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PSI-7977 Trial Adds New Regimens

SUMMARY
The ELECTRON trial, testing the HCV polymerase inhibitor PSI-7977, has added new arms looking at regimens with shorter duration or no interferon for people with HCV genotypes 1, 2, and 3.

Direct-acting antiviral agents that interfere with various steps of the hepatitis C virus (HCV) lifecycle will revolutionize treatment. Initially these drugs will be used with standard therapy consisting of pegylated interferon alfa (Pegasys or PegIntron) plus ribavirin. While such regimens have higher cure rates and shorter durations, people with hepatitis C eagerly await combinations without interferon and its difficult side effects.

The experimental nucleotide HCV polymerase inhibitor PSI-7977 has demonstrated potent activity in early studies to date, suggesting that it may be a good candidate for use in interferon-sparing regimens. This might be especially true for people with easier-to-treat HCV genotypes 2 or 3. Studies presented at this year's European Association for the Study of the Liver (EASL) meeting showed promising results for people treated with PSI-7977 plus pegylated interferon/ribavirin or an all-oral combo of PSI-7977 plus PSI-938.

Below is an edited excerpt from a Pharmasset press release describing addition of new trial arms to the ongoing ELECTRON study looking at PSI-7977 regimens with no interferon or shorter-duration interferon.

Pharmasset Announces the Expansion of the
ELECTRON Trial in Chronic Hepatitis C

Princeton, N.J. -- June 8, 2011 -- Pharmasset, Inc. (Nasdaq: VRUS) announced today the addition of three treatment cohorts to the ELECTRON trial of PSI-7977, a nucleotide analog polymerase inhibitor, for the treatment of chronic hepatitis C (HCV). The rapid and consistent antiviral effects and high barrier to resistance demonstrated with PSI-7977 to date provide the rationale for additional exploratory regimens in this setting. This amendment will add one arm exploring 12 weeks of PSI-7977 monotherapy (without peginterferon and ribavirin) and two arms of interferon-sparing therapy: one for 8 weeks of PSI-7977 plus peginterferon and ribavirin (Peg-IFN/RBV) in patients with HCV genotype 2 (GT2) or 3 (GT3) and one for 12 weeks of PSI-7977 plus Peg-IFN/RBV in patients with HCV genotype 1 (GT1) prior null responses.

"The combination data reported at EASL demonstrated that SVRs were achievable with two oral DAAs in the absence of peginterferon and ribavirin," stated Bill Symonds, PharmD, Pharmasset's Senior Vice President of Clinical Pharmacology and Translational Medicine, "We continue to explore the potential for removing peginterferon and ribavirin from the HCV treatment regimen. Given the encouraging data we are seeing in ELECTRON, we have decided to expand the study to investigate PSI-7977 monotherapy, as well as shorter treatment regimens based on the promising data we reported at EASL from PROTON."

Pharmasset anticipates reporting results from the first four arms of the trial (n=40) during the second half of 2011. We have submitted a number of abstracts to the 2011 American Association for the Study of Liver Diseases (AASLD) meeting, including data from the ELECTRON and PROTON trials.

About the Trial


The ELECTRON trial is an exploratory study of PSI-7977 for the treatment of chronic HCV infection. Part 1 of the trial is evaluating 12-week regimens of PSI-7977 400 mg QD [once-daily] in combination with ribavirin (RBV) only, and in separate arms with abbreviated durations of Peg-IFN for 4, 8, or 12 weeks in treatment-naive patients with HCV GT2 or GT3. The primary endpoint of the trial is the safety and tolerability of PSI-7977 400 mg QD and RBV for 12 weeks, administered with or without Peg-IFN. On May 11, 2011, Pharmasset announced the completed enrollment of Part 1 of ELECTRON in patients with HCV GT 2 or GT 3:

PSI-7977 400 mg with RBV for 12 weeks (no peginterferon);
PSI-7977 400 mg with RBV for 12 weeks; Peg-IFN weeks 1-4 only;
PSI-7977 400 mg with RBV for 12 weeks, Peg-IFN weeks 1-8 only;
PSI-7977 400 mg with Peg-IFN and RBV for 12 weeks.

In Part 2 of ELECTRON, Pharmasset will enroll an additional 30 patients into exploratory regimens of monotherapy and abbreviated durations of total therapy. Following on the first four Cohorts of ELECTRON a 5th cohort will be added to explore 7977 400 mg monotherapy in treatment-naive patients with HCV GT2 or GT3:

PSI-7977 400 mg monotherapy for 12 weeks.

With the previously reported 100% SVR12 in naive GT2/3 subjects in PROTON, a 6th and 7th cohort will be added to ELECTRON to explore shorter treatment durations in both GT2/3 naive subjects and HCV GT1 subjects who have documented null responses (less than 2 log(10) IU/mL reduction in HCV RNA after 12 weeks of Peg-IFN/RBV):

PSI-7977 400 mg with Peg-IFN/RBV for 8 weeks
PSI-7977 400 mg QD with Peg-IFN/RBV for 12 weeks.

About Pharmasset

Pharmasset is a clinical-stage pharmaceutical company committed to discovering, developing, and commercializing novel drugs to treat viral infections. Pharmasset's primary focus is the development of oral therapeutics for the treatment of hepatitis C virus (HCV) infection. Our research and development efforts are focused on nucleoside/tide analogs, a class of compounds which act as alternative substrates for the viral polymerase, thus inhibiting viral replication.

We currently have three clinical-stage product candidates advancing in trials in various populations. Our pyrimidine, PSI-7977, an unpartnered uracil nucleotide analog, is currently under study in three Phase 2b trials in patients with HCV genotypes 1 through 6, including abbreviated duration interferon and interferon-free regimens. Our purine, PSI-938, an unpartnered guanosine nucleotide analog, recently reported safety and efficacy data from 14 days of monotherapy as well as 14 days in combination with the pyrimidine, PSI-7977. An SVR-endpoint study of the purine-pyrimidine combination is anticipated to begin in the third quarter of 2011. Mericitabine (RG7128) continues in two Phase 2b trials and one interferon-free trial being conducted through a strategic collaboration with Roche.

6/14/11

Source
Pharmasset, Inc. Pharmasset Announces the Expansion of the ELECTRON Trial in Chronic Hepatitis C. Press release. June 8, 2011.

 






 



 




 



 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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