Biotech Values

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Pharmasset Announces Clevudine Presentation at AASLD
Friday October 27, 7:05 am ET
-- The 57th Annual Meeting of the American Association for the Study of Liver Diseases --

PRINCETON, N.J., Oct. 27 /PRNewswire/ -- Pharmasset announced today that a "Late Breaker" presentation describing the results of Study 303, a 48 week follow-on study to the Korean Phase 3 drug registration trial of Clevudine for the treatment of Hepatitis B, will be presented at the 57th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) being held in Boston, Massachusetts from October 27-31, 2006. The Clevudine abstract can be viewed on the AASLD website at http://www.aasld.org.


Clevudine is a nucleoside analogue that has shown potent anti-HBV activity in both in vitro and late-stage clinical studies in over 600 HBV-infected patients. The poster presentation at AASLD will describe the results of a study conducted by Bukwang Pharmaceuticals. In this study, Clevudine demonstrated potent antiviral activity in e-antigen positive (HBeAg+) and e-antigen negative (HBeAg-) patient populations, along with a marked 12-week post-treatment antiviral effect or sustained virological response (SVR) in both patient populations. Clevudine was generally well tolerated throughout the course of this study. Clevudine received conditional drug approval from the Korean Food & Drug Administration in July 2006, and the product launch in Korea is anticipated by the end of 2006.

"In this study, 31% of HBeAg+ patients and 92% of HBeAg -- patients have undetectable HBV 12 weeks after the end of treatment," stated Schaefer Price, Pharmasset's President & CEO. "The duration of Clevudine's post-treatment effect is unique. To our knowledge, Clevudine is the only HBV therapeutic agent, investigational or approved, that has demonstrated potentially clinically meaningful SVR levels at 12 weeks and 24 weeks post-treatment. We look forward to initiating our U.S. and European registration studies of Clevudine in 2007."

Dr. Young Hwa Chung of the Asan Medical Center in Seoul, South Korea, who is a principal investigator in the Korean Phase 3 registration studies, will present the poster, entitled "Six month maintenance therapy with 10 mg Clevudine maintains the viral suppression and biochemical improvement achieved with six months therapy with 30 mg," on Monday, October 30, 2006 at 8:00am (EST) in Exhibit Hall C at the John B. Hynes Convention Center in Boston. The published abstract summary follows:

Background: In the pivotal Korean phase III clinical trials, clevudine 30 mg once daily for 6 months showed potent antiviral activity along with a marked post-treatment antiviral effect. E-max modeling has shown that the 30 mg dose achieved >90% of maximum predicted effect compared to approximately 77% at the 10 mg dose.

Objective: To evaluate the effect of 6 months maintenance therapy with 10 mg clevudine once daily in treatment-naive patients following 6 months therapy at 30 mg once daily.


Method: Safety, antiviral activity, biochemical improvement and serologic
response were monitored in patients receiving clevudine 30 mg for 24 weeks
followed by clevudine 10 mg for an additional 24 weeks as a maintenance
therapy with a 12-week follow-up period. Preliminary results from the 54 naive
patients (39 HBeAg(+), 15 HBeAg(-)) who have completed the study are presented
here.

Results:
HBeAg Positive HBeAg Negative
Week Week Week Week Week Week
24(1) 48(2) 60(3) 24(1) 48(2) 60(3)
Percentage of
Patients with
HBV DNA <300 53 68 31 100 100 92
copies/ml

Percentage of
Patients with
ALT 82 89 89 67 100 85
Normalization

Percentage of
Patients with 8 16 17 - - -
HBeAg Loss

(1)End of 24 week treatment with 30mg of Clevudine
(2)End of 24 week treatment with 10mg of Clevudine
(3)End of 12 week follow-up period

Conclusion: Clevudine 30 mg once daily therapy was well tolerated and demonstrated significant viral suppression and biochemical improvement. While a maintenance dose of 10 mg once daily is not recommended due to the potential for resistance selection, it was able to sustain the antiviral and biochemical responses achieved with 30 mg.

About Clevudine

Clevudine is an oral, once-daily pyrimidine nucleoside analog that we are developing for the treatment of HBV. We licensed clevudine from Bukwang Pharm. Co., Ltd., a South Korean pharmaceutical company. Clevudine is not an HBV DNA chain terminator like existing nucleoside analog drugs for the treatment of Hepatitis B. In contrast, Clevudine acts directly on the HBV-polymerase to reduce its ability to incorporate nucleosides into new viral DNA chains. In preclinical animal models, Clevudine also demonstrated the ability to significantly reduce covalently closed circular DNA, or cccDNA, the form of HBV that is believed to be responsible for the persistence of an HBV infection.

Clevudine has been studied in twelve completed clinical trials in a total of more than 600 patients. In two completed South Korean Phase 3 clinical trials, Studies 301 and 302, clevudine demonstrated the ability to significantly reduce HBV viral load in patients. In addition, 24 weeks after cessation of treatment, the average viral load for patients who had received clevudine was still statistically significantly lower than the average viral load for patients who had received placebo. To our knowledge, no other HBV oral therapeutic has demonstrated this prolonged anti-viral effect. We also believe that clevudine may be complementary to existing HBV treatments and has the potential to be used as either a single agent or in combination with existing therapies.