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Better Early Response to Tenofovir/FTC Than to AZT/3TC
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Mark Mascolini
October 31, 2004
A preliminary 24-week analysis charted better virologic responses to tenofovir/emtricitabine (FTC)/efavirenz than to AZT/3TC/efavirenz in people starting their first antiretroviral regimen (1). The once-a-day tenofovir/FTC combo (licensed as Truvada) also did better than twice-daily AZT/3TC (Combivir) in people beginning treatment with a viral load above 100,000 copies/mL.
The 509 study participants included in the week-24 analysis began treatment with an average viral load of 100,000 copies/mL and an average CD4 count of 246 cells/µL. Using the FDA's time to loss of virologic failure (TLOVR) algorithm, researchers figured that 87% taking Truvada/efavirenz and 78% taking Combivir/efavirenz had a viral load below 400 copies/mL after 24 weeks, a significant difference (P = 0.01). Trudvada/efavirenz also pushed viral loads below 50 copies/mL in more people than Combivir/efavirenz at week 24 (73% versus 65%, P = 0.038).
Among people starting antiretroviral therapy with more than 100,000 HIV RNA copies/mL, 67% randomized to Truvada versus 54% randomized to Combivir trimmed their viral load to less than 50 copies/mL (P = 0.021).
The M184V/I mutation, which can develop with either FTC or 3TC, emerged at similar rates in the two study arms, as did mutations conferring resistance to efavirenz. The tenofovir-linked K65R mutation emerged in no one; nor did any AZT/d4T-related mutation.
At the 24-week point more people dropped out of the Combivir arm (9%) than the Truvada arm (3%) because of side effects (P = 0.008). Because of the higher dropout rate in the Combivir arm, an on-treatment analysis found that 99% taking Truvada/efavirenz and 98% taking Combivir/efavirenz had a viral load under 400 copies/mL at week 24.
Reference
1. Gazzard B, DeJesus E, Campo R, et al. The combination of tenofovir DF, emtricitabine (FTC) and efavirenz (EFV) has significantly greater response vs fixed dose zidovudine/lamivudine and EFV in antiretroviral naive patients: a 24 week preliminary analysis. 44th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). October 30-November 2, 2004. Washington, DC. Abstract H-1137c.
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