Controlled Release Compositions for Interferon Based on PEGT/PBT Block Copolymers

A method for the preparation of microparticles comprising one or more active compounds selected from the group of interferons and one or more biodegradable block copolymers constructed from poly(ethylene glycol) terephthalate (PEGT) and poly(butylene terephthalate) (PBT), comprising the steps of:

• (a) preparing an emulsion comprising
• (aa) an aqueous inner phase comprising the one or more active compounds, and
• (ab) an organic outer phase comprising the one or more biodegradable block copolymer and at least one organic solvent;
• (b) solidifying the one or more biodegradable block copolymer into microparticles by removing at least a fraction of the organic solvent from the emulsion prepared in step (a);
• (c) collecting and drying the microparticles formed in step (b) wherein step (b) is carried out by emulsifying the emulsion prepared in step (a) in a coherent aqueous phase to obtain a w/o/w-double emulsion, wherein the coherent aqueous phase comprises an osmotic agent, wherein the osmolality of the coherent aqueous phase is higher than that of the aqueous inner phase.