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  HIV and Hepatitis.com Coverage of the
 44th Annual Meeting of the European Association for
 the Study of the Liver (EASL 2009)
  April 22 - 26, 2009, Copenhagen, Denmark
 The material posted on HIV and Hepatitis.com about EASL 2009 is not approved by nor is it a part of EASL 2009.

Addition of Emtricitabine (Emtriva) Does Not Improve Response to Tenofovir (Viread) for Chronic Hepatitis B

By Liz Highleyman

Emtricitabine (Emtriva)
Tenofovir (Viread)

The U.S. Food and Drug Administration approved tenofovir (Viread) for the treatment of chronic hepatitis B virus (HBV) infection in August 2008.

Tenofovir is also active against HIV, and is a component of 2 widely used fixed-dose combination pills, Truvada (tenofovir/emtricitabine) and Atripla (tenofovir/emtricitabine/efavirenz). Emtricitabine (Emtriva) is structurally related to lamivudine (3TC, Epivir). Like tenofovir, these drugs are also active against both HBV and HIV; lamivudine is approved for both diseases, while emtricitabine at this time is only approved for HIV.

As described in a poster presented at the 44th Annual Meeting of the European Association for the Study of the Liver (EASL 2009) last month in Copenhagen, T. Berg and an international team of colleagues conducted Study 106, comparing the efficacy of tenofovir/emtricitabine combination therapy versus tenofovir alone for the treatment of chronic hepatitis B.

The study included 105 chronic hepatitis B patients who had an incomplete virological response after receiving adefovir (Hepsera) for at least 24 but less than 96 weeks (mean of about 60 weeks); HBV viral load was at least 1000 copies/mL. Most were men, about 40% each were Asian and white, and the mean age was about 40 years; about 75% were hepatitis B "e" antigen (HBeAg) positive. Patients with HIV or hepatitis C virus (HCV) coinfection were not included.

About 60% of the participants had at least 1 year of prior lamivudine experience. Sequencing of baseline HBV genetic sequences showed that 13 patients had pre-existing lamivudine-associated resistance mutations and 10 had adefovir-associated resistance mutations.

Participants were randomly assigned to receive either 300 mg tenofovir plus 200 mg emtricitabine once-daily using the Truvada pill or 300 mg once-daily tenofovir monotherapy. Patients in both treatment arms could switch to open-label tenofovir/emtricitabine after 24 weeks if they had persistent HBV viral load greater than 400 copies/mL.

Intention-to-treat analyses were conducted using both non-completer = failure (NC=F) and non-completer or switch = failure (NC/S=F) criteria.

Results

9 patients in the tenofovir/emtricitabine arm and 16 in the tenofovir monotherapy arm switched to open-label tenofovir/emtricitabine due to persistent viremia at week 24.

At 96 weeks, in the NC=F analysis, 83% of patients originally assigned to the tenofovir/emtricitabine arm and 89% originally assigned to tenofovir monotherapy achieved HBV DNA < 400 copies/mL, not a statistically significant difference (P = 0.52).

In the NC/S=F analysis, 75% of patients assigned to tenofovir/emtricitabine and 68% assigned to tenofovir alone achieved HBV DNA < 400 copies/mL, again not a significant difference (P = 0.41).

Among patients with pre-existing adefovir resistance mutations, 100% in the tenofovir/emtricitabine arm and 88% in the tenofovir monotherapy arm achieved HBV DNA < 400 copies/mL.

Among patients with pre-existing lamivudine resistance mutations, 100% in both treatment arms achieved undetectable HBV DNA.

ALT was within normal limits in 77% of patients in the tenofovir/emtricitabine arm and 65% in the tenofovir monotherapy arm.

15% of patients in the combination therapy arm and 13% in the tenofovir monotherapy arm achieved HBeAg loss.

13% and 8%, respectively, experienced HBeAg seroconversion.

4% of patients in the tenofovir monotherapy arm -- but none in the combination arm -- achieved hepatitis B surface antigen (HBsAg) loss.

For HBsAg seroconversion, the corresponding figures were 2% and none.

Combination therapy and tenofovir monotherapy were both well tolerated, with no discontinuations due to adverse events.

15% of patients in the tenofovir/emtricitabine arm and 8% in the tenofovir monotherapy arm experienced serious adverse events, but none were considered drug-related.

No serious kidney-related events were observed in either arm.

Based on these findings, the investigators concluded, "Both treatment strategies [tenofovir monotherapy and tenofovir/emtricitabine]…were equivalent through 96 weeks of follow-up in this heavily pretreated, highly viremic population."

They continued, "There is a non significant trend favoring combination [therapy] for antiviral efficacy when considering subjects who added [emtricitabine] or switched from blinded [emtricitabine/tenofovir] to open-label as failures."

Finally, they noted, "Virologic response was independent of pre-existing adefovir or lamivudine-associated mutations."

Medizinische Klinik mit Schwerpunkt Hepatologie & Gastroenterologie, Charite Campus Virchow-Klinikum; Praxis Dr. Möller, Berlin, Germany; San Jose Gastroenterology, San Jose, CA; Office of Sing Chan, MD, Flushing, NY; Hopital Beaujon, Clichy, France; Hospital Universitario de Valme, Sevilla, Spain; Gilead Sciences, Durham, NC.

5/05/09

References

T Berg, B Moller, H Trinh, and others. Tenofovir disoproxil fumarate (TDF) versus emtricitabine plus TDF (FTC/TDF) for treatment of chronic hepatitis B (CHB) in patients with persistent viral replication receiving adefovir dipivoxil. 44th Annual Meeting of the European Association for the Study of the Liver (EASL 2009). Copenhagen, Denmark. April 22-26, 2009. Abstract 903.

Evolution of Viral Load and Genome Sequence in a Clinical Trial of Tenofovir/Emtricitabine Combination versus Tenofovir Monotherapy for Patients with Previous Adefovir Dipivoxil Failure. EASL 2009). Copenhagen, Denmark. April 22-26, 2009.

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