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Tenofovir Resistance Not Found in Study 934: Presented at IAS-HIV
By Ed Susman
RIO DE JANEIRO, BRAZIL -- July 29, 2005 -- Researchers analyzing results of a key 934 clinical trial found that human immunodeficiency virus (HIV) did not develop the K65R mutation, despite the presence of tenofovir, combined with emtricitabine and efavirenz.
"No patient in this study developed K65R mutation," said Damian McColl, PhD, research scientist at Gilead Science Inc., Foster City, California, who headed the analyses of resistance in the 934 Trial.
However, the analysis did show that primary non-nucleoside reverse transcriptase inhibitor-resistance was present at baseline in 4.3% of antiretroviral therapy-naive patients in Study 934, which "was significantly associated (P =.001) with risk of treatment failure on efavirenz-containing regimens."
Study 934 compared treatment with tenofovir-emtricitabine-efavirenz to treatment with zidovudine-lamivudine-efavirenz. The 48-week results of the trial found that the tenofovir arm outperformed the zidovudine arm, with 81% and 70% of patients, respectively, achieving undetectable viral loads at 48 weeks (P =.005).
Dr. McColl's analyzed resistance at baseline and in the course of treatment. He reported the results of the analysis here July 26th at the 3rd International AIDS Society Conference on HIV Pathogenesis and Treatment (IAS-HIV).
At baseline, the same number of patients in both treatment groups had resistance to non-nucleoside reverse transcriptase inhibitors -- the same class as efavirenz.
At baseline 7 patients on the tenofovir arm had resistance to nucleoside reverse transcriptase inhibitors -- the same class as emtricitabine. There were 6 patients on the zidovudine arm that had resistance to nucleoside analogs such as zidovudine and lamivudine. But all 13 of these patients remained on treatment and 12 of the 13 were able to suppress their virus to undetectable levels.
"[After 48 weeks,] resistance to tenofovir-emtricitabine-efavirenz developed infrequently -- 4% of treated patients -- and was primarily associated with non-nucleoside reverse transcriptase inhibitor-resistance development," Dr. McColl said.
"By week 48, M184V/I developed less frequently on tenofovir-emtricitabine-efavirenz -- 1% -- compared with Cambivir plus efavirenz -- 3% -- but that difference did not achieve statistical significance," he added.
[Presentation title: Lack of Resistance to Tenofovir at Week 48 and Impact of Baseline Resistance Mutations on Treatment Response in Study 934. TuPp0305]
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