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 alter ing its integrity, into biodegradable microspheres using a novel cryog enic process. A single injection of microspheres in monkeys resulted i n elevated serum levels of recombinant hGH (rhGH) for more than one mo nth. Insulin-like growth factor-I (IGF-I) and its binding protein IGFB P-3, both of which are induced by hGH, were also elevated for four wee ks by the rhGH containing microspheres to a level greater than that in duced by the same amount of rhGH administered by daily injections. The se results show that, by using appropriate methods of stabilization an d encapsulation, the advantages of sustained-release formulations prev iously demonstrated for low-molecular-weight drugs can now be extended to protein therapeutics.