodiment 68. The method of any one of embodiments 65 to 67, wherein the EPO polypeptides are isolated by Capto Butyl column chromatography, cation-exchange column chromatography, or anion-exchange column chromatography.
Embodiment 69. The method of any one of embodiments 65 to 68, wherein the EPO polypeptides are isolated by mixed-mode column chromatography.
Embodiment 70. The method of any one of embodiment 65 to 69, wherein the EPO polypeptides are isolated by hydrophobic interaction column chromatography.
Embodiment 71. The method of any one of embodiments 65 to 70, wherein the EPO polypeptides are isolated by a combination of chromatography columns.
Embodiment 72. The method of any one of embodiments 65 to 71, wherein the method further comprises inactivating and/or removing viruses.
Embodiment 73. The method of any one of embodiments 65 to 72, wherein the EPO polypeptides have a range of isoelectric points of from about 1 to about 3.5, of from about 1.5 to about 3.5, of from about 2 to about 3.5, of from about 2.5 to about 3.5, of from about 3 to about 3.5, of about 3.5 or less, or of about 3 or less, as determined by isoelectric focusing.
Embodiment 74. The method of any one of embodiments 65 to 72, wherein the EPO polypeptides have a range of isoelectric points of from about 3.5 to about 6, of from about 4 to about 6, of from about 4.5 to about 6, of from about 5 to about 6, of from about 5.5 to about 6, of from about 3.5 to about 5, of from about 4 to about 5, of from about 4.5 to about 5, of about 3.5 or greater, of about 4 or greater, or of about 4.5 or greater, as determined by isoelectric focusing.
Embodiment 75. A pharmaceutical composition comprising the EPO polypeptide of any one of embodiments 1 to 47, the composition of embodiments 48 or 49, the combination of embodiment 50, the nucleic acid of any one of embodiments 51 to 55, the vector of any one of embodiments 56 to 58, or the expression system of any one of embodiments 59 to 63; and a pharmaceutically acceptable carrier.
Embodiment 76. A pharmaceutical composition comprising an EPO polypeptide and a pharmaceutically acceptable carrier, wherein the pharmaceutically acceptable carrier comprises a) sodium phosphate, sodium chloride, and polysorbate 80; b) sodium phosphate, sodium chloride, and polysorbate 20; c) sodium citrate, sodium chloride, and polysorbate 80; or d) sodium citrate, sodium chloride, and polysorbate 20.
Embodiment 77. A pharmaceutical composition comprising an EPO polypeptide and a pharmaceutically acceptable carrier, wherein the pharmaceutically acceptable carrier comprises sodium citrate, sodium chloride, polysorbate 80, and m-cresol.
Embodiment 78. A pharmaceutical composition comprising an EPO polypeptide and a pharmaceutically acceptable carrier, wherein the pharmaceutically acceptable carrier comprises sodium phosphate, sodium chloride, polysorbate 20, and benzyl alcohol.
Embodiment 79. The pharmaceutical composition of any one of embodiments 76 to 78, wherein the concentration of sodium chloride is about 140 mM.
Embodiment 80. The pharmaceutical composition of any one of embodiments 76 to 79, wherein the concentration of sodium phosphate or sodium citrate is about 20 mM.
Embodiment 81. The pharmaceutical composition of any one of embodiments 76 to 80, wherein the concentration of polysorbate 20 or polysorbate 80 is about 650 nM.
Embodiment 82. The pharmaceutical composition of any one of embodiments 77, or 79 to 81, wherein the concentration of m-cresol is about 0.2%.
Embodiment 83. The pharmaceutical composition of any one of embodiments 78 to 82, wherein the concentration of benzyl alcohol is about 1%.
Embodiment 84. The pharmaceutical composition of any one of embodiments 76 to 83, wherein the pharmaceutically acceptable carrier comprises

- a) sodium phosphate at a concentration of about 20 mM, sodium chloride at a concentration of about 140 mM, polysorbate 80 at a concentration of about 650 nM or
- b) sodium phosphate at a concentration of about 20 mM, sodium chloride at a concentration of about 140 mM, polysorbate 20 at a concentration of about 650 nM.

Embodiment 85. The pharmaceutical composition of any one of embodiments 76 to 84, wherein the pharmaceutically acceptable carrier comprises sodium citrate at a concentration of about 20 mM, sodium chloride at a concentration of about 140 nM, polysorbate 80 at a concentration of about 650 nM, and m-cresol at a concentration of about 0.2%.
Embodiment 86. The pharmaceutical composition of any one of embodiments 76 to 85, wherein the pharmaceutically acceptable carrier comprises sodium phosphate at a concentration of about 20 mM, sodium chloride at a concentration of about 140 nM, polysorbate 20 at a concentration of about 650 nM, and benzyl alcohol at a concentration of about 1%.
Embodiment 87. The pharmaceutical composition of any one of embodiments 76 to 86, wherein the EPO polypeptide is the EPO polypeptide of any one of embodiments 1 to 47, the composition of embodiment 48 or embodiment 49, or the combination of embodiment 50.
Embodiment 88. A method of delivering an EPO polypeptide to a companion animal species comprising administering the EPO polypeptide of any one of embodiments 1 to 47, the composition of embodiments 48 or 49, the combination of embodiment 50, or the pharmaceutical composition of embodiment 75 or embodiment 87 parenterally.
Embodiment 89. A method of delivering an EPO polypeptide to a companion animal species comprising administering the EPO polypeptide of any one of embodiments 1 to 47, the composition of embodiments 48 or 49, the combination of embodiment 50, or the pharmaceutical composition of embodiment 75 or embodiment 87 by an intramuscular route, an intraperitoneal route, an intracerebrospinal route, a subcutaneous route, an intra-arterial route, an intrasynovial route, an intrathecal route, or an inhalation route.
Embodiment 90. A method of delivering an isolated nucleic acid encoding an EPO polypeptide to a companion animal species comprising administering the nucleic acid of any one of embodiments 51 to 55, the vector of any one of embodiments 56 to 58, or the expression system of any one of claims 59 to 63 parenterally.
Embodiment 91. A method of treating a companion animal species having anemia, the method comprising administering to the companion animal species a therapeutically effective amount of the EPO polypeptide of any one of embodiments 1 to 47, the composition of embodiments 48 or 49, the combination of embodiment 50, or the pharmaceutical composition of embodiment 75 or embodiment 87.
Embodiment 92. A method of treating a companion animal species having anemia, the method comprising administering to the companion animal species a therapeutically effective amount of the nucleic acid of any one of embodiments 51 to 55, the vector of any one of embodiments 56 to 58, or the expression system of any one of embodiments 59 to 63.
Embodiment 93. The method of embodiment 91 or embodiment 92, wherein the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition is administered parenterally.
Embodiment 94. The method of any one of embodiments 91 to 93, wherein the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition is administered by an intramuscular route, an intraperitoneal route, an intracerebrospinal route, a subcutaneous route, an intra-arterial route, an intrasynovial route, an intrathecal route, or an inhalation route.
Embodiment 95. The method of any one of embodiments 88 to 94, wherein the companion animal species is feline, canine, or equine.
Embodiment 96. The method of any one of embodiments 91 to 95, wherein the anemia is caused by chronic kidney disease, inflammatory bowel disease, or myelodysplasia.
Embodiment 97. The method of any one of embodiments 88 to 96, wherein the EPO polypeptide is administered in an amount of from about 1 μg/kg body weight to about 10 μg/kg body weight, or about 1 μg/kg body weight to about 5 μg/kg body weight, or about 1 μg/kg body weight, or about 3 μg/kg body weight, or about 5 μg/kg body weight, or about 10 μg/kg body weight.
Embodiment 98. The method of any one of embodiments 88 to 97, wherein the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition is administered every 7 to 10 days.
Embodiment 99. The method of any one of embodiments 88 to 98, wherein the method further comprises administering iron dextran.
Embodiment 100. The method of any one of embodiments 88 to 99, wherein the companion animal species has a baseline hematocrit percentage of from about 15% to about 30%, of from about 15% to about 25%, of from about 20% to about 25%, of from about 25% to about 30%, of below about 15%, of below about 18%, of below about 20%, of below about 25%, of below about 29%, or of below about 30% prior to administration of the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition.
Embodiment 101. The method of any one of embodiments 88 to 100, wherein the hematocrit percentage of the companion animal species increases to at least 25%, or at least 26%, or at least 27%, or at least 28%, or at least 29%, or at least 30%, or at least 32%, or at least 35%, or at least 38%, or at least 40%, or at least 42%, or at least 45%, or at least 48% following administration of the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition.
Embodiment 102. The method of embodiment 101, wherein the hematocrit percentage of the companion animal species increases to at least 25%, or at least 27%, or at least 30%, or at least 32%, or at least 35% at 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, or 6 weeks after a first administration of the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition.
Embodiment 103. The method of any one of embodiments 88 to 102, wherein the body weight of the companion animal species is maintained or increased compared to baseline following administration of the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition.
Embodiment 104. The method of embodiment 103, wherein the body weight of the companion animal species is maintained or increased at 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, or 6 weeks after a first administration of the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition.
Embodiment 105. The method of any one of embodiments 88 to 104, wherein the level of symmetric dimethylarginine or serum creatine renal biomarker is decreased compared to baseline following administration of the EPO polypeptide, composition, nucleic acid, vector, expression system, or pharmaceutical composition.
Embodiment 106. A method of expressing an EPO polypeptide in a target cell, comprising:

- a) transferring a nucleic acid, vector, or expression system into the target cell, wherein the nucleic acid, vector, or expression system comprises:
  - i) a nucleic acid encoding the EPO polypeptide of any one of embodiments 1 to 41, and
  - ii) a regulatory sequence; and
- b) culturing the cell under conditions supportive for expression of the EPO polypeptide.

Embodiment 107. A method of expressing an EPO polypeptide in a target cell, comprising:

- a) transferring a nucleic acid, a vector, or an expression system into the target cell, wherein the nucleic acid, vector, or expression system comprises:
  - i) a nucleic acid encoding an EPO polypeptide having the amino acid sequence of SEQ ID NO: 2 or an EPO polypeptide having the amino acid sequence of SEQ ID NO: 13, and
  - ii) a regulatory sequence, wherein the regulatory sequence is not a constitutive promoter; and
- b) culturing the cell under conditions supportive for expression of the EPO polypeptide.

Embodiment 108. The method of embodiment 106 or embodiment 107, wherein the regulatory sequence is an inducible regulatory sequence, such as a tetracycline response element or a hypoxia-inducible promoter; a tissue specific promoter; an enhancer; a silencer; or encodes a micro RNA or transcription factor.
Embodiment 109. The method of any one of embodiments 106 to 108, wherein the vector is a viral vector or a bacterial vector.
Embodiment 110. The method of any one of embodiments 106 to 109, wherein the vector is a retroviral vector, a herpesviral vector, an adenoviral vector, an adeno-associated viral vector, or a pox viral vector.
Embodiment 111. The method of any one of embodiments 106 to 110, wherein the cell is a cell of a companion animal species.
Embodiment 112. The method of any one of embodiments 106 to 111, wherein the cell is located in a living companion animal species.
Embodiment 113. The method of embodiment 111 or embodiment 112, wherein the companion animal species is a canine, feline, or equine.
Embodiment 114. An erythropoietin (EPO) polypeptide comprising:

- a) at least one amino acid substitution at a position corresponding to a position selected from position 5, 8, 10, 11, 14, 15, 78, 96, 97, 99, 100, 103, 104, 107, 108, or 110 of SEQ ID NO: 13;
- b) at least one amino acid substitution of SEQ ID NO: 9 that corresponds to a position selected from position 5, 8, 10, 11, 14, 15, 78, 96, 97, 99, 100, 103, 104, 107, 108, or 110 of SEQ ID NO: 13;
- c) at least one amino acid substitution of SEQ ID NO: 10 that corresponds to a position selected from position 5, 8, 10, 11, 14, 15, 78, 96, 97, 99, 100, 103, 104, 107, 108, or 110 of SEQ ID NO: 13;
- d) at least one amino acid substitution of SEQ ID NO: 11 that corresponds to position selected from position 5, 8, 10, 11, 14, 15, 78, 96, 97, 99, 100, 103, 104, 107, 108, or 110 of SEQ ID NO: 13; or
- e) at least one amino acid substitution of SEQ ID NO: 12 that corresponds to a position selected from position 5, 8, 10, 11, 14, 15, 78, 96, 97, 99, 100, 103, 104, 107, 108, or 110 of SEQ ID NO: 13.

Embodiment 115. The EPO polypeptide of embodiment 114, wherein the at least one amino acid substitution is:

- a) a substitution at a position corresponding to position 103 of SEQ ID NO: 13;
- b) a substitution of SEQ ID NO: 9 that corresponds to position 103 of SEQ ID NO: 13;
- c) a substitution of SEQ ID NO: 10 that corresponds to position 103 of SEQ ID NO: 13;
- d) a substitution of SEQ ID NO: 11 that corresponds to position 103 of SEQ ID NO: 13; or
- e) a substitution of SEQ ID NO: 12 that corresponds to position 103 of SEQ ID NO: 13.

Embodiment 116. The EPO polypeptide of embodiment 114 or 115, wherein an alanine is substituted at a position corresponding to position 103 of SEQ ID NO: 13.
Embodiment 117. The EPO polypeptide of any one of embodiments 114 to 116, wherein the at least one amino acid substitution comprises substitution with an amino acid derivative.
Embodiment 118. The EPO polypeptide of any one of embodiments 114 to 117, wherein the EPO polypeptide comprises an amino acid sequence of SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, or SEQ ID NO: 19.
Embodiment 119. A polypeptide comprising an amino acid sequence of SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, or SEQ ID NO: 19.
Embodiment 120. An isolated nucleic acid encoding the EPO polypeptide of any one of embodiments 114 to 119.
Embodiment 121. A host cell comprising the nucleic acid of embodiment 120.
Embodiment 122. A method of producing a composition comprising EPO polypeptides comprising culturing the host cell of embodiment 121 and isolating the EPO polypeptides.
Embodiment 123. A pharmaceutical composition comprising the EPO polypeptide of any one of embodiments 114 to 119 and a pharmaceutically acceptable carrier.
Embodiment 124. The pharmaceutical composition of any one of embodiments 76 to 86, wherein the EPO polypeptide is the EPO polypeptide of any one of embodiments 114 to 119.
Embodiment 125. A polypeptide comprising an extracellular domain of a feline erythropoietin receptor (EPOR) polypeptide comprising the amino acid sequence of SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32; and a heterologous polypeptide sequence.
Embodiment 126. A polypeptide comprising the amino acid sequence of SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, or SEQ ID NO: 32; and a heterologous polypeptide sequence.
Embodiment 127. The polypeptide of embodiment 115 or embodiment 116 comprising the amino acid sequence of SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, or SEQ ID NO: 22.
Embodiment 128. An isolated nucleic acid encoding the polypeptide of any one of embodiments 125 to 127.
Embodiment 129. A host cell comprising the nucleic acid of embodiment 128.
Embodiment 130. A method of producing a polypeptide comprising culturing the host cell of embodiment 129 and isolating the polypeptide.
Embodiment 131. A pharmaceutical composition comprising the polypeptide of any one of embodiments 126 to 127 and a pharmaceutically acceptable carrier.
Embodiment 132. A method of treating a subject having polycythemia, the method comprising administering to the subject a therapeutically effective amount of the EPO polypeptide of any one of embodiments 114 to 119, the polypeptide of any one of embodiments 125 to 127, the nucleic acid of embodiment 120 or embodiment 128, or the pharmaceutical composition of embodiment 123, embodiment 124, or embodiment 131.
Embodiment 133. The method of embodiment 132, wherein the EPO polypeptide, polypeptide, nucleic acid, or pharmaceutical composition is administered parenterally.
Embodiment 134. The method of embodiment 132 or embodiment 133, wherein the EPO polypeptide, the polypeptide, nucleic acid, or pharmaceutical composition is administered by an intramuscular route, an intraperitoneal route, an intracerebrospinal route, a subcutaneous route, an intra-arterial route, an intrasynovial route, an intrathecal route, or an inhalation route.
Embodiment 135. The method of any one of embodiments 132 to 132, wherein the subject is a companion animal species.
Embodiment 136. The method of embodiment 135, wherein the companion animal species is feline, canine, or equine.
Embodiment 137. The method of any one of embodiments 132 to 134, wherein the subject is a human.
Embodiment 138. The method of any one of embodiments 132 to 137, wherein the polycythemia is caused by a mutation in JAK2, overproduction and/or secretion of EPO from a tumor.
These and other aspects and various embodiments are described more fully below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows isoelectric focusing (IEF) and FIG. 1B shows SDS-PAGE of isolated basic and acidic Analog 6-30 GV Mature fractions.

FIG. 2A and FIG. 2B show IEF gels to demonstrate separation of various sialylation states. pI marker locations are indicated.

FIG. 3 shows a Western blot of isolated feline EPO Analog 6-30 GV Mature (SEQ ID NO: 14). Lane 1: molecular weight marker; Lanes 2-6: isolated Analog 6-30 GV Mature at 1 μg, 0.5 μg, 0.2 μg, 0.1 μg, and 0.05 μg, respectively.

FIGS. 4A-4B show sialic acid analysis as DMB-sialic acid using HPLC with a fluorescence detector. FIG. 4A shows sialic acid analysis of a commercial standard of Neu5Gc/Neu5A at a known concentration. FIG. 4B shows sialic acid analysis of isolated Analog 6-30 GV Mature.

FIG. 5 shows results of a TF-1 cell proliferation assay demonstrating that high sialylation feline EPO (acidic fraction) has lower activity compared to lower sialylation feline EPO (basic fraction).

FIG. 6A shows the pharmacokinetic (PK) profile of low sialylation Analog 6-30 GV Mature (basic fraction) in two cats (Dot and Salem) following subcutaneous (SQ) injection. FIG. 6B shows the average PK profile and parameters of high sialylation Analog 6-30 GV Mature (acidic fraction) in four cats following intravenous (IV) injection. FIG. 6C shows the average PK profile and parameters of high sialylation Analog 6-30 GV Mature (acidic fraction) in four cats following subcutaneous (SQ) injection. FIG. 6D shows the average PK profile and parameters of high sialylation Analog 6-30 GV Mature (acidic fraction) in three cats following intramuscular (IM) injection.

FIGS. 7A-7D are a series of Western blots showing expression of fEPOR201-N-flag, fEPOR202-N-flag, fEPOR201_ECD-Fc, fEPOR202_ECD-Fc, and fEPOR203_ECD-Fc. FIG. 7A is a Western blot using anti-human Fc antibody to identify feline EPOR201-ECD-Fc (lane 1) and feline EPOR202-ECD-Fc (lane 2). FIG. 7B and FIG. 7C are Western blots using anti-flag antibody to identify feline EPOR201-N-flag (lanes 3 and 4) and feline EPOR202-N-flag (lanes 6 and 7) compared to an untransfected control (lane 5). FIG. 7D is a Coomassie stain of an SDS-PAGE of feline EPOR203-ECD-Fc (lane 9) and a molecular weight standard (lane 8).

FIG. 8 shows results of a TF-1 cell proliferation assay of recombinant human EPO and Analog 6-30 GV Mature and calculated EC₅₀values.

FIG. 9 shows proposed interactions between E18 and R14, Y15 and K97 of feline EPO.

FIG. 10 shows results of a TF-1 cell proliferation assay of Analog 6-30 EV Mature and a 50/50 mixture of Analog 6-30 EV Mature and Analog 6-30GV Mature.

FIG. 11 shows an ELISA binding assay between Feline Analog 6-30 EV Mature (SEQ ID NO: 15) and Feline EPOR2E3_39A_ECD_Fc (SEQ ID NO: 26). The four parameters represented are A: minimum value; D: maximum value; C: point of inflection; and D: Hill's slope of the curve.

FIG. 12 is a graph showing the absolute reticulocyte percentage in cats at 1 day prior to and at 5, 7, 10, and 14 days after administration of placebo or Feline Analog 6-30 EV Mature (SEQ ID NO: 15) at one of three dose levels (1 μg/kg (“EPO1;” n=5), 3 μg/kg (“EPO3;” n=5), or 10 μg/kg (“EPO10;” n=5)).

FIG. 13 is a graph showing the absolute reticulocyte percentage in cats at 4 days prior to and at 3, 5, 10, 17, 19, 24, 31, and 33 days after administration of Feline Analog 6-30 GV Mature (SEQ ID NO: 14; 10 μg/kg; n=4).

DESCRIPTION OF CERTAIN SEQUENCES

Table 1 provides a listing of certain sequences referenced herein.

TABLE 1

Description of Certain Sequences

SEQ ID
NO:	SEQUENCE	DESCRIPTION

1	MGSCECPALLLLLSLLLLPLGLPVLGAPPRLIC	Felis catus
	DSRVLERYILGAREAENVTMGCAEGCSFSENITV	Erythropoietin (EPO)
	PDTKVNFYTWKRMDVGQQAVEVWQGLALLSE	precursor form “wild-type
	AILRGQALLANSSQPSETLQLHVDKAVSSLRSLTS	feline EPO G44”
	LLRALGAQKEATSLPEATSAAPLRTFTVDTLCKL
	FRIYSNFLRGKLTLYTGEACRRGDR

2	MGSCECPALLLLLSLLLLPLGLPVLG APPRLIC	Felis catus
	DSRVLERYIL E AREAENVTMGCAEGCSFSENITV	EPO precursor form “wild-
	PDTKVNFYTWKRMDVGQQAVEVWQGLALLSE	type feline EPO E44”
	AILRGQALLANSSQPSETLQLHVDKAVSSLRSLTS
	LLRALGAQKEATSLPEATSAAPLRTFTVDTLCKL
	FRIYSNFLRGKLTLYTGEACRRGDR

3	MGSCECPALLLLLSLLLLPLGLPVLG APPRLIC	Feline EPO Analog 6-30
	DSRVLERYIL G AREAENVTMGC N E T CSFSENITV	G44V113 precursor form or
	PDTKVNFYTWKRMDVGQQAVEVWQGLALLSE	“Analog 6-30 GV Precursor”
	AILRGQALLANSSQ VN ETLQLHVDKAVSSLRSLT
	SLLRALGAQKEATSLPEATSAAPLRTFTVDTLCK
	LFRIYSNFLRGKLTLYTGEACRRGDR

4	MGSCECPALLLLLSLLLLPLGLPVLG APPRLIC	Feline EPO Analog 6-30
	DSRVLERYIL E AREAENVTMGC N E T CSFSENITV	E44V113 precursor form or
	PDTKVNFYTWKRMDVGQQAVEVWQGLALLSE	“Analog 6-30 EV Precursor”
	AILRGQALLANSSQ VN ETLQLHVDKAVSSLRSLT
	SLLRALGAQKEATSLPEATSAAPLRTFTVDTLCK
	LFRIYSNFLRGKLTLYTGEACRRGDR

5	MDHLWAPLWPGVGSLCLLLAGAAWAMDYKDD	Flag_feline EPOR201_full-
	DDKAPPPNPLDPKFESKVNMVCMRAPEASACGS	length (fEPOR201-N-flag)
	SERLEDLVCFWEEAASAGVGPDNYSFFYQLEGEP
	WKPCSLHQAPTARGAVRFWCSLPTADASSFVPL
	ELRVTAVSSGAPRYHRIIHINEVVLLDPPAGLLAR
	RADEGGHVVLRWLPPPGAPVASLIRYEVNISSGN
	VAGGAQKVEILDGRTECALSNLRGRTRYTFMVR
	ARMAEPSFGGFWSAWSEPASLLTASDLDPLILTL
	SLILVLILLLLAVLALLSHRRFTRTLKQKIWPGIPS
	PESEFEGLFTTHKGNFQLWLYQNEGCLWWSPCA
	PFAEDPPSPLEVLSERCWGATQAAEPGAEEGPLL
	EPLGSEHTQDTYLVLDKWLLPRNPPSEDLPRPDG
	SLDMVAMHKGSEASSCSSALSLKPGPEGALGAS
	FEYTILDPSSQLLRPRALPPELPPTPPHIKYLYLMV
	SDSGISTDYSSGGSQEAQGDSSTGPYLNPYENSLI
	PATETSPPSYVACS

6	MDHLWAPLWPGVGSLCLLLAGAAWAMDYKDD	Flag_feline EPOR202_full-
	DDKAPPPNPLDPKFESKGKDGSVCRPPQWFLEGN	length (fEPOR202-N-flag)
	AEERLEDLVCFWEEAASAGVGPDNYSFFYQLEG
	EPWKPCSLHQAPTARGAVRFWCSLPTADASSFV
	PLELRVTAVSSGAPRYHRIIHINEVVLLDPPAGLL
	ARRADEGGHVVLRWLPPPGAPVASLIRYEVNISS
	GNVAGGAQKVEILDGRTECALSNLRGRTRYTFM
	VRARMAEPSFGGFWSAWSEPASLLTASDLDPLIL
	TLSLILVLILLLLAVLALLSHRRTLKQKIWPGIPSP
	ESEFEGLFTTHKGNFQLWLYQNEGCLWWSPCAP
	FAEDPPSPLEVLSERCWGATQAAEPGAEEGPLLE
	PLGSEHTQDTYLVLDKWLLPRNPPSEDLPRPDGS
	LDMVAMHKGSEASSCSSALSLKPGPEGALGASF
	EYTILDPSSQLLRPRALPPELPPTPPHIKYLYLMVS
	DSGISTDYSSGGSQEAQGDSSTGPYLNPYENSLIP
	ATETSPPSYVACS

7	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Feline
	PKFESKVNMVCMRAPEASACGSSERLEDLVCFW	EPOR201_ECD_human Fc
	EEAASAGVGPDNYSFFYQLEGEPWKPCSLHQAP
	TARGAVRFWCSLPTADASSFVPLELRVTAVSSGA
	PRYHRIIHINEVVLLDPPAGLLARRADEGGHVVL
	RWLPPPGAPVASLIRYEVNISSGNVAGGAQKVEI
	LDGRTECALSNLRGRTRYTFMVRARMAEPSFGG
	FWSAWSEPASLLTASDLDIEGRMDPKSCDKTHTC
	PPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTC
	VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPRE
	EQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSN
	KALPAPIEKTISKAKGQPREPQVYTLPPSRDELTK
	NQVSLTCLVKGFYPSDIAVEWESNGQPENNYKT
	TPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSV
	MHEALHNHYTQKSLSLSPGK

8	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Feline
	PKFESKGKDGSVCRPPQWFLEGNAEERLEDLVCF	EPOR202_ECD_human Fc
	WEEAASAGVGPDNYSFFYQLEGEPWKPCSLHQA
	PTARGAVRFWCSLPTADASSFVPLELRVTAVSSG
	APRYHRIIHINEVVLLDPPAGLLARRADEGGHVV
	LRWLPPPGAPVASLIRYEVNISSGNVAGGAQKVE
	ILDGRTECALSNLRGRTRYTFMVRARMAEPSFG
	GFWSAWSEPASLLTASDLDIEGRMDPKSCDKTHT
	CPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVT
	CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPR
	EEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVS
	NKALPAPIEKTISKAKGQPREPQVYTLPPSRDELT
	KNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK
	TTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCS
	VMHEALHNHYTQKSLSLSPGK

9	APPRLICDSRVLERYLLEAKEAENITTGCAEHCSL	Human EPO mature form
	NENITVPDTKVNFYAWKRMEVGQQAVEVWQGL
	ALLSEAVLRGQALLVNSSQPWEPLQLHVDKAVS
	GLRSLTTLLRALGAQKEAISPPDAASAAPLRTITA
	DTFRKLFRVYSNFLRGKLKLYTGEACRTGDR

10	APPRLICDSRVLERYILEAREAENVTMGCAQGCS	Canis lupus EPO mature form
	FSENITVPDTKVNFYTWKRMDVGQQALEVWQG
	LALLSEAILRGQALLANASQPSETPQLHVDKAVS
	SLRSLTSLLRALGAQKEAMSLPEEASPAPLRTFTV
	DTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

11	APPRLICDSRVLERYILEAREAENVTMGCAEGCS	Equus caballus EPO mature
	FGENVTVPDTKVNFYSWKRMEVEQQAVEVWQG	form
	LALLSEAILQGQALLANSSQPSETLRLHVDKAVS
	SLRSLTSLLRALGAQKEAISPPDAASAAPLRTFAV
	DTLCKLFRIYSNFLRGKLKLYTGEACRRGDR

12	APPRLICDSRVLERYILGAREAENVTMGCAEGCS	Felis catus
	FSENITVPDTKVNFYTWKRMDVGQQAVEVWQG	EPO mature form ″wild-type
	LALLSEAILRGQALLANSSQPSETLQLHVDKAVS	feline EPO G18″
	SLRSLTSLLRALGAQKEATSLPEATSAAPLRTFTV
	DTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

13	APPRLICDSRVLERYIL E AREAENVTMGCAEGCS	Felis catus
	FSENITVPDTKVNFYTWKRMDVGQQAVEVWQG	EPO mature form ″wild-type
	LALLSEAILRGQALLANSSQPSETLQLHVDKAVS	feline EPO E18″
	SLRSLTSLLRALGAQKEATSLPEATSAAPLRTFTV
	DTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

14	APPRLICDSRVLERYIL G AREAENVTMGC N E T CS	Feline EPO Analog 6-30
	FSENITVPDTKVNFYTWKRMDVGQQAVEVWQG	G18V87 mature form or
	LALLSEAILRGQALLANSSQ VN ETLQLHVDKAVS	″Analog 6-30 GV Mature″
	SLRSLTSLLRALGAQKEATSLPEATSAAPLRTFTV
	DTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

15	APPRLICDSRVLERYIL E AREAENVTMGC N E T CS	Feline EPO Analog 6-30
	FSENITVPDTKVNFYTWKRMDVGQQAVEVWQG	E18V87 mature form or
	LALLSEAILRGQALLANSSQ VN ETLQLHVDKAVS	″Analog 6-30 EV Mature″
	SLRSLTSLLRALGAQKEATSLPEATSAAPLRTFTV
	DTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

16	APPRLICDSRVLERYLLEAKEAENITTGCAEHCSL	Human erythropoietin second
	NENITVPDTKVNFYAWKRMEVGQQAVEVWQGL	site mutation R103A
	ALLSEAVLRGQALLVNSSQPWEPLQLHVDKAVS
	GL A SLTTLLRALGAQKEAISPPDAASAAPLRTITA
	DTFRKLFRVYSNFLRGKLKLYTGEACRTGDR

17	APPRLICDSRVLERYIL E AREAENVTMGCAEGCS	Felis catus
	FSENITVPDTKVNFYTWKRMDVGQQAVEVWQG	Erythropoietin second site
	LALLSEAILRGQALLANSSQPSETLQLHVDKAVS	mutation R103A
	SL A SLTSLLRALGAQKEATSLPEATSAAPLRTFTV
	DTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

18	APPRLICDSRVLERYILEAREAENVTMGCAQGCS	Canis lupus erythropoietin
	FSENITVPDTKVNFYTWKRMDVGQQALEVWQG	second site mutation R103A
	LALLSEAILRGQALLANASQPSETPQLHVDKAVS
	SL A SLTSLLRALGAQKEAMSLPEEASPAPLRTFT
	VDTLCKLFRIYSNFLRGKLTLYTGEACRRGDR

19	APPRLICDSRVLERYILEAREAENVTMGCAEGCS	Equus caballus erythropoietin
	FGENVTVPDTKVNFYSWKRMEVEQQAVEVWQG	second site mutation R103A
	LALLSEAILQGQALLANSSQPSETLRLHVDKAVS
	SL A SLTSLLRALGAQKEAISPPDAASAAPLRTFAV
	DTLCKLFRIYSNFLRGKLKLYTGEACRRGDR

20	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Felis catus
	PKFESK X ALLAARGPEELLCFTERLEDLVCFWEE	EPO receptor Sequence
	AASAGVGPDNYSFFYQLEGEPWKPCSLHQAPTA	EPOR203
	RGAVRFWCSLPTADASSFVPLELRVTAVSSGAPR	NCBI Reference Sequence:
	YHRIIHINEVVLLDPPAGLLARRADEGGHVVLRW	XP_019673378.1
	LPPPGAPVASLIRYEVNISSGNVAGGAQKVEILDG
	RTECALSNLRGRTRYTFMVRARMAEPSFGGFWS
	AWSEPASLLTASDLDPLILTLSLILVLILLLLAVLA
	LLSHRRTLKQKIWPGIPSPESEFEGLFTTHKGNFQ
	LWLYQNEGCLWWSPCAPFAEDPPSPLEVLSERC
	WGATQAAEPGAEEGPLLEPLGSEHTQDTYLVLD
	KWLLPRNPPSEDLPRPDGSLDMVAMHKGSEASS
	CSSALSLKPGPEGALGASFEYTILDPSSQLLRPRA
	LPPELPPTPPHIKYLYLMVSDSGISTDYSSGGSQE
	AQGDSSTGPYLNPYENSLIPATETSPPSYVACS

21	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Felis catus EPO receptor
	PKFESK A ALLAARGPEELLCFTERLEDLVCFWEE	EPOR203_39A
	AASAGVGPDNYSFFYQLEGEPWKPCSLHQAPTA
	RGAVRFWCSLPTADASSFVPLELRVTAVSSGAPR
	YHRIIHINEVVLLDPPAGLLARRADEGGHVVLRW
	LPPPGAPVASLIRYEVNISSGNVAGGAQKVEILDG
	RTECALSNLRGRTRYTFMVRARMAEPSFGGFWS
	AWSEPASLLTASDLDPLILTLSLILVLILLLLAVLA
	LLSHRRTLKQKIWPGIPSPESEFEGLFTTHKGNFQ
	LWLYQNEGCLWWSPCAPFAEDPPSPLEVLSERC
	WGATQAAEPGAEEGPLLEPLGSEHTQDTYLVLD
	KWLLPRNPPSEDLPRPDGSLDMVAMHKGSEASS
	CSSALSLKPGPEGALGASFEYTILDPSSQLLRPRA
	LPPELPPTPPHIKYLYLMVSDSGISTDYSSGGSQE
	AQGDSSTGPYLNPYENSLIPATETSPPSYVACS

22	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Feline
	PKFESK A ALLAARGPEELLCFTERLEDLVCFWEE	EPOR203_39A_ECD_Fc
	AASAGVGPDNYSFFYQLEGEPWKPCSLHQAPTA
	RGAVRFWCSLPTADASSFVPLELRVTAVSSGAPR
	YHRIIHINEVVLLDPPAGLLARRADEGGHVVLRW
	LPPPGAPVASLIRYEVNISSGNVAGGAQKVEILDG
	RTECALSNLRGRTRYTFMVRARMAEPSFGGFWS
	AWSEPASLLTASDLDPGGGSPKSCDKTHTCPPCP
	APELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVD
	VSHEDPEVKFNWYVDGVEVHNAKTKPREEQYN
	STYRVVSVLTVLHQDWLNGKEYKCKVSNKALP
	APIEKTISKAKGQPREPQVYTLPPSRDELTKNQVS
	LTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVL
	DSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEA
	LHNHYTQKSLSLSPGK

23	PPPNPLDPKFESKVNMVCMRAPEASACGSSERLE	Feline EPOR201 ECD
	DLVCFWEEAASAGVGPDNYSFFYQLEGEPWKPC
	SLHQAPTARGAVRFWCSLPTADASSFVPLELRVT
	AVSSGAPRYHRIIHINEVVLLDPPAGLLARRADE
	GGHVVLRWLPPPGAPVASLIRYEVNISSGNVAGG
	AQKVEILDGRTECALSNLRGRTRYTFMVRARMA
	EPSFGGFWSAWSEPASLLTASDLD

24	PPPNPLDPKFESKGKDGSVCRPPQWFLEGNAEER	Feline EPOR202 ECD
	LEDLVCFWEEAASAGVGPDNYSFFYQLEGEPWK
	PCSLHQAPTARGAVRFWCSLPTADASSFVPLELR
	VTAVSSGAPRYHRIIHINEVVLLDPPAGLLARRA
	DEGGHVVLRWLPPPGAPVASLIRYEVNISSGNVA
	GGAQKVEILDGRTECALSNLRGRTRYTFMVRAR
	MAEPSFGGFWSAWSEPASLLTASDLD

25	PPPNPLDPKFESK X ALLAARGPEELLCFTERLEDL	Feline EPOR203 ECD
	VCFWEEAASAGVGPDNYSFFYQLEGEPWKPCSL
	HQAPTARGAVRFWCSLPTADASSFVPLELRVTA
	VSSGAPRYHRIIHINEVVLLDPPAGLLARRADEG
	GHVVLRWLPPPGAPVASLIRYEVNISSGNVAGGA
	QKVEILDGRTECALSNLRGRTRYTFMVRARMAE
	PSFGGFWSAWSEPASLLTASDLDP

26	PPPNPLDPKFESK A ALLAARGPEELLCFTERLEDL	Feline EPOR203_39A ECD
	VCFWEEAASAGVGPDNYSFFYQLEGEPWKPCSL
	HQAPTARGAVRFWCSLPTADASSFVPLELRVTA
	VSSGAPRYHRIIHINEVVLLDPPAGLLARRADEG
	GHVVLRWLPPPGAPVASLIRYEVNISSGNVAGGA
	QKVEILDGRTECALSNLRGRTRYTFMVRARMAE
	PSFGGFWSAWSEPASLLTASDLDP

27	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Felis catus
	PKFESKVNMVCMRAPEASACGSSERLEDLVCFW	EPO receptor Sequence
	EEAASAGVGPDNYSFFYQLEGEPWKPCSLHQAP	EPOR201
	TARGAVRFWCSLPTADASSFVPLELRVTAVSSGA	UniProtKB - M3X491
	PRYHRIIHINEVVLLDPPAGLLARRADEGGHVVL	(M3X491_FELCA)
	RWLPPPGAPVASLIRYEVNISSGNVAGGAQKVEI
	LDGRTECALSNLRGRTRYTFMVRARMAEPSFGG
	FWSAWSEPASLLTASDLDPLILTLSLILVLILLLLA
	VLALLSHRRFTRTLKQKIWPGIPSPESEFEGLFTT
	HKGNFQLWLYQNEGCLWWSPCAPFAEDPPSPLE
	VLSERCWGATQAAEPGAEEGPLLEPLGSEHTQD
	TYLVLDKWLLPRNPPSEDLPRPDGSLDMVAMHK
	GSEASSCSSALSLKPGPEGALGASFEYTILDPSSQ
	LLRPRALPPELPPTPPHIKYLYLMVSDSGISTDYSS
	GGSQEAQGDSSTGPYLNPYENSLIPATETSPPSYV
	ACS

28	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Felis catus
	PKFESKGKDGSVCRPPQWFLEGNAEERLEDLVCF	EPO receptor Sequence
	WEEAASAGVGPDNYSFFYQLEGEPWKPCSLHQA	EPOR202
	PTARGAVRFWCSLPTADASSFVPLELRVTAVSSG
	APRYHRIIHINEVVLLDPPAGLLARRADEGGHVV
	LRWLPPPGAPVASLIRYEVNISSGNVAGGAQKVE
	ILDGRTECALSNLRGRTRYTFMVRARMAEPSFG
	GFWSAWSEPASLLTASDLDPLILTLSLILVLILLLL
	AVLALLSHRRTLKQKIWPGIPSPESEFEGLFTTHK
	GNFQLWLYQNEGCLWWSPCAPFAEDPPSPLEVL
	SERCWGATQAAEPGAEEGPLLEPLGSEHTQDTY
	LVLDKWLLPRNPPSEDLPRPDGSLDMVAMHKGS
	EASSCSSALSLKPGPEGALGASFEYTILDPSSQLL
	RPRALPPELPPTPPHIKYLYLMVSDSGISTDYSSG
	GSQEAQGDSSTGPYLNPYENSLIPATETSPPSYVA
	CS

29	DPKFESKVNMVCMRAPEASACGSSERLEDLVCF	Feline EPOR201 ECD
	WEEAASAGVGPDNYSFFYQLEGEPWKPCSLHQA	(minimal)
	PTARGAVRFWCSLPTADASSFVPLELRVTAVSSG
	APRYHRIIHINEVVLLDPPAGLLARRADEGGHVV
	LRWLPPPGAPVASLIRYEVNISSGNVAGGAQKVE
	ILDGRTECALSNLRGRTRYTFMVRARMAEPSFG
	GFWSAWSEPASLLT

30	DPKFESKGKDGSVCRPPQWFLEGNAEERLEDLV	Feline EPOR202 ECD
	CFWEEAASAGVGPDNYSFFYQLEGEPWKPCSLH	(minimal)
	QAPTARGAVRFWCSLPTADASSFVPLELRVTAVS
	SGAPRYHRIIHINEVVLLDPPAGLLARRADEGGH
	VVLRWLPPPGAPVASLIRYEVNISSGNVAGGAQK
	VEILDGRTECALSNLRGRTRYTFMVRARMAEPSF
	GGFWSAWSEPASLLT

31	DPKFESK A ALLAARGPEELLCFTERLEDLVCFWE	Feline EPOR203 ECD
	EAASAGVGPDNYSFFYQLEGEPWKPCSLHQAPT	(minimal)
	ARGAVRFWCSLPTADASSFVPLELRVTAVSSGAP
	RYHRIIHINEVVLLDPPAGLLARRADEGGHVVLR
	WLPPPGAPVASLIRYEVNISSGNVAGGAQKVEIL
	DGRTECALSNLRGRTRYTFMVRARMAEPSFGGF
	WSAWSEPASLLT

32	MDHLWAPLWPGVGSLCLLLAGAAWAPPPNPLD	Felis catus
	PKFESKGKDGSVCRPPQXXXXTERLEDLVCFWE	EPO receptor Sequence
	EAASAGVGPDNYSFFYQLEGEPWKPCSLHQAPT	UniProtKB - M3W333
	ARGAVRFWCSLPTADASSFVPLELRVTAVSSGAP	(M3W333_FELCA)
	RYHRIIHINEVVLLDPPAGLLARRADEGGHVVLR
	WLPPPGAPVASLIRYEVNISSGNVAGGAQKVEIL
	DGRTECALSNLRGRTRYTFMVRARMAEPSFGGF
	WSAWSEPASLLTASDLDPLILTLSLILVLILLLLAV
	LALLSHRRTLKQKIWPGIPSPESEFEGLFTTHKGN
	FOLWLYQNEGCLWWSPCAPFAEDPPSPLEVLSE
	RCWGATQAAEPGAEEGPLLEPLGSEHTQDTYLV
	LDKWLLPRNPPSEDLPRPDGSLDMVAMHKGSEA
	SSCSSALSLKPGPEGALGASFEYTILDPSSQLLRPR
	ALPPELPPTPPHIKYLYLMVSDSGISTDYSSGGSQ
	EAQGDSSTGPYLNPYENSLIPATETSPPSYVACS

DETAILED DESCRIPTION OF THE INVENTIONS

The present disclosure provides structural evidence that wild-type feline EPO having a glycine at position 18 (EPO G18) in the mature form may have modified effect on the second receptor binding site and that a glutamic acid at position 18 (EPO E18) may have improved feline EPO second site binding activity. The present disclosure describes how E18 was identified as potentially interacting with at least three amino acids (R14, T15 and L97) at the second binding site of feline EPO. The second binding site is understood to facilitate EPO receptor dimerization.
The present disclosure provides analogs of wild-type feline EPO E44 precursor (SEQ ID NO: 2, where E44 corresponds to E18 in the mature EPO) and wild-type feline EPO E18 mature (SEQ ID NO: 13) polypeptides having one or more additional glycosylation sites. For example, amino acid locations of feline EPO suitable for introducing additional N-linked glycosylation sites (singly or in any combination) are provided. Methods of producing or purifying the feline EPO polypeptides, including acidic and basic fractions of feline EPO polypeptides, are also provided as are methods of treatment using feline EPO polypeptides. Formulations for single dose and/or multi dose pharmaceutical compositions of EPO polypeptides, including feline EPO polypeptides, are also described. Nucleic acids, vectors, expression systems encoding feline EPO polypeptides and methods of expressing those polypeptides, including controlled expression, by gene therapy methods are described.
EPO polypeptides having a mutation in the second binding site and methods of administering those EPO polypeptides or nucleic acids expressing those EPO polypeptides for the treatment of polycythemia in mammals are also described herein. EPO polypeptides having a mutation in the second binding site may maintain high affinity for the first EPO receptor yet have defects in EPO receptor dimerization. EPO polypeptides having a second-site mutation may prevent endogenous EPO from functioning by occupying EPO receptors. Also, described herein are polypeptides comprising an extracellular domain of feline EPO receptor and methods of administering those EPOR polypeptides or nucleic acids encoding those EPOR polypeptides for the treatment of polycythemia in mammals.
For the convenience of the reader, the following definitions of terms used herein are provided.
As used herein, numerical terms such as K_dare calculated based upon scientific measurements and, thus, are subject to appropriate measurement error. In some instances, a numerical term may include numerical values that are rounded to the nearest significant figure.
As used herein, “a” or “an” means “at least one” or “one or more” unless otherwise specified. As used herein, the term “or” means “and/or” unless specified otherwise. In the context of a multiple dependent claim, the use of “or” when referring back to other claims refers to those claims in the alternative only.

Exemplary EPO Polypeptides

Novel feline EPO polypeptides are provided, for example, EPO polypeptides comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 13 except for the presence of at least one N-linked glycosylation site not present in SEQ ID NO: 2 or SEQ ID NO: 13.
“Amino acid sequence” means a sequence of amino acids in a protein, and includes sequences of amino acids in which one or more amino acids of the sequence have had their side-groups chemically modified, as well as those in which, relative to a known sequence, one or more amino acids have been replaced, inserted or deleted, without thereby eliminating a desired property, such as ability to bind EPO receptor. An amino acid sequence may also be referred to as a peptide, oligopeptide, or protein.
“Erythropoietin,” “EPO,” or “EPO polypeptide,” as used herein, is a polypeptide comprising the entirety or a fragment of EPO.
For example, “EPO” refers to an EPO polypeptide from any vertebrate source, including mammals such as primates (e.g., humans and cynomolgus monkeys), rodents (e.g., mice and rats), and companion animals (e.g., dogs, cats, and equine), unless otherwise indicated. In some embodiments, EPO polypeptide comprises the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15.
“Erythropoietin receptor,” “EPO receptor,” or “EPOR,” as used herein, is a polypeptide comprising the entirety or a portion of EPO receptor that binds to an EPO polypeptide.
For example, “EPOR” refers to an EPOR polypeptide from any vertebrate source, including mammals such as primates (e.g., humans and cynomolgus monkeys), rodents (e.g., mice and rats), and companion animals (e.g., dogs, cats, and equine), unless otherwise indicated. In some embodiments, EPOR comprises the amino acid sequence of SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, SEQ ID N: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, or SEQ ID NO: 31.
The term “companion animal species” or “companion animal” refers to an animal suitable to be a companion to humans. In some embodiments, a companion animal is a dog, cat, or horse. In some embodiments, a companion animal is a rabbit, ferret, guinea pig, or rodent, etc. In some embodiments, a companion animal is a cow or pig.
An “extracellular domain” (“ECD”) is the portion of a polypeptide that extends beyond the transmembrane domain into the extracellular space. The term “extracellular domain,” as used herein, may comprise a complete extracellular domain or may comprise a truncated extracellular domain missing one or more amino acids, that binds to its ligand. The composition of the extracellular domain may depend on the algorithm used to determine which amino acids are in the membrane. Different algorithms may predict, and different systems may express, different extracellular domains for a given protein.
An extracellular domain of an EPOR polypeptide may comprise a complete extracellular domain or a truncated extracellular domain of EPOR that binds EPO. In some embodiments, an extracellular domain of an EPOR polypeptide is an extracellular domain of an EPOR polypeptide derived from a companion animal species. For example, in some embodiments, an extracellular domain of an EPOR polypeptide is derived from canine EPOR, feline EPOR, equine EPOR, or human EPOR. In some embodiments, an extracellular domain of an EPOR polypeptide comprises the amino acid sequence of SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 30, or SEQ ID NO: 31.
“Wild-type” refers to a non-mutated version of a polypeptide that occurs in nature, or a fragment thereof. A wild-type polypeptide may be produced recombinantly.
A “biologically active” entity, or an entity having “biological activity,” is an entity having any function related to or associated with a metabolic or physiological process, and/or having structural, regulatory, or biochemical functions of a naturally-occurring molecule. A biologically active polypeptide or fragment thereof includes one that can participate in a biological reaction, including, but not limited to, a ligand-receptor interaction or antigen-antibody binding. The biological activity can include an improved desired activity, or a decreased undesirable activity. An entity may demonstrate biological activity when it participates in a molecular interaction with another molecule, when it has therapeutic value in alleviating a disease condition, when it has prophylactic value in inducing an immune response, when it has diagnostic and/or prognostic value in determining the presence of a molecule.
An “analog” is a polypeptide that differs from a reference polypeptide by single or multiple amino acid substitutions, deletions, and/or additions that substantially retains at least one biological activity of the reference polypeptide.
As used herein, “percent (%) amino acid sequence identity” and “homology” with respect to a polypeptide sequence are defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the specific peptide or polypeptide sequence, after aligning the sequences and introducing gaps, if necessary to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN, or MEGALINE™ (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of sequences being compared.
In some embodiments, an analog has at least about 50% amino acid sequence identity, at least about 60% amino acid sequence identity, at least about 65% amino acid sequence identity, at least about 70% amino acid sequence identity, at least about 75% amino acid sequence identity, at least about 80% amino acid sequence identity, at least about 85% amino acid sequence identity, at least about 90% amino acid sequence identity, at least about 95% amino acid sequence identity, at least about 97% amino acid sequence identity, at least about 98% amino acid sequence identity, or at least about 99% amino acid sequence identity with the wild-type sequence polypeptide.
An amino acid substitution may include but is not limited to the replacement of one amino acid in a polypeptide with another amino acid. Exemplary substitutions are shown in Table 2. Amino acid substitutions may be introduced into a molecule of interest and the products screened for a desired activity, for example, retained/improved receptor binding, decreased immunogenicity, or improved pharmacokinetics.

	TABLE 2

	Original
	Residue	Exemplary Substitutions

	Ala (A)	Val; Leu; Ile
	Arg (R)	Lys; Gln; Asn
	Asn (N)	Gln; His; Asp; Lys; Arg
	Asp (D)	Glu; Asn
	Cys (C)	Ser; Ala
	Gln (Q)	Asn; Glu
	Glu (E)	Asp; Gln
	Gly (G)	Ala
	His (H)	Asn; Gln; Lys; Arg
	Ile (I)	Leu; Val; Met; Ala; Phe;
		Norleucine
	Leu (L)	Norleucine; Ile; Val; Met; Ala;
		Phe
	Lys (K)	Arg; Gln; Asn
	Met (M)	Leu; Phe; Ile
	Phe (F)	Trp; Leu; Val; Ile; Ala; Tyr
	Pro (P)	Ala
	Ser (S)	Thr
	Thr (T)	Val; Ser
	Trp (W)	Tyr; Phe
	Tyr (Y)	Trp; Phe; Thr; Ser
	Val (V)	Ile; Leu; Met; Phe; Ala;
		Norleucine

Amino acids may be grouped according to common side-chain properties:

- (1) hydrophobic: Norleucine, Met, Ala, Val, Leu, Ile;
- (2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gln;
- (3) acidic: Asp, Glu;
- (4) basic: His, Lys, Arg;
- (5) residues that influence chain orientation: Gly, Pro;
- (6) aromatic: Trp, Tyr, Phe.

Non-conservative substitutions will entail exchanging a member of one of these classes with another class.
In some embodiments, the EPO polypeptide comprises the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 13 except for the presence of at least one N-linked glycosylation site not present in SEQ ID NO: 2 or SEQ ID NO: 13. In some embodiments, the at least one N-linked glycosylation site comprises the sequence asparagine-xaa-serine, wherein xaa is any amino acid except proline. In some embodiments, the at least one N-linked glycosylation site comprises the sequence asparagine-xaa-threonine, wherein xaa is any amino acid except proline. In some embodiments, the at least one N-linked glycosylation site does not overlap with another N-linked glycosylation site.
In some embodiments, the EPO polypeptide comprises an N-linked glycosylation site at amino acid positions 47-49, 55-57, 56-58, 60-62, 61-63, 79-81, 82-84, 91-93, 92-94, 97-99, 98-100, 99-101, 112-114, 113-115, 114-116, 115-117, 116-118, 137-139, 140-142, 141-143, 142-144, 143-145, 144-146, 145-147, 146-148, 147-149, 148-150, 149-151, 150-152, 161-163, 162-164, 184-186, and/or 186-188 of SEQ ID NO: 2.
In some embodiments, the EPO polypeptide comprises an N-linked glycosylation site at amino acid positions 21-23, 29-31, 30-32, 34-36, 35-37, 53-55, 56-58, 65-67, 66-68, 71-73, 72-74, 73-75, 86-88, 87-89, 88-90, 89-91, 90-92, 111-113, 114-116, 115-117, 116-118, 117-119, 118-120, 119-121, 120-122, 121-123, 122-124, 123-125, 124-126, 135-137, 136-138, 158-160, and/or 162-164 of SEQ ID NO: 13.
In some embodiments, the EPO polypeptide comprises a valine at an amino acid position corresponding to position 113 of SEQ ID NO: 2.
In some embodiments, the EPO polypeptide comprises the amino acid sequence of SEQ ID NO: 4 or SEQ ID NO: 15.
In some embodiments, the EPO polypeptide comprises one or more amino acid modifications listed in Table 3, below.

TABLE 3

	Amino acid substitutions for N-linked glycosylation sites

Analog	Based on wt fEPO E44 precursor	Based on wt fEPO E18 mature
No.	sequence (SEQ ID NO: 2)	sequence (SEQ ID NO: 13)

1	N47S49	N21S23
2	N47T49	N21T23
3	N55S57	N29S31
4	N55T57	N29T31
5	N56S58	N30S32
6	N56T58	N30T32
7	N60	N34
8	N60T62	N34T36
9	N61S63	N35S37
10	N61T63	N35T37
11	N79S81	N53S55
12	N79T81	N53T55
13	N82S84	N56S58
14	N82T84	N56T58
15	N91S93	N65S67
16	N91T93	N65T67
17	N92S94	N66S68
18	N92T94	N66T68
19	N97S99	N71S73
20	N97T99	N71T73
21	N98S100	N72S74
22	N98T100	N72T74
23	N99S101	N73S75
24	N99T101	N73T75
25	N112*X113	N86*X87
26	N112*X113T114	N86*X87T88
27	N113S115	N87S89
28	N113T115	N87T89
29	N114S116	N88S90
30	N114	N88
31	N115S117	N89S91
32	N115T117	N89T91
33	N116S118	N90S92
34	N116T118	N90T92
35	N137S139	N111S113
36	N137T139	N111T113
37	N140S142	N114S116
38	N140T142	N114T116
39	N141S143	N115S117
40	N141T143	N115T117
41	N142S144	N116S118
42	N142T144	N116T118
43	N143S145	N117S119
44	N143	N117
45	N144	N118
46	N144T146	N118T120
47	N145S147	N119S121
48	N145T147	N119T121
49	N146S148	N120S122
50	N146T148	N120T122
51	N147*X148S149	N121*X122S123
52	N147*X148T149	N121*X122T123
53	N148S150	N122S124
54	N148T150	N122T124
55	N149S151	N123S125
56	N149	N123
57	N150	N124
58	N150T152	N124T126
59	N161S163	N135S137
60	N161	N135
61	N162S164	N136S138
62	N162T164	N136T138
63	N184S186	N158S160
64	N184T186	N158T160
65	N186S188	N162S164
66	N186T188	N162T164

*X indicates any amino acid except proline.

An “amino acid derivative,” as used herein, refers to any amino acid, modified amino acid, and/or amino acid analogue, that is not one of the 20 common natural amino acids found in humans. Exemplary amino acid derivatives include natural amino acids not found in humans (e.g., seleno cysteine and pyrrolysine, which may be found in some microorganisms) and unnatural amino acids. Exemplary amino acid derivatives, include, but are not limited to, amino acid derivatives commercially available through chemical product manufacturers and distributors (e.g., sigmaaldrich.com/chemistry/chemistry-products.html?TablePage=16274965, accessed on May 6, 2017, which is incorporated herein by reference). One or more amino acid derivative maybe incorporated into a polypeptide at a specific location using translation systems that utilize host cells, orthogonal aminoacyl-tRNA synthetases derived from eubacterial synthetases, orthogonal tRNAs, and an amino acid derivative. For further descriptions, see, e.g., U.S. Pat. No. 9,624,485.
In some embodiments, an EPO polypeptide or other polypeptide described herein comprises an amino acid substitution with an amino acid derivative. In some embodiments, the amino acid derivative is an asparagine derivative, a serine derivative, a threonine derivative, or an alanine derivative.
“Glycosylated,” as used herein, refers to a polypeptide having one or more glycan moieties covalently attached.
A “glycan” or “glycan moiety,” as used herein, refers to monosaccharides linked glycosidically.
Glycans are attached to glycopeptides in several ways, of which N-linked to asparagine and O-linked to serine and threonine are the most relevant for recombinant therapeutic glycoproteins. N-linked glycosylation occurs at the consensus sequence Asn-Xaa-Ser/Thr, where Xaa can be any amino acid except proline.
“Sialylated,” as used herein, refers to a polypeptide having one or more sialyic acid moieties covalently attached.
A variety of approaches for producing glycosylated and sialylated proteins have been developed. See, e.g., Savinova, et al., Applied Biochem & Microbiol. 51(8):827-33 (2015).
“PEGylated,” as used herein, refers to a polypeptide having one or more polyethylene glycol (PEG) moieties associated or covalently or non-covalently attached.
In some embodiments, the EPO polypeptide is glycosylated. In some embodiments, the EPO polypeptide comprises at least one glycan moiety attached to an N-linked glycosylation site. In some embodiments, the EPO polypeptide is sialylated. In some embodiments, the EPO polypeptide is PEGylated. In some embodiments, the EPO polypeptide is PEGylated at a glycan. In some embodiments, the EPO polypeptide is PEGylated at a primary amine. In some embodiments, the EPO polypeptide is PEGylated at the N-terminal alpha-amine. In some embodiments, the EPO polypeptide is glycosylated, sialylated, and/or PEGylated.

Exemplary EPO Polypeptide Expression and Production

Polynucleotide sequences that encode all or part of an EPO polypeptide with or without a signal sequence are provided. If a homologous signal sequence (i.e., a signal sequence of wild-type EPO) is not used in the construction of the nucleic acid molecule, then another signal sequence may be used, for example, any one of the signal sequences described in PCT/US06/02951.
Typically, a nucleotide sequence encoding the polypeptide of interest, such as an EPO polypeptide or another polypeptide described herein, is inserted into an expression vector, suitable for expression in a selected host cell.
The term “vector” is used to describe a polynucleotide that can be engineered to contain a cloned polynucleotide or polynucleotides that can be propagated in a host cell. A vector can include one or more of the following elements: an origin of replication, one or more regulatory sequences (such as, for example, promoters or enhancers) that regulate the expression of the polypeptide of interest, or one or more selectable marker genes (such as, for example, antibiotic resistance genes and genes that can be used in colorimetric assays, for example, 0-galactosidase). The term “expression vector” refers to a vector that is used to express a polypeptide of interest in a host cell.
A vector may be a DNA plasmid deliverable via non-viral methods (e.g., naked DNA, formulated DNA, or liposome), or via viral methods. In some embodiments, the vector is a viral vector, such as a retroviral vector, a herpesviral vector, an adenoviral vector, an adeno-associated viral vector, or a poxviral vector. The vector may be a bacterial vector.
The term “expression system,” as used herein, refers to a combination of an expression vector and at least one additional vector. The combination may be deliverable via non-viral or via viral methods.
In some embodiments, the expression system comprises an expression vector and a vector comprising a regulatory sequence (e.g., a nucleic acid sequence encoding a transcription factor or microRNA).
Expression of an EPO or EPOR polypeptide described herein may be regulated to prevent excessive production of EPO or EPOR in vivo. Controlled expression may reduce immunogenicity, polycythemia (over production of red blood cells), or other negative effects. There are many known methods of controlling gene regulation in vitro and in vivo, such as tetracycline responsive systems, micro RNA regulated systems, or hypoxia-inducible systems (e.g., use of prolyl hydroxylase to activate hypoxia-inducible promoters or enhancers).
The term “regulatory sequence” (also referred to as a “regulatory region” or “regulatory element”) refers to a nucleic acid sequence that facilitates and/or controls gene expression and/or protein expression, either directly or indirectly. A regulatory sequence may be a promoter, enhancer, silencer, or a nucleic acid sequence encoding a micro RNA (miRNA) or transcription factor. Regulatory sequences may increase or decrease gene expression and/or protein expression.
In some embodiments, a regulatory sequence binds regulatory proteins, such as transcription factors, to control gene expression and/or protein expression. In some embodiments, a regulatory sequence encodes a transcription factor that controls gene expression and/or protein expression. In some embodiments, a regulatory sequence encodes a miRNA that binds to a target mRNA to control protein expression.
In some embodiments, the regulatory sequence is a controllable regulatory sequence. In some embodiments, the regulatory sequence is an uncontrollable regulatory sequence, such as a constitutive promoter (e.g., a CMV promoter). In some embodiments, the regulatory sequence is a positive regulatory sequence, such as a promoter. In some embodiments, the regulatory sequence is a negative regulatory sequence, such as a silencer. In some embodiments, the regulatory sequence provides for transient, inducible (e.g., tetracycline-responsive promoter, or hypoxia-inducible promoter), and/or tissue-specific gene expression and/or protein expression.
In some embodiments, the regulatory sequence is operably linked to the nucleic acids encoding the EPO polypeptides (coding sequence) of the present disclosure. The regulatory sequence need not be contiguous with the coding sequence as long as they function to direct the expression of the encoded polypeptides. Thus, for example, intervening untranslated yet transcribed sequences may be present between a promoter sequence and a coding sequence and the promoter sequence may still be considered “operably linked” to the coding sequence.
In some embodiments, the regulatory sequence is not operably linked to the nucleic acids encoding the EPO polypeptides of the present disclosure. For example, the regulatory sequence may be a microRNA sequence or transcription factor expressed from the same vector or a different vector as the nucleic acids encoding the EPO polypeptides.
A “host cell” refers to a cell that may be or has been a recipient of a vector or isolated polynucleotide. Host cells may be prokaryotic cells or eukaryotic cells. Exemplary eukaryotic cells include mammalian cells, such as primate or non-primate animal cells; fungal cells, such as yeast; plant cells; and insect cells. Nonlimiting exemplary mammalian cells include, but are not limited to, NS0 cells, PER.C6® cells (Crucell), 293 cells, and CHO cells, and their derivatives, such as 293-6E, DG-44, CHO-S, and CHO-K cells. Host cells include progeny of a single host cell, and the progeny may not necessarily be completely identical (in morphology or in genomic DNA complement) to the original parent cell due to natural, accidental, or deliberate mutation. A host cell includes cells transfected in vivo with a polynucleotide(s) encoding an amino acid sequence(s) provided herein.
The term “isolated” as used herein refers to a molecule that has been separated from at least some of the components with which it is typically found in nature or produced. For example, a polypeptide is referred to as “isolated” when it is separated from at least some of the components of the cell in which it was produced. Where a polypeptide is secreted by a cell after expression, physically separating the supernatant containing the polypeptide from the cell that produced it is considered to be “isolating” the polypeptide. Similarly, a polynucleotide is referred to as “isolated” when it is not part of the larger polynucleotide (such as, for example, genomic DNA or mitochondrial DNA, in the case of a DNA polynucleotide) in which it is typically found in nature, or is separated from at least some of the components of the cell in which it was produced, for example, in the case of an RNA polynucleotide. Thus, a DNA polynucleotide that is contained in a vector inside a host cell may be referred to as “isolated.”
In some embodiments, the EPO polypeptide or another polypeptide described herein is isolated using chromatography, such as size exclusion chromatography, ion exchange chromatography, protein A column chromatography, hydrophobic interaction chromatography, CHT chromatography, and/or synthetic molecule conjugated resin chromatography (e.g., His tag affinity column chromatography). In some embodiments, the EPO polypeptide or another polypeptide described herein is isolated using Capto Butyl column chromatography, cation-exchange column chromatography, anion-exchange column chromatography, and/or mixed-mode column chromatography. In some embodiments, the EPO polypeptide or another polypeptide described herein is isolated using a combination of chromatography methods and/or columns.
In some embodiments, the method of production or isolation further comprises inactivating or removing any viruses.
The term “isoelectric point” or “pI,” as used herein refers to the pH at which a molecule carries no net electrical charge and/or does not migrate further in an electric field, as determined by isoelectric focusing.
The term “range of isoelectric points,” as used herein refers to the range of pHs at which a plurality of molecules carries no net electrical charge and/or do not migrate further in an electric field, as determined by isoelectric focusing.
In some embodiments, a composition comprises EPO polypeptides having a range of isoelectric points of from about 1 to about 3.5, of from about 1.5 to about 3.5, of from about 2 to about 3.5, of from about 2.5 to about 3.5, of from about 3 to about 3.5, of about 3.5 or less, or of about 3 or less, as determined by isoelectric focusing. In some embodiments, a composition comprises an acidic fraction of EPO polypeptides having a range of isoelectric points of from about 1 to about 3.5, of from about 1.5 to about 3.5, of from about 2 to about 3.5, of from about 2.5 to about 3.5, of from about 3 to about 3.5, of about 3.5 or less, or of about 3 or less, as determined by isoelectric focusing. In some embodiments, a composition comprises a high sialylation fraction of EPO polypeptides having a range of isoelectric points of from about 1 to about 3.5, of from about 1.5 to about 3.5, of from about 2 to about 3.5, of from about 2.5 to about 3.5, of from about 3 to about 3.5, of about 3.5 or less, or of about 3 or less, as determined by isoelectric focusing.
In some embodiments, a composition comprises EPO polypeptides having a range of isoelectric points of from about 3.5 to about 6, of from about 4 to about 6, of from about 4.5 to about 6, of from about 5 to about 6, of from about 5.5 to about 6, of from about 3.5 to about 5, of from about 4 to about 5, of from about 4.5 to about 5, of about 3.5 or greater, of about 4 or greater, or of about 4.5 or greater, as determined by isoelectric focusing. In some embodiments, a composition comprises a basic fraction of EPO polypeptides having a range of isoelectric points of from about 3.5 to about 6, of from about 4 to about 6, of from about 4.5 to about 6, of from about 5 to about 6, of from about 5.5 to about 6, of from about 3.5 to about 5, of from about 4 to about 5, of from about 4.5 to about 5, of about 3.5 or greater, of about 4 or greater, or of about 4.5 or greater, as determined by isoelectric focusing. In some embodiments, a composition comprises a low sialylation fraction of EPO polypeptides having a range of isoelectric points of from about 3.5 to about 6, of from about 4 to about 6, of from about 4.5 to about 6, of from about 5 to about 6, of from about 5.5 to about 6, of from about 3.5 to about 5, of from about 4 to about 5, of from about 4.5 to about 5, of about 3.5 or greater, of about 4 or greater, or of about 4.5 or greater, as determined by isoelectric focusing.

Exemplary EPO Polypeptide Affinity to EPOR

The term “affinity” means the strength of the sum total of noncovalent interactions between a single binding site of a molecule (for example, an antibody) and its binding partner (for example, an antigen). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (K_D). Affinity can be measured by common methods known in the art, such as, for example, immunoblot, ELISA KD, KinEx A, biolayer interferometry (BLI), or surface plasmon resonance devices.
The terms “K_D,” “K_d,” “Kd” or “Kd value” as used interchangeably to refer to the equilibrium dissociation constant of an antibody-antigen interaction. In some embodiments, the K_dof the antibody is measured by using biolayer interferometry assays using a biosensor, such as an Octet® System (Pall ForteBio LLC, Fremont, CA) according to the supplier's instructions. Briefly, biotinylated antigen is bound to the sensor tip and the association of antibody is monitored for ninety seconds and the dissociation is monitored for 600 seconds. The buffer for dilutions and binding steps is 20 mM phosphate, 150 mM NaCl, pH 7.2. A buffer only blank curve is subtracted to correct for any drift. The data are fit to a 2:1 binding model using ForteBio data analysis software to determine association rate constant (k_on), dissociation rate constant (k_off), and the K_d. The equilibrium dissociation constant (K_d) is calculated as the ratio of k_off/k_on. The term “kon” refers to the rate constant for association of an antibody to an antigen and the term “koff” refers to the rate constant for dissociation of an antibody from the antibody/antigen complex.
The term “binds” to a ligand or receptor is a term that is well understood in the art, and methods to determine such binding are also well known in the art. A molecule is said to exhibit “binding” if it reacts, associates with, or has affinity for a particular cell or substance and the reaction, association, or affinity is detectable by one or more methods known in the art, such as, for example, immunoblot, ELISA KD, KinEx A, biolayer interferometry (BLI), surface plasmon resonance devices, or etc.
“Surface plasmon resonance” denotes an optical phenomenon that allows for the analysis of real-time biospecific interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIAcore™ system (BIAcore International AB, a GE Healthcare company, Uppsala, Sweden and Piscataway, N.J.). For further descriptions, see Jonsson et al. (1993) Ann. Biol. Clin. 51: 19-26.
“Biolayer interferometry” refers to an optical analytical technique that analyzes the interference pattern of light reflected from a layer of immobilized protein on a biosensor tip and an internal reference layer. Changes in the number of molecules bound to the biosensor tip cause shifts in the interference pattern that can be measured in real-time. A nonlimiting exemplary device for biolayer interferometry is an Octet® system (Pall ForteBio LLC). See, e.g., Abdiche et al., 2008, Anal. Biochem. 377: 209-277.
To “reduce” or “inhibit” means to decrease, reduce, or arrest an activity, function, or amount as compared to a reference. In some embodiments, by “reduce” or “inhibit” is meant the ability to cause an overall decrease of 20% or greater. In some embodiments, by “reduce” or “inhibit” is meant the ability to cause an overall decrease of 50% or greater. In some embodiments, by “reduce” or “inhibit” is meant the ability to cause an overall decrease of 75%, 85%, 90%, 95%, or greater. In some embodiments, the amount noted above is inhibited or decreased over a period of time, relative to a control dose (such as a placebo) over the same period of time.
To “increase” or “stimulate” means to increase, improve, or augment an activity, function, or amount as compared to a reference. In some embodiments, by “reduce” or “inhibit” is meant the ability to cause an overall increase of 20% or greater. In some embodiments, by “increase” or “stimulate” is meant the ability to cause an overall increase of 50% or greater. In some embodiments, by “increase” or “stimulate” is meant the ability to cause an overall increase of 75%, 85%, 90%, 95%, or greater. In some embodiments, the amount noted above is stimulated or increased over a period of time, relative to a control dose (such as a placebo) over the same period of time.
A “reference” as used herein, refers to any sample, standard, or level that is used for comparison purposes. A reference may be obtained from a healthy or non-diseased sample. In some examples, a reference is obtained from a non-diseased or non-treated sample of a companion animal. In some examples, a reference is obtained from one or more healthy animals of a particular species, which are not the animal being tested or treated.
In some embodiments, administration of an EPO polypeptide or nucleic acid of the present invention may result in an increase of the hematocrit percent to increases to at least 25%, or at least 26%, or at least 27%, or at least 28%, or at least 29%, or at least 30%, or at least 32%, or at least 35%, or at least 38%, or at least 40%, or at least 42%, or at least 45%, or at least 48%.

Exemplary Pharmaceutical Compositions

The terms “pharmaceutical formulation” and “pharmaceutical composition” refer to a preparation which is in such form as to permit the biological activity of the active ingredient(s) to be effective, and which contains no additional components that are unacceptably toxic to a subject to which the formulation would be administered.
A “pharmaceutically acceptable carrier” refers to a non-toxic solid, semisolid, or liquid filler, diluent, encapsulating material, formulation auxiliary, or carrier conventional in the art for use with a therapeutic agent that together comprise a “pharmaceutical composition” for administration to a subject. A pharmaceutically acceptable carrier is non-toxic to recipients at the dosages and concentrations employed and is compatible with other ingredients of the formulation. The pharmaceutically acceptable carrier is appropriate for the formulation employed. Examples of pharmaceutically acceptable carriers include alumina; aluminum stearate; lecithin; serum proteins, such as human serum albumin, canine or other animal albumin; buffers such as phosphate, citrate, tromethamine or HEPES buffers; glycine; sorbic acid; potassium sorbate; partial glyceride mixtures of saturated vegetable fatty acids; water; salts or electrolytes, such as protamine sulfate, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium chloride, zinc salts, colloidal silica, or magnesium trisilicate; polyvinyl pyrrolidone, cellulose-based substances; polyethylene glycol; sucrose; mannitol; or amino acids including, but not limited to, arginine.
In some embodiments, the pharmaceutically acceptable carrier has a pH of from about 6.2 to about 7, of from about 6 to about 7.2, of from about 6.4 to about 6.8, of about 6, or of about 7 and comprises sodium phosphate and sodium chloride. In some embodiments, the pharmaceutically acceptable carrier has a pH of from about 6.2 to about 7, of from about 6 to about 7.2, of about 6, of from about 6.4 to about 6.8, or of about 7 and comprises sodium citrate and sodium chloride.
In some embodiments, the pharmaceutically acceptable carrier comprises sodium phosphate, sodium chloride, and polysorbate 80. In some embodiments, the pharmaceutically acceptable carrier comprises sodium phosphate, sodium chloride, and polysorbate 20. In some embodiments, the pharmaceutically acceptable carrier comprises sodium citrate, sodium chloride, and polysorbate 20. In some embodiments, the pharmaceutically acceptable carrier comprises sodium citrate, sodium chloride, and polysorbate 80.
In some embodiments, the pharmaceutically acceptable carrier comprises sodium chloride at a concentration of from about 100 nM to about 180 nM, of from about 110 nM to about 170 nM, of from about 120 nM to about 160 nM, of from about 130 nM to about 150 nM, of about 140 nM, of from about 130 nM to about 160 nM, of from about 120 nM to about 150 nM, of about 100 nM, of about 110 nM, of about 120 nM, of about 130 nM, of about 140 nM, of about 150 nM, of about 160 nM, of about 170 nM, or of about 180 nM.
In some embodiments, the pharmaceutically acceptable carrier comprises sodium phosphate at a concentration of from about 100 nM to about 180 nM, of from about 110 nM to about 170 nM, of from about 120 nM to about 160 nM, of from about 130 nM to about 150 nM, of about 140 nM, of from about 130 nM to about 160 nM, of from about 120 nM to about 150 nM, of about 100 nM, of about 110 nM, of about 120 nM, of about 130 nM, of about 140 nM, of about 150 nM, of about 160 nM, of about 170 nM, or of about 180 nM.
In some embodiments, the pharmaceutically acceptable carrier comprises a polysorbate at a concentration of about 550 nM to about 750 nM, of about 570 nM to about 730 nM, of about 590 nM to about 720 nM, of about 600 nM to about 700 nM, of about, 620 nM to about 680 nM, of about 640 nM to about 660 nM, of about 650 nM, of about 570 nM to about 670 nM, of about 550 nM to about 650 nM, of about 650 nM to about 750 nM, of about 630 nm to about 700 nM, or of about 670 nM to about 600 nM. In some embodiments, the polysorbate is polysorbate 80. In some embodiments, the polysorbate is polysorbate 20.
In some embodiments, the pharmaceutically acceptable carrier comprises m-cresol or benzyl alcohol. In some embodiments, the concentration of m-cresol is about 0.2%, of from about 0.1% to about 0.3%, of from about 0.08% to about 0.25%, or of from about 0.05% to about 0.25%. In some embodiments, the concentration of benzyl alcohol is about 1%, of from about 0.5% to about 2%, of from about 0.2% to about 2.5%, of about 1% to about 5%, of about 0.5% to about 5%, or of about 1% to about 3%.
The pharmaceutical composition can be stored in lyophilized form; thus, in some embodiments, the preparation process includes a lyophilization step. The lyophilized composition is then reformulated, typically as an aqueous composition suitable for parenteral administration, prior to administration to the cat. In other embodiments, particularly where the protein is highly stable to thermal and oxidative denaturation, the pharmaceutical composition can be stored as a liquid, i.e., aqueous, composition, which may be administered directly, or with appropriate dilution, to the dog, cat, or horse. It can be reconstituted with sterile Water for Injection (WFI), and Bacteriostatic reagents such benzyl alcohol may be included. Thus, the invention provides pharmaceutical compositions in both solid and liquid form.
The pH of the pharmaceutical compositions typically will be in the range of from about pH 6 to pH 8 when administered, for example about 6, about 6.2, about 6.4, about 6.6, about 6.8, about 7, about 7.2. The formulations of the invention are sterile if they are to be used for therapeutic purposes. Sterility can be achieved by any of several means known in the art, including by filtration through sterile filtration membranes (e.g., 0.2 micron membranes). Sterility may be maintained with or without anti-bacterial agents.
The pharmaceutical formulations of the invention are useful in the methods of the invention for treating anemia associated conditions in companion animals, such as cats. For example, the methods described herein include administering a therapeutically effective dose of a nucleic acid or polypeptide of the disclosure to a cat. In many embodiments, the therapeutically effective dose is administered parenterally, for example by subcutaneous administration, intravenous infusion, intravenous bolus injection, or intramuscular injection.
Thus, in accordance with the methods of the invention, an EPO polypeptide or nucleic acid, other polypeptide or nucleic acid of the present invention, or a pharmaceutical composition is administered in a therapeutically effective dose to a feline, canine, equine, or human.
In some embodiments, the therapeutically effective dose is administered once per week for at least two or three consecutive weeks, and in some embodiments, this cycle of treatment is repeated two or more times, optionally interspersed with one or more weeks of no treatment. In other embodiments, the therapeutically effective dose is administered once per day for two to five consecutive days, and in some embodiments, this cycle of treatment is repeated two or more times, optionally interspersed with one or more days or weeks of no treatment.

Exemplary Uses of EPO and EPOR ECD Polypeptides

The EPO polypeptides comprising one or more additional N-glycosylation site(s) or pharmaceutical compositions comprising the EPO polypeptides disclosed herein may be useful for treating non-regenerative anemia. A non-regenerative anemia condition may be exhibited in a companion animal, including, but not limited to, canine, feline, or equine.
The EPO polypeptides comprising an amino acid substitution in the second binding site or pharmaceutical compositions comprising second site mutant EPO polypeptides disclosed herein may be useful for treating polycythemia.
The polypeptides comprising an extracellular domain of EPOR or pharmaceutical compositions comprising the EPOR ECD polypeptides disclosed herein may be useful for treating polycythemia.
As used herein, “treatment” is an approach for obtaining beneficial or desired clinical results. “Treatment” as used herein, covers any administration or application of a therapeutic for disease in a mammal, including a companion animal. For purposes of this disclosure, beneficial or desired clinical results include, but are not limited to, any one or more of: alleviation of one or more symptoms, diminishment of extent of disease, preventing or delaying spread of disease, preventing or delaying recurrence of disease, delay or slowing of disease progression, amelioration of the disease state, inhibiting the disease or progression of the disease, inhibiting or slowing the disease or its progression, arresting its development, and remission (whether partial or total). Also, encompassed by “treatment” is a reduction of pathological consequence of a proliferative disease. The methods provided herein contemplate any one or more of these aspects of treatment. In-line with the above, the term treatment does not require one-hundred percent removal of all aspects of the disorder.
In some embodiments, an EPO polypeptide, nucleic acid, vector, expression system, or pharmaceutical compositions comprising it can be utilized in accordance with the methods herein to treat EPO deficient or EPO insensitivity-induced conditions. In some embodiments, an EPO polypeptide, nucleic acid, vector, expression system or pharmaceutical composition is administered to a companion animal, such as a canine, a feline, or equine, to treat EPO deficient or EPO insensitivity-induced conditions. In some embodiments, an EPO polypeptide, nucleic acid, vector, expression system, or pharmaceutical compositions is administered to a companion animal, such as a canine, a feline, or equine, to treat anemia.
A “therapeutically effective amount” of a substance/molecule, agonist or antagonist may vary according to factors such as the type of disease to be treated, the disease state, the severity and course of the disease, the type of therapeutic purpose, any previous therapy, the clinical history, the response to prior treatment, the discretion of the attending veterinarian, age, sex, and weight of the animal, and the ability of the substance/molecule, agonist or antagonist to elicit a desired response in the animal. A therapeutically effective amount is also one in which any toxic or detrimental effects of the substance/molecule, agonist or antagonist are outweighed by the therapeutically beneficial effects. A therapeutically effective amount may be delivered in one or more administrations. A therapeutically effective amount refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic or prophylactic result.
In some embodiments, an EPO or EPOR polypeptide, polypeptide, nucleic acid, vector, or expression system or pharmaceutical composition is administered parenterally, by subcutaneous administration, intravenous infusion, or intramuscular injection. In some embodiments, an EPO or EPOR polypeptide, polypeptide, nucleic acid, vector, expression system, or pharmaceutical composition is administered as a bolus injection or by continuous infusion over a period of time. In some embodiments, an EPO or EPOR polypeptide, polypeptide, nucleic acid, vector, expression system, or pharmaceutical composition is administered by an intramuscular, an intraperitoneal, an intracerebrospinal, a subcutaneous, an intra-arterial, an intrasynovial, an intrathecal, or an inhalation route.
An EPO or EPOR polypeptide described herein may be administered in an amount in the range of 0.0001 mg/kg body weight to 100 mg/kg body weight per dose. In some embodiments, an EPO or EPOR polypeptide may be administered in an amount in the range of 0.0005 mg/kg body weight to 50 mg/kg body weight per dose. In some embodiments, an EPO or EPOR polypeptide may be administered in an amount in the range of 0.001 mg/kg body weight to 10 mg/kg body weight per dose. In some embodiments, an EPO polypeptide may be administered in an amount in the range of from about 1 μg/kg body weight to about 10 μg/kg body weight, or about 1 μg/kg body weight to about 5 μg/kg body weight, or about 1 μg/kg body weight, or about 3 μg/kg body weight, or about 5 μg/kg body weight, or about 10 μg/kg body weight.
An EPO or EPOR polypeptide, nucleic acid, vector, expression system, or a pharmaceutical composition can be administered to a companion animal at one time or over a series of treatments. For example, an EPO or EPOR polypeptide, nucleic acid, vector, expression system, or pharmaceutical composition may be administered at least once, more than once, at least twice, at least three times, at least four times, or at least five times, or chronically use.
In some embodiments, the dose is administered once per week for at least two or three consecutive weeks, and in some embodiments, this cycle of treatment is repeated two or more times, optionally interspersed with one or more weeks of no treatment. In other embodiments, the therapeutically effective dose is administered once per day for two to five consecutive days, and in some embodiments, this cycle of treatment is repeated two or more times, optionally interspersed with one or more days or weeks of no treatment.
Administration “in combination with” one or more further therapeutic agents includes simultaneous (concurrent) and consecutive or sequential administration in any order. The term “concurrently” is used herein to refer to administration of two or more therapeutic agents, where at least part of the administration overlaps in time or where the administration of one therapeutic agent falls within a short period of time relative to administration of the other therapeutic agent. For example, the two or more therapeutic agents are administered with a time separation of no more than about a specified number of minutes. The term “sequentially” is used herein to refer to administration of two or more therapeutic agents where the administration of one or more agent(s) continues after discontinuing the administration of one or more other agent(s), or wherein administration of one or more agent(s) begins before the administration of one or more other agent(s). For example, administration of the two or more therapeutic agents are administered with a time separation of more than about a specified number of minutes. As used herein, “in conjunction with” refers to administration of one treatment modality in addition to another treatment modality. As such, “in conjunction with” refers to administration of one treatment modality before, during or after administration of the other treatment modality to the animal.
Provided herein are methods of using the EPO polypeptides and polynucleotides for detection, diagnosis and monitoring of an anemia condition. For example, anemia may be detected, diagnosed, or monitored by measuring hematocrit percentage (HCT %) using standard methods. Provided herein are methods of determining whether a companion animal will respond to EPO polypeptide. In some embodiments, the method comprises detecting whether the animal has cells that express EPOR using an EPO polypeptide. In some embodiments, the method of detection comprises contacting the sample with an EPO polypeptide or polynucleotide and determining whether the level of binding differs from that of a reference or comparison sample (such as a control). In some embodiments, the method may be useful to determine whether the antibodies or polypeptides described herein are an appropriate treatment for the subject animal.
In some embodiments, the sample is a biological sample. The term “biological sample” means a quantity of a substance from a living thing or formerly living thing. In some embodiments, the biological sample is a cell or cell/tissue lysate. In some embodiments, the biological sample includes, but is not limited to, blood, (for example, whole blood), plasma, serum, urine, synovial fluid, and epithelial cells.
Various methods known in the art for detecting specific ligand-receptor binding can be used. Exemplary immunoassays which can be conducted include fluorescence polarization immunoassay (FPIA), fluorescence immunoassay (FIA), enzyme immunoassay (EIA), nephelometric inhibition immunoassay (NIA), enzyme linked immunosorbent assay (ELISA), and radioimmunoassay (RIA). An indicator moiety, or label group, can be attached to the subject antibodies and is selected so as to meet the needs of various uses of the method which are often dictated by the availability of assay equipment and compatible immunoassay procedures. Appropriate labels include, without limitation, radionuclides (for example ¹²⁵I, ¹³¹I, ³⁵S, ³H, or ³²P), enzymes (for example, alkaline phosphatase, horseradish peroxidase, luciferase, or p-galactosidase), fluorescent moieties or proteins (for example, fluorescein, rhodamine, phycoerythrin, GFP, or BFP), or luminescent moieties (for example, Qdot™ nanoparticles supplied by the Quantum Dot Corporation, Palo Alto, Calif.). General techniques to be used in performing the various immunoassays noted above are known to those of ordinary skill in the art.
For purposes of diagnosis, the polypeptide including EPO or EPOR can be labeled with a detectable moiety including but not limited to radioisotopes, fluorescent labels, and various enzyme-substrate labels know in the art. Methods of conjugating labels to a protein are known in the art.
The following examples illustrate particular aspects of the disclosure and are not intended in any way to limit the disclosure.

EXAMPLES

Example 1

Identification of N-Linked Glycosylation Sites for Feline EPO

Wild-type feline EPO has three N-linked glycosylation sites—at amino acid positions 50-52, 64-66, and 109-111 of wild-type feline EPO G44 precursor form (SEQ ID NO: 1 or “wild-type feline EPO G44”) and at amino acid positions 24-26, 38-40, and 83-85 of wild-type G18 feline EPO mature form (SEQ ID NO: 12 or “wild-type feline EPO G18”).
Additional N-linked glycosylation sites may be introduced into wild-type feline EPO amino acid sequences. For example, one, two, three, four, five, or six additional N-linked glycosylation sites may be introduced into wild-type feline EPO amino acid sequences. The N-linked glycosylation site may have a consensus sequence of Asn-Xaa-Ser/Thr, where Xaa is any amino acid except proline. Addition of one or more glycosylation sites may increase the molecular size of a feline EPO molecule, provide more sialylation sites, and/or improve the half-life of the molecule in an animal's serum.
Table 4 lists amino acid substitutions of wild-type feline EPO G44 that may be used to generate one or more additional N-linked glycosylation sites.

TABLE 4

	Amino acid substitutions for N-linked glycosylation sites

Analog	Based on wt feline EPO G44	Based on wt feline EPO G18
No.	sequence (SEQ ID NO: 1)	sequence (SEQ ID NO: 12)

Example 2

Expression of Feline EPO with Additional N-Linked Glycosylation Sites

The nucleotide sequence encoding a EPO polypeptide having additional N-linked glycosylation sites compared to wild-type feline EPO G44 precursor form was chemically synthesized. Specifically, the sequence encoded “Analog 6-30 GV Precursor” (SEQ ID NO: 3), which has a glycine at position 44, a valine substitution at position 113, and two additional N-linked glycosylation sites at positions 56-58 (N56T58) and 114-116 (N114) of wild-type feline EPO precursor.
The nucleotide sequence was inserted into an expression vector and transfected into CHO DG-44 host cells. The CHO DG-44 cells were selected for high yield and stability of expression of the EPO polypeptide, using a DHFR gene on the expression vector and methotrexate-mediated gene amplification, as is known in the art. The mature form of the EPO polypeptide, named “Analog 6-30 GV Mature” (SEQ ID NO: 14) was secreted into the culture media.

Example 3

Isolation of Feline EPO

Cell lines expressing feline EPO polypeptides may be cultured until sufficient quantities of the EPO polypeptide are produced. The polypeptide may be isolated by one or more of various steps, including Capto Butyl column chromatography, cation-exchange (CEX) column chromatography, anion-exchange (AEX) column chromatography, or other chromatographic methods. Other chromatographic methods may include ion exchange column chromatography, hydrophobic interaction column chromatography, mixed mode column chromatography (e.g., CHT and/or ultimodal mode column chromatography, such as CaptoMMC). Low pH or other viral inactivation and viral removal steps may be applied. The isolated EPO polypeptide may be admixed with excipients, and sterilized by filtration to prepare a pharmaceutical composition of the invention. The pharmaceutical composition may be administered to a cat with anemia in a dose sufficient to stimulate hematopoietic activity.
When cell viabilities dropped below 95%, the supernatant was harvested by clarifying the conditioned media. For example, a combination of chromatography steps was used to purify Analog 6-30 GV Mature polypeptide (SEQ ID NO: 14). Media from CHO cells expressing the EPO polypeptide was collected and conditioned with the addition of sodium chloride (NaCl) such that the media would have an NaCl concentration of greater than 1 M NaCl so that the EPO polypeptide could bind to a Capto Butyl column (GE Healthcare Life Sciences) by hydrophobic interaction chromatography (HIC). EPO is understood to bind to a Capto Butyl column at a pH of about 5.75 to about 8.5 with about 1 to about 2.5 M NaCl. The conditioned media was clarified by centrifugation and filtration and loaded onto the Capto Butyl column. Bound EPO polypeptide was eluted from the column with 30% isopropanol at a pH of about 5.6.
The host cell proteins fractionated away were analyzed using CHO host cell protein analysis ELISA kit (Catalog No. CM015; Cygnus Technologies). At least about 95% of host cell proteins were fractionated away from EPO proteins by this purification method.
The eluate from the Capto Butyl column was loaded directly onto an SP cation-exchange (CEX) column (GE Healthcare Life Sciences) as a subtraction chromatography step. Under this loading condition of 30% isopropanol at a pH of about 5.6, EPO polypeptides flow through the SP CEX column while host cell proteins should bind.
The flow-through from the SP CEX column was loaded directly onto a Capto Q anion-exchange (AEX) column (GE Healthcare Life Sciences), which binds EPO polypeptides in 30% isopropanol at a pH of about 5.6. A pH 4 wash was added to remove a fraction of basic EPO polypeptides while a fraction acidic EPO polypeptides remained with the solid phase. The EPO polypeptide acidic fraction was eluted with 0.15 M NaCl at pH 4 and the eluate kept at pH 4 for greater than 90 minutes at ambient temperature to inactivate viruses. This step also increased the concentration of the EPO polypeptide acidic fraction.
The eluate containing the EPO polypeptide acidic fraction was loaded directly onto an SP CEX column (GE Healthcare Life Sciences) to fractionate away any residual endotoxin and basic EPO polypeptide fraction, along with further concentrating the EPO polypeptide acidic fraction. The EPO polypeptide acidic fraction was eluted with 0.5 M NaCl at pH 4 and the eluate kept at pH 4 for greater than 90 minutes at ambient temperature to inactivate viruses.
Tangential flow filtration (TFF) may be used to concentrate the acidic and basic fractions EPO polypeptide fractions. A gel filtration step using Sperdex200 may be performed to remove any aggregates and as a buffer exchange to the desired buffer (e.g. a formulation buffer as described below). A nanofiltration step may be performed to remove any residual viral contaminants.

Example 4

EPO Buffer Formulations

Thermostability of feline EPO in various buffer formulations was analyzed. Buffers containing 20 mM sodium citrate or 20 mM sodium phosphate at pH 6.2 and pH 7 were considered. Sodium chloride at a final concentration of 140 mM was used in all buffers. Polysorbate 80 and 20 were compared. Bacteriostatic reagents benzyl alcohol and m-cresol were also compared. The melting temperature (Tm) of feline EPO Analog 6-30 GV Mature at a concentration of 6 μg/μL in each buffer was measured by differential scanning fluorescence technique from 20° C. to 95° C. Table 5 lists Tm values of feline EPO in the various buffers tested.

TABLE 5

Formulation		Melting temperature
Designation	Buffer Formulation	(Tm ° C.)

A1	20 mM sodium citrate	55
	140 mM sodium chloride
	pH 6.2
A2	A1 +	54
	650 nM polysorbate 80
A3	A1 +	52
	650 nM polysorbate 20
A4	A2 +	42
	1% benzyl alcohol
A5	A2 +	50
	0.2% m-cresol
A6	A3 +	no peak*
	1% benzyl alcohol
A7	A3 +	35
	0.2% m-cresol
B1	20 mM sodium citrate	50
	140 mM sodium chloride
	pH 7
B2	B1 +	51
	650 nM polysorbate 80
B3	B1 +	50
	650 nM polysorbate 20
B4	B2 +	no peak*
	1% benzyl alcohol
B5	B2 +	45
	0.2% m-cresol
B6	B3 +	no peak*
	1% benzyl alcohol
B7	B3 +	40
	0.2% m-cresol
C1	20 mM sodium phosphate	51
	140 mM sodium chloride
	pH 6.2
C2	C1 +	53
	650 nM polysorbate 80
C3	C1 +	50
	650 nM polysorbate 20
C4	C2 +	38
	1% benzyl alcohol
C5	C2 +	35
	0.2% m-cresol
C6	C3 +	50
	1% benzyl alcohol
C7	C3 +	43
	0.2% m-cresol
D1	20 mM sodium phosphate	51
	140 mM sodium chloride
	pH 7
D2	D1 +	53
	650 nM polysorbate 80
D3	D1 +	51
	650 nM polysorbate 20
D4	D2 +	38
	1% benzyl alcohol
D5	D2 +	40
	0.2% m-cresol
D6	D3 +	34
	1% benzyl alcohol
D7	D3 +	40
	0.2% m-cresol

*No peak indicates that no distinct melting point was observed.

Formulations A1, A2, A3, B1, B2, B3, C1, C2, and C3, which do not contain antibacterial agents and have a Tm of 50° C. or above may be more desirable for single dosing. Among the formulations containing antibacterial agents, Formulations A5 and C6, which have a Tm of 50° C. appear to be more desirable for multi-dosing.

Example 5

Characterization of Analog 6-30 GV Mature

Feline EPO Analog 6-30 GV Mature (SEQ ID NO: 14) isolated using the method of Example 3 was characterized.
Basic and acidic Analog 6-30 GV Mature fractions were visualized through isoelectric focusing (IEF) (FIG. 1A and FIG. 2 ) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gel (FIG. 1B).
For the Western analysis, serial dilutions of an acidic fraction of Analog 6-30 GV Mature (1 μg, 0.5 μg, 0.2 μg, 0.1 μg, and 0.05 μg) were separated by SDS-PAGE, transferred to a PVDF membrane, and the membrane probed with a rabbit anti-human EPO polyclonal antibody (Catalog No. AB-386-NA, R&D Systems) at a 1:1000 dilution (FIG. 3 ). The antibody was specific to the N-terminal 19 amino acids of human EPO, which are the same N-terminal 19 amino acids of feline EPO. The molecular weight of glycosylated wild-type feline EPO mature form is likely about 34 kDa. Based on FIG. 3 , the molecular weight of Analog 6-30 GV Mature appears to be about 50-55 kDa. The additional glycosylation appears to have contributed to the increase in molecular size.
Sialylated glycosylation on a protein may enhance its in vivo pharmacokinetics. Common sialic acids that are expressed as terminal units on all vertebrate glycans typically include N-glycolylneuraminic acid (Neu5Gc) and N-acetylneuraminic acid (Neu5Ac). Sialic acid analysis of Analog 6-30 GV Mature was performed. Briefly, an acidic fraction of Analog 6-30 GV Mature was treated with 2 M acetic acid at 80° C. for 3 hours after which the acetic acid was removed under vacuum centrifuge. The treated EPO sample was filtered through a 3K spin filtering unit to remove unhydrolyzed proteins. The flow-through sample was reacted with DMB reagent. An injection amount of 0.04 μg was profiled by high-performance liquid chromatography (HPLC) using a C18 column and a fluorescence detector. N-acetylneuraminic acid was identified as the predominant form of sialic acid present on Analog 6-30 GV Mature expressed by the transfected CHO DG44 cells. No detectable N-glycolylneuraminic acid was identified (FIGS. 4A-4B).
The N-terminal sequence of Analog 6-30 GV Mature was confirmed by Edman sequencing. Briefly, isolated Analog 6-30 GV Mature was separated by SDS-PAGE and transferred to a PVDF membrane (BioRad). The protein band was isolated from the membrane and subjected to N-terminal sequencing using Edman degradation at the Molecular Structure Facility at University of California, Davis. The N-terminal sequence was identified as Ala Pro Xaa Arg Leu Ile Xaa Asp Ser Arg Val, which corresponds to the N-terminal sequence of SEQ ID NO: 14.
Isolated Analog 6-30 GV Mature (SEQ ID NO: 14) was treated with N-Glycanase® (PNGase F) (Catalog No. GKE-5006A, ProZyme, CA) using the manufacturer's instructions to remove N-linked glycans. The deglycosylation process was monitored by SDS-PAGE until a 19 kD band was visualized, indicating the polypeptide was deglycosylated. The sequences of fragments of the deglycosylated Analog 6-30 GV Mature sample were analyzed using tandem mass spectrometry at Scripps Center for Metabolomics and Mass Spectrometry in California. The sequence of Analog 6-30 Mature was confirmed by mapping 77% of the peptide sequence (data not shown).

Example 6

Effect of Sialylation of Feline EPO on In Vitro Activity

The in vitro activity of an acidic fraction and a basic fraction of isolated Analog 6-30 GV Mature were compared by TF-1 cell proliferation assay. TF-1 cells are factor-dependent human erythroleukemic cells. EPO is one of the factors that promotes TF-1 cell proliferation. The acidic (or high sialyation) fraction had an isoelectric point range of about 2 to about 3.5 and the basic (or low sialyation) fraction had an isoelectric point range of about 3.5 to about 5.
For the proliferation assay, TF-1 cells (ATCC CRL-2003) were cultivated in RPMI 1640 (Irvine Catalog No. 9160) supplemented with 10% (v/v) Fetal Bovine Serum, 2 mM L-glutamine, 100 units/mL Penicillin, 100 μg/mL Streptomycin, and 2 ng/mL rhGM-CSF (R&D Systems Catalog No. 215-GM). Before treatment with either acidic fraction or basic fraction of Analog 6-30 GV Mature, the TF-1 cells were seeded in a 96-flat well plate at 2×10⁵cells per mL and allowed to attach overnight. The next morning, the cells were treated with different concentrations of acidic and basic fractions of Analog 6-30 GV Mature. Following incubation for 48 hours, MTT reagent (Catalog No. CGD1, Sigma-Aldrich) was added to the cells for another 48-72 hours, according to the manufacturer's instructions. The insoluble purple reaction product was then dissolved with isopropanol, and the plate was read at 570 and 690 nm. The proliferation intensity was measured as a difference in optical density between 570 nm and 690 nm (AOD) with the background corrected. The acidic fraction of isolated Analog 6-30 GV Mature demonstrated lower potency than the basic fraction in the cell-based functional assay (FIG. 5 ), suggesting that higher sialyation leads to lower activity.

Example 7

Effect of Sialylation on Pharmacokinetics

A pharmacokinetics study in cats involving a single injection of a 10 μg/kg dose of a basic fraction of isolated Analog 6-30 GV Mature or a 10 μg/kg dose of an acid fraction of isolated Analog 6-30 GV Mature was conducted. The basic (or low sialylation) fraction investigated had an isoelectric point range of about 4 to about 6 and the acidic fraction had an isoelectric point range of about 2 to about 3.5. Two cats were injected subcutaneous with the basic fraction and 11 cats were injected with the acidic fraction (4 cats via intravenous injection; 4 cats via subcutaneous injection, and 3 cats via intramuscular injection).
EPO concentrations from serum before injection (Time 0) and at various time points after injection were analyzed by ELISA. A sample of the basic faction of isolated Analog 6-30 GV Mature was used in the ELISA as a reference with a detection limit of 0.4 ng/mL. Very little EPO was detected over time in the serum of cats injected subcutaneous with the basic fraction of isolated Analog 6-30 GV Mature, suggesting a very short half-life of the low sialylated form (FIG. 6A). EPO concentration in the serum of cats injected with the acid fraction of isolated Analog 6-30 GV Mature by intravenous, subcutaneous, and intramuscular administration is shown in FIG. 6B, FIG. 6C, and FIG. 6D, respectively. Pharmacokinetic parameters calculated as mean values are listed in Table 6, below.

TABLE 6

	Pharmacokinetic parameter (mean)

Route of	AUC	T_1/2	C_max	T_max	Bioavailability*
Administration	(ng*hr/mL)	(hrs)	(ng)	(hrs)	(%)

Intravenous	1170	11.3			100
Subcutaneous	222	11.5	6.8	8	20
Intramuscular	602	24	14.2	8	51

*Bioavailability is calculated based on an assumption of 100% bioavailability in the IV group.

High sialylation of Analog 6-30 GV Mature appears to have enhanced the pharmacokinetics of the polypeptide in vivo, but to have reduced its potency in an in vitro cell-based functional assay (Example 6). While the pharmacokinetics of feline EPO may be enhanced in vivo with high sialylation, the tradeoff may be lower affinity and activity. And while low sialylated feline EPO may have better affinity and activity, it likely exhibits a shorter half-life.

Example 8

Expression of Feline EPO Receptor

Several feline EPO receptor (EPOR) proteins having a single transmembrane domain result from alternatively-spliced mRNA sequences originating from differences in the nucleotide sequences of exon 3. The amino acid sequences of two EPOR proteins were obtained from the National Center for Biotechnology Information (NCBI) database: UniProtKB-M3X491 M3X491_FELCA (SEQ ID NO: 27) and UniProtKB—M3W333 M3W333_FELCA (SEQ ID NO: 32). The amino acid sequence of M3X491_FELCA is also designated as Feline EPOR201 (fEPOR201) herein. The amino acids at positions 50-53 of M3W333, however, were not known and are represented in the database by an “X.” Using three-dimensional protein structure analysis, the amino acid sequence for M3W333 was modified and amino acids inserted at positions 50-53 to yield fEPOR202 (SEQ ID NO: 28).
Nucleotide sequences encoding soluble, extracellular domains of feline EPOR201 and EPOR202 (SEQ ID NOs: 23 and 24, respectively) fused to human Fc (SEQ ID NOs: 7 and 8, respectively) were synthesized, cloned into a mammalian expression vector, and expressed in CHO cells. Supernatant from the cell pellet was analyzed by SDS-PAGE and Western blot using anti-Fc antibody as a probe, demonstrating that both fEPOR201_ECD-Fc and fEPOR202_ECD-Fc can be recombinantly expressed (FIG. 7A). Extracellular domains of EPOR201 and EPOR202 comprising the amino acid sequence of SEQ ID NOs 29 and 30, respectively, may also be used.
Nucleotide sequences encoding full-length feline EPOR201 and EPOR202 with an N-terminal flag tag (SEQ ID NOs: 5 and 6, respectively) were synthesized and cloned in a mammalian expression vector. Each expression vector was transfected into CHO cells and a stable pool cells from each transfection was selected. Lysate from the cell pellet was analyzed by SDS-PAGE and Western blot using anti-flag antibody as a probe, demonstrating that both fEPOR201-N-flag and fEPOR202-N-flag can be recombinantly expressed (FIG. 7B and FIG. 7C). Feline full length EPOR expression cell line can be used for feline EPO binding assay or functional assay with or without proper modifications. Both EPOR201 proteins (SEQ ID NOs: 5 and 7) were isolated using standard Protein A chromatography.

Example 9

Analog 6-30 GV Mature Binding to Feline EPO Receptor

The binding of Analog 6-30 GV Mature (SEQ ID NO: 12) to fEPOR201_ECD-Fc (SEQ ID NO: 7) and fEPOR202_ECD-Fc (SEQ ID NO: 8) was tested separately. The binding analysis was performed as follows. Briefly, fEPOR201_ECD-Fc and fEPOR202_ECD-Fc were biotinylated using EZ-Link NHS-LC-biotin (Catalog No. 21336, Thermo Scientific). The free unreacted biotin was removed by dialysis. Biotinylated fEPOR201_ECD-Fc and fEPOR202_ECD-Fc were captured on streptavidin sensor tips (Catalog No. 18-509, ForteBio).
The association of five different concentrations (150, 50, 17, 5.6, and 1.9 nM) of Analog 6-30 GV Mature was monitored for ninety seconds. Dissociation was monitored for 600 seconds. A buffer only blank curve was subtracted to correct for any drift. The data were fit to a 1:1 binding model using ForteBio™ data analysis software to determine the k_on(association rate constant), k_off(dissociation rate constant) and the K_d(dissociation constant). The binding statistics fell within acceptable parameters (Chi-squared less than or equal to 3.0; R-squared greater than or equal to 0.9). The buffer for dilutions and all binding steps was: 200 mM phosphate, 150 mM NaCl, 0.02% Tween-20, 0.05% sodium azide, and 0.1 mg BSA, pH7.4. The K_dof Analog 6-30 GV Mature and fEPOR201_ECD-Fc (SEQ ID NO: 7) was 4×10⁻¹⁰M and the K_dof Analog 6-30 GV Mature and fEPOR202_ECD-Fc (SEQ ID NO: 8) was 1.7×10⁻¹⁰M.

Example 10

Comparison of Analog 6-30 GV Mature and Human EPO Binding to Human EPO Receptor

The binding of Analog 6-30 GV Mature and recombinant human EPO (Catalog No. E5627, Sigma-Aldrich) to human EPO receptor (EPOR) was compared. Briefly, extracellular domain of human EPOR (Catalog No. 963-ER-050, R&D Systems) was biotinylated. The free unreacted biotin was removed from biotinylated human EPOR by extensive dialysis. Biotinylated human EPOR was captured on streptavidin sensor tips. The association of five different concentrations (20, 6.7, 2.2, 0.74, and 0.25 nM) of either Analog 6-30 GV Mature or human EPO with human EPOR was monitored for ninety seconds. Dissociation was monitored for 600 seconds. A buffer only blank curve was subtracted to correct for any drift. The data were fit to a 1:1 binding model using ForteBio™ data analysis software to determine the k_on(association rate constant), k_off(dissociation rate constant), and the K_d(dissociation constant). The binding statistics fell within acceptable parameters (Chi-squared less than or equal to 3.0; R-squared greater than or equal to 0.9). The buffer for dilutions and all binding steps was 200 mM phosphate, 150 mM NaCl, 0.02% Tween-20, 0.05% sodium azide, and 0.1 mg BSA, pH 7.4. The K_dof human EPO and human EPOR was 1.07×10⁻¹⁰M and the K_dof Analog 6-30 GV Mature and human EPOR was 9.76×10⁻¹¹M. Analog 6-30 GV Mature and human EPO appear to have similar binding affinity to human EPOR.

Example 11

Comparison of Analog 6-30 GV Mature and Human EPO Proliferative Effect on TF-1 Cells

EPO polypeptides have two EPO receptor binding sites. In vitro binding assays, like the assay described in Example 10, largely reflect first site binding kinetics since second site binding is understood to be weak (˜500- to 1000-fold less affinity compared to first site) in humans. See Philo, J. S., et al., Dimerization of the extracellular domain of the erythropoietin (EPO) receptor by EPO: one high-affinity and one low-affinity interaction. Biochemistry 35, 1681-91 (1996). EPO-dependent cell proliferation assays, like the assay described in this example, can assess EPO activity as it relates to the integrity of the first binding site as well as the second binding site.
The proliferative effect of Analog 6-30 GV Mature on TF-1 cells expressing human EPOR was compared to that of recombinant human EPO (Catalog No E5627, Sigma-Aldrich). For the proliferation assay, TF-1 cells were cultivated in RPMI 1640 (Irvine Catalog No. 9160) supplemented with 10% (v/v) Fetal Bovine Serum, 2 mM L-glutamine, 100 units/mL Penicillin, 100 μg/mL Streptomycin, and 2 ng/mL rhGM-CSF (R&D Systems Catalog No. 215-GM). Before treatment with either Analog 6-30 GV Mature or recombinant human EPO, the TF-1 cells were seeded in a 96-flat well plate at 2×10⁵cells per mL and allowed to attach overnight. The next morning, the cells were treated with different concentrations of Analog 6-30 GV Mature or recombinant human EPO. Following incubation for 48 hours, MTT reagent was added to the cells for another 48-72 hours, according to the manufacturer's instructions. The insoluble purple reaction product was then dissolved with isopropanol, and the plate was read at 570 and 690 nm. The proliferation intensity was measured as a difference in optical density between 570 nm and 690 nm (AOD) with the background corrected.
Proliferation response of TF-1 cells to Analog 6-30 GV Mature and recombinant human EPO is shown in FIG. 8 . The concentration of EPO polypeptide that gives half-maximal response (EC₅₀) was determined for each proliferation curve. Unexpectedly, the similar affinity of Analog 6-30 GV Mature and recombinant human EPO to human EPOR (as measured in Example 10) did not appear to translate to a similar EC50 between the two EPO polypeptides based on this MTT assay. The EC50 for Analog 6-30 GV Mature (0.3 IU/mL) was an order of magnitude higher than the EC50 for recombinant human EPO (0.02 IU/mL), suggesting a lower proliferation activity for Analog 6-30 GV Mature compared to recombinant human EPO.

Example 12

Protein Structure Analysis of Feline EPO

To identify possible reasons for the decreased proliferative effect of Analog 6-30 GV Mature compared to recombinant human EPO, the structure of the second receptor binding site of wild-type feline EPO G18 and human EPO were compared.
First, the three-dimensional structure of feline EPO G18 and human EPO were obtained through protein structure modeling understood by persons in the art. Based on the location of the second binding site of human EPO, the second binding site of wild-type feline EPO G18 was identified. Next, the interface residues of the second receptor binding sites of wild-type feline EPO G18 and human EPO were compared and found unlikely to have affected second site binding of wild-type feline EPO G18. Then, amino acid residues at the interior of the second binding site of wild-type feline EPO G18 were considered. Unexpectedly, glycine (G) at position 18 was identified at the interior of the second binding site. In addition, empty volume in the protein structure was observed around G18.
This led to the investigation of the protein structure of wild-type feline EPO E18. Wild-type feline EPO E18 had been characterized as a variant and any difference in biological function (e.g., proliferative effect, etc.) between wild-type feline EPO G18 and EPO E18 was unclear. Based on this protein structure analysis, unlike G18, E18 appeared to form hydrogen bonds with R14 and hydrogen/Van der Waals forces with Y15. E18 appeared to also interact with K97. See FIG. 9 . R14, Y15, and K97 are located at the interface of the second binding site and may be directly involved in maintaining second receptor binding.
In addition, the amino acid sequences of other mammalian species were considered and all of those considered were found to share not only E18, but also R14, Y15, and K97. All four amino acids (R14, Y15, E18 and K97) are conserved in human, dog, horse, Cynomolgus monkey, Rhesus monkey, mouse, rat, sheep, and pig.
Based on this analysis, G18 of Analog 6-30 GV Mature may have affected its second site binding and have attributed to its decreased proliferative effect.

Example 13

Expression and Isolation of Analog 6-30 EV

Upon discovering that E18 may be important for second site binding, studies involving analogs of wild-type feline EPO E18 were conducted. A nucleotide sequence encoding an EPO polypeptide having additional N-linked glycosylation sites compared to wild-type feline EPO E44 precursor form was chemically synthesized. Specifically, the sequence encoded “Analog 6-30 EV Precursor” (SEQ ID NO: 4), which has a glutamic acid at position 44, a valine substitution at position 113, and two additional N-linked glycosylation sites at positions 56-58 (N56T58) and 114-116 (N114) of wild-type feline EPO E44 precursor.
The nucleotide sequence was inserted into an expression vector and transfected into CHO DG-44 host cells. The CHO DG-44 cells were selected for high yield and stability of expression of the EPO polypeptide, using a DHFR gene on the expression vector and methotrexate-mediated gene amplification, as is known in the art. The mature form of the EPO polypeptide, named “Analog 6-30 EV Mature” (SEQ ID NO: 15) was secreted into the culture media. Analog 6-30 EV Mature was isolated according to the method described in Example 3.

Example 14

N-Linked Glycosylation Sites for Feline EPO E44

Wild-type feline EPO E44 precursor form (SEQ ID NO: 2 or “wild-type feline EPO E44”) has three N-linked glycosylation sites at amino acid positions 50-52, 64-66, and 109-111, which correspond to amino acid positions 24-26, 38-40, and 83-85 of wild-type feline EPO E44 mature form (SEQ ID NO: 13 or “wild-type feline EPO E18”).
Additional N-linked glycosylation sites may be also introduced into wild-type feline EPO E44 and wild-type feline EPO E18 amino acid sequences. For example, one, two, three, four, five, or six additional N-linked glycosylation sites may be introduced into wild-type feline EPO E44/E18 amino acid sequences. The N-linked glycosylation site may have a consensus sequence of Asn-Xaa-Ser/Thr, where Xaa is any amino acid except proline. Addition of one or more glycosylation sites may increase the molecular size of a feline EPO molecule, provide more sialylation sites, and/or improve the half-life of the molecule in an animal's serum.
Table 7 lists amino acid substitutions of wild-type feline EPO E44 and E18 that may be used to generate one or more additional N-linked glycosylation sites.

TABLE 7

	Amino acid substitutions for N-linked glycosylation sites

Analog	Based on wt feline EPO E44	Based on wt feline EPO E18
No.	sequence (SEQ ID NO: 2)	sequence (SEQ ID NO: 13)

Example 15

Analog 6-30 EV Mature and Analog 6-30 GV Mature Binding to EPOR

Binding of an acidic (high sialylation) fraction of Analog 6-30 EV Mature (SEQ ID NO: 15), an acidic (high sialylation) fraction of Analog 6-30 GV Mature (SEQ ID NO: 14) having an isoelectric point range of about 2 to about 3.5, and a basic (low sialylation) fraction of Analog 6-30 GV Mature having an isoelectric point range of about 4 to about 5 to human EPOR-Fc (Catalog No. 963-ER-050, R&D Systems) was tested by ELISA.
A 96-well plate was coated with a mouse anti-EPO specific antibody (Catalog No. MAB287, clone 9C21D11, R&D Systems) to capture the EPO polypeptides. The EPO-bound wells were incubated with human EPOR-Fc at a concentration of 200 ng/mL and the bound EPOR was detected by anti-human Fc HRP conjugated antibody. The ELISA was performed a second time, but the three samples of EPO polypeptides were first treated with neuraminidase to remove the sialic acid. The resulting EC50s are listed in Table 8, below.

TABLE 8

	EC50

Feline EPO analog	ELISA	1	ELISA 2*

Analog 6-30 EV Mature (acidic fraction)	45 ng/ml	20 ng/ml
Analog 6-30 GV Mature (acidic fraction)	100 ng/ml	18 ng/ml
Analog 6-30 GV Mature (basic fraction)	35 ng/ml	31 ng/mL

*EPO samples were neuraminidase-treated prior to performing ELISA 2.

The acidic (high sialylation) fraction of Analog 6-30 GV Mature exhibited a higher EC50 value compared to the basic (low sialylation) fraction, suggesting reduced receptor binding affinity with the acidic fraction. This result was consistent with the binding assay results of Example 6 comparing an acidic and basic fraction of Analog 6-30 GV Mature. When sialic acid residues were removed for the second ELISA, the EC50 values for Analog 6-30 EV Mature and Analog 6-30 GV Mature were generally similar, suggesting similar binding affinities for EPO receptor.

Example 16

Proliferative Effect of Analog 6-30 EV Mature and Analog 6-30 GV Mature

The integrity of first and second receptor binding sites of Analog 6-30 EV Mature (SEQ ID NO: 15) and Analog 6-30 GV Mature (SEQ ID NO: 14) were compared by a TF-1 cell proliferation assay as described in Example 11. In this assay, two samples were tested: 1) Analog 6-30 EV Mature and 2) a mixture of 50% Analog 6-30 EV Mature and 50% Analog 6-30 GV Mature.
TF-1 cells were treated with different concentrations of samples 1 and 2 and MTT reagent was used to measure proliferation. The reaction product was dissolved with isopropanol and the plate read at 570 and 690 nm. The proliferation intensity was measured as a difference in optical density between 570 nm and 690 nm (ΔOD) with the background corrected. Proliferation response of TF-1 cells to Samples 1 and 2 are shown in FIG. 10 .
The concentration of EPO polypeptide that gives half-maximal response (EC₅₀) was determined for each proliferation curve. The EC50s for Sample 1 (4.78 ng/mL) and Sample 2 (4.54 ng/mL) were similar, suggesting that it is likely that the presence of 50% Analog 6-30 GV Mature in Sample 2 did not affect the EC50. However, Analog 6-30 GV Mature appeared to reduce the span or proliferation signal of Sample 2 (ΔOD=0.29) when compared to Sample 1 (ΔOD=0.44). The reduction in proliferation activity between the two samples suggests that G18 attenuates second site binding activity.

Example 17

EPO Second Site Mutants

EPO having a defect in the second binding site (or a “site 2 defect”) may be used to antagonize endogenous EPO activity. For example, EPO with a defect in second site binding may compete for EPO receptor binding and block signaling, thus prevent new red blood cell generation. Thus, EPO with second site mutation(s) may be agent to treat disease such as certain forms of polycythemia (elevated red blood cell counts) due to excess EPO production, such as a condition caused by tumors (e.g., kidney tumors) that secrete excess EPO or inherited disorders of overproduction of EPO.
In cases where the endogenous EPO receptor is hypersensitive, or self-activating, administration of EPO having a defect in the second binding site may block the mutant receptor. At high dose, EPO having a site 2 defect may kill the target cells, when needed, to form excessive 1:1 ratio of EPO:receptor complex and/or reduce red blood cell formation.
One or more second site mutations of human EPO, feline EPO, or canine EPO are selected from an amino acid substitution at a position corresponding to position L(5), D(8), R(10), V(11), R(14), Y(15), Q(78), D(96), K(97), V(99), S(100), R(103), S(104), T/S (107), L(108), or R(110) of a wild-type feline EPO polypeptide. For example, R(103) can be mutated to Ala or other amino acid to disrupt second site activity.

Example 18

Sialic Acid Characterization of Analog 6-30 EV Mature

The sialic acid content of an acidic fraction of Analog 6-30 EV Mature (SEQ ID NO: 15) was analyzed and compared to that of an acidic fraction of Analog 6-30 GV Mature (SEQ ID NO: 14), which had approximately 20 sialic acid molecules per polypeptide. The IEF profiles of Analog 6-30 EV Mature and Analog 6-30 GV Mature were similar suggesting that the E analog had a similar sialic acid content to the G analog. N-acetylneuraminic acid was identified as the predominant form of sialic acid present on both analogs.
Sialic acid analysis was performed as follows. Sialic acid was released from Analog 6-30 EV Mature (SEQ ID NO: 15) by mixing 30 μL of sample with 4 μL of glacial acetic acid. The mixture was incubated at 80° C. for 2 hours. Free sialic acid was labeled with fluorescence dye 1,2-diamino-4,5-methylenoxybenzene (DMB). The florescence labelling was performed by mixing 20 μL of the DMB-thionite solution with 5 μL of the free sialic acid samples. The mixture was incubated at 50° C. for 3 hours. The reaction was stopped by adding 75 μL of distilled, deionized water. The DMB labeled sialic acid was analyzed by HPLC using either a Zorbax SB-C18 column (5μ, 4.6×150 mm) or Extend C18 column (5μ, 4.6×150 mm) (Agilent Technologies), with isocratic mobile phase containing 7% methanol, 9% acetonitrile, and 84% water. All the neuraminic acids, e.g., Neu5Gc (NGNA); Neu5Ac (NANA); Neu5,7Ac2; Neu5,Gc9Ac; Neu5,9Ac2; and Neu5,7(8),9Ac are base line resolved in 30 minutes.

Example 19

Feline EPO E18 Binding to Feline EPOR

A predicted protein sequence for an alternatively-spliced variant of feline EPOR (fEPOR203 (SEQ ID NO: 27)) was obtained from the NCBI database as Accession No. XP_019673378.1. The amino acid at position 39 was not known and is represented in the database by an “X.” Three-dimensional protein structural modeling was performed and placement of alanine at position 39 of EPOR203 (SEQ ID NO: 21) was determined to maintain the right N-terminal protein conformation.
A soluble, extracellular domain of EPOR203 was identified (EPOR203_39A ECD; SEQ ID NO: 26) and the nucleotide sequence encoding a signal sequence, EPOR203_39A ECD, a linker, and human Fc (EPOR203_39A_ECD_Fc; SEQ ID NO: 22) was synthesized, cloned into a mammalian expression vector, and expressed in HEK or CHO cells. EPOR203_39A_ECD_Fc was purified from the cell culture supernatant by Protein A affinity column chromatography and formulated in PBS at neutral pH. FIG. 7D shows a Coomassie stain of SDS-PAGE analysis of feline EPOR203-ECD-Fc. An extracellular domain of EPOR203 comprising the amino acid sequence of SEQ ID NO: 31 may also be used.

Example 20

Analog 6-30 EV Mature Binding to Feline EPO Receptor

The binding of Analog 6-30 EV Mature (SEQ ID NO: 15) to feline EPOR203_39A_ECD_Fc (SEQ ID NO: 26) was assessed using an ELISA-based assay in duplicate. A MaxiSorp 96-well plate was coated overnight with anti-human EPO antibody (4 μg/mL) at refrigeration temperature (2-8° C.) and blocked with 5% BSA in PBS for 1 hour at room temperature. Analog 6-30 EV Mature was prepared in 2-fold serial dilutions starting with a concentration of 500 ng/mL in 1% BSA-PBST (0.05% Tween-20) buffer. Dilutions of Analog 6-30 EV Mature (100 μL) were transferred to each well and incubated at room temperature for 2 hours. Feline EPOR203_39A_ECD_Fc (200 ng/mL in 1% BSA-PBST buffer) was added to each well and binding allowed to proceed for 1 hour at room temperature. A rabbit anti-human Fc antibody and horseradish peroxidase (HRP) conjugate (0.2 μg/mL) was used for detection and left in the wells for 1 hour at room temperature. 3,3,5,5′-Tetramethylbenzidine (TMB) was applied to the wells as the HRP substrate and kept in the well for 5 to 7 minutes for signal development. Binding between Analog 6-30 EV Mature (SEQ ID NO: 15) and feline EPOR203_39A_ECD_Fc was demonstrated. The mean detection signal was plotted against Analog 6-30 EV Mature concentration and curve fit analysis performed (FIG. 11 ).

Example 21

Administration of Analog 6-30 EV Mature to Normal Cats

A single dose of Analog 6-30 EV Mature (SEQ ID NO: 15) at 1 μg/kg (n=5), 3 μg/kg (n=5), or 10 μg/kg (n=5), Analog 6-30 GV Mature (SEQ ID NO: 14) at 10 μg/kg (n=4), or PBS was administered subcutaneously to normal cats. Absolute reticulocyte percentages were measured as an indicator of EPO bioactivity. In brief, EPO binds to EPO receptor on erythroid cells and the dimerization of the receptor activates the JAK2 pathway and signaling of erythropoiesis. Erythroid cells differentiate into reticulocytes, then red blood cells. Thus, an increase in EPO bioactivity and erythropoiesis is evidenced by an increase in the percentage of absolute reticulocytes.
FIG. 12 shows the mean absolute reticulocyte percentage in cats at 1 day before dosing and at day 5, 7, 10, and 14 after subcutaneous administration of placebo or Analog 6-30 EV Mature or PBS (n=4). FIG. 13 shows the mean absolute reticulocyte percentage in cats at 4 days before dosing and at day 3, 5, 10, 17 19, 24, 31, and 33 after subcutaneous administration of Analog 6-30 GV. An increase in erythropoiesis was demonstrated in the groups treated with Analog 6-30 EV Mature, but not in the group treated with Analog 6-30 GV Mature.

Example 22

Efficacy Study of Analog 6-30 EV Mature in Anemic Cats

An open-label, historical controlled (compared cats' post-treatment and pre-treatment data), pilot efficacy study was conducted to evaluate the effectiveness of Analog 6-30 EV Mature (SEQ ID NO: 15) on red blood cells (RBC), reticulocytes, and Quality of Life (QoL) in client-owned cats with International Renal Interest Society (IRIS) Stage 3 Chronic Kidney Disease (CKD) and anemia. Safety was also evaluated by the collation of any adverse events (AE) and the presence of neutralizing antibodies. Preliminary data from two cats that completed the study showed an improvement of anemia (i.e., increased hematocrit percentage (HCT %)), suggested an improvement in the symmetric dimethylarginine (SDMA) and serum creatinine renal biomarker tests specific to kidney function, and showed maintenance or improvement in body weight.
Cats with IRIS Stage 3 CKD and anemia that met all the following eligibility criteria were enrolled:
Inclusion Criteria
The cat:

- 1. Is manageable and cooperative with study procedures
- 2. Has rapidly progressive CKD with a 25% increase in fasting serum creatinine between two consecutive evaluations
- 3. Is at least 1 year of age on Day 0 and is: any gender; intact or neutered; non-pregnant, non-lactating; any breed and any weight
- 4. Has IRIS Stage 3 CKD, defined as:
  - a) A Screening Visit fasting serum creatinine of 2.9-5.0 mg/dL and a previous medical history of serum creatinine of 2.9-5.0 mg/dL within 6 months of Day 0 (fasting or unfasted); and
  - b) Urine specific gravity (USG)<1.035
- 5. Has non-regenerative anemia and a 15-30% HCT
- 6. Is receiving standard of care therapy for CKD

Exclusion Criteria
The cat:

- 1. Resides mostly outdoors (>60% of each day is spent outside)
- 2. Has rapidly progressive CKD with a 25% increase in fasting serum creatinine between two consecutive evaluations
- 3. Has ever been treated with an erythropoietin stimulating agent
- 4. Has been administered whole or packed red blood cells within 6 weeks of Day 0;
- 5. Has a urinary tract infection (UTI) with the following exception: cats with a UTI may be enrolled post-treatment with the appropriate antibiotic therapy (based on culture/sensitivity) for 3 weeks and repeat negative culture
- 6. Has any of the following diseases/conditions:
  - Neoplasia
  - Liver disease
  - Feline leukemia virus (FeLV)
  - Feline immunodeficiency virus (FIV)
  - Diabetes mellitus (DM)
  - Hyperthyroidism
  - Hematocrit<15%
  - Systemic blood pressure>160 mmHg
- 7. Requires a new prescription or a prescription change (dose or dose frequency) to an existing concurrent medication or therapy for CKD two weeks before Day 0.

Two cats were administered Analog 6-30 EV Mature (SEQ ID NO: 15) subcutaneously twice at a starting dose of 3 μg/kg approximately 7-10 days apart, and followed for six weeks. Cats were concurrently administrated iron dextran.
The following data was collected and/or evaluated at all visits (scheduled or unscheduled): physical examination with a medical history, quality of life (vitality, comfort, and emotional wellbeing), appetite, activity (Vetrax activity sensor affixed to a neck collar), blood pressure, and owner diary of observed events. At initial Screening and Week 6 Visits, hematology, biochemistry, urinalysis with urine protein to creatinine ratio, and SDMA assessments were made. Urine culture±sensitivity was assessed at baseline and as needed throughout the study. Hematocrit was assessed in-house at all scheduled and unscheduled visits.
The baseline hematocrit improved from a baseline of 22.8% to a maximum of 35.9% (at Week 4) in Cat WEX-201 (Table 9) and from a baseline 26.6% to a maximum of 35.5% (at Week 2) in Cat LUN-201 (Table 10). Since the anemia (HCT) improved in both cats following the second dose of Analog 6-30 EV Mature, additional doses were not administered during the study; however, the decline in HCT by Week 6 in WEX-201 and Week 5 in LUN-201 suggests further treatment may be administered to maintain the HCT. The SDMA renal biomarker test improved (i.e., reduced) from 30 to 14 μg/dL in Cat WEX-201 (Table 9) and from 29 to 17 μg/dL in Cat LUN-201 (Table 10). The body weight was either maintained (LUN-201; Table 10) or improved (WEX-201; Table 9) during the study.

TABLE 9

WEX-201 Data

		Dose			Serum
	Hematocrit	(3 μg/kg)		SDMA	creatinine
VISIT	(%)	administered	BW (kg)	(ug/dL)	(mg/dL)

Screening	22.8	N/A	3.9	30	3.4
Day 0	27.9	Yes	4	N/A	N/A
Unscheduled	26	No	3.8	N/A	N/A
Week
1	23.5	Yes	4	N/A	N/A
Week
2	31.2	No	4.5	N/A	N/A
Week
3	35	No	4.3	N/A	N/A
Week
4	35.9	No	4.3	N/A	N/A
Week
5	35	No	4.3	N/A	N/A
Week
6	17	N/A	4.5	14	1.3

TABLE 10

LUN-201 Data

		Dose			Serum
	Hematocrit	(3 μg/kg)		SDMA	creatinine
VISIT	(%)	administered	BW (kg)	(ug/dL)	(mg/dL)

Screening	26.6	N/A	3.1	29	3.3
Day 0	25.9	Yes	3.1	N/A	N/A
Week
1	30.8	Yes	3.1	N/A	N/A
Week
2	35.5	No	3.0	N/A	N/A
Week
3	33.0	No	3.2	N/A	N/A
Week
4	32.7	No	3.1	N/A	N/A
Week
5	30.6	No	3.1	N/A	N/A
Week
6	29.6	N/A	3.1	17	2.0

The trend for improved SDMA and serum creatinine renal biomarkers observed in the cats suggests improved renal function post-treatment with Analog 6-30 EV Mature. It is not uncommon for cats with late stage CKD and anemia to experience clinically relevant comorbidities that result in undesired weight loss. Treatment with Analog 6-30 EV Mature was effective to either increase (WEX-201) or maintain (LUN-201) body weight.

Claims

1. An erythropoietin (EPO) polypeptide comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 13 except for the presence of at least one N-linked glycosylation site not present in SEQ ID NO: 2 or SEQ ID NO: 13, wherein the N-linked glycosylation site comprises the sequence asparagine-xaa-serine or asparagine-xaa-threonine, wherein xaa is any amino acid except proline, and wherein one N-linked glycosylation site does not overlap with another N-linked glycosylation site.

2. The EPO polypeptide of claim 1, wherein each of the at least one N-linked glycosylation site is present at:

a) a position selected from position 47-49, 55-57, 56-58, 60-62, 61-63, 79-81, 82-84, 91-93, 92-94, 97-99, 98-100, 99-101, 112-114, 113-115, 114-116, 115-117, 116-118, 137-139, 140-142, 141-143, 142-144, 143-145, 144-146, 145-147, 146-148, 147-149, 148-150, 149-151, 150-152, 161-163, 162-164, 184-186, and 186-188 of SEQ ID NO: 2; or

b) a position selected from position 21-23, 29-31, 30-32, 34-36, 35-37, 53-55, 56-58, 65-67, 66-68, 71-73, 72-74, 73-75, 86-88, 87-89, 88-90, 89-91, 90-92, 111-113, 114-116, 115-117, 116-118, 117-119, 118-120, 119-121, 120-122, 121-123, 122-124, 123-125, 124-126, 135-137, 136-138, 158-160, and 162-164 of SEQ ID NO: 13.

3. The EPO polypeptide of claim 1 comprising valine at a position corresponding to position 113 of SEQ ID NO: 4.

4. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 47 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 48 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 49 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 21 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 22 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 23 of SEQ ID NO: 13.

5. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 55 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 56 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 57 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 29 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 30 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 31 of SEQ ID NO: 13.

6. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 56 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 57 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 58 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 30 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 31 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 32 of SEQ ID NO: 13.

7. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 60 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 61 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 62 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 34 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 35 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 36 of SEQ ID NO: 13.

8. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 61 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 62 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 63 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 35 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 36 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 37 of SEQ ID NO: 13.

9. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 79 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 80 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 81 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 53 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 54 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 55 of SEQ ID NO: 13.

10. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 82 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 83 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 84 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 56 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 57 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 58 of SEQ ID NO: 13.

11. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 91 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 92 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 93 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 65 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 66 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 67 of SEQ ID NO: 13.

12. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 92 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 93 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 94 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 66 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 67 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 68 of SEQ ID NO: 13.

13. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 97 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 98 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 99 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 71 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 92 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 73 of SEQ ID NO: 13.

14. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 98 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 99 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 100 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 72 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 73 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 74 of SEQ ID NO: 13.

15. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 99 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 100 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 101 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 73 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 74 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 75 of SEQ ID NO: 13.

16. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 112 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 113 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 114 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 86 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 87 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 88 of SEQ ID NO: 13.

17. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 113 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 114 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 115 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 87 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 88 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 89 of SEQ ID NO: 13.

18. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 114 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 115 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 116 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 88 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 89 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 90 of SEQ ID NO: 13.

19. The EPO polypeptide of claim 1 comprising:

a) asparagine at a position corresponding to position 115 of SEQ ID NO: 2, any amino acid except proline at a position corresponding to position 116 of SEQ ID NO: 2, and serine or threonine at a position corresponding to position 117 of SEQ ID NO: 2; or

b) asparagine at a position corresponding to position 89 of SEQ ID NO: 13, any amino acid except proline at a position corresponding to position 90 of SEQ ID NO: 13, and serine or threonine at a position corresponding to position 91 of SEQ ID NO: 13.

20. The EPO polypeptide of claim 1 comprising:

21.-138. (canceled)