Presidio Pharmaceuticals, Inc. announced today successful completion of Phase 1b clinical testing of its lead HCV NS5A inhibitor in patients with HCV genotype-1 infection, with positive efficacy and safety observations supporting advancement of PPI-668 to Phase 2 combination studies.
The randomized, blinded Phase 1b trial of PPI-668 involved sequential cohorts of treatment-naïve HCV genotype-1 patients who received oral doses of PPI-668 of 40, 80, 160 or 240 mg, once daily for three consecutive days. Within each 10-patient cohort, patients were randomized 8:2 to PPI-668 or placebo.
In all of the Phase 1b dose cohorts, PPI-668 was well tolerated with no serious or severe adverse events, no premature treatment discontinuations and no apparent pattern of treatment-related clinical side effects or laboratory abnormalities.
The Phase 1 clinical results indicate that PPI-668 had a favorable pharmacokinetic (PK) profile that included rapid achievement of high (micromolar) plasma levels, prolonged maintenance of potentially effective levels between doses, and achievement of steady-state pharmacokinetics after the first dose.
The Phase 1b efficacy observations indicated consistently rapid, marked reductions in patients’ serum viral load (HCV RNA levels), that were dose-related. Patients’ HCV RNA reductions typically exceeded 3 log10 IU/ml (99.9%) by Day 2. During the 3-day treatment period, mean maximal HCV RNA reductions for the 4 dosing groups were:
- 3.2 log10 IU/mL in the 40 mg dose group
- 3.5 log10 IU/mL in the 80 mg dose group
- 3.5 log10 IU/mL in the 160 mg dose group
- 3.7 log10 IU/mL in the 240 mg dose group
There was only one minimal-responder in the trial. A patient in the 240 mg dose group was found to be fully resistant at baseline with 100% of this patient’s pre-treatment HCV RNA containing 3 genetically linked NS5A resistance mutations. This patient was excluded from the efficacy analysis of the 240 mg cohort, since he was pre-resistant and could not contribute to dose-response inferences.
Five other patients with detectable resistance mutations at baseline, including those harboring the relatively common L31M variant, responded well to PPI-668 treatment, with multi-log HCV RNA reductions.
A protocol amendment has been completed to explore the pan-genotypic clinical efficacy of PPI-668 in HCV genotype-2a/3a patients. Recruitment is currently underway for this added cohort.
“The rapid 3.5 to 3.7 log10 HCV RNA reductions observed with PPI-668 at the three higher dose levels and the encouraging safety profile support advancement of PPI-668 to Phase 2 combination studies with other promising HCV antiviral agents,” said Nathaniel A. Brown, M.D., Presidio’s Chief Medical Officer. “The PK profile of PPI-668 appears to be a major factor in its efficacy profile, with rapid achievement of potentially effective plasma levels and with inter-dose plasma concentrations exceeding those needed to inhibit both wild-type HCV and many naturally-occurring HCV variants.”
Detailed results of the completed trial are expected to be presented at a scientific meeting in the fall of 2012.