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Viramidine Fails to Show Non-inferiority to Ribavirin at Tested Doses, but Causes Less Anemia

SUMMARY: The pro-drug viramidine did not work as well as ribavirin in combination with pegylated interferon for treatment of chronic hepatitis C, according to results of the ViSER2 study reported in the January 2010 Journal of Hepatology. Viramidine was significantly less likely to produce blood cell deficiencies, but also caused more diarrhea.

By Liz Highleyman

Anemia is a decrease in the normal number of red blood cells.

Standard therapy for chronic hepatitis C virus (HCV) infection consists of pegylated interferon plus ribavirin. Ribavirin significantly lowers the risk of relapse after treatment, but it can cause red blood cell damage. More than 20% of patient lower their doses or stop taking ribavirin due to anemia.

Viramidine (previously known as taribavirin) is a pro-drug of ribavirin that more directly targets the liver, and therefore is less likely to cause anemia. In the ViSER2 trial, Patrick Marcellin and colleagues evaluated the safety and efficacy of viramidine versus ribavirin plus pegylated interferon alfa-2a (Pegasys) in chronic hepatitis C patients.

All participants received the same dose of pegylated interferon (180 mcg), but 644 patients were randomly assigned to receive 600 mg twice-daily viramidine, while the remaining 318 received 1000-1200 mg/day weight-based ribavirin. Treatment duration was 24 weeks for people with HCV genotypes 2 or 3 and 48 weeks for those with other genotypes.


40% of viramidine recipients achieved sustained virological response (continued undetectable HCV RNA 24 weeks post-treatment), compared with 55% of ribavirin recipients.
Based on these results, viramidine did not meet criteria for non-inferiority to ribavirin.
However, improved efficacy was seen in people with higher viramidine exposure on a mg per kg basis.
Viramidine caused significantly fewer "hemoglobin events" than ribavirin, (54% vs 80%, respectively; P < 0.001).
Rates of other adverse events were similar in the 2 groups, except diarrhea was more common in the viramidine arm (30% vs 16%, respectively; P < 0.0001).

The researchers concluded that, "Viramidine 600 mg [twice daily] did not meet the primary efficacy non-inferiority end point but met the safety end point."

However, they added, "[d]etermination of a viramidine dosage that would yield superior efficacy over ribavirin is needed."

It is clear that weight-based dosing of ribavirin is superior to a fixed dose, since it helps ensure that people of different weights reach similar drug concentrations in the body. This study suggests the same is true for the pro-drug.

In late 2008, Valeant Pharmaceutical announced that at 48 weeks, weight-based viramidine produced HCV viral load reductions comparable to those of weight-based ribavirin. However, further information, including SVR rates, have not been forthcoming.

Hôpital Beaujon, Clichy, France; California Pacific Medical Center, San Francisco, CA; Crawford Long Hospital, Emory University, Atlanta, GA; Valeant Pharmaceuticals, Aliso Viejo, CA; Fundacion de Investigacion de Diego, Santurce, Puerto Rico.



Safety and efficacy of viramidine versus ribavirin in ViSER2: Randomized, double-blind study in therapy-naive hepatitis C patients. Journal of Hepatology 52(1): 32-38 (Abstract). January 2010.






















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