GlaxoSmithKline (GSK) announced data for a new investigational Protease Inhibitor (PI) (640385) which is active against HIV, including strains that have become resistant to multiple protease inhibitor drugs, at the XIIIth International HIV Resistance Workshop.

Data were presented in two abstracts for 640385, an aspartyl protease inhibitor (PI) that is currently in phase I clinical trials. The first of these abstracts presented in vitro evaluations to determine what mutations might lead to resistance when tested in the clinic. Based on these experiments 640385 appears to select for a mutation at A28S on the virus. This mutation has not been reported by any of the currently marketed PIs. The significance of these findings will need to be confirmed in clinical trials.

"These continued findings on the understanding of the resistance patterns for 640385 will aid in the development of the molecule and which may help patients who have experienced virologic failure on protease inhibitor therapy, including amprenavir," said Ken Batchelor, senior vice-president, Metabolic and Viral Diseases, Drug Discovery at GSK.

In a second study further data were presented that showed patients who experienced virologic failure while taking an amprenavir or fosamprenavir -containing regimen could potentially benefit from 640385. In this in vitro evaluation, a panel of clinical isolates from patients who had been on a regimen that included amprenavir/fosamprenavir and experienced virologic failure were tested for resistance to 640385 and amprenavir/fosamprenavir.

This compound was jointly discovered by GSK and Vertex Pharmaceuticals.