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Positive Phase II Results for Miravirsen in HCV Infection

First RNA-targeted drug to enter clinical trials (Mar. 27)

Positive results from a new phase IIa study of miravirsen (Santaris Pharma), a pan-hepatitis C virus (HCV) genotype-1 antiviral agent, have been published online in the New England Journal of Medicine. Miravirsen is the first microRNA-targeted drug to enter clinical trials for the treatment of HCV infection.

In the new study, 4 weeks of miravirsen monotherapy provided dose-dependent antiviral activity, with a mean reduction of 2 to 3 logs from baseline in HCV RNA (log10 IU/mL).

Other findings included:

  • Miravirsen was safe and well tolerated, and provided prolonged antiviral activity well after the last dose of miravirsen monotherapy (five weekly injections).
  • There were no signs of viral resistance.
  • Adverse events were infrequent and mild, and did not lead to discontinuation of the study drug.
  • There were no dose-limiting toxicities or discontinuations due to adverse events.
  • Miravirsen was associated with dose-dependent reductions in HCV RNA that were sustained well beyond the end of the four-week dosing period.
  • Four out of nine patients treated at the highest dose (7 mg/kg) had undetectable HCV RNA after five weekly doses of miravirsen monotherapy.

The randomized, double-blind, placebo-controlled phase IIa study assessed the safety and tolerability of miravirsen in treatment-naïve patients with chronic HCV genotype-1 infection. The patients were randomly assigned to three cohorts (nine active-treatment and three placebo patients per cohort) at miravirsen doses of 3, 5, and 7 mg/kg. Miravirsen was administered as a total of five weekly subcutaneous injections over 29 days.

Miravirsen inhibits miR-122, a liver-specific microRNA that HCV requires for replication. Miravirsen is designed to recognize and sequester miR-122, making it unavailable to HCV. As a result, viral replication is inhibited, and the level of HCV infection is reduced.

Sources: Santaris Pharma; March 27, 2013; and NEJM; March 27, 2013.

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