Key Developments For Pharmasset, Inc.
Pharmasset, Inc. (VRUS.O) (Consolidated Issue listed on NASDAQ Global Market)
Pharmasset, Inc. And InterMune, Inc. Announces Results From All Patients Cohorts Of INFORM-1 trial
Pharmasset, Inc. and InterMune, Inc. announced the results from all patient cohorts of the INFORM-1 trial, a Phase 1 study of two direct-acting antiviral (DAA) compounds administered without interferon or ribavirin for the treatment of patients chronically infected with the hepatitis C virus (HCV).(i) The study, conducted by Roche as part of its collaborations with InterMune and Pharmasset, combined the oral NS3 protease inhibitor RG7227 and the oral nucleoside analog polymerase inhibitor RG7128. Viral Kinetic Performance of Twice-Daily Regimens The full dose combination of RG7128 1000mg and RG7227 900mg administered twice-daily without pegylated interferon or ribavirin, the current standard of care for HCV, for 13 days resulted in 88% of HCV-positive treatment-naive patients achieving HCV RNA below the lower limit of quantification (LLOQ; <43 IU/mL), and 63% of patients having HCV RNA below the lower limit of detection (LLOD; <15 IU/mL). The same regimen in null responders resulted in 50% of patients with HCV RNA below LLOQ and 25% of patients with HCV RNA below LLOD. Null responders were defined as patients with an HCV RNA reduction of <1 log10 IU/mL in 4 weeks or <2 log10 IU/mL in 12 weeks of prior treatment with pegylated interferon and ribavirin. At the twice-daily dose of 600mg of RG7227 in combination with 1000mg of RG7128 twice-daily for 13 days in treatment-experienced patients, somewhat lower viral load reduction and categorical responses were observed.
Pharmasset, Inc. Reports Positive Preliminary Antiviral Data With PSI-7851 For The Treatment of Hepatitis C
Pharmasset, Inc. announced positive preliminary results from its phase I clinical trial of PSI-7851 for the treatment of hepatitis C (HCV). PSI-7851 is a second generation nucleotide polymerase inhibitor of HCV. In June 2009, Pharmasset initiated a phase 1 multiple ascending dose study with PSI-7851. The trial was conducted at two US centers, as a blinded, randomized, and placebo-controlled study, in 30 patients chronically infected with HCV genotype 1. The primary objective was to assess the safety, tolerability, and pharmacokinetics of PSI-7851 after once-daily (QD) dosing for 3 days. The secondary objective was to assess antiviral activity by measuring the change in HCV RNA. Patients were randomized to receive either PSI-7851 (8 patients per cohort) or placebo (2 patients per cohort). Three dose cohorts of PSI-7851 (50mg QD, 100mg QD, 200mg QD) were evaluated. PSI-7851 demonstrated potent antiviral activity with a mean HCV RNA decrease of -0.49 log(10) IU/mL, -0.61 log(10) IU/mL and -1.01 log(10) IU/mL in patients receiving 50mg QD, 100mg QD, and 200mg QD, respectively.
Pharmasset, Inc. Nominates PSI-938 As New Nucleotide Analog Inhibitor Of Hepatitis C Virus Infection
Pharmasset, Inc. announced the nomination of PSI-352938 (PSI-938) as a lead development candidate from two series of purine analogs for the treatment of chronic hepatitis C virus (HCV) infection. PSI-938 is a proprietary nucleotide analog polymerase inhibitor of HCV that is being advanced into studies required for submission of an Investigational New Drug (IND) application with the FDA or equivalent foreign regulatory application. Purine nucleos(t)ide analogs have many of the benefits of pyrimidine nucleos(t)ide analogs, like R7128 and PSI-7851, in that they have demonstrated in vitro activity across multiple genotypes, a higher barrier to resistance than other classes of HCV small molecules in development, and the potential to be combined with other direct acting antivirals targeting HCV. In addition, these purine analogs are also active against the S282T resistant variant selected in vitro by the pyrimidine analogs, and are metabolized to the active triphosphate form through a different phosphorylation pathway than the pyrimidines. Given these characteristics, purine and pyrimidine analogs have the potential to be combined as part of a future treatment regimen.
Pharmasset, Inc. Initiates Phase 1b Multiple Ascending Dose Clinical Trial of PSI-7851 in Chronic Hepatitis C Patients
Pharmasset, Inc. announced that it has completed the single ascending dose study and begun dosing in a multiple ascending dose trial with PSI-7851, a nucleotide analog polymerase inhibitor for the treatment of chronic hepatitis C virus (HCV) infection. This study is designed to assess the safety, tolerability and antiviral activity of PSI-7851 over 3 days in HCV-infected individuals. Following single doses (Phase 1a) and in patients chronically infected with HCV genotype 1 following repeat dosing for 3 days (Phase 1b). The Phase 1b study will additionally investigate hepatitis C viral dynamics and monitor for the development of drug resistance. Subjects in the phase 1a single ascending dose study received single doses of PSI-7851 ranging from 25mg to 800mg or a matching placebo. Preliminary data from the phase 1a single ascending dose study demonstrated: no serious adverse events or discontinuations; no dose-related adverse events; no grade III / IV lab abnormalities; no clinically significant changes in vital signs or ECGs. A Phase 1b multiple ascending dose trial has now been initiated in patients with chronic HCV genotype 1 infection. Subjects will be enrolled at multiple centers and randomized to PSI-7851 (8 per cohort) or placebo (2 per cohort). Based upon the results from the SAD study, the first dose of PSI-7851 to be tested will be 50mg once daily. Results from both studies are expected in the second half of 2009.
Roche, Pharmasset, Inc. and InterMune, Inc Announces Results From Hepatitis C Trial-Reuters
Reuters reported that Roche Holding Ltd. announced promising results from a study of a combination therapy for patients chronically infected with hepatitis C. Roche Holding Ltd. announced the results along with InterMune, Inc. and Pharmasset, Inc. which they presented at the annual meeting of the European Association for the Study of the Liver in Copenhagen. They said the study, which combined two oral direct-acting antivirals, R7227 and R7128, showed no serious adverse effects during 14 days of dosing and showed "significant" potency in reducing the viral load of hepatitis C patients. Roche Holding Ltd. is developing R7227, a protease inhibitor, with InterMune, and R7128, a nucleoside polymerase inhibitor, with Pharmasset.
