Clinical

Emtricitabine has anti-HBV activity but selects for resistance mutations

Last Updated: 2006-01-12 15:21:05 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Emtricitabine for 48 weeks produces significant histologic, virologic, and biochemical improvement in patients with chronic hepatitis B (HBV) but is associated with a high rate of resistance mutations and virologic relapse is likely when the drug is stopped, a study shows.

Emtricitabine, a lamivudine-like nucleoside analogue approved for treatment of HIV infection, has clinical activity against HBV, the researchers note.

Dr. Seng Gee Lim from National University Hospital in Singapore and international colleagues compared the safety and efficacy of 48 weeks of emtricitabine (200 mg, once daily) against placebo in 248 patients with chronic HBV who had no past exposure to nucleosides or nucleotides. Gilead Sciences of Durham, North Carolina provided funding for the study.

According to the team's report in the January 9th Archives of Internal Medicine, emtricitabine led to significant histologic improvement in 62% of patients, normalization of alanine aminotransferase (ALT) in 65%, and complete viral suppression in 54% (39% of HBeAg-positive and 79% of HBeAg-negative) compared with placebo.

In the placebo arm, the percentage of patients seeing improvement in these three parameters was 25%, 2%, and 25%, respectively.

Exacerbation of HBV infection occurred in 23% of emtricitabine-treated patients when the drug was halted and emtricitabine resistance mutations were detected in 13% of those taking the drug.

This, the authors of an editorial say, is "ultimately, the most important weakness" of emtricitabine for chronic HBV.

Dr. Anna S. Lok from University of Michigan Medical Center in Ann Arbor, and co-author Dr. Stephen N. Wong, contend that "with the advent of newer antiviral agents with significantly lower risk of resistance, emtricitabine on its own will not have a role in the treatment of hepatitis B. Whether the combination of emtricitabine and tenofovir is superior to other approved treatments for hepatitis B remains to be determined."

Arch Intern Med 2006;166:9-12,49-56.