05 Sep 1998

Puny polymer pellets show promise as a vehicle for delivering nerve-growth factor (NGF) to the basal forebrain, where the substance could rescue or even regenerate neurons damaged by Alzheimer's disease. For some years, the idea of introducing NGF into the brains of AD patients has tantalized researchers, but several technical obstacles stood in the way. The substance has a very short half life in the blood, on the order of minutes, very little of it reaches the brain (around 0.1 percent), and there it diffuses rather slowly, all of which conspire against having enough NGF reach its target area. In a presentation made last month at the American Chemical Society meeting in Boston, Mark Saltzman and Nadya Belcheva described advances in a method to embed NGF molecules in biostable polymer microspheres, which can be implanted through a large-bore needle directly into the basal forebrain. There, the polymer matrix protects NGF molecules from being degraded, and allows for controlled release over many months. The novel drug-delivery system is being tested in rats, where it has been shown to boost production of acetylcholinesterase in transplanted nerve cells. Further refinements and testing are still needed to make the approach applicable to humans. Saltzman speculates that this drug delivery system might well offer a one-time treatment that would remain in the brain for the remainder of a patient's life. The polymer-pellet delivery system, he says, could in theory deliver drugs directly to the areas of the brain implicated in a number of degenerative diseases, including Parkinson's, Huntington's chorea and amyotrophic lateral sclerosis.—June Kinoshita