AASLD 2014: Entecavir and Tenofovir Work Well for People with Resistant Hepatitis B Virus

alt

A combination of entecavir plus tenofovir effectively suppressed hepatitis B virus (HBV) in people with resistance to other antivirals, according to results from the ENTEBE study presented at the American Association for the Study of Liver Diseases (AASLD) Liver Meeting last month in Boston. Another study, however, showed that for some resistant patients, tenofovir worked equally well on its own.

Antiviral therapy using nucleoside/nucleotide analogs such as entecavir (Baraclude), tenofovir (Viread), adefovir (Hepsera), telbivudine (Tyzeka), or lamivudine (Epivir) is the mainstay of chronic hepatitis B treatment. Although they effectively suppress HBV replication during therapy, they typically do not eradicate the virus and may be used long-term. But HBV often develops resistance to antivirals -- especially the oldest drug, lamivudine -- which can lead to treatment failure.

Entecavir + Tenofovir

Fabien Zoulim from Hospices Civils de Lyon in France and colleagues conducted the Phase 3b ENTEBE trial to evaluate the safety and efficacy of entecavir plus tenofovir combination therapy for chronic hepatitis B patients who experienced previous nucleoside/nucleotide treatment failure.

Developing resistance to one antiviral can confer cross-resistance to similar drugs. But combining entecavir (a guanosine nucleoside analog) and tenofovir (an adenosine nucleotide analog) may provide a single regimen that works for all patients with prior nucleoside analog failure, the researchers suggested as background. These drugs both have high barriers to resistance and non-overlapping resistance profiles.

ENTEBE enrolled 144 previously treated participants in Europe between May 2010 and September 2011, of whom 92 started treatment. Three-quarters were men, most were white, and the median age was 42 years. Two-thirds were initially hepatitis B "e" antigen (HBeAg) positive and one-third HBeAg negative. A majority (54%) had HBV genotype D and 32% had genotype A. The median alanine aminotransferase (ALT) level was 36.5 (near the upper limit of normal) and they had compensated liver disease.

Participants had last taken nucleoside antivirals more than 7 days ago. Just over half had previously used entecavir, 22% had used lamivudine, 12 had used tenofovir, 4% had used adefovir, and the remainder had used telbivudine or 2-drug regimens. They had experienced treatment failure, defined as HBV DNA >50 IU/mL, with primary non-response (less than a 1-log decline; 10%), partial virological response (57%), or viral breakthrough on therapy (33%). Among patients with available viral sequencing data, 58% had at least 1 resistance mutation, including 52% with lamivudine resistance, 26% with entecavir resistance, and 7% with adefovir resistance.

All participants received 1.0 mg entecavir plus 300 mg tenofovir once-daily. Treatment continued through 96 week and patients were followed for a further 24 weeks off treatment. A total of 89 patients completed 48 weeks of treatment (the primary analysis) and 86 people completed 96 weeks.

Results

"Entecavir combined with [tenofovir] is a highly effective and well tolerated option for rescue therapy, regardless of the type of prior [nucleoside analogs] used," the researchers concluded. They added that lower baseline HBV viral load -- but not baseline resistance profile -- was a predictor of virological response.

Tenofovir Monotherapy

In a related study, Young-Suk Lim of University of Ulsan College of Medicine in Seoul and colleagues compared tenofovir plus entecavir versus tenofovir alone for chronic hepatitis B patients with entecavir-resistant HBV who did not achieve viral suppression on current or prior antiviral treatment.

This Korean study included 90 patients; 76% were men and the mean age was 51 years. Most (89%) were HBeAg positive and nearly one-quarter had liver cirrhosis.

A majority (57%) had previously been exposed to entecavir, lamivudine, and adefovir, with a further 10% also having used telbivudine; 18% had tried entecavir and lamivudine, 8% had used entecavir and adefovir, and 6% had used entecavir alone. About half were currently on entecavir plus adefovir, 32% were on entecavir alone, and the rest were on antiviral regimens without entecavir. None, however, had used tenofovir. The most frequently detected entecavir resistance mutations at baseline were M204V/I, L180M, T184, and S202G.

Participants were randomly assigned to receive either tenofovir plus entecavir or tenofovir monotherapy for 48 weeks. This study had a stricter threshold for undetectable viral load, HBV DNA <15 IU/mL.

Results

Comparing patients taking tenofovir plus entecavir or tenofovir alone, the researchers concluded that there was no significant difference in either the proportion of patients who achieved virological response or in the degree of HBV DNA reduction.

"[Tenofovir] monotherapy may be a reasonable option for the rescue therapy of patients infected with entecavir-resistant HBV," they recommended.

12/17/14

References

F Zoulim, MS Jablkowski, M Diculescu, et al. The Safety and Efficacy of Entecavir and Tenofovir Combination Therapy for Chronic Hepatitis B in Patients with Previous Nucleos(t)ide Treatment Failure: Week 96 Results of the ENTEBE study. American Association for the Study of Liver Diseases (AASLD) Liver Meeting. Boston, November 7-12, 2014. Abstract 230.

Y-S Lim, KS Byun, G-Y Gwak, et al. Tenofovir Disoproxil Fumarate Alone or in Combination with Entecavir in Patients with Entecavir-Resistant Chronic Hepatitis B: Multicenter Randomized Trial. American Association for the Study of Liver Diseases (AASLD) Liver Meeting. Boston, November 7-12, 2014. Abstract 231.