Analysis of Ushercell HIV Trials Reveals Difference in Seroconversion Groups Not Statistically Significant

Polydex Continues Contraceptive Development

TORONTO, Ontario, July 25, 2007 -- Polydex Pharmaceuticals Limited (NASDAQ:POLXF) reports that today at the International AIDS Society 2007 Conference in Sydney Australia, Dr. Lut Van Damme of CONRAD, principal investigator of the Phase III clinical trial of Ushercell, reported further analysis of HIV results from the trial. The trial of Ushercell, a potential microbicide also known as cellulose sulfate, was halted in January of this year (see News Release January 31, 2007 <http://www.polydex.com/v2/news/07-01-31.html> ). Women who ‘seroconverted’ tested positive for HIV during the course of the clinical trials referred to herein.

Latest analysis of the data from the CONRAD study showed that the difference in HIV seroconversions between the Ushercell group and the placebo group was not statistically significant. There were more seroconversions in the Ushercell group, but the difference was not large enough to exclude the possibility that it could have occurred by chance. Out of 1,425 women who were enrolled in the trial, 41 seroconverted – 25 using Ushercell and 16 using the placebo gel. CONRAD will continue its investigation into the trial data and will do additional work to provide a scientific explanation for the seroconversions.

A separate HIV Phase III clinical trial of Ushercell conducted by Family Health International in Nigeria was also halted due to the safety concerns raised in the CONRAD trial, even though the interim results from that study did not show an increased risk of HIV infection among women using Ushercell. Of the 1,644 participants enrolled in that trial, 23 women tested positive for HIV while participating in the study, 10 of whom were in the group using Ushercell and 13 of them were using the placebo.

These studies were conducted in countries and communities hard-hit by the HIV epidemic. In South Africa, for example, 50% of the women who volunteered for trial participation were unable to participate because they were already HIV positive at the time of their screening visit. In Uganda, the rate was 32% at screening. Thus, each new infection that occurred during the trial must be viewed in the context of a truly devastating pandemic.

During the course of the trials, each woman received medical care, HIV/STI prevention counseling, and free condoms. Women who tested HIV positive during these studies also have access to HIV care and antiretroviral treatment when needed.

Ushercell had undergone 11 safety and tolerance trials prior to the commencement of these Phase III trials, and is considered to have demonstrated a strong safety profile in those studies.

George Usher, President and CEO of Polydex said, “Although two kinds of statistical analysis revealed differing information on HIV seroconversions trends, much work has yet to be done to explain the cause of those seroconversions. And while these findings lead investigators to conclude that Ushercell may have been no more effective at preventing HIV than the placebo gel as it was used in this trial, there is no evidence to suggest that Ushercell is no longer considered safe for use in other contexts, such as a lubricant or contraceptive product.”

In January of 2006, the Company announced results of a Phase II contraceptive efficacy trial that determined Ushercell is a highly effective contraceptive, concluding that the chance of pregnancy in 6 menstrual cycles of perfect use of Ushercell was 3.9% ( News Release January 26, 2006 <http://www.polydex.com/v2/news/06-01-26.html> ).

Mr. Usher also said, “Our vision has always been to develop Ushercell as a contraceptive product and we plan to now move forward with this aspect of the development plan. We are also awaiting results from a small Phase II trial in Brazil to determine if Ushercell may be effective in preventing bacterial vaginosis, which may lead to further development of this compound for additional uses”.

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.

Note: This press release may contain 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 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.

Contact for Polydex Pharmaceuticals Limited: Linda Hughes, 1-877-945-1621, Linda@northarm.com Linda@northarm.com>

Posted: July 2007

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