Shot in the arm for protein delivery.

The nicotine patches worn by desperate smokers and the 12-hour antihistamine pills swallowed by hapless allergy sufferers highlight the growing ability of pharmaceutical companies to control the delivery of simple drugs over time. That skill, however, has long eluded scientists working with proteins and other large molecules.

For example, the complicated three-dimensional structures of proteins seldom survive the high temperatures and watery solutions traditionally used to encapsulate small molecules or peptides in biodegradable microspheres that slowly release their contents in the body.

Researchers from two biotech companies now report success at encapsulating human growth hormone, a protein sometimes prescribed for treating children of unusually small stature. "We've used an entirely novel process to make the microspheres," says Scott D. Putney of Alkermes in Cambridge, Mass. In monkeys, a single injection of hormone-laden spheres provided sustained release of the protein for more than a month, scientists from Alkermes and Genentech in South San Francisco report in the July Nature Medicine. The new encapsulation method, which involves lower temperatures and no water, should also work with other therapeutic proteins, says Putney. If the microspheres prove as safe and effective in humans as in monkeys, people may soon be able to avoid the daily injections now required for most forms of protein therapy, says Putney.