Bevirimat Data Presented at 15th Conference on Retroviruses and Opportunistic Infections.

WATERTOWN, Mass. -- Panacos Pharmaceuticals, Inc. (NASDAQ:PANC), a biotechnology company dedicated to developing the next generation of antiviral therapeutic products, today announced that its lead product candidate, the HIV maturation inhibitor bevirimat (PA-457), was the subject of two presentations at the 15th Conference on Retroviruses and Opportunistic Infections (CROI) held this week in Boston, MA.

Scientists from Panacos and Monogram Biosciences presented a study titled: "Measurement of Maturation Inhibitor Susceptibility using the PhenoSense[TM] HIV Assay." In this study, Monogram modified their PhenoSense drug susceptibility assay to analyze the activity of bevirimat against HIV strains with known bevirimat resistance mutations, as well as a reverse transcriptase and protease inhibitor multi-drug resistant virus. The assay provided activity data consistent with previous in vitro studies of bevirimat-resistant virus, suggesting that it is suitable for further development as a high-throughput phenotyping assay to measure the sensitivity of HIV from patients to bevirimat or other maturation inhibitors. The study reported that many of the bevirimat-resistant HIV-1 strains had reduced replication capacity (were less fit) than wild type virus. Using the phenotyping assay it was also shown that an HIV strain resistant to protease inhibitors and reverse transcriptase inhibitors was hypersusceptible to bevirimat.

In the second presentation, Dr. Catherine Adamson of Dr. Eric Freed's laboratory at the National Cancer Institute presented the results of another collaboration with Panacos, titled: "Viral Resistance to the HIV-1 Maturation Inhibitor Bevirimat (PA-457) in the Context of a Protease that Confers Resistance to Protease Inhibitors." In this study, recombinant HIV strains bearing both protease resistance and bevirimat resistance mutations were found in many cases to have impaired replication compared to viruses with just one of the resistance mutations. The authors concluded that protease inhibitor-resistant mutants may be less likely than wild-type isolates to develop bevirimat resistance.

"These two studies highlight the potential importance of bevirimat in the context of modern HIV therapy," said Graham Allaway, Ph.D., Panacos' Chief Operating Officer. "While we are continuing to look at a variety of factors that may contribute to patient response to bevirimat, Monogram's work demonstrates the power of its technology for assessing HIV drug resistance to maturation inhibitors. Dr. Adamson's presentation further highlights the potential utility of bevirimat in the protease inhibitor-resistant population."

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 33 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 strains, including those that are resistant to existing classes of drugs. The Company has completed nine clinical studies of bevirimat in over 475 patients and healthy volunteers, showing significant reductions in viral load in HIV-infected patients and a promising safety profile, and is currently in Phase 2b clinical trials. The Company also has a second-generation program in HIV maturation inhibition in clinical testing and a research program to develop oral HIV fusion inhibitors.

Phenosense[TM] HIV is a Trademark of Monogram Biosciences.

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, 2006. 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.