Idenix Pharmaceuticals has announced interim data from the ongoing phase II 12-week HELIX-1 clinical trial evaluating an all-oral, direct-acting antiviral ( DAA ) HCV combination regimen of Samatasvir, once-daily pan-genotypic NS5A inhibitor, and Simeprevir ( Galexos, Olysio, Sovriad ), a once-daily protease inhibitor, plus Ribavirin.
The combination regimen was well-tolerated in the study.
In the treatment-naïve, non-cirrhotic, genotype 1b or 4 HCV-infected patients receiving 50 mg of Samatasvir and 150 mg of Simeprevir plus Ribavirin, 85% ( n=17/20 ) remained undetectable for HCV RNA four weeks after completing therapy ( SVR4 ).
The HELIX-1 trial is a phase II 12-week, randomized, parallel-group study evaluating the antiviral activity, safety and tolerability of Samatasvir and Simeprevir in treatment-naïve, non-cirrhotic, genotype 1b or 4 HCV-infected patients.
Patients in Part A of the study ( n=63 ) were enrolled in one of three treatment groups receiving 50, 100, or 150 mg Samatasvir once-daily for 12 weeks in combination with 150 mg of Simeprevir plus a weight-based dose of Ribavirin.
In Part B of the ongoing HELIX-1 study, exploratory cohorts of patients have been added to evaluate the safety and antiviral activity of Simeprevir and Ribavirin in combination with 1) a 25 mg dose of Samatasvir in genotype 1b-infected patients and 2) a 100 mg dose of Samatasvir in genotype 6-infected patients.
The combination treatment regimen has been well-tolerated, and there have been no treatment-related serious adverse events in the clinical trial to date.
The most frequently reported adverse events were fatigue, pruritus, anemia, nausea and insomnia.
The Interferon-free regimen containing Samatasvir plus Simeprevir and Ribavirin has demonstrated an 85% sustained response rate at 4 weeks post-treatment ( SVR4 ).
Based on these data, the 50 mg dose was selected to be evaluated as part of the 3-DAA combination regimen in the recently initiated HELIX-2 clinical trial.
Samatasvir is an NS5A inhibitor with low picomolar, pan-genotypic antiviral activity in vitro. To date, Samatasvir has been safe and well-tolerated after single and multiple doses of up to 150 mg in healthy volunteers up to 14 days duration, and in HCV-infected patients up to 12 weeks duration. There have been no treatment-related serious adverse events reported in the program.
Samatasvir has demonstrated potent pan-genotypic antiviral activity in HCV-infected patients with mean maximal viral load reductions up to approximately 4.0 log10 IU/mL across HCV genotypes 1-4 in a proof-of-concept, three-day monotherapy study. ( Xagena )
Source: Idenix Pharmaceuticals, 2014