Isis Pharmaceuticals, Inc. has granted an exclusive worldwide license to ImQuest Pharmaceuticals Inc. for the development and commercialization of ISIS 5320, a compound that has been shown in vitro and in vivo to be a potent and specific inhibitor of HIV, the virus that causes AIDS. ImQuest plans to develop ISIS 5320 as a topical microbicide therapy to prevent the sexual transmission of HIV throughout the world, but especially in developing countries.

ISIS 5320, a phosphorothioate oligonucleotide, specifically and potently inhibits the attachment of HIV to target cells by interfering with the interaction of the HIV receptor gp120 with CD4 on target cells. The safety of ISIS 5320 has been demonstrated in human clinical trials as a therapeutic treatment for systemic HIV infection and thus ImQuest projects that the time to develop the agent as a microbicide will be significantly shortened, allowing the microbicide to enter human clinical trials in early 2007. ImQuest is also exploring the use of ISIS 5320 in combination with other microbicide products in their drug portfolio. ImQuest expects to file a new Investigational New Drug Application (IND) with the FDA in the fourth quarter of 2006.

Dr. Robert W. Buckheit, Jr., President and Chief Scientific Officer of ImQuest Pharmaceuticals said, "Our company is dedicated to playing a major role in the humanitarian global effort to develop an effective female controlled preventive therapy that will result in decreased incidence of HIV transmission, especially in developing countries of Africa and Southeast Asia. ISIS 5320 is one of a series of novel microbicides that we believe will provide significant therapeutic options for women when used as a single-agent or in combination with other drugs."

"Licensing ISIS 5320 to ImQuest will allow us to benefit from ImQuest's expertise and highly focused research efforts in anti-HIV therapeutics, while ImQuest will benefit from our experience in oligonucleotide drug development and access to our intellectual property," C. Frank Bennett, Ph.D., Senior Vice President, Research at Isis Pharmaceuticals said adding, "This transaction with ImQuest is yet another example of our successful satellite company strategy, where we gain from a partner's knowledge in concentrated research programs and we grant our partner access to our expertise in RNA-based drug development and access to our proprietary chemistries and leading patent estate. Through these relationships, we are expanding the reach and potential of our discoveries in RNA-based therapeutics and participating in the success of multiple companies and products."

As part of the agreement, ImQuest Pharmaceuticals will have sole responsibility for clinical development and commercialization of the drug and will pay Isis royalties on product sales.