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Procyon BioPharma Inc. (PBP.TO) Reports First Pharmacokinetic Results For Its HIV Protease Inhibitor, PPL-100

10/19/2005 5:13:06 PM

MONTREAL, March 23 /PRNewswire-FirstCall/ -- Procyon Biopharma Inc. (TSX:PBP) reported today the first pharmacokinetics results with PPL-100, a phosphorylated pro-drug of its protease inhibitor, PL-100. Initial in vitro study results indicated that PPL-100 is 1000-fold more water soluble than its precursor, PL-100. More importantly, pharmacokinetics studies conducted in rats showed a two- to three-fold improvement in key pharmacokinetic parameters such as maximum plasma concentration (Cmax) and oral bioavailability compared to PL-100. Plasma levels obtained with PPL-100 in rats suggest that PPL-100's previously-reported broad and favorable cross resistance profile will be supported in a clinical setting by encouraging pharmacokinetics results at this time. Dr. Jinzi J. Wu, Vice President, Preclinical and Basic Research, will present the latest resistance and pharmacokinetic data on PPL-100 at the 6th International Workshop on Clinical Pharmacology of HIV Therapy, on April 28 in Quebec City.

"As oral bioavailability remains a challenge for the HIV protease inhibitor class, we are most happy to report significant progress with the development of PPL-100, a pro-drug of PL-100, which is much more water soluble as well as more bioavailable," said Hans Mader, President and Chief Executive Officer of Procyon Biopharma Inc. "PPL-100 presents the same favorable cross-resistance profile as the original molecule acquired from Pharmacor. However, its improved solubility and bioavailability should allow for the same therapeutic effect on drug-resistant HIV-infection but with potentially improved dosing characteristics," he added.

Previously, the results of cross-resistance studies conducted at ViroLogic Inc. showed that PPL-100's median EC95 (i.e. the concentration required to inhibit 95% of the viral replication of the diverse drug-resistant HIV-1 variants tested) was 72 to 83 ng/ml. When adjustments were made for protein binding, the median EC95 was estimated to be 430 to 500 ng/ml. Oral dosing with 100 mg/kg of PPL-100 in conjunction with 17 mg/kg of ritonavir, used as a pharmacokinetic boosting agent, in rats showed that adequate plasma levels could be maintained above this level for up to 10 hours. On the basis of PPL-100's cross-resistance data and these pharmacokinetics results, it is expected that equivalent doses of PPL-100 in man will effectively inhibit replication of protease-resistant HIV strains. Moreover, this preliminary data also suggests that PPL-100 could be administered using a convenient twice-daily dosing regimen.

As reported in February 2005, a large viral cross-resistance study in collaboration with ViroLogic showed that PPL-100 and its back-up analogue PL-337 had a highly competitive and unique cross-resistance profile when compared to other commercially available protease inhibitors. PPL-100, its back-up compound, PL-337, and six commercially available protease inhibitors: amprenavir, atazanavir, indinavir, lopinavir, nelfinavir and saquinavir were tested for antiviral activity against 63 drug resistant HIV strains. On average, PPL-100 showed better cross-resistance profile than the approved protease inhibitors tested. Both median and mean fold-change in EC50 for PPL-100 were significantly lower than the approved protease inhibitors tested. In addition the viral strains selected for the study also contained important resistant mutations for two other compounds currently in clinical studies by pharmaceutical companies. These strains were found to be susceptible to both PPL-100 and PL-337.

Procyon is planning to conduct additional pharmacokinetics studies in another animal species to confirm the results obtained in rodents. The Company is also conducting 14 to 28 day GLP toxicology studies in two different animal species and is on track to file an Investigational New Drug (IND/CTA) submission and initiate a Phase I first-in-man trial (FIM) with healthy volunteers during the second half of 2005.

About Procyon Biopharma

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 partnerships and licensing. Procyon's core products are PCK3145, a non-toxic peptide soon to enter a Phase II North American trial for advanced metastatic prostate cancer; and PPL-100, a protease inhibitor for drug-resistant HIV/AIDS soon to enter the clinic. Headquartered in Montreal, Procyon shares are listed on the Toronto Stock Exchange (TSX) under the ticker symbol PBP. ( )

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: Christian Marcoux, M.Sc.Director, Communications, ProcyonBiopharma Inc., (514) 685-2000,

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