TORONTO, Feb. 26, 2008 (PRIME NEWSWIRE) -- Polydex Pharmaceuticals Limited (Nasdaq:POLXF) reports that CONRAD, a lead investigator of Ushercell, has completed a clinical trial using rhesus monkeys. The results of that trial have today been reported at the Microbicides 2008 conference ongoing in New Delhi, India. Ushercell is a cellulose sulphate, cotton based gel envisioned for use as a contraceptive and in the prevention of sexually transmitted infections, including HIV.
This trial was undertaken after the Phase III human clinical trials were halted in January of 2007, when an interim analysis of data revealed a higher than expected seroconversion rate among participants at some, but not all trial sites. (See news release January 31, 2007). This new trial was commenced with the objective to try and understand why Ushercell had not shown effectiveness in the trials with women. Prior to the commencement of the Phase III HIV trials, scientists had evaluated data from 11 previous clinical studies done in Africa, India, the U.S. and Europe. None of the data suggested that the product could increase the susceptibility to HIV.
In this trial, two groups of 6 rhesus macaques each were treated intravaginally with 2 ml of HEC-based "universal" placebo or 6% Ushercell gel (the same clinical formulas used in the Phase III trials) and challenged 30 minutes later with a mixture of R5 and X4 tropic simian-human immunodeficiency viruses (SHIV). The gel/virus exposures were repeated at weekly intervals for up to 13 weeks and infection monitored for 24 weeks after the first exposure to the virus.
While 5 of 6 macaques were infected in the placebo group, none of the animals in the Ushercell gel group were infected. This data suggested that consistent vaginal application of Ushercell gel effectively reduced the infectivity of the virus, significantly decreasing the rate of vaginal mucosal SHIV transmission following repeated virus exposures.
There is not a clear explanation at this point for why Ushercell would demonstrate effectiveness in monkeys and not in humans, however certain hypotheses are plausible. According to CONRAD researchers, humans may not have consistently used the gel with every act of intercourse. Another CONRAD hypothesis is that they may have used the gels much more frequently than in the monkey study, possibly irritating the vaginal mucosa or changing its microflora. Although scientifically sound, the monkey model has not been clinically validated yet and may differ from the actual human conditions of transmission in a way that affects its predictive power.
High frequency of use may have been a factor in the enhanced HIV transmission seen in certain groups of women. This may be due to a possible cervicovaginal inflammation or disruption of the normal mucosal immune responses. If these adverse events were induced by formulation ingredients other than cellulose sulphate, the formula could be changed to prevent this from happening. For example, the preservative in the Ushercell formulation, benzyl alcohol, is thought to cause a slight tingling sensation amongst users and may also be responsible for producing an irritative effect.
As reported on December 23, 2007, CONRAD has also commenced a Phase I trial to assess the safety of several vaginal products, including Ushercell. The safety study of 60 women is being done using existing and new methodologies for evaluating candidate vaginal products, and includes new safety markers that have not previously been studied in women using any microbicide candidate. In addition to providing information about these products, the study will look at the correlation between clinical and preclinical results, thereby making it easier to use preclinical studies to eliminate products that may have an inflammatory effect.
Polydex Pharmaceuticals Limited, based in Toronto, Ontario, Canada, is engaged in the research, development, manufacture and marketing of biotechnology-based products for the human pharmaceutical market, and also manufactures bulk pharmaceutical intermediates for the worldwide veterinary pharmaceutical industry. www.Polydex.com
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CONRAD is a cooperating agency of USAID committed to improving reproductive health by expanding the contraceptive choices of women and men and by helping to prevent the transmission of HIV/AIDS and other sexually transmitted diseases. CONRAD is administered through the Department of Obstetrics and Gynecology at Eastern Virginia Medical School (EVMS) in Norfolk, VA and headquartered in Arlington, VA. www.conrad.org
Note: This press release contains forward-looking statements, within the meaning of the United States Securities Act of 1933, as amended, and the United States Securities Exchange Act of 1934, as amended, regarding Polydex Pharmaceuticals Limited, including, without limitation, statements regarding expectations about future revenues or business opportunities and developments relating to Ushercell, partner relationships or other potential research projects. These statements are typically identified by use of words like "may", "could", "might", "expect", "anticipate" or similar words. Actual events or results may differ materially from the Company's expectations, which are subject to a number of known and unknown risks and uncertainties including but not limited to changing market conditions, future actions by the United States Food and Drug Administration or equivalent foreign regulatory authorities as well as results of pending or future clinical trials. Other risk factors discussed in the Company's filings with the United States Securities and Exchange Commission may also affect the actual results achieved by the Company.
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