Procyon BioPharma Inc. Reports New Data For Its Lead HIV Protease Inhibitor, PPL-100, Showing A Potentially High Genetic Barrier Against The HIV Virus

Published: Nov 16, 2005

MONTREAL, Nov. 16 /PRNewswire-FirstCall/ - Procyon Biopharma Inc. , a biotechnology company developing innovative therapeutics in the fields of cancer and HIV/AIDS, announced today results of a one year in vitro resistance selection study showing that its lead HIV protease inhibitor, PPL- 100, when subjected to a "forced resistance study" showed a potentially high genetic barrier confirming the potential utility of the drug for resistant HIV. The study was conducted in collaboration with Professor Mark Wainberg of the McGill University AIDS Center.

The last decade has marked a major improvement in the treatment of HIV positive patients thanks to the Highly Active AntiRetroviral Treatment (HAART) consisting of a cocktail of Reverse Transcriptase Inhibitors (RTI) and Protease Inhibitors (PI). Nevertheless, the emergence of multi-resistant viruses continues to challenge the clinical community. The resistance to PIs is mainly due to the appearance of mutations in the virus, particularly in the protease gene. The resistant mutations to marketed PIs most likely result from the prolonged use of these PIs in the HIV positive patients. For this reason, new antiviral drugs with a high genetic barrier (more difficult for the virus to develop resistance) need to be developed to fight the emergence of resistant HIV viruses.

Procyon's PI, PPL-100, when subjected to in vitro resistance selection, using another PI (Amprenavir from Glaxo SmithKline) as a control, showed that after 52 weeks of evaluation, only four mutations in the Protease gene occurred. Two of these, K45R and M461 were known mutations while the other two, T80I and P81S were novel. The novel ones were in the active site of the enzyme whereas the known mutations were in the area outside the active site (flap mutations). For the drug to experience a mild degree of resistance, all four mutations would at least have to be present, indicating that PPL-100 has a potentially high genetic barrier.

The study also showed that these mutations selected did not induce any cross-resistance to currently marketed PIs. On the contrary, it was determined that the T80I mutation potentially causes hypersensitivity of HIV to two other PIs (Saquinavir from Hoffman-La Roche and Nelfinavir from Pfizer).

"We are very pleased with the "forced resistance" data from the collaborative study with Professor Wainberg's group on our lead HIV protease inhibitor PPL-100, as this complements the cross-resistance study reported last February by Procyon", said Hans J. Mader, president and chief executive officer of Procyon Biopharma. "We have now a high degree of confidence that when used in the clinical setting, PPL-100 will potentially have a high genetic barrier and hence give a lower chance for resistant HIV strains to arise", he added. "We plan to file for the first-in-man Phase 1 study this month and expect to have results available within the next 4 to 5 months", he concluded.

"The results we have obtained on the mutations developed in the HIV protease gene when subjected to PPL-100 over a 52 week period, using a "forced resistance protocol", are very encouraging and merit the rapid development of the drug in the upcoming clinical studies," said Professor Wainberg. "Such studies usually mimic the development of viral resistance in the treatment of HIV/AIDS, hence our observations bode well for PPL-100 as a unique protease inhibitor," he concluded.


PPL-100, is a phosphorylated Pro-drug of Procyon's PL-100 protease inhibitor. PL-100 is the active antiviral agent that is potent, specific and non-cytotoxic with a favorable cross-resistance profile in drug and multi-drug resistant strains of HIV-1. PL-100 is active against several HIV-1 strains specifically selected for key mutations that render these strains resistant to currently-marketed protease inhibitors. Preclinical safety studies as well as animal pharmacokinetic studies have recently been completed and human clinical studies expected to commence by the end of the year.


Procyon Biopharma Inc. is a biotechnology company actively engaged in the discovery and development of innovative therapeutics in the fields of cancer and HIV/AIDS. The Company leverages its strengths in research and clinical development, bringing products through late-stage clinical trials and then evaluating the best options for further development, such as co-development and licensing. Procyon's pipeline includes: PCK3145, a non-toxic peptide soon to enter a Phase II North American trial for the treatment of advanced metastatic prostate cancer; TVT-Dox, a tumor vasculature targeting technology for the treatment of solid tumors for which an IND filing is expected within 12 months; and, PPL-100, a protease inhibitor for the treatment of drug- resistant HIV/AIDS soon to enter the clinic. Procyon has won the 2005 Frost & Sullivan Award for Excellence in Technology for its overall scientific and technological contributions towards the advancement of cancer therapy. Headquartered in Montreal, Procyon shares are listed on the Toronto Stock Exchange (TSX) under the ticker symbol PBP. For more information, visit .

This release contains forward-looking statements that reflect the company's current expectation regarding future events. The forward- looking statements involve risks and uncertainties. Actual events could differ materially from those projected herein and depend on a number of factors including, but not limited to, changing market conditions, successful and timely completion of clinical studies, uncertainties related to the regulatory approval process, establishment of corporate alliances and other risks detailed from time to time in the company's filings.


CONTACT: Procyon Biopharma Inc.: Julie M. Thibodeau, Director,Communications, ; ;(514) 685-2000 ext 118

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