8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 26, 2008

PANACOS PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Delaware	0-24241	11-3238476
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

134 Coolidge Avenue

Watertown, Massachusetts 02472

(Address of principal executive offices and zip code)

Registrant’s telephone number, including area code: (617) 926-1551

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

ITEM 8.01 OTHER EVENTS.

On October 26, 2008, Panacos Pharmaceuticals, Inc. announced that data from its Phase 2b study of bevirimat, Panacos’ lead HIV-1 Gag maturation inhibitor, was shown in an oral presentation at the Interscience Conference on Antimicrobial Agents and Chemotherapy in Washington, DC. The key findings from Study 203 demonstrated that bevirimat appeared safe and effective in both treatment-experienced and treatment-naïve HIV-positive patients, established the bevirimat dose response curve, and prospectively confirmed factors that predict patient response to bevirimat treatment. A copy of the press release is filed herewith as Exhibit 99.1 and is incorporated herein by reference.

On October 27, 2008, Panacos announced that the bevirimat Study 204 achieved its primary objective by demonstrating bevirimat plasma levels in HIV-positive patients to be in a target range for virologic reduction. A copy of the press release is filed herewith as Exhibit 99.2 and is incorporated herein by reference.

ITEM 9.01 FINANCIAL STATEMENTS AND EXHIBITS.

(d) Exhibits.

Exhibit No.	Description
99.1	Press release of Panacos Pharmaceuticals, Inc. dated October 26, 2008.
99.2	Press release of Panacos Pharmaceuticals, Inc. dated October 27, 2008.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	PANACOS PHARMACEUTICALS, INC.
Dated: October 28, 2008	By:	/s/ Alan W. Dunton
		Alan W. Dunton, M.D. President and Chief Executive Officer

EXHIBIT INDEX

Exhibit No.	Description
99.1	Press release of Panacos Pharmaceuticals, Inc. dated October 26, 2008.
99.2	Press release of Panacos Pharmaceuticals, Inc. dated October 27, 2008.

EX-99.1

Exhibit 99.1

Jane Pritchett Henderson Chief Financial and Business Officer Panacos Pharmaceuticals 617-926-1551 Catherine Watts Collier Vice President Burns McClellan 212-213-0006 (office) 917-886-5586 (mobile)

Panacos Presents Phase 2b Bevirimat Data at the 48th Annual

Interscience Conference on Antimicrobial Agents and Chemotherapy

Watertown, MA (October 26, 2008) – Panacos Pharmaceuticals, Inc. (NASDAQ: PANC), a biotechnology company dedicated to developing the next generation of antiviral therapeutic products, today announced that data from the Company’s Phase 2b study of bevirimat, Panacos’ lead HIV-1 Gag maturation inhibitor, was shown in an oral presentation at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Washington, DC. The key findings from Study 203 demonstrated that bevirimat appeared safe and effective in both treatment-experienced and treatment-naive HIV-positive patients, established the bevirimat dose-response curve, and prospectively confirmed factors that predict patient response to bevirimat treatment.

The data demonstrated a mean viral load reduction was - -1.18 log₁₀ copies/mL after 14 days of bevirimat treatment in the 31 bevirimat-treated patients in Study 203 who were free of key baseline Gag polymorphisms and who had bevirimat trough levels above the minimum target of 20 µg/mL. In addition, 91% of patients with these two response predictors had at least a 0.5 log₁₀ viral load reduction by week 2 with a maximum treatment response of 2.03 log₁₀.

Consistent with earlier studies, bevirimat was well-tolerated, with a safety profile comparable to earlier studies where bevirimat have been indistinguishable from placebo through the 14 days of treatment.

The Study 203 data were shown earlier today in an oral presentation by Dr. Jacob Lalezari, Assistant Clinical Professor of Medicine at UC San Francisco/Mount Zion Hospital, at the 48th ICAAC in Washington, D.C. Dr. Lalezari commented, “I am pleased to have presented these important data, which strongly support the further development of this first-in-class HIV maturation inhibitor. The data support the clinical use of bevirimat in treatment-experienced patients who often have limited options.”

“In addition to the significant viral load reduction seen in two weeks and the encouraging short-term safety profile, these results demonstrate that patients free of specific baseline Gag polymorphisms are most likely to respond to bevirimat,” Scott McCallister, M.D., Panacos’ Chief Medical Officer. “Pending regulatory concurrence, these predictors of response will be used to guide the selection of patients in Phase 3 clinical studies.”

In a separate poster presentation, Panacos reported additional data from Study 203, confirming the top of the dose-response curve was achieved at doses of less than 400mg daily in a liquid formulation. Furthermore, the pharmacokinetic/pharmacodynamics modeling supported the finding that patients with a bevirimat trough level of > 20 µg/mL and who are free of polymorphisms at Gag positions 369, 370 and 371 were the most likely to respond to bevirimat treatment with a relevant virologic response.

In the U.S., multi-center, double-blind, randomized Phase 2b study (Study 203), 75 patients were given bevirimat for 14 days. Baseline clinical and virological variables were assessed to establish that the determinants of bevirimat response were critical baseline Gag polymorphisms, or variants in the amino acid sequence. The prospective component of Study 203 confirmed that these Gag polymorphisms are predictors of response to treatment with bevirimat.

The polymorphisms that predict response to bevirimat are located at three codon positions on the 500-amino acid HIV-1 Gag protein. Bevirimat specifically blocks a late step in processing of Gag, leading to the production of virus particles that are structurally defective and are incapable of spreading infection around the body. Patients with the virus containing the most commonly occurring amino acids at positions 369, 370 or 371 on Gag are more likely to respond to bevirimat treatment. In contrast, those patients whose virus has polymorphisms at these positions are less likely to respond to the drug.

The frequency of Gag polymorphisms is variable, depending on the population tested. Based on a North American academic patient database and a 2007 publication from HIV clinics in France, the range of patients free of Gag polymorphisms (and hence expected to have an optimal treatment response) was approximately 60-68%. Any change in the amino acid sequence of Gag may be determined easily with a simple and rapid genotype assay, the type of HIV resistance test most frequently ordered by HIV-treating clinicians.

Panacos plans to use a newly developed 100mg tablet formulation of bevirimat in future clinical studies.

More information on the oral and poster presentations at ICAAC:

Sunday, October 26, 8:30 am EST

Slide Session #80 Antiretroviral Therapy; Location: Independence A (Grand Hyatt)

• Oral Presentation by Dr. Jacob Lalezari: A Phase 2 Safety and Efficacy Study of Bevirimat (BVM) in Heavily Treatment Experienced HIV+ Patients Identifies the Target Phase 3 Study Profile

Sunday, October 26, 11:15 am – 12:15 pm EST

Poster Session #91 HIV Pharmacokinetics/Dynamics; Location: Hall C

• Pharmacokinetics/Pharmacodynamics of Bevirimat (BVM) in a 14-day Functional Monotherapy Trial in HIV-infected Patients

The poster and the slides from ICAAC will be available on the Panacos’ website beginning on Monday, October 27, 2008.

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. Approximately 1 million people in the United States and approximately 33

million people worldwide are living with HIV. Approximately 475,000 patients are treated annually for HIV in the United States. 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.

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, 2007. 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.

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EX-99.2

Exhibit 99.2

CONTACT:

Jane Pritchett Henderson

Chief Financial and Business Officer

617-926-1551

Panacos Announces Preliminary Results of Bevirimat Study 204

Results confirm bevirimat tablet formulation

dosed twice daily achieves target plasma levels

Watertown, MA (October 27, 2008) – Panacos Pharmaceuticals, Inc. (NASDAQ: PANC) announced today the bevirimat Study 204 achieved its primary objective by demonstrating bevirimat plasma levels in HIV-positive patients to be in a target range for virologic reduction. Bevirimat is a novel HIV-1 Gag maturation inhibitor in Phase 2b testing, and the data from the successful completion of this study will be used to optimize the bevirimat tablet dose for future Phase 2 as well as Phase 3 registration trials.

After 14 days of bevirimat treatment given twice daily at doses of 200mg or 300mg (using the 50mg tablet), 100% of 32 treatment-naïve and treatment-experienced patients in Study 204 had bevirimat plasma concentrations well above the previously identified minimum target of 20µg/mL. In addition, bevirimat’s safety profile was comparable to earlier studies where it had been indistinguishable from placebo.

Taken in combination with the recent bioavailability data from Study 114, which utilized the newly developed 100mg tablets, these findings from Study 204 indicate that upcoming Phase 2 and Phase 3 registration trials will utilize a convenient patient-friendly bevirimat formulation that consistently attains plasma levels in a desirable range.

“Study 204 was an important clinical milestone for Panacos and validated that twice daily dosing with a tablet formulation is a viable option to bring our patients to plasma levels well above the previously established target concentration required to have a treatment response. In addition, the short-term safety profile remains very encouraging and is similar to earlier studies, comparable to placebo. All of the data generated to date consistently point to the value of bevirimat as a useful component of antiviral drug regimens for people living with HIV,” stated Alan W. Dunton, MD, President and Chief Executive of Panacos. “We plan to initiate Study 205, our extended-duration trial of bevirimat in 100mg tablets, in the first half of 2009.”

Panacos Announces Results of Bevirimat Prospective Study, which Confirm Patient Response Predictors

Study 204 was a 14-day trial in 32 HIV patients (26 treatment-naïve and 6 treatment-experienced) conducted in Australia. Patients received bevirimat 50mg tablet doses of either 200mg or 300mg given twice a day for 14 days. Patients were not screened for inclusion based on the presence or absence of Gag polymorphisms, although this data was collected. The primary endpoint of the study was pharmacokinetics (i.e., Cmin, the level of bevirimat measured at Day 14 in blood plasma). Viral load also was measured. Patients who wished to continue treatment after Day 14 and include bevirimat in their optimized regimen were given that option, if they had achieved a 0.5 log₁₀ viral load reduction after 2 weeks of bevirimat monotherapy.

As noted, bevirimat was well-tolerated with the rate and type of adverse events similar to earlier studies. There were no serious adverse events and no adverse event-related discontinuations.

Bevirimat was well absorbed; all 32 patients exceeded the minimum target plasma concentration of 20µg/ml. Patients receiving 200mg BID had a mean Cmin of 47µg/mL, and patients receiving 300mg BID had a mean Cmin of 74µg/mL.

In the 26 treatment-naïve patients, the mean viral load reduction was -0.74 log₁₀ copies/mL, with individual responses up to -2.05 log₁₀ copies/mL. In the treatment-naïve patients who were free of Gag polymorphisms at positions 369, 370 or 371 (which the Company has determined to be the predictors of response to bevirimat), the mean viral load reduction was -0.93 log₁₀ copies/mL. In the treatment-naïve patients with Gag polymorphisms at one or more of these three positions, the mean viral load reduction was -0.60 log ₁₀ copies/mL. These results continue to support the use of Gag polymorphisms to determine response to bevirimat, and the Company plans to refine this genotyping approach further.

In the six treatment-experienced patients, the virologic data are not being included in the overall analysis because they stopped their prior treatment regimen just three days before beginning bevirimat monotherapy treatment, which resulted in highly variable viral load dynamics. Their data are being used for safety and pharmacokinetic analysis.

Panacos Announces Results of Bevirimat Prospective Study, which Confirm Patient Response Predictors

Based on a review of three independent North American and European patient data sets comprising 1,034 HIV-positive patients, 62% of patients are free of baseline Gag polymorphisms at codons 369, 370 or 371. While only 14 of the 32 patients in Study 204 from four clinics in Sydney, Australia, were free of these same polymorphisms, this does not significantly impact the growing database being used to assess the prevalence of Gag polymorphisms worldwide.

As announced on October 27, 2008, Panacos will provide a development update on its quarterly financial results call that will be held on November 5, 2008. The details can be found on the Company’s website at www.panacos.com.

Panacos’ Development Programs

Panacos’ lead compound, bevirimat (PA-457), is the first in the new class of HIV drugs under development called maturation inhibitors, discovered by Company scientists and their academic collaborators. Bevirimat is designed to have potent activity against a broad range of HIV strains, and studies have shown bevirimat is a potent inhibitor of HIV isolates that are resistant to currently approved drugs. Panacos has completed 15 clinical studies with bevirimat in nearly 650 patients and healthy volunteers, showing significant reductions in viral load in HIV-infected patients and a promising safety profile. It is currently in Phase 2b clinical studies. The Company previously determined the optimal dose range of bevirimat and identified patient response predictors to bevirimat, which now have been confirmed in multiple laboratory analyses and the prospective study. Panacos has recently developed a tablet formulation of bevirimat that demonstrates bioavailability and pharmacokinetics comparable to that of the previous solution formulation (Study 114). The Company completed its Phase 2b study of bevirimat (Study 204) that confirmed an optimal dose can be achieved with a twice daily dose of bevirimat tablets. Efficacy and additional safety obtained from Study 204 support the 100mg bevirimat tablet formulation should be studied further in HIV patients.

In addition to bevirimat, the Company has a second-generation program in HIV maturation inhibition that includes compounds with activity against HIV containing Gag polymorphisms. Panacos has also selected a lead compound, PA-161, for preclinical development in its oral HIV fusion inhibitor program.

Panacos Announces Results of Bevirimat Prospective Study, which Confirm Patient Response Predictors

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. Approximately 1 million people in the United States and approximately 33 million people worldwide are living with HIV. Approximately 475,000 patients are treated annually for HIV in the United States. 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.

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, 2007. 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.

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