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No Tenofovir Resistance Seen In 2 Years of Hepatitis B Treatment

No cases of resistance to tenofovir (Viread) were detected among chronic hepatitis B patients with prior resistance to lamivudine (3TC or Epivir) through 96 weeks of treatment, according to a study described in the June 11 advance edition of Clinical Gastroenterology and Hepatology. Adding emtricitabine (Emtriva) did not improve effectiveness compared with tenofovir alone.

Amoreena Corsa of Gilead Sciences and colleagues compared the efficacy of tenofovir disoproxil fumarate versus tenofovir plus emtricitabine, the 2 drugs in the Truvada coformulation used for HIV treatment and prevention.

The analysis included 280 chronic hepatitis B patients, 99% of whom were found to have pre-existing lamivudine resistance. In addition, 22% had been previously exposed to adefovir (Hepsera) and 1.8% were resistant, while 12% had prior exposure to entecavir (Baraclude) or entecavir resistance.

Participants were randomly assigned (1:1) to receive either tenofovir alone or tenofovir/emtricitabine for up to 96 weeks. The HBV polymerase gene was sequenced to determine resistance at baseline for all patients, and again at 96 weeks (or at the time of study discontinuation) for people with continued HBV viremia.

Results

• 18 participants (6.4%) qualified for the second sequence analysis, including 1 person who experienced viral breakthrough during treatment and 17 who had persistent viremia, or did not reach detectable HBV DNA viral load.
• 6 of these patients (33%) did not show any sequence changes in HBV reverse transcriptase from baseline, while sequence analysis could not be performed for 5 people (28%).
• 2 patients who qualified for phenotypic analysis (1 taking tenofovir, 1 taking tenofovir/emtricitabine) showed no evidence of resistance to tenofovir.
• Previous treatment and pre-existing resistance to entecavir or adefovir did not affect viral kinetics, or speed and magnitude of viral decline on therapy.
• However, patients with continued viremia had a significantly higher mean baseline HBV DNA level than people who achieved viral suppression by 96 weeks (7.28 vs 5.62 log IU/mL).

"No resistance to [tenofovir] was detected through 96 weeks of treatment in patients with [lamivudine-resistant] chronic hepatitis B," the study authors concluded. "Prior treatment or resistance to entecavir or adefovir did not affect viral kinetics through 96 weeks."

"No additional benefit was observed with the addition of emtricitabine vs [tenofovir] monotherapy," they added.

6/27/14

Reference

AC Corsa, Y Liu, JF Flaherty, et al. No Resistance to Tenofovir Disoproxil Fumarate Through 96 Weeks of Treatment in Patients With Lamivudine-resistant Chronic Hepatitis B. Clinical Gastroenterology and Hepatology. June 11, 2014 (Epub ahead of print).