Panacos Presents Bevirimat Overview at 10th International Meeting of the Institute of Human Virology.

WATERTOWN, Mass. -- Panacos Pharmaceuticals, Inc. (Nasdaq:PANC), a biotechnology company dedicated to developing the next generation of antiviral therapeutic products, today announced that Panacos' President and COO, Graham P. Allaway, Ph.D., made a plenary presentation on bevirimat (PA-457) at the 10th International Meeting of the Institute of Human Virology (IHV) in Baltimore, MD on November 17, 2006.

Additional virology analysis has been completed on clinical patient isolates from the completed bevirimat Phase 2a study, where bevirimat was administered orally to HIV infected patients for 10 days as a monotherapy. Potent antiviral effects were found in that study, with a median viral load reduction on day 11 of approximately 1 log10 at the highest (200mg) dose with individual patients having greater than a 1.5 log10 reduction at that time point. As previously reported, standard population genetic sequencing analyses demonstrated that no bevirimat-resistant virus developed in patients who received bevirimat in this Phase 2a study. At the IHV conference Dr. Allaway provided the results of phenotyping experiments where viruses from all patients in the 200mg cohort were propagated and tested for in vitro sensitivity to bevirimat. He reported that viruses from these patients were sensitive to the drug, with IC50 (median inhibitory concentration) values ranging from 12.0 to 88.2 nM, similar to the range seen with other patient isolates.

Dr. Allaway also presented results of several recently completed in vitro studies of bevirimat, including an extended analysis of in vitro synergy between bevirimat and approved drugs. Previous in vitro studies of bevirimat found synergy with most approved drugs tested. In the most recent studies, bevirimat was also found to be synergistic with emtricitabine, tenofovir, and lopinavir. Additivity was observed with all other drug combinations tested, including atazanavir, and there was no evidence of antagonism between bevirimat and any approved drugs tested in these studies.

Finally, Dr. Allaway presented data on the Panacos second generation maturation inhibitor program. One goal of this program is to develop maturation inhibitors that may have activity against bevirimat-resistant HIV, should that appear in patients in the future. Panacos has identified analogs of bevirimat that appear to have the same mechanism of action as bevirimat and similar antiviral potency. Some of these analogs retain wild-type activity against a viral mutant found in in vitro studies that exhibits resistance to bevirimat. Furthermore, analogs with reduced human serum protein binding have been identified, which could have greater in vivo activity against bevirimat-resistant virus.

Panacos plans to file an IND by the end of 2006 to initiate clinical testing of a second generation maturation inhibitor.

About Panacos

Panacos is developing the next generation of anti-infective products through discovery and development of small molecule oral drugs for the treatment of HIV and other major human viral diseases. HIV infects approximately 1.7 million people in North America and Western Europe and approximately 40 million people worldwide. Approximately 650,000 patients are treated annually for HIV in the United States and Western Europe. Resistance to currently available drugs is one of the most pressing problems in HIV therapy and the leading cause of treatment failure. Panacos' proprietary discovery technologies are designed to combat resistance by focusing on novel targets in the virus life cycle, including virus maturation and virus fusion.

Panacos' lead candidate, bevirimat (PA-457), is the first in a new class of oral HIV therapeutics under development called maturation inhibitors, discovered by Panacos scientists and their academic collaborators. Based on its novel mechanism of action, bevirimat is designed to have potent activity against a broad range of HIV, including strains that are resistant to existing classes of drugs. The Company has completed seven clinical studies of bevirimat in over 300 subjects, showing significant reductions in viral load in HIV-infected subjects and a promising safety profile, and is currently in Phase 2b clinical trials. In Phase 2b, bevirimat is being tested in combination with approved drugs, with the goal of selecting a dose or doses to take into pivotal clinical trials. Initial data from the first cohort is targeted for release by the end of this year.

About The Institute of Human Virology

IHV is a center of The University of Maryland Biotechnology Institute and is affiliated with the University of Maryland School of Medicine. For more information visit www.ihv.org/meeting.

Except for the historical information contained herein, statements made herein, including those relating to bevirimat's clinical development, the potential results of treatment with bevirimat and future clinical trials and clinical practice are forward-looking statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. These statements involve risks as set forth in the Company's filings with the Securities and Exchange Commission, including, but not limited to, the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2005. These risks and uncertainties could cause actual results to differ materially from any forward-looking statements made herein. The Company undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise, except as required by applicable law.