Panacos Pharmaceuticals, Inc. (NASDAQ: PANC), a biotechnology company dedicated to developing the next generation of antiviral therapeutic products, today announced that its programs were the subject of five poster presentations at the fourth International AIDS Society Conference on Pathogenesis, Treatment, and Prevention (IAS) held this week, July 22-25, in Sydney, Australia. The data presented ranged from pre-clinical virology of new antiviral compounds in discovery to clinical studies of the Company's lead compound, bevirimat, in healthy volunteers and HIV-positive patients.

The first presentation was an analysis of the safety of bevirimat (PA-457), Panacos' lead HIV drug candidate, in completed multiple-dose clinical trials. This analysis was presented by Dr. Scott McCallister, Panacos' Chief Medical Officer, in a poster titled, ?Multiple dosing of the novel HIV-1 maturation inhibitor bevirimat (BVM): aggregate adverse event (AE) and laboratory data from four short-term studies.? The presentation was based on combined laboratory and safety data from four clinical studies where bevirimat was administered over a range of doses to 165 individuals. The data showed bevirimat was well-tolerated, had an adverse event rate similar to placebo, and had no clinically relevant laboratory test abnormalities.

The second presentation described a study examining the potential for drug interactions when bevirimat and the approved anti-HIV drug ritonavir are co-administered. Titled, ?Minimal effect of ritonavir (RTV) on the pharmacokinetics (PK) of bevirimat (BVM) in healthy volunteers,? it was presented by Dr. David Martin, Panacos' Senior Vice President of Drug Development. The study concluded that co-administration of bevirimat with ritonavir was well-tolerated and that bevirimat did not impact the pharmacokinetics of ritonavir. A modest reduction in bevirimat plasma concentrations was observed when co-administered with ritonavir, which Panacos does not believe will be clinically relevant.

Dr. Martin also presented a study of the pharmacokinetics and distribution of bevirimat in animals titled, ?The Disposition of 14C-Bevirimat (BVM) in Rats and Marmosets.? After administration of radiolabeled bevirimat in rats and marmosets, bevirimat was found to be widely distributed into peripheral tissues, including potential sanctuary sites for HIV infection. As found in previous studies, metabolism was primarily by glucuronidation, a pathway that is unlikely to result in significant drug interactions with approved HIV drugs.

Panacos' first candidate in its second-generation maturation inhibitor program was reviewed in an oral poster discussion titled, ?Characterization of PA1050040 [PA-040], a second generation HIV-1 maturation inhibitor,? presented by Ms. Nicole Kilgore of Panacos. The presentation notes that PA-040 has reduced serum protein binding compared to bevirimat, as well as a unique resistance profile, while retaining bevirimat's advantageous metabolic characteristics that minimize the potential for drug-drug interactions.

Finally, an update on Panacos' HIV fusion inhibitor program was provided in ?Discovery of a Novel Class of Orally Bioavailable HIV-1 Fusion Inhibitors,? an oral poster discussion presented by Dr. Karl Salzwedel of Panacos. This presentation outlined the identification of three structurally distinct series of drug-like small molecules, which inhibit HIV fusion at a different site than the approved HIV fusion inhibitor FUZEON. These compounds potentially represent a new approach to target HIV infection. The program is currently at the lead selection stage, with the goal of initiating Phase 1 clinical studies in 2008.

?The broad scope of these presentations highlights the strength of Panacos' portfolio,? said Graham P. Allaway, Ph.D., Panacos' President and Chief Operating Officer. ?The bevirimat presentations highlight several key attributes of this first-in-class HIV maturation inhibitor, currently in Phase 2b clinical testing. We are also pleased to report progress on our second generation maturation inhibitor and fusion inhibitor programs.?

For more information about IAS, please visit www.ias2007.org.

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 strains, including those 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 conducting 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.

FUZEON is a trademark of Trimeris, Inc.

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, and the development, anticipations and plans for the Company's second generation HIV-1 maturation inhibitor program, and the Company's HIV fusion inhibitor program 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 and the Company's Quarterly Reports on Form 10-Q. 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.

Panacos Pharmaceuticals, Inc.
Jill Smith
Director, Corporate Communications
240-449-1250
jsmith@panacos.com
or
Peyton Marshall
EVP and Chief Financial Officer
617-926-1551
pmarshall@panacos.com