WO2008109880A1 - Bioreactor system for pharmacokinetic-pharmacodynamic analysis - Google Patents

Abstract

The invention provides an in vitro cell culturing bioreactor device capable of supporting the growth of protozoan parasites, such as, for example species of the genera Trypanosoma, Toxoplasma, Leishmania, and Plasmodium, but which can also be utilized to grow other cell types, including, for example, cancer cells, virus-infected cells, bacteria, and mycobacteria. The invention also provides methods for monitoring and/or measuring the effects of therapeutic agents on cells, for determining the pharmacokinetic- pharmacodynamic relationship between a drug and a target cell, and for determining an effective dosing regime for a drug or therapeutic agent.

Description

Attorney Docket No. 81248WO(71699)

TITLE OF THE INVENTION

BIOREACTOR SYSTEM FOR PHARMACOKINETIC-PHARMACODYNAMIC ANALYSIS

CROSS-REFERENCE TO RELATED APPLICATIONS/PATENTS & INCORPORATION BY REFERENCE

This application claims priority to U.S. Provisional Application Serial No.

60/905,653, filed March 8, 2007, and to U.S. Provisional Application Serial No.

60/931,131, filed May 21 , 2007, the contents each of which are incorporated herein by reference in their entireties. Any and all references cited in the text of this patent application, including any

U.S. or foreign patents or published patent applications, International patent applications, as well as, any non-patent literature reference, including any manufacturer's instructions, are hereby expressly incorporated by reference.

STATEMENT OF POTENTIAL GOVERNMENT INTEREST The United States government may have certain rights in this invention by virtue of grant number National Institutes of Health Grant No. AI28855.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to in vitro cell culturing methods and devices for evaluating the effects of pharmaceuticals and other therapeutic agents on cells. The invention further relates to methods and devices capable of analyzing and evaluating the pharmacokinetic and pharmacodynamic relationship of drugs and other agents on cells.

2. Background of the Related Art

Hollow fiber bioreactor technology is an economical and useful alternative to traditional methods for cell and tissue culturing for the culturing of cells, production of

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cell-derived products, and for investigating the effects (e.g., pharmacokinetics and pharmacodynamics) of various agents on the growth, behavior and characteristics of cells.

In traditional cell culture methods, cells derived from either primary tissues or from descendants of such cells are grown in nutrient-supported culture dishes. Cells, however, require periodic splitting as the surface area of the culture dishes is limited and the levels of waste, pH and nutrients are in constant flux.

Hollow fiber bioreactors typically are described as including a cartridge shell which encloses a bundle of hollow porous capillary fibers. Cell culture medium is pumped through the capillary fibers (the intra-fiber (or intra-capillary) space/compartment), while the cells are grown in space outside of the fibers or the outer surfaces of the fibers themselves (the extra- fiber (or extra-capillary) space/compartments). The porous capillary fibers create a semi-permeable barrier between the extra- fiber compartment and intra-fiber compartment through which the cell medium flows. Medium and nutrients pass through the fiber walls to continually nourish cell growth, whereas cellular waste may be removed through the capillary walls and removed with the circulating medium. Expression products, if any, can be accumulated in the extracapillary space. Access ports for the sampling and removing of material from the extracapillary space can be included in the cartridge.

Typically, the hollow fibers that serve to separate the cells and the circulating medium provide a predetermined molecular weight cutoff as to the passage of smaller molecules, e.g., 10 kDa, while preventing the passage of larger molecules and the cells themselves. Therefore, with cells being maintained in the extra-fiber space, nutrients such as glucose and oxygen are delivered in medium and passed through the fibers. The nutrients are able to pass through the fibers to be fed to the cells, while waste products,

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such as lactate and carbon dioxide, can pass through the fibers to be removed with the circulating medium.

There are a number of advantages to using hollow fiber bioreactors. In the case of their use in the production of proteins, such bioreactors typically result in higher cell densities than with traditional cell culture methods, which in turn, enables a greater yield of expressed proteins. Also, the use of a semi-permeable membrane to retain high molecular weight proteins in the extra- fiber space allows for more efficient use of costly medium components while producing a highly concentrated product. As a result, such bioreactors are associated with lower costs, which are attributed to continuous production, reduced costs for feeding cells, and reduced costs for purification of products.

A hollow fiber bioreactor generally of this kind is described in U.S. Patent No. 5,622,857 (to Goffe, entitled "High performance cell culture bioreactor and method"), which describes a bioreactor comprising a reaction chamber through which a central strand of porous hollow fibers extend along the longitudinal axis of the chamber. The hollow fibers carry nutrient cell growth media. This bundle of hollow fibers is concentrically surrounded by a plurality of strands of gas-permeable hollow fibers, through which gaseous medium, such as oxygen or carbon dioxide, is conveyed to provide the necessary gaseous requirements during cell growth. In this system, cells of interest are introduced into the reaction chamber of the bioreactor and then incubated while passing nutrient media through the porous hollow fibers and oxygen containing gas through the gas permeable hollow fibers. Thereafter, the cells and/or their products can be removed from the reaction chamber.

Another example of such a bioreactor is described in U.S. Patent No. 4,391,912 (to Yoshida et al., entitled "Cell cultivation method and floating animal cell culture unit for the same"). Yoshida et al. relates to a cell culture bioreactor that comprises open ended

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permeable hollow fibers enclosed by a shell. The culture medium is flowed through the interior of the permeable hollow fibers, while cells of interest grow and proliferate in the extra-fiber space.

In yet another example, U.S. Patent No. 6,001,585 (to Gramer, entitled "Micro hollow fiber bioreactor") defines such a bioreactor for use in culturing cells, as well as for characterizing the growth and metabolic activities of the cells in the context of various process conditions. The '585 patent relates to a hollow fiber bioreactor that includes an oxygen permeable tube disposed within and traversing a bundle of hollow fibers to create an inter- fiber space and an extra fiber space. In this bioreactor, the cells can be inoculated in either the inter- fiber or extra- fiber space.

In a further example, U.S. Patent No. 6,670,169 (to Schob et al, entitled "Bioreactor") describes a hollow fiber bioreactor which purportedly mitigates contamination problems arising with other hollow fiber bioreactor systems by using such a bioreactor in connection with either a disposable media pump or an airlift reactor. An additional advantage of hollow fiber bioreactors is the ease by which they may be used to study the interactions and effects of various agents on cells, such as, for example, the pharmacokinetic and pharmacodynamic relationship between a therapeutic agent and the administration thereof. Traditionally, animal models have been used to measuring the effects of therapeutic agents of living tissues and cells, e.g., dosing experiments. Such determinations typically take many years of research and study, in particular where the optimal dosage of a therapeutic agent or drug is sought. Further, animal studies can be problematic because there may be no correlation between the animal model and the effect on humans, or there may be no suitable animal model to begin with. The limitations of animal testing have popularized in- vitro studies, wherein dosing of a therapeutic agent or drug can be tested in an artificial system. For example, an

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antiviral drug can be tested by culturing or simply placing virus-infected cells into an artificial system which simulates human body characteristics. The cells in the artificial system are exposed to a pre-determined concentration-time profiles of the drug during the experiment. The artificial system can be used to measure various effects on the cells and/or virus, such as, for example, expression of certain virus-encoded genes or cell death. Such in vitro studies are advantageous because they provide important pre-clinical data, which can be evaluated before investing the time and expense needed to carry out clinical studies. In-vitro studies can allow a researcher or drug manufacturer to more quickly and economically test a variety of approaches and dosages than would be possible with animal models alone. As a result, some of the more ineffective drugs and/or approaches can be avoided before clinical studies are commenced, which can provide a significant savings in both cost and time to the researcher and drug manufacturer.

Examples of such in vitro systems for evaluating the effects of drugs or therapeutic agents on cells include U.S. Patent Nos. 5,962,317 (to Hamzeh et al., "Dosage modeling system") and 6,287,848 (to Hamzeh et al., "Dosage modeling system"), each of which are incorporated herein by reference. The '317 and '848 patents relate to an in vitro cell perfusion system which allows the study of the pharmacokinetics and pharmacodynamics of therapeutic agents.

The relationship between the dose of a drug given to a patient and the utility of that drug in treating the patient's disease is described by two fundamental areas of pharmacology— pharmacokinetics (PK) and pharmacodynamics (PD). Pharmacokinetics concerns the absorption, distribution, biotransformation (metabolism, if it exists), and the elimination of drugs, i.e., what the body does to the drug. Relevant pharmacokinetic terms include C_max, the peak (maximum) concentration; AUC, the area under the drug concentration-time curve; T_max, the time of peak drug concentration; Cl (clearance rate),

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the measure of the body's ability to eliminate the drug (volume per unit time); volume of distribution, the ratio of the amount of drug in the body to the concentration of the drug in the blood; and C_m1n, the concentration before the next dose is administered.

Pharmacodynamics is the study of the relationship between drug concentration and intensity of pharmacological effect, i.e., what the drug does to the body or target cell.

Relevant pharmacodynamic terms include E_max, the maximum effect, ED₅₀, the dose which produces 50% of the maximum effect, and EC50, the concentration observed at half the maximal effect, or any other possible measurable change in a characteristic or phenotype of the target cell. The '317 and '848 patents purports to relate to a bioreactor designed to simulate various dosage techniques, including parenteral dosing, intravenous dosing, and oral administration. Parameters, including absorption, distribution, and elimination can be simulated and manipulated using the disclosed bioreactor. In particular, the '317 and '848 patents relate to a bioreactor and method of monitoring the effect of therapeutic agents on cells comprising circulating a simulated body fluid along a first circulation loop in fluid communication with a bioreactor including cells and a dosing element capable of passing at least one therapeutic agent into the first circulation loop; passing the therapeutic agent into the first circulation loop and mixing the therapeutic agent with said simulated body fluid; removing a mixture of therapeutic agent and simulated body fluid from the first circulation loop; and monitoring the effect of the therapeutic agent on the cells in the bioreactor.

Despite the developments in hollow fiber bioreactor technologies over the course of the past couple of decades, the present inventors have observed significant problems with currently available bioreactors for applications with protozoan parasites, particularly those commercially available cartridge bioreactors which typically have a polymer shell

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enclosing semi-permeable cellulose or polyvinyl sulfone fibers. The present inventors have observed that such bioreactors do not support their growth, such as, those protozoan parasites that cause malaria (e.g., Plasmodium falciparum, Plasmodium vivax) and African sleeping sickness (e.g, Trypanosoma bruceϊ). Such pathogens are widespread around the world, but especially in tropical and subtropical regions, including parts of the Americas, Asia and Africa. Each year, for example, malaria causes disease in approximately 515 million people, killing between one and three million of them, the majority of whom are young children. Thus, such diseases represent major health and economic concerns to the world and are the focus of major drug development efforts worldwide by organizations such as the World Health Organization (WHO).

In order to progress more rapidly towards identifying effective new therapeutic solutions to treat diseases linked to protozoan parasites, such as malaria and African sleeping sickness, as well as to maximize the effectiveness of existing anti-protozoan drugs and therapeutics, there is an urgent need in the art for in vitro bioreactor systems which can effectively be used in the development and testing of safe and efficacious antiparasitic therapeutics. SUMMARY OF THE INVENTION

The present invention relates to in vitro cell culturing methods and devices which solve the at the above problems and deficiencies of in vitro cell culturing methods and devices known in the art, while providing additional advantages and utilities. In one aspect, the invention relates to a bioreactor for in vitro cell culturing which can advantageously enable the growth of protozoan parasites, such as, for example species of the genera Trypanosoma, Toxoplasma, Leishmania, and Plasmodium, but which can also be utilized to grow any other type of cell, including, for example, cancer cells, virus- infected cells, bacteria, and mycobacteria. The inventive bioreactor advantageously is

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capable of growing a broad array of cell types, but which does not, unlike the prior art, preclude the growth of protozoan parasites. The invention further relates to methods that utilize the bioreactor of the invention to analyze and evaluate the effects of therapeutic agents (e.g., drugs) on cells, such as, for example, the effect of anti-protozoan drugs versus protozoan parasites. In a particular aspect, the present invention relates to a bioreactor device suitable for growth of any cell, including a protozoan parasite, that may be utilized to determine the relationship between pharmacokinetic parameters and a desired pharmacodynamic effect on the cells.

In one embodiment, the present invention provides a bioreactor capable of growing protozoan parasites, having: an elongate chamber comprising an inlet and an outlet; a semi-permeable tubular member connecting the inlet and the outlet whereby an intra- membrane compartment and an extra-membrane compartment are formed in the chamber; and optionally one or more ports; wherein the extra-membrane compartment comprises cells. In one aspect, the inlet and outlet are disposed at the ends of the elongate chamber. The inlet and outlet may also be disposed generally opposite one another along at the ends of the elongate chamber.

The elongate chamber may be any form or shape as long as it can comprise or hold the semi-permeable tubular member. For example, the elongate chamber can be cylindrical, box-like shaped, rectangular-like shaped, bag-like shaped, spherically shaped, and the like. The shape of the chamber and the particular positioning of the inlet, outlet and optional ports may be designed in various configurations such that the chamber is capable of being coupled via necessary tubing and the like (i.e., adapted to fit) to a suitable external fluid circulation system, such as those described in U.S. Patent Nos. 5,962,317 (to Hamzeh et al, "Dosage modeling system"), 6,287,848 (to Hamzeh et al, "Dosage modeling system"), 3,883,393 (to Knazek et al.), 4,220,725 (to Knazek et al.) 4,144,136

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(to Corbeil), 4,391,912 (to Yoshida et al), 5,290,700 (to Binot et al), 5,955,353 (to Amiot), 5,622,857 (to Goffe), 6,001,585 (to Gramer), 4,889,812 (to Guinn et al.), 4,999,298 (to Wolfe et al.), 5,763,261 (to Gruenberg), and 7,270,996 (to Cannon et al.), and U.S. Published Application No. 2004/0029265 (to Doi et al.), each of which are incorporated in their entireties herein by reference. The fluid circulation system preferably is one whereby one or more desired pharmacokinetic parameters can be set such that PK of a particular drug or therapeutic agent can be mimicked.

Such PK parameters can include the maximum concentration (C_max), the area under the drug concentration-time curve (AUC), the time of peak drug concentration (T_mαx), the clearance rate (Cl), the drug elimination rate (volume per unit time), the volume of distribution, the ratio of the amount of drug in the body to the concentration of the drug in the blood; the concentration before the next administered dose (C_mm), the drug half-life (T ₁/₂) or any combination thereof.

The chamber of the inventive bioreactor for enclosing the semi-permeable tubular member may be any material so long as the vessel per se has no toxicity to cells and gives no adverse influences on the cells by denaturation, decomposition, etc. as a result of sterilization, washing or upon its contact with a culture liquid, or similar operation which is necessary when it is used in culture, and can enclose and contain the hollow fibers and the cell substrate. For example, there may be employed any polymeric material such as polycarbonates, polystyrenes, acrylic resins, and polyolefin resins. There may also be employed metallic materials including iron, aluminum, etc., or inorganic materials such as glass and ceramics. Thus, the bioreactor chamber can be glass, polycarbonate, polystyrene, silicone polymer, polysulfone, polyethylene, polyurethane, or any combination thereof. In a preferred embodiment, where the cells are a protozoan parasite, such as, Plasmodium falciparum or Trypanosoma brucei, the chamber is glass.

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Where protozoa are the cells of interest, the cells can be any protozoan parasite, such as, a species of the genus Trypanosoma, Toxoplasma, Leishmania, Plasmodium. The protozoan parasite can be Plasmodium falciparum or Trypanosoma brucei.

The semi-permeable tubular member of the bioreactor can be any material so long it is a hollow fiber or membrane does not have toxicity towards cells and gives no adverse influences on the cells by denaturation, decomposition, etc. upon its contact with a sterilization, washing or culture liquid, or similar operation which is necessary when it is used in a culture and it has the property of a semipermeable membrane such that it is not permeated by a protein-like substance that the cells produce but has permeability to substances having smaller molecular weights than the protein-like substance. Examples of the material include organic materials such as cellulose resins, polyolefins, fluoro resins, polysulfones, polyether sulfones, polycarbonates, and acrylic resins as well as inorganic materials such as ceramics, and dialysis tubing. The material may also include various surface treated membranes such as those treated by a chemical treatment or surface modification as long as it is a hollow fiber that satisfies the above-mentioned properties.

The semi-permeable tubular member can have pores having a molecular weight cut off between about 1 kDa and about 100 kDa and a pore size of about 0.01 micron and about 1 micron. Other pore and MWCO are feasible and disclosed herein.

The bioreactor may also include one or more ports adapted for accessing the extra- membrane compartment. The bioreactor may also be configured to retain a portion of its internal volume for a gas, such as oxygen, carbon dioxide, nitrogen or a mixture thereof, to assist in the aeration of cultures.

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In another embodiment, the invention provides a method of making a bioreactor system for growing cells, the bioreactor comprising: an elongate chamber comprising an inlet and an outlet; dialysis tubing connecting the inlet and the outlet whereby an intra- membrane compartment and an extra-membrane compartment are formed in the chamber; and optionally one or more ports; wherein the method comprises threading the dialysis tubing from the inlet to the outlet, and sealing the ends of the dialysis tubing to the inlet and outlet thereby forming the intra-membrane and extra-membrane compartments. The step of connecting further may be carried out by inverting the ends of the dialysis tubing over the ends of the inlet and outlet to form the intra-membrane compartment, over which tubing may be placed over to connect the cartridge to an external fluid circulation system. In another embodiment, the present invention provides a method of monitoring the effect of at least one therapeutic agent on cells, comprising: growing cells in the extra- membrane compartment of the bioreactor of the invention; contacting the cells with at least one therapeutic agent; measuring an effect of the therapeutic agent on the cells; and determining a result. The step of growing the cells comprises inoculating a cell of interest in growth media contained in the extra-membrane compartment, and continually flowing new growth media through the intra-membrane compartment (e.g. with an external fluid circulation system), thereby replenishing the growth media of the extra-membrane compartment, wherein cell waste is removed by diffusion into the intra-membrane compartment. The cells can include a protozoan parasite, such as, a species of the genera Trypanosoma, Toxoplasma, Leishmania, Plasmodium.

In certain aspects, the therapeutic agent of interest can be a candidate or a known anti-protozoan agent, such as, melarsoprol, quinacrine, metronidazole, tinidazole, furazolidone, paromomycin, amphotericin B, ketoconazole, clotrimazole, propamidine

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isothionate, iodoquinol, diloxanide furoate, dehydroemetine, trimethoprim- sulfamethoxazole (TMP-SMX), or albendazole.

In yet another embodiment, the present invention relates to a method of determining the relationship between a pharmacokinetic parameter of a therapeutic agent and a pharmacodynamic effect of the agent on target cells, comprising: growing the cells in the extra-membrane compartment of the bioreactor of the fluid circulation system of claim 34; contacting the cells with at least one therapeutic agent; adjusting the fluid circulation system to establish one or more pharmacokinetic parameters; measuring at least one pharmacodynamic effect of the agent on target cells; and determining a result. Growing the cells can be carried by inoculating a cell of interest in growth media contained in the extra-membrane compartment, and continually flowing new growth media through the intra-membrane compartment, thereby replenishing the growth media of the extra-membrane compartment, wherein cell waste is removed by diffusion into the intra-membrane compartment. The cells can include a protozoan parasite, such as, a species of the genera

Trypanosoma, Toxoplasma, Leishmania, Plasmodium. In a particular aspect, where the cell is a protozoan parasite, the chamber of the bioreactor is glass, and the semi-permeable tubular member is dialysis tubing, e.g., one or more units of dialysis tubing.

In certain aspects, the therapeutic agent of interest can be a candidate or a known anti-protozoan agent, such as, melarsoprol, quinacrine, metronidazole, tinidazole, furazolidone, paromomycin, amphotericin B, ketoconazole, clotrimazole, propamidine isothionate, iodoquinol, diloxanide furoate, dehydroemetine, trimethoprim- sulfamethoxazole (TMP-SMX), or albendazole.

The pharmacokinetic parameters that are established by adjusting the fluid circulation system can include the peak maximum concentration (C_max), the area under the

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drug concentration-time curve (AUC), the time of peak drug concentration (T_mαx), the clearance rate (Cl), the drug elimination rate (volume per unit time), the volume of distribution, the ratio of the amount of drug in the body to the concentration of the drug in the blood; the concentration before the next administered dose (C_mm), the drug half-life (T ₁/₂) or any combination thereof.

The pharmacodynamic parameter to be measured can be the maximum effect of the agent (E_mαx), the dose which produces 50% of the maximum effect (ED₅₀), the concentration observed at half the maximal effect (EC50), the level of growth, the level of cell death, the change in the expression of a gene, the change in the level of a metabolic product of the cell or of the drug itself, or any combination thereof.

Other aspects of the invention are described in the following disclosure, and are within the ambit of the invention. BRIEF DESCRIPTION OF THE FIGURES

The following Detailed Description, given by way of example, but not intended to limit the invention to specific embodiments described, may be understood in conjunction with the accompanying drawings, incorporated herein by reference. Various preferred features and embodiments of the present invention will now be described by way of non- limiting example and with reference to the accompanying drawings in which:

Figure 1 schematically depicts various views of a first and second embodiment of the cartridge or shell of the bioreactor of the invention. Figure l(a) depicts a top view of both the first 100 and second 200 embodiment. Figure l(b) depicts a side view of the first embodiment 100. Figure l(c) depicts the end view of the first embodiment 100. Figure l(d) depicts a side view of the second embodiment 200. Figure l(e) depicts an end view of the second embodiment 200.

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Figure 2 schematically depicts a side cross-sectional view of bioreactor 300, including inlet 301, outlet 302, ports 303, 303', cartridge or shell 304, and a semipermeable tubular member 305, which is shown as connecting the inlet 301 and outlet 302 by folding over the ends of the semi-permeable tubular member over the ends of the inlet and outlet at 306.

Figure 3 schematically depicts various views of third and fourth embodiments of the cartridge or shell of the bioreactor of the invention. Figure 3 (a) depicts a top view of a first embodiment 400 or a second embodiment 500. Figure 3(b) depicts a side view of the first embodiment 400. Figure 3(c) depicts the end view of the first embodiment 400. Figure 3(d) depicts a side view of the second embodiment 500. Figure 3(e) depicts an end view of the second embodiment 500. Collars are represented by 407 and 407', which assist in retaining tubing connected thereto.

Figure 4 schematically depicts a side cross-sectional view of bioreactor 600, including inlet 601, outlet 602, ports 603, 603', cartridge or shell 604, and dialysis tubing 605, which is shown at 606 as being connected to the inlet 601 and outlet 602 by folding over the ends of the dialysis tube over the ends of the inlet and outlet. Collars are represented by 607 and 607', which assist in retaining tubing connected thereto.

Figure 5 provides two photographs showing the operation of an embodiment of the inventive bioreactor for growing (a) Trypanosoma and (b) Plasmodium. The arrow in (a) points to a visible dialysis tubing connecting an inlet and an outlet at the ends of the cartridge shell.

Figure 6 shows the growth of (a) Plasmodium falciparum malaria parasites and (b) Trypanosoma brucei (African trypanosomes) in tissue culture flasks (- ♦ -), a bioreactor of the invention (glass) (-■-) and commercial bioreactor (-A-). Flow rate through the primary loop of the system was maintained at 40 ml/min. The dialysis tubing of the

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bioreactor was treated by boiling in 0.5% NaHCCh for 10 min and then flush thoroughly with water.

Figure 7 shows growth of Plasmodium falciparum malaria parasites in a tissue culture flask (- ♦ -), the glass cartridge (untreated dialysis tubing) (-■-). Figure 8 shows growth of Plasmodium falciparum malaria parasites in a tissue culture flask (- ♦ -), a bioreactor of the invention (glass) (treated dialysis tubing) (-■-) for multiple growth cycles.

Figure 9 shows simulated PK profiles in a bioreactor cartridge of the invention in the treatment of a protozoan parasite with melarsoprol in accordance with melarsoprol. Total AUC is 1.68 μM-hour. Bolus (— -) regimen C_max = 0.247 μM. Infusion (— ) C = 0.07 μM. MIC = 0.03 μM. See Example 1 for further details.

Figure 10 shows parasite killing efficiency of different dosing regimens of melarsoprol. DETAILED DESCRIPTION OF THE INVENTION The present inventors have observed that commercially available hollow fiber bioreactors and those previously known in the art are toxic to protozoan parasites and do not support their growth, and thus, are not feasible for studying the effects of therapeutic agents on protozoan parasites, including especially determining the relationship between pharmacokinetic parameters and a desired pharmacodynamic effect on the cells, i.e., the pharmacokinetic -pharmacodynamic (PK-PD) relationship of a drug to a target cell. Thus, the present invention relates to a bioreactor for in vitro cell culturing of cells, including protozoan parasites (e.g., species of the genera Trypanosoma, Toxoplasma, Leishmania, and Plasmodium), and which can be utilized in methods to analyze and evaluate the effects of therapeutic agents (e.g., drugs) on cells, such as, for example, the effect of anti- protozoan drugs versus protozoan parasites. In a particular aspect, the present invention

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relates to a bioreactor device suitable for growth of any cell, including a protozoan parasite, that may be utilized to determine the pharmacokinetic -pharmacodynamic (PK- PD) relationship of a drug to a target cell. Definitions The term "external fluid circulating system," as used here, refers to any system sufficient to continuously supply nutrient medium to the intra-capillary space of a bioreactor of the invention. In addition, such a systems should continuously remove stale medium from extra-capillary space. In one embodiment, for example, Figure 11 depicts a bioreactor of the invention coupled to an external fluid circulating system that comprises a central reservoir, which circulates fresh fluid to the bioreactor and receives spent fluid from the bioreactor. The central reservoir may itself be replenished with fresh media obtained via an input, e.g., from an input reservoir, and expelling spent media through an output, e.g., to an output reservoir. Any known external fluid circulating system can be used in connection with the bioreactor of the invention, e.g., those systems described in U.S. Patent Nos. 3,883,393 (to Knazek et al), 4,220,725 (to Knazek et al.) 4,144,136 (to Corbeil), 4,391,912 (to Yoshida et al.), 5,290,700 (to Binot et al.), 5,955,353 (to Amiot), 6,287,848 (to Hamzeh et al.), 5,962,317 (to Hamzeh et al.), 5,622,857 (to Goffe), and 6,001,585 (to Gramer), each of which are incorporated herein by reference. The term "intra-capillary space" ("ICS"), which can be used herein interchangeably with the terms "intra-membrane space" or "intra-fiber space," refers to space defined by a lumen of a semi-permeable tubular member of the invention, e.g., the lumen of a dialysis tube.

The term "extra-capillary space" ("ECS"), which can be used herein interchangeably with the terms "extra-membrane space" or "extra-fiber space," refers to the space within a bioreactor chamber not occupied by the intra-membrane space.

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The term "bioreactor," which can be used interchangeably with synonymous terms, including "hollow fiber bioreactor," "hollow fiber perfusion bioreactor," "in vitro cell culture bioreactor," and "shell-and-tube type bioreactor," include a semi-permeable tubular member forming one or more channels through a hollow shell forming intra- fiber and extra-fiber compartments or space.

The term "obtaining" as in "obtaining" the "photosensitizer composition," "linker" or "binder," is intended to include purchasing, synthesizing or otherwise acquiring the elements of the invention.

In this disclosure, "comprises," "comprising," "containing" and "having" and the like can have the meaning ascribed to them in U.S. Patent law and can mean " includes," "including," and the like; "consisting essentially of or "consists essentially" likewise has the meaning ascribed in U.S. Patent law and the term is open-ended, allowing for the presence of more than that which is recited so long as basic or novel characteristics of that which is recited is not changed by the presence of more than that which is recited, but excludes prior art embodiments.

Other definitions appear in context throughout this disclosure. Bioreactor

In one aspect, the present invention relates to a bioreactor for growing and culturing cells, in particular, protozoan parasites, in an in vitro environment. While the bioreactor of the invention is not meant to be limited to a certain type of cell, the inventive bioreactor is particularly suitable for growing protozoan parasites, which prior to the present invention, were unable to be grown effectively in commercially bioreactors. The bioreactor comprises a shell having an inlet, an outlet, and optional sampling ports, wherein the shell encloses a semi-permeable tubular member joining the inlet and outlet through the interior of the shell thereby forming an intra-membrane compartment and an

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extra-membrane compartment. In a preferred embodiment, the shell is glass and the semipermeable tubular member is dialysis tubing. Growth media is added to the extra- membrane compartment and is inoculated with cells of interest. The bioreactor can be coupled to an external fluid circulating system for the continual flow and circulation of fresh growth medium through the intra-membrane compartment. The semi-permeable tubular member preferably allows (a) nutrients and/or (b) any metabolizing gases to pass from the cell-culture media of the intra-membrane compartment through the walls of the semi-permeable tubular member to the cells contained in the extra-membrane compartment. In addition, (c) cell waste products and (4) gaseous waste products may pass from the extra-membrane space through the walls of the semi-permeable tubular member to the circulating cell-culture medium, while retaining the cells and any large secreted products within the extra-membrane compartment. Cells and/or their products may be sampled through ports leading to the extra-membrane space.

This portion of the specification now describes, by reference to the Figures, the bioreactor of the present invention. The bioreactor of the invention, however, should be not be construed as being limited to the embodiments depicted in the Figures.

Referring to Figure 1, several embodiments of the cartridge or shell of the bioreactor of the invention are depicted. Figure l(a) depicts a top view of both a first 100 and second 200 embodiment of the bioreactor shell. Inlet 101 and outlet 102 are shown as being generally longitudinally opposed. The inlet 101 and outlet 102 may be connected by tubing to an external fluid circulating system to allow for the continual flow and circulation of fresh growth medium through the intra-membrane compartment formed when a semi-permeable tubular member (not shown) is used to connect the inlet and outlet through the interior of the shell. Shell 105 is shown as having a generally longitudinal

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configuration, however, any suitable shape (e.g., elongate, elliptical, spherical, etc.) may be utilized.

No particular limitation is placed on the materials that can be used to form the shell of the bioreactor. Preferably, the material does not harm or is not toxic to the cells of the bioreactor. Examples of such materials include glass, polycarbonate, polystyrene, silicone polymer, polysulfone, polyethylene, polyurethane, etc. For supplying sufficient amounts of oxygen to proliferating cells, materials having excellent gas permeability may be used, such as a thin silicone polymer film or tube, a thin silicone polymer film reinforced by a polyester mesh, a thin polybutadiene film or tube, a thin silicone-polycarbonate copolymer film or tube, a porous teflon film, a porous polypropylene film, etc., the thickness of which can be from 0.01 mm to 3 mm, 0.05 mm to 5 mm, or 1.0 to 10 mm, or any other suitable thickness. In embodiments where the bioreactor is used to grow protozoan parasites, such as, for example, species of Trypanosoma, Toxoplasma, Leishmania, Plasmodium, the shell is preferably glass. The shell of Figure l(a) also shows optional ports 103 and 103', which can be incorporated into the body the shell 105 to enable the sampling of cells, media and/or cell products, the testing of various characteristics of the media (e.g., pH), or the adding of additional growth supplements and nutrients to the extra-membrane compartment, such as, for example, larger molecular weight materials which do not pass through the semi- permeable tubular member of the bioreactor. One or more ports 103/103' may be employed and may be configured in any suitable position or orientation with respect to the general shape of the shell 105. Such design alterations can be made without undue experimentation.

Figure l(b) depicts a side view of the first embodiment 100. The inlet 101 and outlet 102 are generally longitudinally opposed and positioned generally along the

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longitudinal axis of the shell 105, however, other configurations are possible, such as longitudinally offset inlets and outlets, or Figure l(c) depicts the end view of the first embodiment 100. Figure l(d) depicts a side view of the second embodiment 200, which is configured to have the inlet 101 and outlet 102 position generally below the longitudinal axis of the shell 105 to allow head room at the top of the shell 105 for holding gas (e.g., oxygen, nitrogen, carbon dioxide, or some combination thereof). Figure l(e) depicts an end view of the second embodiment 200. The numbers referring to distance aspects of the various features are meant to be in millimeters. For example, inlet 101 and outlet 102 are indicated as having a 5 mm diameter. Figure 2 schematically depicts a side cross-sectional view of bioreactor 300, including inlet 301, outlet 302, ports 303, 303', cartridge or shell 304, and a semipermeable tubular member 305, which is shown as connecting the inlet 301 and outlet 302 by folding over the ends of the semi-permeable tubular member over the ends of the inlet and outlet at 306. The semi-permeable tubular members may be made of any semi-permeable substance which preferably exerts no adverse influences on the cells of the bioreactor. Suitable examples of such substances include, but are not limited to, polysulfone, polyether sulfone, polyacrylonitrile, cellulose acetate, polycarbonate, polymethyl methacrylate, cuprammonium cellulose and the like. Where the bioreactor is utilized for growing protozoan parasites, such as, for example, Trypanosoma, Toxoplasma, Leishmania, Plasmodium, the semi-permeable tubular member is dialysis tubing.

Generally, the semi-permeable tubular members can be any porous tube or fiber that is capable of being integrated into the bioreactor of the invention, while enabling perfusion of nutrient media to cells growing in the extra-membrane space. The following are examples of tubes or fibers that can be used in this invention:

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(i) hollow fibers and tubes with dialysis, ultrafiltration and microfiltration properties, i.e., (a) molecular weight cutoff (MWCO) ranging from about 1 kD to 1,000 kD; and (b) pore size ranging from 0.01 μm to 5.0 μm, more preferably from about 1 kDa to about 100 kDa and a pore size of about 0.01 μm to about 1 μm; (ii) Materials of construction include polymers, graphite, and ceramics (including porous glass fiber). Typically, polymers are preferred to have good physical properties (e.g., tensile strength, melt temperature and glass transition temperature). These include cellulose, polyethylene, polypropylene, polysulfone (and other engineering thermoplastics), polymethyl methacrylate, polyacrylonitrile, various polymer blends and the like.

Dialysis tubing is well known to the skilled artisan and can be obtained from any commercial source, e.g., Spectra/Por® Dialysis Tubing by Spectrum® Laboratories Inc. Spectra/Por® dialysis tubing is made of either regenerated cellulose (RC) or cellulose ester (CE). Cellulose has long been used for dialysis as it is uncharged and does not readily absorb solutes. Further, the selectivity of cellulose membranes is not altered greatly by many chemicals or reasonable pH and temperature ranges. Processed cellulose has crystalline regions and these regions cross-link chains to introduce structural integrity to the cellulose. Depending upon how the cellulose is processed the number of crystalline areas varies and the resultant regions between the cross-links can act like size-selective pores.

The bioreactor of the invention can function with any dialysis tubing having pores with any molecular weight cut off (MWCO), e.g., those pores having a molecular weight cut off between about 1 kDa and about 100 kDa or a pore size of about 0.01 micron and about 1 micron. Many dialysis membranes are available with molecular weight cut offs from as little as 0.1 kDa all the way up to 300 kDa (e.g., Spectra/Por® CE membranes

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come in 0.1, 0.5, 1, 10, 100 and 300 kDa MWCOs, basic Spectra/Por® RC membranes come in 3.5, 6-8 and 12-14 kDa MWCOs and more expensive Spectra/Por® RC membranes have a range of MWCOs from 1-50 kDa). MWCO values are established by dialysis tubing manufacturer and typically represent the size at which a solute is at least 80%, more preferably at least about 85% to 90 %, more preferably still at least about 90% to about 95% or even 99% retained during dialysis. Certain parameters such as pH may however alter MWCOs and thus appropriate tubing needs to be established for a particular situation.

Figure 3 schematically depicts various views of additional embodiments of the cartridge or shell of the bioreactor of the invention. Figure 3 (a) depicts a top view of a first embodiment 400 or a second embodiment 500. Figure 3(b) depicts a side view of the first embodiment 400. Figure 3(c) depicts the end view of the first embodiment 400. Figure 3(d) depicts a side view of the second embodiment 500. Figure 3(e) depicts an end view of the second embodiment 500. Collars are represented by 407 and 407', which assist in retaining tubing connected thereto. Like numbers between the figures are meant to refer to a corresponding feature. The numbers referring to distance aspects of the various features are meant to be in millimeters. For example, inlet 401 and outlet 402 are indicated as having a 5 mm diameter. The embodiments of Figure 3 are meant to be depicted with the same features as the embodiments of Figure 1, except that the collars 407 and 407' are added to the ends of the ports 403 and 403' and to the ends of the inlet 401 and outlet 402. The collars can be any means suitable to allow the attachment of an external fluid circulating system without the need for any retaining devices to secure the associated tubing.

Figure 4 schematically depicts a side cross-sectional view of bioreactor 600, including inlet 601, outlet 602, ports 603, 603', cartridge or shell 604, and a semi-

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permeable tubular member 605 (e.g., dialysis tubing), which is shown at 606 as being connected to the inlet 601 and outlet 602 by folding over the ends of the semi-permeable tubular member over the ends of the inlet and outlet. Collars are represented by 607 and 607'. Figure 5 provides two photographs showing the operation of an embodiment of the inventive bioreactor for growing (a) Trypanosoma and (b) Plasmodium. The arrow in (a) points to a visible dialysis tubing connecting an inlet and an outlet at the ends of the cartridge shell. The tubing shown connected to the inlet and outlet are in turn connected to an external fluid circulating system. The ports are also connected to associated tubing to assist in sampling and/or keeping contamination out of the system during sampling.

The bioreactor of the invention can be utilized to grow essentially any suitable organism or cell. Cells that can be grown in the bioreactor of the invention include, for example, bacterial or eukaryotic cells, including protozoan cells, yeast cells, or cells derive directly from tissues or organs or cells derived from descendants thereof, cells from various cells lines. Any the cells of the invention may be genetically engineered to impart new and/or different physical characteristics to the cells or to cause the expression of innate or foreign genes and proteins, e.g., inclusion of expression vectors encoding particular proteins of interest. In a particular embodiment, the bioreactor of invention is suitable for the growth of protozoan cells, e.g. protozoan parasites, such as, for example, any species or isolate of the genera Trypanosoma (e.g., Trypanosoma brucei, the causative agent of African sleeping sickness), Toxoplasma, Leishmania, Plasmodium (e.g., Plasmodium falciparum, the causative agent of malaria), Giardia, Naegleria, Acanthamoeba, Entamoeba, Cryptosporidium, Cyclospora, and Isospora. In a particular embodiment suitable for the growth of protozoan parasites, the bioreactor comprises a glass shell and dialysis tubing as the semi-permeable tubular member.

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In another aspect, the bioreactor of the invention can include microcarriers for enhancing the growth of cells, in particular, adherent type cells. Microcarriers are small spheres with surfaces designed to achieve high yield monolayers of anchorage-dependent (or adherent) cells in culture. Microcarriers are usually suspended in culture media by gentle stirring. In the present invention, microcarriers may be employed in the extracapillary space to increase surface area for the growth of adherent type cells. Six characteristics contribute to the optimum microcarrier: (1) suitable surface properties for cell attachment, spreading growth, and (for certain applications) genetic transformation; (2) density only slightly greater than the surrounding media (i.e., 1.030-1.045 g/mL); (3) narrow size distribution within the range of 100-230 μm diameter; (4) optical clarity for observing cell behavior; (5) non-toxic; and (6) some degree of compressibility to minimize cell damage when particles collide. Microcarriers may be categorized into four groups by their surface properties and applications: (a) cationic functional group microcarriers (e.g., microcarriers coupled to cationic amino acids or lipids), (b) neutral functional group microcarriers, (c) anionic functional group microcarriers (e.g., microcarriers coupled with nucleic acids), and (d) microcarriers coated with extracellular matrix materials (e.g., collagen, fibronectin, vitronectin, laminin, and proteoglycans).

For conventional microcarrier suspension cell culture applications, the Poisson distribution equation: P = (e ^λ λ") I n is used to determine the proportion (P) of microcarriers carrying a specific number of cells (n)at various cell/microcarrier ratios (λ). The critical cell-to-microcarrier inoculation ratio necessary to obtain a negligible proportion of empty microcarriers in culture is calculated. An inoculation ratio of >7 ensures that <5% of microcarriers are unoccupied, and maximizes the use of available surface area. Inoculation ratios when microcarriers are employed in the HPBr can range from 7 to several hundred depending on the specific application. The highest inoculation

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STM 246258 1 Attorney Docket No. 81248WO(71699)

ratios are used for very high density cell culture applications (e.g., bioartificial liver device). For gene transfection of adherent cells the inoculation ratio would be markedly lower.

In operation, the bioreactor of the invention can be coupled to an external fluid circulating system. In one embodiment, for example, Figure 11 depicts a bioreactor of the invention coupled to an external fluid circulating system that comprises a central reservoir, which circulates fresh fluid to the bioreactor and receives spent fluid from the bioreactor. The central reservoir may itself be replenished with fresh media obtained via an input, e.g., from an input reservoir, and expelling spent media through an output, e.g., to an output reservoir. Any known external fluid circulating system can be used in connection with the bioreactor of the invention, e.g., those systems described in U.S. Patent Nos. 3,883,393 (to Knazek et al.), 4,220,725 (to Knazek et al.) 4,144,136 (to Corbeil), 4,391,912 (to Yoshida et al.), 5,290,700 (to Binot et al.), 5,955,353 (to Amiot), 6,287,848 (to Hamzeh et al.), 5,962,317 (to Hamzeh et al.), 5,622,857 (to Goffe), and 6,001,585 (to Gramer), each of which are incorporated herein by reference.

Generally, the bioreactor of the present invention, when coupled with a suitable external fluid circulating system, can be used to grow cells, e.g., protozoan parasites, and monitor their growth by sampling the media and/or cells from the extra-membrane compartment and measuring or characterizing the cell growth base on various factors, such as, pH, metabolite composition, protein expression, gene expression, presence of extracellular expression products (e.g., certain enzymes etc.) and observable physical cell features or phenotypes (e.g., motility for certain protozoan parasites).

In another aspect, the bioreactor of the present invention, when coupled with a suitable external fluid circulating system, can be used to test and monitor the effect of therapeutic agents, compounds, drugs, or other test compounds on the cells grown in a

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bioreactor, such as, growth inhibition, cell death, gene and protein expression, or observable physical phenotypes or characteristics.

In a particularly preferred aspect, the bioreactor of the invention is used to study and determine the relationship between various pharmacokinetic parameters and a desired pharmacodynamic effect on cells of interest, i.e., the pharmacokinetic -pharmacodynamic ("PK-PD") relationship of a drug to a target cell. Preferably, the bioreactor of the invention should be coupled to an external fluid circulating system which is capable of incorporating one or more therapeutic agents of interest and is capable of being set or adjusted to mimic desirable pharmacokinetic parameters. Pharmacokinetics concerns the absorption, distribution, biotransformation (metabolism, if it exists), and the elimination of drugs, i.e., what the body does to the drug. Relevant pharmacokinetic terms include Cπmx, the peak (maximum) concentration; AUC, the area under the drug concentration-time curve; T_max, the time of peak drug concentration; Cl (clearance rate), the measure of the body's ability to eliminate the drug (volume per unit time); volume of distribution, the ratio of the amount of drug in the body to the concentration of the drug in the blood; T ₁/₂, drug half-life and C_mn, the concentration before the next dose is administered.

Once the target cells of the bioreactor are exposed to one or more therapeutic agents or drugs under a particular set of pharmacokinetic parameters, pharmacodynamic parameters can be determined. Pharmacodynamics is the study of the relationship between drug concentration and intensity of pharmacological effect, i.e., what the drug does to a target cell. Relevant pharmacodynamic parameters include essentially any characteristic or phenotype of a cell or the surrounding medium which can be assayed, e.g., growth, death, change in expression of a gene or protein, induced or reduced expression of a protein, marker, or enzymatic activity, appearance or disappearance of a metabolic product or intermediate product. More traditional pharmacodynamic

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STM 246258 1 Attorney Docket No. 81248WO(71699)

parameters that could be determined could include E_max, the maximum effect, ED50, the dose which produces 50% of the maximum effect, and EC50, the concentration observed at half the maximal effect. Cells and medium from the extra-membrane compartment of the bioreactor can be directly sample via one or more ports. Methods and techniques for measuring the above pharmacodynamic parameters will depend entirely on which parameters are sought, the particular cells of interest, the drug or therapeutic agent of interest, etc. One of ordinary skill in the art will be able to measure and/or determine such parameters without undue experimentation as such methods are conventional in the art. The bioreactor of the invention is thus useful in determining the relationship between pharmacokinetic parameters (which can be set using the system) and desired pharmacodynamic parameters with respect to a particular drug or agent and a particular target cell, thus enabling a method to determine a dosing regimen to best achieve a desired pharmacodynamic effect on the target cell of interest, e.g., a protozoan parasite.

Examples of external fluid circulating systems which can be used in connection with the bioreactor of the invention for which various pharmacokinetic parameters can be adjusted include, U.S. Patent Nos. 5,962,317 (to Hamzeh et al., "Dosage modeling system"), 6,287,848 (to Hamzeh et al., "Dosage modeling system"), 3,883,393 (to Knazek et al.), 4,220,725 (to Knazek et al.) 4,144,136 (to Corbeil), 4,391,912 (to Yoshida et al.), 5,290,700 (to Binot et al.), 5,955,353 (to Amiot), 5,622,857 (to Goffe), 6,001,585 (to Gramer), 4,889,812 (to Guinn et al.), 4,999,298 (to Wolfe et al.), 5,763,261 (to

Gruenberg), and 7,270,996 (to Cannon et al.), and U.S. Published Application No. 2004/0029265 (to Doi et al.), each of which are incorporated in their entireties herein by reference. In each case, the bioreactor of the present invention can be modified without undue experimentation to be used in conjunction with the above systems.

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STM 246258 1 Attorney Docket No. 81248WO(71699)

In a particular example, the '317 patent describes an in vitro cell perfusion system in which both the concentration of one or more therapeutic agents (e.g., drugs and/or drug candidates), and the rate of elimination of the agent(s) can be manipulated and monitored in order to mimic first order human pharmacokinetics. The bioreactor of the present invention can be utilized with the perfusion system (e.g. an embodiment shown in Fig. 2 of the '317 patent) by substituting bioreactor 270 of Fig. 2 with the bioreactor of the present invention.

In such a format, using the fluid circulation system or perfusion systems of the '317 patent or other conventional or commercially available fluid circulation system (e.g., FiberCell Systems, Inc.), the bioreactor of the invention can be used to study pharmacokinetics and pharmacodynamics of therapeutic agents such as, but not limited to, antiviral agents, antimicrobial agents (e.g., antibiotics), antineoplastic agents, antiarrhythmic drugs, cardiovascular drugs (e.g., antihypertensive drugs), antiinflammatory agents, immunosuppressive agents, immunostimulatory drugs, drugs used in the test of hyperlipoproteinemias, and asthma, drugs acting on the central nervous system (CNS), hormones, hormone antagonists, vitamins, hematopoietic agents, anticoagulants, anti-parasitic agents (i.e., anti-protozoan parasitic agents, e.g., melarsoprol), thrombolytic and antiplatelet drugs. In a preferred embodiment, the bioreactor of the invention is used with the perfusion or fluid circulation system of the '317 patent or other conventional or commercially available system to grow protozoan parasites (e.g., Plasmodium falciparum or Trypanosoma bruceϊ) and to determine the relationship between pharmacokinetics and pharmacodynamics of therapeutic agents in order to optimize dosing regimens.

Anti-protozoan agents that could be tested include, but are not limited to, melarsoprol, quinacrine, metronidazole, tinidazole, furazolidone, paromomycin,

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amphotericin B, ketoconazole, clotrimazole, propamidine isothionate, iodoquinol, diloxanide furoate, dehydroemetine, trimethoprim-sulfamethoxazole (TMP-SMX), and albendazole.

Depending on the cell and drug/therapeutic agent of interest and the particular pharmacokinetic parameters used, e.g., a protozoan parasite and melarsoprol, the present invention allows one to measure various pharmacodynamic parameters, in a time- dependent fashion, including the expression of pathogen and/or cellular products, e.g., DNA, RNA (mRNA), and other products. In this system, one has access to the target cells where the drug/agent will produce its effect, so one can measure pathogen and/or cellular DNA, RNA, and proteins, such as core proteins, receptors, antigens (e.g., autoantigens, alloantigens, heteroantigens), antibodies, and enzymes. In particular, where virus-infected cells are targeted, such as HIV-infected cells, viruses like HIV encode for particular enzymes such as reverse transcriptase, and integrase. HIV viral genes and their gene products, for example, such as env (gpl60, gpl20, gp41), pol (p66, p51, p31), gag (p55, p24, p 17), tat (pi 4), and rev (p20), can be measured and monitored. Inhibition of the production of critical genes and proteins by new drugs is desired in the case of virus- infected cells to prevent the formation of, for example, mature core proteins and virions. Other examples include the measurement of antigens such as autoimmune and tumor associated antigens. Autoantigens are associated with diseases (autoimmune thyroiditis, myasthenia gravis, arthritis, lupus). Cell surface tumor associated antigens (TAA) have been associated with RNA and DNA viruses. Viral antigens have been associated with the following cancer types: nasopharyngeal carcinoma (EBV), cervical carcinoma (human papilloma virus), hepatocellular carcinoma (hepatitis B virus), T cell leukemia and lymphomas (human T-lymphotropic virus). Normal cellular antigens may also be tested.

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For example, measuring prostate-specific antigen (PSA) levels in prostatic cancer and CA 125 levels in patients with ovarian cancer may be valuable as new drugs are tested.

The present invention is additionally described by way of the following illustrative, non-limiting Examples that provide a better understanding of the present invention and of its many advantages. EXAMPLES

Example 1. Determining the pharmacokinetic-pharmacodynamic relationship of melarsoprol, an antitrypanosomal drug Introduction African sleeping sickness, a deadly disease caused by the protozoan parasite

Trypanosoma brucei, is fatal if not treated. The toxic organoarsenical melarsoprol is the only drug that can cure all forms of human disease. Current treatment strategies require extended dosing regimens that have been designed without any analysis of the pharmacokinetic -pharmacodynamic (PK-PD) relationship of the drug. This Example describes the an in vitro PK-PD determination system that supports the growth of

Trypanosoma brucei. Elucidation of the PK-PD relationship of melarsoprol reveals that Cπ_mx is the primary determinant of melarsoprol' s effect. The implications of this finding for optimizing dosing are discussed. The PK-PD system will allow testing of candidate antitrypanosomal compounds early in the development process and facilitate the discovery of new drugs for sleeping sickness.

African sleeping sickness, caused by the parasitic protozoan Trypanosoma brucei, and transmitted by the tsetse fly, is widely prevalent in sub-Saharan Africa. The disease progresses in two stages, with the parasites invading the cerebrospinal compartment of the patient in the late stage and causing the classic symptoms of sleeping sickness. There are two forms of the disease, caused by T. brucei gambiense and T. brucei rhodesiense, which

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differ in temporal progression; both forms are lethal if left untreated. Only one drug -the organoarsenical melarsoprol-can treat late-stage sleeping sickness caused by both T. b. gambiense and T. b. rhodesiense.

Melarsoprol is an antiquated drug that is difficult to handle, administer and is highly toxic. Drug-related encephalopathies kill 5-10% of patients. The oldest dosing regimen in use consists of 3-4 sets of 3-4 graded daily doses (1.8 mg/kg through 3.6 mg/kg), administered at weekly intervals. Recently, a 10-day course of constant daily doses (2.16 mg/kg) has been approved (5, 14). A third regimen, comprising 3 sets of 3 fixed daily doses (3.6 mg/kg) administered at weekly intervals (13), has also been tested. Interestingly, all three regimens yield similar efficacy and toxicity. The scenario of near- identical results obtained through widely differing dosing regimens suggests that melarsoprol dosing strategies may benefit from further rational modification.

It is an established fact that the pharmacokinetics (PK) of an administered drug, such as total exposure (AUC- Area Under the concentration-time curve), Cπ_mx (maximum drug concentration achieved), and T_MIC (Time above Minimum Inhibitory Concentration) can significantly influence drug pharmacodynamics (PD). Knowledge of the PK-PD relationship can facilitate many stages of drug development including the designing of preclinical efficacy and toxicity studies and defining dosing regimens for human phase I/II trials. While there has been much study of the PK properties of melarsoprol in vitro

(Burri, 1993) and in vivo (Burri, 2001; Burri, 1994) a formal PK-PD analysis has never been reported. All dosage modeling and optimization has been based on the initial empirically determined graded regimen. The complexity of human sleeping sickness coupled with the lack of good animal models necessitates the construction of an in vitro system, such as that of the present invention, wherein dose effect relationships between the

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drug and the parasite can be studied in a simplified setting. The present invention in its various embodiments provides an in vitro PK-PD modeling system for parasites, like African trypanosomes, and enables the analysis of the PK-PD relationship of antiparasitic drugs versus a target organisms, e.g., melarsoprol versus T. brucei. This Example demonstrates that C_max is the leading parameter influencing trypanosome killing by melarsoprol and discuss the clinical implications of this finding. Methods and Materials Cells, media and drugs

Trypanosoma brucei brucei strain 427 blood stream form cells were cultured in HMI-9 with 10% fetal bovine serum (Invitrogen, USA), 10% Serum Plus (JRH

Biosciences, USA) (7) and IX Pen-Strep (Invitrogen, USA). Cells were cultured at 37 ⁰C in 5% CO2. Melarsoprol (Arsobal, 3.6 % w/v in propylene glycol) was obtained from the Centers for Disease Control, Atlanta, GA. Cell number was monitored by counting motile trypanosomes in a haemocytometer. In vitro PK-PD system

In this Example, a bioreactor (or "cartridge" or "cartridge bioreactor") comprising a glass shell (7 cm length, 2 cm outer diameter; Adams and Chittenden Scientific Glass, CA, USA) was divided into the intra-capillary space ("ICS") and extra-capillary space ("ECS") by threading dialysis tubing through the glass shell (50 kDa molecular weight cutoff; Spectrapor 7, Spectrum Laboratories, USA). Dialysis tubing was boiled for 10 min in 0.5% NaHCθ3 and washed extensively with distilled water prior to use. Cartridges were assembled and sterilized by autoclaving (121 ⁰C, 20 min, liquid cycle) and used within a few hours of preparation. Trypanosomes were inoculated in the ECS while continually fresh media (and drug) was circulated through the ICS. Media in the ECS and ICS are in contact only across the dialysis tubing. The volume of the ECS was 12.5 mL

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STM 246258 1 Attorney Docket No. 81248WO(71699)

while the total volume of the primary circuit (ECS + ICS + medium reservoir and tubing) was 47.5 mL. Drug was dosed into the medium reservoir and entered the cell-containing ECS via diffusion through the dialysis tubing. Manipulating drug concentrations in the primary circuit results in the cells in the ECS being exposed to desired PK profiles. Determination of drug sensitivity

Melarsoprol sensitivity was determined using an acid-phosphatase based colorimetric micro titer-plate assay (Burri, 1993), with a starting cell concentration of 2 X 10⁵ cells/mL. The antitrypanosomal activity of melarsoprol in the cartridge was assessed by harvesting ECS contents and counting motile trypanosomes. The Minimal Inhibitory Concentration (MIC) of melarsoprol in the PK-PD system was defined as the drug concentration capable of achieving a 20% kill (in the PK-PD system) when administered as an infusion for 24 h and was determined to be 0.03 μM. Micro titer plate assays established that propylene glycol had no effect on trypanosome growth; the cartridge experiments were run with only a medium control. Validation of programmed PK profile

All experiments were conducted for 24 h. Half-life and clearance were set at 4.8 h and 6.9 ml/h respectively. Under these parameters, 97% of the bolus melarsoprol dose is expected to be cleared in 24 h. Programmed PK profiles were validated by running the experiment in cell- free cartridges, sampling the ECS and ICS at 0, 2, 4, 6, 8, and 10 hours post-dose, and assaying trypanocidal activity in the 96-well plate cytotoxicity assay. Melarsoprol concentration in the samples was calculated using a standard melarsoprol concentration curve on the same plate. Results Construction and testing of in vitro PKJPD system

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This Example utilized an in vitro bioreactor system in accordance with the invention to identify the PK parameter exerting the maximum influence on melarsoprol PD, i.e., trypanosomal killing. Various versions of in vitro PK-PD systems have been constructed and utilized to elucidate dose-effect relationships for anti-viral (Drusano, 2001; Moore, 1994) and anti-bacterial agents (Deziel, 2005) (each of which are incorporated herein in their entireties by reference). This Example such PK-PD systems to study PK-PD relationships of antitrypanosomal drugs using a bioreactor of the present invention. The present inventors have observed that trypanosomes do not proliferate in commercially available cartridges made of polycarbonate shells and polyvinylsulfone fibers. The present invention in one embodiment utilizes a fabricated a cartridge shell made of glass and divided it into the ECS and ICS compartments using dialysis tubing. Trypanosomes proliferated in the cartridge at the same rate as in a flask, increasing more than 10-fold in 24 h, and growth was linear till a cell density of 5 X 10⁶ cells/mL ECS (data not shown). Subsequently, experiments were performed at starting densities of 2 X 10⁵/mL ECS; cell densities at the end of the run did not exceed 5 X 10⁶ cells/mL ECS. Growth in the glass cartridge also did not affect the sensitivity of the trypanosomes to the test drug melarsoprol. Determination of the PKJPD relationship of melarsoprol

Trypanosomes were exposed to a fixed total amount of drug (AUC₂₄) for 24 hours using two different PK regimens: (a) a single bolus or (b) a constant infusion (see Figure 13 and Figure 14). The 24 h infusion replicates the conditions of the cytotoxicity assay and allows direct comparison of the cartridge to the static 96-well plate. The single bolus regimen yields a higher Cπ_mχ/MIC and a lower T_Mic than the constant infusion (see Figure 14). Harvesting ECS contents at 24 h, and counting motile trypanosomes revealed that, for all AUC₂₄ values tested, the single bolus, high C_max/MIC regimen consistently

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STM 246258 1 Attorney Docket No. 81248WO(71699)

achieved better cell killing than the constant, high T_MIC infusion (see Figure 14). Interestingly, the ratio of efficacy of the bolus and the infusion converges towards unity as drug exposure rises (see Figure 14). The Cπ_mχ/MIC preference persisted when the experiment was started with 5 X 10⁵ cells/ml ECS (data not shown). These data indicate that C_ma_x is the parameter governing melarsoprol efficacy. Discussion

Pharmacokinetic studies on melarsoprol have been performed in vitro (Burri, 1993) and in non-human primates (Burri, 1994). Additionally there are substantial data available on the pharmacokinetics of the drug in patients treated with the graded dosing regimen (Burri, 2001). Together, these results indicate that approximately 5% of administered drug accesses the cerebrospinal compartment (CSF), with concentrations in the low nanomolar ranges when detectable. Monkey studies comparing graded dosing and the 10-day regimen reveal that the latter results in slightly higher drug levels in the CSF, but total time of drug persistence is shorter (Burri, 1994). Recently, a head-to-head comparison of the three regimens has revealed a greater relapse rate in patients treated with the graded regimen (Pepin, 2006). It has been speculated that this may be attributable to the lower initial drug levels in the CSF.

This Example shows that C_max is the parameter most closely associated with melarsoprol efficacy. This result supports the hypothesis that drug concentrations achieved in the CSF may influence outcome (Pepin, 2006). While this effect is modest in vitro, it is manifest at drug levels comparable to those achieved in patients. Additionally, the lower parasite load in vivo, coupled with longer drug residence times, suggests that this effect will be significant (and probably amplified) in patients.

The results suggest that melarsoprol dosing should be targeted towards rapidly achieving maximum possible drug concentrations in the CSF. This may be achieved by

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STM 246258 1 Attorney Docket No. 81248WO(71699)

increasing the daily dose. The maximum tolerated single dose of melarsoprol is not known, and escalation from currently used levels is a distinct possibility. Alternatively, strategies to enhance blood-brain barrier penetration by co-administration of agents that modulate p-glycoprotein function (Bauer, 2005) may also be examined. A dosing strategy that maximizes drug concentrations in the CSF will permit shortening of the treatment regimen, with obvious practical benefits. Although the molecular basis of drug-related encephalopathies is unknown (Pepin, 1995), it is tempting to speculate that shorter treatment schedules, resulting in shorter total drug exposure, may even reduce the incidence of these debilitating, and often lethal, adverse events. In summary, this Examples describes an in vitro PK-PD determination system that permits the growth of African trypanosomes. This will allow testing of candidate molecules early in preclinical development. This Example also demonstrates that Cπmx is the determining parameter for the killing effects of melarsoprol, a finding that may lead to further optimization of drug dosing in patients.

Although the subject invention has been described with respect to preferred embodiments, those skilled in the art will readily appreciate that changes and modifications may be made thereto without departing from the spirit and scope of the subject invention as defined by the appended claims. REFERENCES

Anscomb, Anne. "Outsourcing In Drug Development: The Contract Research Market From Preclinical to Phase IV", 2^nd Edition, A Kalorama Information Market Intelligence Report, May 2006.

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Bauer, B., A. M. Hartz, G. Fricker, and D. S. Miller. 2005. Modulation of p- glycoprotein transport function at the blood-brain barrier. Exp Biol Med (Maywood) 230: 118-27.

Bodley, A. L., M. W. McGarry, and T. A. Shapiro. 1995. Drug cytotoxicity assay for African trypanosomes and Leishmania species. J Infect Dis 172: 1157-9.

Burri, C, T. Baltz, C. Giroud, F. Doua, H. A. Welker, and R. Brun. 1993. Pharmacokinetic properties of the trypanocidal drug melarsoprol. Chemotherapy 39:225- 34.

Burri, C, and J. Keiser. 2001. Pharmacokinetic investigations in patients from northern Angola refractory to melarsoprol treatment. Trop Med Int Health 6:412-20.

Burri, C, S. Nkunku, A. Merolle, T. Smith, J. Blum, and R. Brun. 2000. Efficacy of new, concise schedule for melarsoprol in treatment of sleeping sickness caused by Trypanosoma brucei gambiense: a randomized trial. Lancet 355: 1419-25.

Burri, C, J. D. Onyango, J. E. Auma, E. M. Burudi, and R. Brun. 1994. Pharmacokinetics of melarsoprol in uninfected vervet monkeys. Acta Trop 58:35-49.

Carruthers, V. B., and G. A. Cross. 1992. High-efficiency clonal growth of bloodstream- and insect-form Trypanosoma brucei on agarose plates. Proc Natl Acad Sci U S A 89:8818-21.

Craig, W. A. 1998. Pharmacokinetic/pharmacodynamic parameters: rationale for antibacterial dosing of mice and men. Clin Infect Dis 26: 1-10; quiz 11-2.

Deziel, M. R., H. Heine, A. Louie, M. Kao, W. R. Byrne, J. Basset, L. Miller, K. Bush, M. Kelly, and G. L. Drusano. 2005. Effective antimicrobial regimens for use in humans for therapy of Bacillus anthracis infections and postexposure prophylaxis. Antimicrob Agents Chemother 49:5099-106.

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Drusano, G. L., J. A. Bilello, S. L. Preston, E. O'Mara, S. Kaul, S. Schnittman, and R. Echols. 2001. Hollow- fiber unit evaluation of a new human immunodeficiency virus type 1 protease inhibitor, BMS-232632, for determination of the linked pharmacodynamic variable. J Infect Dis 183 : 1126-9. Hamzeh et. al. "Dosage Modeling System", United States Patent 5,962,317,

October 2, 1999; Hamzeh et. al. "Dosage Modeling System", United States Patent 6,287,848, September 11, 2001.

Lister, P. D., Pharmacodynamics of moxifloxacin and levofloxacin against Staphylococcus aureus and Staphylococcus epidermidis in an in vitro pharmacodynamic model. Clin Infect Dis, 2001. 32 Suppl 1 : p. S33-8.

Kirstein, M.N., et al., Characterization of an in vitro cell culture bioreactor system to evaluate anti-neoplastic drug regimens. Breast Cancer Res Treat, 2006. 96(3): p. 217- 25.

Moore, M. R., F. M. Hamzeh, F. E. Lee, and P. S. Lietman. 1994. Activity of (S)- l-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine against human cytomegalovirus when administered as single-bolus dose and continuous infusion in in vitro cell culture perfusion system. Antimicrob Agents Chemother 38:2404-8.

Pepin, J., and B. Mpia. 2006. Randomized controlled trial of three regimens of melarsoprol in the treatment of Trypanosoma brucei gambiense trypanosomiasis. Trans R Soc Trop Med Hyg 100:437-41.

Pepin, J., F. Milord, A. N. Khonde, T. Niyonsenga, L. Loko, B. Mpia, and P. De WaIs. 1995. Risk factors for encephalopathy and mortality during melarsoprol treatment of Trypanosoma brucei gambiense sleeping sickness. Trans R Soc Trop Med Hyg 89:92-7.

Schmid, C, M. Richer, C. M. Bilenge, T. Josenando, F. Chappuis, C. R.

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Manthelot, A. Nangouma, F. Doua, P. N. Asumu, P. P. Simarro, and C. Burri. 2005. Effectiveness of a 10-day melarsoprol schedule for the treatment of late-stage human African trypanosomiasis: confirmation from a multinational study (IMPAMEL II). J Infect Dis 191: 1922-31.

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STM 246258 1

Claims

Attorney Docket No. 81248WO(71699)WHAT IS CLAIMED IS;

1. A bioreactor capable of growing protozoan parasites, comprising:

(a) an elongate chamber comprising an inlet and an outlet;

(b) a semi-permeable tubular member connecting the inlet and the outlet whereby an intra-membrane compartment and an extra-membrane compartment are formed in the chamber; and

(c) optionally one or more ports; wherein the extra-membrane compartment comprises cells.

2. The bioreactor according to claim 1, wherein the inlet and outlet are disposed at the ends of the elongate chamber.

3. The bioreactor according to claim 1, wherein the inlet and outlet are disposed generally opposite one another along at the ends of the elongate chamber.

4. The bioreactor according to claim 1, wherein the inlet and outlet are disposed generally opposite one another at the ends of the elongate chamber and in line with the longitudinal axis thereof.

5. The bioreactor according to claim 1, wherein the inlet is adapted to receive a solution, which flows through the semi-permeable tubular member and exits from the outlet.

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STM 246258 1 Attorney Docket No. 81248WO(71699)

6. The bioreactor according to claim 1, wherein the elongate chamber is glass, polycarbonate, polystyrene, silicone polymer, polysulfone, polyethylene, polyurethane, or any combination thereof.

7. The bioreactor according to claim 1, wherein the bioreactor is coupled to a fluid circulation system.

8. The bioreactor according to claim 1, wherein the fluid circulation system can optionally be adjusted to establish one or more desired pharmacokinetic parameters.

9. The bioreactor according to claim 8, wherein the pharmacokinetic parameters are maximum concentration (C_max), the area under the drug concentration-time curve (AUC), the time of peak drug concentration (T_mαx), the clearance rate (Cl), the drug elimination rate (volumer per unit time), the volume of distribution, the ratio of the amount of drug in the body to the concentration of the drug in the blood; the concentration before the next administered dose (C_mm), the drug half-life (Ty₂) or any combination thereof.

10. The bioreactor according to claim 1, where the cells comprise a protozoan parasite.

11. The bioreactor according to claim 10, wherein the protozoan parasite is an isolate or species of the genus Trypanosoma, Toxoplasma, Leishmania, Plasmodium.

12. The bioreactor according to claim 11, wherein the protozoan parasite is Plasmodium falciparum or Trypanosoma brucei.

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STM 246258 1 Attorney Docket No. 81248WO(71699)

13. The bioreactor according to claim 1, wherein the semi-permeable tubular member is cellulose, polyethylene, polypropylene, polysulfone, polymethyl, metacrylate, polyacrylonitrile, poly(vinylidene fluoride), dialysis tubing, or a combination thereof.

14. The bioreactor according to claim 1, wherein the semi-permeable tubular member is dialysis tubing.

15. The bioreactor according to claim 1, wherein the semi-permeable tubular member comprises pores having a molecular weight cut off between about 1 kDa and about 100 kDa and a pore size of about 0.01 micron and about 1 micron.

16. The bioreactor according to claim 1, comprising at least one port adapted for accessing the extra-membrane compartment.

17. The bioreactor according to claim 16, comprising two ports.

18. The bioreactor according to claim 1, wherein the elongate chamber further comprises a space to hold a gas.

19. The bioreactor according to claim 18, wherein the gas comprises oxygen, nitrogen, carbon dioxide, or a mixture thereof.

20. A method of making a bioreactor system for growing cells, said bioreactor comprising: an elongate chamber comprising an inlet and an outlet; dialysis tubing connecting the inlet and the outlet whereby an intra-membrane compartment and an extra-

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STM 246258 1 Attorney Docket No. 81248WO(71699)

membrane compartment are formed in the chamber; and optionally one or more ports; wherein the method comprises threading the dialysis tubing from the inlet to the outlet, and sealing the ends of the dialysis tubing to the inlet and outlet thereby forming the intra- membrane and extra-membrane compartments.

21. The method according to claim 20, wherein the step of connecting further comprises inverting the ends of the dialysis tubing over the ends of the inlet and outlet to form the intra-membrane compartment.

22. A method of monitoring the effect of at least one therapeutic agent on cells, comprising:

(a) growing cells in the extra-membrane compartment of the bioreactor of claim 1;

(b) contacting the cells with at least one therapeutic agent;

(c) measuring an effect of the therapeutic agent on the cells; and

(d) determining a result.

23. The method according to claim 22, wherein growing the cells comprises inoculating a cell of interest in growth media contained in the extra-membrane compartment, and continually flowing new growth media through the intra-membrane compartment, thereby replenishing the growth media of the extra-membrane compartment, wherein cell waste is removed by diffusion into the intra-membrane compartment.

24. The method according to claim 22, wherein the cells include a protozoan parasite.

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STM 246258 1 Attorney Docket No. 81248WO(71699)

25. The method according to claim 24, wherein the protozoan parasite is an isolate or species of the genus Trypanosoma, Toxoplasma, Leishmania, Plasmodium.

26. The method according to claim 24, wherein the protozoan parasite is Plasmodium falciparum or Trypanosoma brucei.

27. The method according to claim 22, wherein monitoring the effect on the cells includes measuring a pharmacodynamic parameter.

28. The method according to claim 22, wherein the elongate chamber of the bioreactor is glass, polycarbonate, polystyrene, silicone polymer, polysulfone, polyethylene, polyurethane, or any combination thereof.

29. The method according to claim 22, wherein the elongate chamber of the bioreactor is glass.

30. The method according to claim 22, wherein the semi-permeable tubular member of the bioreactor is cellulose, polyethylene, polypropylene, polysulfone, polymethyl, metacrylate, polyacrylonitrile, poly(vinylidene fluoride), dialysis tubing, or a combination thereof.

31. The method according to claim 22, wherein the semi-permeable tubular member of the bioreactor is dialysis tubing.

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STM 246258 1 Attorney Docket No. 81248WO(71699)

32. The method according to claim 22, wherein the therapeutic agent is a candidate or a known anti-protozoan agent.

33. The method according to claim 32, wherein the anti-protozoan agent is selection from melarsoprol, quinacrine, metronidazole, tinidazole, furazolidone, paromomycin, amphotericin B, ketoconazole, clotrimazole, propamidine isothionate, iodoquinol, diloxanide furoate, dehydroemetine, trimethoprim-sulfamethoxazole (TMP-SMX), and albendazole.

34. A fluid circulation system further comprising the bioreactor of claim 1.

35. A method of determining the relationship between a pharmacokinetic parameter of a therapeutic agent and a pharmacodynamic effect of the agent on target cells, comprising:

(a) growing the cells in the extra-membrane compartment of the bioreactor of the fluid circulation system of claim 34;

(b) contacting the cells with at least one therapeutic agent;

(c) adjusting the fluid circulation system to establish one or more pharmacokinetic parameters;

(d) measuring at least one pharmacodynamic effect of the agent on target cells; and

(e) determining a result.

36. The method according to claim 35, wherein growing the cells comprises inoculating a cell of interest in growth media contained in the extra-membrane compartment, and continually flowing new growth media through the intra-membrane

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STM 246258 1 Attorney Docket No. 81248WO(71699)

compartment, thereby replenishing the growth media of the extra-membrane compartment, wherein cell waste is removed by diffusion into the intra-membrane compartment.

37. The method according to claim 35, wherein the cells include a protozoan parasite.

38. The method according to claim 35, wherein the protozoan parasite is an isolate or species of the genus Trypanosoma, Toxoplasma, Leishmania, Plasmodium.

39. The method according to claim 35, wherein the protozoan parasite is Plasmodium falciparum or Trypanosoma brucei.

40. The method according to claim 35, wherein pharmacokinetic parameters that are established by adjusting the fluid circulation system are the peak maximum concentration (C_ma_x), the area under the drug concentration-time curve (AUC), the time of peak drug concentration (T_mαx), the clearance rate (Cl), the drug elimination rate (volume per unit time), the volume of distribution, the ratio of the amount of drug in the body to the concentration of the drug in the blood; the concentration before the next administered dose (C_mιn), the drug half-life (Ti/₂) or any combination thereof.

41. The method according to claim 35, wherein the elongate chamber of the bioreactor is glass, polycarbonate, polystyrene, silicone polymer, polysulfone, polyethylene, polyurethane, or any combination thereof.

42. The method according to claim 35, wherein the elongate chamber of the bioreactor is glass.

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STM 246258 1 Attorney Docket No. 81248WO(71699)

43. The method according to claim 35, wherein the semi-permeable tubular member of the bioreactor is cellulose, polyethylene, polypropylene, polysulfone, polymethyl, metacrylate, polyacrylonitrile, poly(vinylidene fluoride), dialysis tubing, or a combination thereof.

44. The method according to claim 35, wherein the semi-permeable tubular member of the bioreactor is dialysis tubing.

45. The method according to claim 35, wherein the therapeutic agent is a candidate or a known anti-protozoan agent.

46. The method according to claim 45, wherein the anti-protozoan agent is selection from melarsoprol, quinacrine, metronidazole, tinidazole, furazolidone, paromomycin, amphotericin B, ketoconazole, clotrimazole, propamidine isothionate, iodoquinol, diloxanide furoate, dehydroemetine, trimethoprim-sulfamethoxazole (TMP-SMX), and albendazole.

47. The method according to claim 35, wherein the pharmacodynamic parameter to be measured is the maximum effect of the agent (E_max), the dose which produces 50% of the maximum effect (ED50), the concentration observed at half the maximal effect (EC50), the level of growth, the level of cell death, the change in gene expression, the change in level of metabolic product, or any combination thereof.

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STM 246258 1