Antiviral activity of danoprevir (ITMN-191/RG7227) in combination with pegylated interferon α-2a and ribavirin in patients with hepatitis C.

BACKGROUND: Current therapy options for patients with chronic hepatitis C virus (HCV) infection genotype 1 are effective in <50%. Danoprevir (ITMN-191/RG7227) is a potent, selective, and orally active inhibitor of the HCV NS3/4A serine protease. METHODS: The safety and antiviral efficacy of danoprevir was examined over 14 days in combination with pegylated interferon α-2a (180 µg once weekly) and ribavirin (1000-1200 mg/day) in a double-blind, placebo-controlled, phase 1b, multiple ascending dose study consisting of 6 dose cohorts (400 mg, 600 mg, and 900 mg twice daily and 100 mg, 200 mg, and 300 mg 3 times daily). RESULTS: Danoprevir in combination with pegylated interferon α-2a and ribavirin was safe and generally well tolerated. The median change in HCV RNA level from baseline to the end of treatment with danoprevir at 400 mg, 600 mg, and 900 mg twice daily was -4.7 log(10) IU/mL, -5.4 log(10) IU/mL, and -5.3 log(10) IU/mL, respectively, and at 100 mg, 200 mg, and 300 mg 3 times daily was -5.5 log(10) IU/mL, -5.7 log(10) IU/mL, and -5.6 log(10) IU/mL, respectively. Placebo administered in combination with standard of care resulted in median decrease in HCV RNA level of -2.6 log(10) IU/mL (with twice daily regimen) and -2.0 log(10) IU/mL (with 3 times daily regimen). CONCLUSIONS: Our study showed substantial antiviral efficacy of danoprevir in combination with pegylated interferon α-2a and ribavirin. Exploration of the safety and antiviral efficacy of danoprevir in longer clinical studies is warranted.

Preclinical characteristics of the hepatitis C virus NS3/4A protease inhibitor ITMN-191 (R7227).

Future treatments for chronic hepatitis C virus (HCV) infection are likely to include agents that target viral components directly. Here, the preclinical characteristics of ITMN-191, a peptidomimetic inhibitor of the NS3/4A protease of HCV, are described. ITMN-191 inhibited a reference genotype 1 NS3/4A protein in a time-dependent fashion, a hallmark of an inhibitor with a two-step binding mechanism and a low dissociation rate. Under preequilibrium conditions, 290 pM ITMN-191 half-maximally inhibited the reference NS3/4A protease, but a 35,000-fold-higher concentration did not appreciably inhibit a panel of 79 proteases, ion channels, transporters, and cell surface receptors. Subnanomolar biochemical potency was maintained against NS3/4A derived from HCV genotypes 4, 5, and 6, while single-digit nanomolar potency was observed against NS3/4A from genotypes 2b and 3a. Dilution of a preformed enzyme inhibitor complex indicated ITMN-191 remained bound to and inhibited NS3/4A for more than 5 h after its initial association. In cell-based potency assays, half-maximal reduction of genotype 1b HCV replicon RNA was afforded by 1.8 nM; 45 nM eliminated the HCV replicon from cells. Peginterferon alfa-2a displayed a significant degree of antiviral synergy with ITMN-191 and reduced the concentration of ITMN-191 required for HCV replicon elimination. A 30-mg/kg of body weight oral dose administered to rats or monkeys yielded liver concentrations 12 h after dosing that exceeded the ITMN-191 concentration required to eliminate replicon RNA from cells. These preclinical characteristics compare favorably to those of other inhibitors of NS3/4A in clinical development and therefore support the clinical investigation of ITMN-191 for the treatment of chronic hepatitis C.