A month-long effect from a single injection of microencapsulated human growth hormone.

An injectable sustained-release form of human growth hormone (hGH) was developed by stabilizing and encapsulating the protein, without altering its integrity, into biodegradable microspheres using a novel cryogenic process. A single injection of microspheres in monkeys resulted in elevated serum levels of recombinant hGH (rhGH) for more than one month. Insulin-like growth factor-I (IGF-I) and its binding protein IGFBP-3, both of which are induced by hGH, were also elevated for four weeks by the rhGH containing microspheres to a level greater than that induced by the same amount of rhGH administered by daily injections. These results show that, by using appropriate methods of stabilization and encapsulation, the advantages of sustained-release formulations previously demonstrated for low-molecular-weight drugs can now be extended to protein therapeutics.