Merck & Co., Gilead Sciences Inc, Abbott Laboratories, and other companies are working to come up with all-oral hepatitis C treatments. So far, standard treatments for hepatitis C include interferon, but interferon can be difficult for patients to tolerate. Merck reports that during a midstage clinical trial of an experimental Merck treatment, the drug, MK-5172, suppressed hepatitis C virus in most patients. The drug study also included the use of injected interferon. MK-5172 appears to be more potent than another Merck drug, Victrelis. Merck plans new studies of MK-5172 as an all-oral hepatitis C treatment without interferon.
According to Eliav Bar, vice president of infectious diseases at Merck's research group, MK-5172, a protease inhibitor, is more potent and carries a higher barrier to treatment resistance than Victrelis. In a phase 2 clinical trial of about 330 hepatitis C patients, who received different doses of MK-5172 in combination with ribavirin and interferon for 12 weeks, 96 percent of patients who received the 100 mg dose of MK-5172 had sustained virologic responses 12 weeks after treatment. This was the highest response rate of all of the groups. In the Victrelis group, only 54 percent of patients achieved sustained virologic responses at 12 weeks. However, higher doses of MK-5172 were associated with liver toxicities. Merck plans to conduct phase 2 studies in combination with another experimental oral drug, MK-8742, plus ribavirin, which is also oral. Barr stated that if the experiments go well, the company may consider a combination of MK-5172 with MK-8472.
Abbott Labs reported results of its hepatitis C drugs in October. The results show a combination of three experimental drugs -- ABT-450 combined with a boosting agent ritonavir, ABT-267, and ABT-333 -- plus ribavirin resulted in 12-week sustained virologic response rates of 97 percent in treatment of naïve patients and 93 percent in patients who had received prior treatment. A further trial without ribavirin resulted in a sustained virologic response rate of 87 percent at 12 weeks in treatment-naïve patients. About 1 percent of patients discontinued the study because of adverse events. Abbot has begun phase 3, or late-stage testing of the hepatitis C regimen, with and without ribavirin.
Bristol-Myers Squibb had a recent setback when one of its hepatitis C compounds failed for safety issues, but the company is working on others.
The three companies are expected to present data on their drugs at Liver Meeting® 2012, the annual meeting of the American Association for the Study of Liver Diseases, which is held November 9-13.
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