The results showed that Procyon’s PL-100 and its back-up analogue PL-337 had the most favorable cross-resistance profile of all the protease inhibitors (PIs) studied, as measured by the median fold change in IC50 (50% inhibitory concentration), as well as the percentage of the strains displaying low-level resistance to drug.
The study report was based on 63 HIV resistant strains. The selected viral strains were challenged with PL- 100 and PL-337 and the commercially available PIs, amprenavir (GlaxoSmithKline’s Agenerase), indinavir (Merck & Co’s Crixivan), lopinavir (Abbott’s Kaletra), nelfinavir (Agouron’s Viracept), saquinavir ((Roche’s Fortovase), and the recently available atazanavir (Bristol-Myers Squibb’s Reyataz).
In addition, the viral strains selected for the study also contained important resistant mutations for two other PIs currently in clinical studies by pharmaceutical companies. These strains were found to be susceptible to both PL-100 and PL-337.
“We are very pleased with the latest cross-resistance results showing that in a larger panel of resistant HIV viral isolates, PL-100 and PL-337 performed better than the currently-approved protease inhibitors,” said Hans Mader, president and CEO of Procyon. “This confirms the competitive uniqueness of PL-100 and this together with the pharmacokinetic profile that we expect to obtain very soon will allow us to move PL-100 into human clinical studies later this year.”
On average, PL-100 and PL-337 showed significantly better antiviral activity than the approved protease inhibitors tested. This indicates the potential for good activity against existing protease inhibitor-resistant virus in treatment-experienced patients or in those patients newly-infected with drug-resistant strains with similar patterns of PI mutation.
Procyon is currently completing preclinical work and expects to file an investigational new drug (IND) submission during the second half of 2005 in order to initiate a human clinical phase I trial.