PLGA-BASED MICROPARTICLES CONTAINING A HYDROPHILIC GnRH ANTAGONIST OF THE NEW GENERATION G. Schwach 1 , N. Oudry 2 , P. Broqua 3 , H. Lindner 4 , M. Lück 4 , J. Anderson 5 and R. Gurny 2 1 Interuniversity Center Geneva-Lyon, « Pharmapeptides », F-74166 Archamps, France 2 School of Pharmacy, University of Geneva, CH-1211 Geneva 4, Switzerland 3 School of Medicine, University of Geneva, CH-1211 Geneva 14, Switzerland 4 Ferring Pharmaceuticals, D-24109 Kiel, Germany 5 Institute of Pathology and Dept. of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA e-mail address of presenting author : Gregoire.Schwach@pharm.unige.ch ABSTRACT SUMMARY Incorporation of FE200486, a new GnRH antagonist, in bioresorbable PLGA microparticles was carried out with various formulation technologies, namely double emulsion solvent evaporation, spray drying and ram- or screw- extrusion. The particulate systems were tested for biological potency in the castrated rat model, and exhibited a maximum 1-month plasma LH inhibition. The tolerance of 3 selected formulations obtained with different techniques was documented over 28 days by histology. Keywords: peptide drug delivery, anticancer agents, poly(lactic acid) and copolymers, microspheres, extrusion, biocompatibility. INTRODUCTION Gonadotropin-releasing hormone (GnRH) antagonists are recognized as potent drugs candidates for the treatment of prostate cancer, endometriosis or infertility 1 . FE200486 is a new decapeptide antagonist of GnRH with increased hydrophilicity 2 . Incorporation of FE200486 in PLGA polymeric carriers was of prime interest for the development of a long acting formulation of this new peptide. In this work we wish to present the results obtained in the initial screening phase. EXPERIMENTAL METHODS Polymers Medisorb  5050- 6535- and 7525DL2A poly(DL-lactide-co-glycolide)s were selected in the hydrophilic series (Alkermes, Inc.). Formulation Microspheres were obtained by double emulsion solvent evaporation (H 2 O/CH 2 Cl 2 /H 2 O) in the presence of poly(vinylalcohol) (0.5%) or by spray drying (Büchi 190). Extrusion was either carried out with a custom-made ram-extruder 3 or by screw-extrusion (1/4 inch microtruder, Randcastle), at moderate temperature (T<80°C). Microparticles were obtained after manual grinding of ∅ 2 mm extruded rods Characterization Microparticles were analyzed for peptide purity and peptide core loading by HPLC. Water content (Karl-Fischer titration) and residual CH 2 Cl 2 (Head-space GC) were also determined. Surface morphology was investigated by scanning electron microscopy (JSM-6400, Jeol). Volume mean diameter D[4,3] was obtained from LALLS (Mastersizer S long bed, Malvern). Bioassay Microparticles were injected s.c. in the back of castrated rats (n=4) at a dose of 1.5 mg/kg after resuspension in an appropriate medium (Polysorbate 80 0.2%, sodium carboxy-methyl- cellulose 0.2%, in water for injection). Plasma luteinizing hormone (LH) levels were measured prior to treatment and then at 3 hrs, day 2, day 7 and on a weekly basis as long as LH inhibition was observed. Histology Sprage-Dawley rats (n=3) were treated s.c. with microparticles as described in the bioassay section. At appropriate time points the rats were euthanized and the injection site was removed for