WO2014030993A1

WO2014030993A1 - Neutron activated 153sm labelled microspheres

Info

Publication number: WO2014030993A1
Application number: PCT/MY2013/000147
Authority: WO
Inventors: Basri Johan Jeet ABDULLAH; Chai Hong YEONG; Lip Yong Chung; Kwan Hoong NG
Original assignee: Universiti Malaya (Um)
Priority date: 2012-07-18
Filing date: 2013-08-16
Publication date: 2014-02-27
Also published as: MY150861A

Abstract

The present invention relates to a method of preparation of ¹⁵³Sm labelled microspheres, comprising the steps of incorporating a ¹⁵²Sm compound into insoluble ion-exchange resin or glass beads and subsequently performing neutron activation of the incorporated samarium microspheres. It further includes radioactive microspheres containing¹⁵³SmCI₃ or a hydrate thereof and the clinical use of such radiolabeled microspheres.

Description

NEUTRON ACTIVATED ¹⁵³SM LABELLED MICROSPHERES

Field of the Art The present invention relates to a method of preparation and use of ¹⁵³Sm labelled microspheres.

Background Art Non-invasive imaging techniques are important clinical diagnostic tools in the investigation of gastrointestinal (GI) motility and transit. Several radiological and endoscopic techniques have been developed and are practised in clinical settings (Lin HC, Prather C, Fisher RS, Meyer JH, Summers RW, Pimentel M, et al.: Measurement of gastrointestinal transit. Dig Dis Sci 2005). Among them, gamma scintigraphy is one of the most favoured diagnostic methods because it combines quantitative assessment and visual information from sequential image data. Furthermore this methodology does not involve dense contrast agents such as barium which may alter the GI physiology during the examination.

The assessment of GI transit by gamma scintigraphy requires a tracer which is non-toxic, safe and mirrors the physiological transit. A range of non-absorbable radiopharmaceuticals have previously been used for gastrointestinal studies. In 1989, Camilleri et al. from Mayo Clinic, USA (Camilleri M, Colemont LJ, Phillips SF, Brown ML, Thomforde GM, Chapman N, et al.: Human gastric emptying and colonic filling of solids characterized by a new method. Am J Physiol 1989; 257:G284-G290) successfully developed a method of indium-I l l (III) chloride (^{u l}InCl₃) radiolabeled resin pellets for the assessment of gastric emptying and colonic transit. Amberlite® IR-120 (H⁺) cation resin pellets were successfully labelled with ^{n l}InCl₃ and this method has been widely practised in many centres particularly for whole gut transit studies. This method, however, has certain limitations restricting its application to a broader population, mainly due to the requirement of an industrial cyclotron facility for the production of ^{1 1 1} In, which is not commonly available worldwide. As a consequence the supply of ^{1 1} 'in to some countries can be relatively costly compared to other available radionuclides especially when this involves international shipment with the added cost of lead shielding and agent charges to comply with different national radiation authorities.

In 1998, Mullan et al. (Mullan BP, Camilleri M, Hung JC. Activated charcoal as a potential radioactive marker for gastrointestinal studies. Nucl Med Commun 1998; 19:237-240) suggested a cheaper approach for radiolabelling activated charcoal with technetium-99m pertechnetate (^99mTc0₄) and technetium-99m-diethylene triamine pentaacetic acid(^99mTc- DTPA), which are routinely available in most countries. Some later publications described the use of ^99mTc-radiolabelled ion-exchange resin pellets as an alternative for " 'in radiolabeled resins, however the short physical half-life of ^99mTc (6.02 h) makes this radiotracer formulation only suitable for short time course imaging studies such as oesophageal transit or gastric emptying. The investigation of whole gut transit requires a radiotracer with much longer physical half-life, preferably around 24 to 72 h.

Radionuclides are also gaining increasing importance by providing palliative and curative treatment in an increasing number of malignant diseases. Most radionuclides used in radionuclide therapy emit beta particles, which have a low range of tissue penetration. A few emit auger electrons and alpha particles, and several also emit gamma rays and X-rays during their decay. The most successful metabolic radionuclide for thyroid therapy uses Iodine- 131 (^{l 31}I) as the nuclide for the treatment of benign hyperthyroid conditions and thyroid carcinoma.

Non-resectable primary and metastatic liver cancers carried a bleak prognosis with limited treatment options until recently. Encouraging results of several recent trials suggest radioembolization using Y-90 is achieving the previously elusive goal of destroying hepatic tumor cells while sparing surrounding tissue. The procedure has been approved in the United States for more than a decade, but the past year has witnessed a surge in utilization. Two commercially available agents are FDA-approved for the treatment of liver cancer. TheraSphere, made by MDS Nordion Inc, was approved in late 1999 as a humanitarian use device for hepatocellular carcinoma (HCC), while SIR-Spheres, made by Sirtex Medical Ltd, were sanctioned as a first-line therapy for colorectal liver metastases in 2002.

Microspheres target liver tumors by taking advantage of their hypervascularity. Metastatic liver tumors larger than 3 mm receive 80% to 100% of their blood supply from the hepatic artery while normal liver tissue is predominantly fed by the portal vein. The microspheres are delivered via a fluoroscopic embolization procedure in which millions of 30-micron beads are infused through a catheter into the hepatic artery. The beads become embedded in the liver, and the therapeutic dose is delivered over a period of about two weeks. The beads are bonded with ⁹⁰Y, a beta-emitting radionuclide that acts locally because its relatively low energy means the beta particles travel at most 1 1 mm in the liver. This allows the beads to embed in and irradiate the tumor while sparing healthy liver tissue.

There is the need for meticulous attention to technical detail by a team that includes an interventional radiologist, an anesthesiologist, a nuclear physician, a radiation physicist, an interventional technologist, nurses, and radioisotope technologists. Coordination and timing are so crucial that some companies provide a representative to oversee the entire procedure to confirm that the entire team is present, the precise dose is on hand, and the sophisticated delivery system is functional. Further due to rapid decay of ⁹⁰Y, the cost for most developing countries is prohibitive (RM 22,000) and the minimum time delay for licensing and shipping in 2 to 3 weeks. Samarium-153 (¹⁵³Sm) is a radionuclide produced by neutron activation of a rare earth lanthanide, Samarium-152 (¹⁵²Sm). In spite of the complex decay scheme which includes various beta particles (E_max = 0.632, 0.702, 0.805 MeV), this reactor-produced radiolanthanide also emits low energy gamma radiation (Ε_γ = 0.103 MeV with 28% abundance) which is well- suited for gamma scintigraphic imaging. ¹⁵³Sm has a physical half-life of 46.3 h and its average and maximum beta particle ranges in water are 0.5 mm and 3.0 mm, respectively. ¹⁵²Sm is commercially available in solid (¹⁵²Sm₂0₃) and aqueous (¹⁵²SmCl3) forms. The production of ^l53Sm requires a nuclear reactor facility. Where such reactors are available worldwide this makes the production and use of ¹⁵³Sm cost competitive and more accessible than other radionuclides, for example " 'in and ⁹⁰Y.

The clinical application of ¹⁵³Sm has been introduced since two decades ago. ¹⁵³Sm is most commonly known as a therapeutic agent for bone metastasis pain release in the form of radiopharmaceutical, ^{l 53}Sm-EDTMP. Despite its application in therapeutic medicine, ¹⁵³Sm has also been widely used as a radiotracer in pharmacoscintigraphic studies (Ahrabi et al., 2000, Ahrabi et al., 1999a, Ahrabi et al., 1999b, Awang et al., 1993, Marvola et al., 2004, Marvola et al., 2008, Waaler et al., 1997, Waaler et al., 1999a, Waaler et al., 1999b, Watts et al., 1991 , Watts et al., 1993a, Watts et al., 1993b). The effort of incorporating ¹⁵²Sm₂0₃ into a tablet formulation was first carried out by Parr and Jay in 1985 (Parr et al., 1985). They concluded that, sufficiently small amount of ¹⁵²Sm₂0₃ (less than 3.3% (w/w)) did not alter the drug release properties significantly. Following that, Watts et al. (Watts et al., 1991, Watts et al., 1993a, Watts et al., 1993b) investigated the effects of neutron activation on the physical properties of the radiolabeled polymer microspheres and concluded that the Eudragit® S micro pellets were, unaffected by the added samarium oxide (0.8% (w/w)). ¹⁵³Sm has been studied as non-absorbable faecal marker and has been found to be totally non-absorbable in the GI tract (Fairweather-Tait et al., 1997). This property provides positive effects on radiation safety.

A relatively new clinical application of ¹⁵³Sm is in radiation synovectomy, which is a treatment for chronic synovitis. Samarium-153 particulate hydroxyapatite (¹⁵³Sm-PHYP) is injected intra-articularly to the joint space and flushed through with a mixture of xylocaine and triamcinolone acetonide. The injected radioactivity is absorbed by phagocytic lining cells along the synovial surface. As radionuclide decays, regenerating synovium will be irradiated. ¹⁵³Sm-PHYP is stable and remains tightly bound in vivo. Clinical trials confirm that extraarticular escape of ¹⁵³Sm-PHYP compares favourably with ⁹⁰Y colloids as <1% of injected activity is detectable outside the knee (Clunie G, Lui D, Cullum I, Edwards JCW, Ell PJ. Samarium- 153-particulate hydroxyapatite radiation synovectomy: Biodistnbution data for chronic knee synovitis. J Nucl Med 1995;36:51-7).

The extra-articular whole body radiation (unwanted) dose is approximately 3.8 mSv, which is no more than the estimated dose from an isotope bone scan (3.7 to 6 mSv) (Shields RA, Lawson RS. Effective dose equivalent. Nucl Med Commun 1987;8:851-5). The dose is significantly lower than the dose estimated from ⁹⁰Y synovectomy and similar to the dose after intra-articular dysprosium- 165 macroaggregates. There is no evidence for an increase in chromosome-type damage after ¹⁵³Sm-PHYP therapy (Deutsch E, Brodack JW, Deutsch F. Radiation synovectomy revisited. Eur J Nucl Med 1993;20: 1 1 13-27). There are additionally no local side effects or clinically observed unwanted effects from the injection of the particulate hydroxyapatite (diameter range 5-45 μπι) up to a year after injection (Clunie G, Lui D, Cullum I, Ell PJ, Edwards JCW. Clinical outcome after one year following samarium- 153 particulate hydroxyapatite radiation synovectomy. Scand J Rheumatol 1996;25:360-6).

The present invention provides a method of preparation of ^{l 53}Sm labelled microspheres, preferably resin or glass beads microspheres to be used for diagnostic imaging in GI motility and transit, and as a therapeutic agent for tumors and inflammatory joint disease. Brief description of Drawings

Figure 1 : Gamma spectra of neutron activated ^{l 53}Sm-labelled sample.

Figure 2: Percentages of ¹⁵³Sm³⁺ in the radiolabeled resin compound versus time (error bars show I standard deviation for n = 6). SGF: simulated gastric fluid; SIF: simulated intestinal fluid.

Summary of the Invention

The present invention provides a method of preparation of ¹⁵³Sm microspheres, comprising the steps of incorporating ^{l 52}SmCl₃ or a hydrate thereof into insoluble microspheres and subsequently performing neutron activation of the incorporated samarium. The present invention further provides radioactivemicsopheres containing ¹⁵³SmCl₃ or a hydrate thereof. The present invention also encompasses the use of the ¹⁵³Sm labelled microspheres for the diagnostics of gastrointestinal (GI) motility and transit, and as a therapeutic agent for tumors and inflammatory joint disease.

Detailed description of the Invention

The present invention provides a method of preparation of ¹⁵³Sm labelled microspheres of varying sizes and in various formulations, comprising the steps of incorporating ^{l 52}SmCl₃ or a hydrate thereof into insoluble ion-exchange microspheres and subsequently performing neutron acti vation of the incorporated samarium.

In a preferred embodiment, the incorporated compound is ¹⁵²SmCl₃.6H₂0.

In another preferred embodiment, the micsopheres are insoluble ion-exchange resin or glass beads, more preferably is a cation-exchange (H*) resin or a styrene-divinylbenzene gel type resin with sulfonic acid (H₂S0₄) functionality.

In yet another preferred embodiment, the size of the microspheres is smaller than 1 mm.

In a preferred embodiment, the step of incorporating ^{l 52}SmCl₃ or a hydrate thereof into microspheres is performed by dissolving ^{l 52}SmCl₃ or a hydrate thereof in water, adding the insoluble ion-exchange resin or glass beads and mixing, and then drying the resulting mixture at a temperature of 30 to 80°C.

In a preferred embodiment, the step of performing neutron activation of the incorporated samarium is performed by irradiating of the final dosage form, such as a capsule, preferably a gelatine capsule, filled with the microspheres with incorporated samarium, using a nuclear reactor. In a preferred embodiment, the microspheres with incorporated samarium are irradiated using a thermal nuclear reactor. The recommended neutron flux is between lO¹⁰ to 10¹⁴ n.cm'V. The neutron relevant in the activation process is thermal neutron constitutes energy in the range of 0 to 0.55 eV. The samples are irradiated in the neutron flux for a period of time depending on the neutron flux.

The activity of the neutron activated sample can be calculated through the following equation:

Ν = Ν₀σΦ( 1 - ε^"λι)

Wherein:

σ - neutron absorption cross-section

Φ - neutron flux

No - initial number of target nuclei dependent on the isotopic abundance

λ - decay constant of the nuclide

t - time duration of irradiation

This process in which first a ¹⁵²Sm compound is incorporated into microspheres and subsequently the ¹⁵²Sm is activated by neutrons to form ^{l 53}Sm, avoids the lengthy manipulation with an activated radionuclide during preparation of the administration form and thus decreases the radiation safety of the personnel. Another advantage is that the method is safe, robust and reproducible.

The present invention further provides radioactive microspehres containing ¹⁵³SmCl₃ or a hydrate thereof.

The present invention also encompasses the use of the ¹⁵³Sm labelled microspheres for the diagnostics of gastrointestinal (GI) motility and transit, and as a therapeutic agent for tumors and inflammatory joint disease. For clinical use, the radiolabeled microspheres can be administered within the gelatin capsule, or it can be emptied from the capsule for incorporation into a suitable meal or oral formulation. In another embodiment, the radiolabelledmicrospheres can be filled into syringes for injection and delivered in this form.

The present invention brings namely the following advantages. It allows for incorporation of inactivated ¹⁵²Sm into microspheres of different sizes and formulations with stability for long term storage off the shelf base product. It also enables rapid delivery and local manufacture, activation of several different fixed quantities of samarium to required activity i.e. varying activity and not changing quantity of inactivated samarium used. The fact that there is no need to manipulate dose once activated leads to better safety for the personnel. Furthermore, various administration forms, such as capsules, tablets or syringes, can be prepared, delivered, activated and used.

Examples of carrying out the invention

Example 1 : Preparation of ¹⁵²Sm labelled resin beads The stable nuclide samarium- 152 (III) chloride hexahydrate (¹⁵²SmCl₃.6H20, molecular weight 364.81 g/mol, assay purity >99%) was incorporated into the cation-exchange resin. The resin is a gel type strongly acidic cation exchange resin of the sulfonated polystyrene type. The chemical structure of the resin is as following:

(PC, polymer chain; XL, cross-link; ES, exchange site; EI, exchangeable ion).

The mean size of the resin beads ranged from 0.62 to 0.83 mm. The total exchange capacity of the resin was >1.80 eq.L^-1 (H⁺ form), and the moisture holding capacity was 53-58% (H⁺ form).

For each ¹⁵²Sm-labeIled formulation, 50 mg of ¹⁵²SmCl₃.6H20 was weighed and dissolved in I ml of pure distilled water. A measure of 100 mg of cation (H*) ion-exchange resin was then added to the solution and mixed evenly. The mixture was dried in a laboratory oven for 12 h at a temperature of 70°C. The dried resin beads were then filled into an empty gelatin capsule and sent for neutron activation.

Example 2: Neutron activation The sample was activated using a thermal research reactor. Before irradiation, each capsule was heat-sealed into a polyethylene vial. The vial was then packed into a polyethylene ampoule (commonly known as the 'rabbit'). The ampoule was delivered to the reactor core by a pneumatic transport system (PTS). The sample was irradiated in a neutron flux of lxlO¹³ cm^-2 s^~" for 100 s to achieve a nominal radioactivity of 5 MBq at 66 h after neutron activation. Gamma spectroscopy was carried out to detect any radioactive impurities 24 and 48 h after neutron activation using a coaxial, p-type, germanium detector and D Dspectrum analysis software. The safety requirement is that any net □ peak area not originating from ^{I S3}Sm should not exceed 0.3% of the ¹⁵³Sm main peak at 103 keV and that the total net peak areas not originating from ^l53Sm should not exceed 1% of the ¹⁵³Sm main peak. The capsule was kept in a radioactive storage room for minimum 48 h to allow for decay of the unwanted short-lived activated by-products, primarily sodium-24 (²⁴Na).

Example 3: Testing for labelling efficiency ¹⁵³Sm-radiolabelled resins were weighed and assayed for radioactivity to derive the specific activity. Mean labelling efficiency of 91% was obtained by determining the activity bound to the resin after washing for 5 min with distilled water. Retention of the radioactivity bound to resins over time was measured as described below. Stability of radiolabeled resins in simulated gastric and intestinal fluid:

The stability of the activated ¹⁵³Sm-resin was measured in vitro over a period of 24 h. Artificial gastric juice (pH 1.03) and simulated intestinal fluid (pH 6.8) with enzyme incorporation were prepared according to the recommendation in the British Pharmacopoeia, 2007. The activated ¹⁵³Sm-resins were emptied from the capsule and transferred to glass tubes containing either 10 ml of artificial gastric juice or 10 ml of simulated intestinal fluid. The initial activities of all the samples were measured using a dose calibrator and recorded. The tubes were then placed on a tilt and mix rollerand rolled constantly at 50 rpm for 1 h. The tubes were then transferred to a centrifuge and rotated at 1200 rpm for 5min to separate the resin beads and fluid. After centrifugation, 1 ml of fluid was carefully removed from the middle of the tube without disturbing the resin beads at the bottom using a micropipette. The same procedures of rolling and sampling were repeated every 2 h for 10 h, and a final sample was taken at 24 h. All the samples were then assayed using a gamma counter for measurement of ^{l 53}Sm activity. The gamma counting data were first corrected for background count rates before further analysis. The count rates collected from 1ml samples were normalized according to the volume remaining in the test tube at the time of sampling. The data were then corrected for radioactive decay and expressed as a percentage to the initial activity. The retention of radioactivity was calculated using the following formula:

Initial activity of resin - activity of sample

Retained activity (%) = l00%

Initial activity of resin

Production of ^{l 53}Sm-resin by neutron activation was reproducible. Assay of individual batches by gamma spectroscopy showed that the main photopeaks measured were in the expected energy region of 69.0±1.5 and 102.6±1.5 keV, both were gamma energies emitted by activated ^l53Sm. The gamma spectra of ¹⁵³Sm labelled sample is shown in Error! Reference source not found. Figure 1 .

The net gamma peak area not originating from ¹⁵³Sm did not exceed 0.3% of the ¹⁵³Sm main peak at 103 keV, and the total net peaks areas not originating from ¹⁵³Sm did not exceed 1 % of the ¹⁵³Sm main peak.

The ^{l 53}Sm-radiolabelled resin retention of radionuclide in intestinal fluid achieved almost 100% from all the samples collected over 24 h and also good long term retention artificial gastric juice (see Figure 2).

Claims

CLAIMS 153

1. A method of preparation of Sm labelled microspheres, comprising the steps of incorporating a Sm compound into insoluble microspheres and subsequently performing neutron activation of the incorporated samarium.

2. The method of claim 1 , wherein the incorporated ^{l 52}Sm compound is ¹⁵²SmCl3 or a hydrate thereof, more preferably it is ¹⁵²SmCl₃.6H₂0.

3. The method of claim 1, wherein the insoluble ion-exchange microspheres is an ion- exchange resin beads or glass beads.

4. The method of claim 1, wherein the step of incorporating the ^{I 52}Sm compound into insoluble microspheres is performed by dissolving the ^l52Sm compound in distilled water, adding the insoluble microspheres and mixing, and then drying the resulting mixture at a temperature of 30 to 80°C.

5. The method of claim 1 , wherein the step of performing neutron activation of the incorporated ^l52Sm is performed by irradiating of the final dosage form with incorporated ^{l 52}Sm compound, such as a gelatine capsule filled with the labelled microspheres.

6. The radioactive microspheres containing ¹⁵³SmCl₃ or a hydrate thereof.

7. ^I53Sm labelled microspheres of claim 6 for use for the diagnostics of gastrointestinal motility and transit.

8. ^{l 53}Sm labelled microspheres of claim 6 for use as a therapeutic agent for targeted radiotherapy of tumors and inflammatory joint disease.

9. A gelatine capsule, comprising ^{I 53}Sm labelled microspheres of claim 6.

10. A syringe for injection, comprising ^{I 53}Sm labelled microspheres of claim 6.