NEW YORK (Reuters Health) – New research indicates that tenofovir 300 mg-emtricitabine 200 mg (TDF-FTC) is comparable to abacavir 600 mg-lamivudine 300 mg (ABC-3TC) in anti-HIV efficacy but is associated with fewer serious adverse events.

According to the report in the November 15th issue of Clinical Infectious Diseases, serious non-AIDS events, especially cardiovascular ones, were less common with TDF-FTC during the two-year study. Moreover, TDF-FTC-treated patients were less likely to require lipid-lowering therapy.

Conversely, TDF-FTC was associated with greater bone mineral density loss, but this did not translate into a higher fracture rate, the report indicates.

In the 96-week STEAL study (Simplification with Tenofovir-Emtricitabine or Abacavir-Lamivudine), 357 patients were randomized to replace their current nucleoside treatments with either TDF-FTC or ABC-3TC. The study subjects’ mean age was 45 years, and 98% were men. Thirty percent had been receiving TDF, 20% ABC, and 24% a protease inhibitor. None were positive for human leukocyte antigen-B*5701 and none had HIV levels above 50 copies/mL.

The virologic failure rate, defined as consecutive viral loads of >400 copies/mL, was low and similar in each group: 3.9% for TDF-FTC and 5.6% for ABC-3TC, Dr. Andrew Carr, from St. Vincent’s Hospital, Sydney, Australia, and co-researchers note.

None of the patients developed AIDS, although 18 did experience a serious non-AIDS event, including 4 that were fatal. As noted, patients treated with TDF-FTC had a lower rate of such events than did those given ABC-3TC: 1.2 vs. 4.8 events per 100 patient-years (p = 0.012). This was driven mostly by a lower rate of cardiovascular events in the TDF-FTC group: 0.3 vs. 2.2 events per 100 patient-years.

In a related editorial, Dr. Peter Reiss, from the Academic Medical Center, Amsterdam, the Netherlands, comments, “Given the widespread use of ABC-3TC and TDF-FTC fixed-dose combinations as part of currently preferred combination antiretroviral therapy regimens, the results of the STEAL trial…are both timely and informative.”

Reference:
Clin Infect Dis 2009;49:1591-1601,1602-1604.