The present invention relates to a drug delivery composition comprising proteins and biodegradable polymers. The present invention further relates to a drug delivery system for controlled and long term release of proteins into a biological environment. The drug delivery composition comprises at least a protein and a biodegradable polymer possessing at least two different functional groups selected from the group of chosen among carboxyl-, ester-, amine-, amide-, thiol-, thioester- or hydroxyl groups pendant to the main polymer chain whereby the composition absorbs between 5-10% w/w water when exposed to physiological conditions for at least 20 days. The present invention further relates to a drug delivery system for controlled protein release comprising the composition. The drug delivery system may be chosen from microparticles, films, coatings, fibers, pellets, cylinders, discs, implants, microcapsules, microspheres, nanospheres, wafers, micelles, liposomes or woven or non-woven fabrics.
