Continuous release pharmaceutical compositions

Pharmaceutical compositions for continuous release of a physiologically active substance in which the physiologically active substance comprises a polypeptide covalently conjugated to a water soluble polymer show particularly desirable release characteristics. Polypeptides for use in the pharmaceutical compositions include G-CSF and solution stable derivatives thereof, human calcitonin and interleukin-2. The material of the composition may be a polylactide or biodegradable hydrogel derived from an amphipathic block copolymer. The compositions enable a therapeutically effective polypeptide to be continuously released over a prolonged period of time following a single administration of the pharmaceutical composition to a patient.