December 21, 2004

USHERCELL'S NOVEL CLINICAL TRIAL DESIGN FACES RECRUITMENT CHALLENGES

CONTRACEPTIVE DEVELOPMENT TIMELINE NOT AFFECTED

Toronto, Ontario, December 21, 2004 -- Polydex Pharmaceuticals Limited (NASDAQ:POLXF) (BSE:PXL) previously announced (press releases January 21, 2004 and March 16, 2004) embarking upon two separate clinical trials to assess the efficacy of Cellulose Sulphate (Ushercell) as a contraceptive, and is advised by CONRAD that one of the two trials has been discontinued due to limited patient recruitment.

The other previously reported contraceptive trial involving 200 couples (press release January 21, 2004), remains ongoing and is proceeding according to the trial protocol.

CONRAD had anticipated that the protocol design for the trial announced in March 2004, might present some recruitment challenges, and has provided Polydex with the following statement to explain the decision to discontinue that trial at this time:

"The innovative single-cycle, placebo-controlled contraceptive effectiveness trial of cellulose sulfate (the "True Efficacy" trial, protocol 9821), for which an enrollment of 150 couples was intended, was stopped after enrollment of 68 couples, due to difficulty with recruitment.

The novel design of this trial was different from the traditional contraceptive effectiveness trial in that it sought couples who wished to conceive but were willing to wait one month, during which they would be randomized to use either placebo or cellulose sulfate during each act of intercourse. In a traditional trial, couples are sought who wish to avoid pregnancy and agree to use either the study drug or another contraceptive for at least 6 months. It was anticipated that recruitment for the True Efficacy trial would be difficult in terms of finding couples who were willing use an experimental contraceptive during a time in their life when they desired a pregnancy. It proved to be an insurmountable challenge. Despite opening of an additional site and doubling the length of time allowed for enrollment, less than half the intended number of couples was recruited. This decision should in no way reflect on the potential of cellulose sulfate as a contraceptive."

Discontinuation of the innovative study does not affect the timeline for moving forward on the contraception indication.

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. 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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