[TuPp0305] Lack of Resistance to Tenofovir at Week 48 and Impact of Baseline Resistance Mutations on Treatment Response in Study 934

3rd International AIDS Society Conference on HIV Pathogenesis and Treatment

Rio de Janeiro - July 24 - 27, 2005

LACK OF RESISTANCE TO TENOFOVIR AT WEEK 48 AND IMPACT OF BASELINE RESISTANCE MUTATIONS ON TREATMENT RESPONSE IN STUDY 934

IAS Conf HIV Pathog Treat 2005 Jul 24-27;3rd: Abstract No. TuPp0305

McColl D., Margot N., Lu B., Cheng A., Miller M.
Gilead Sciences, Inc., Foster City, United States of America

INTRODUCTION: A description of the patterns of genotypic resistance at baseline and at week 48 in GS-01-934.

METHODS: GS-01-934 is an open-label, randomized study comparing emtricitabine (FTC), tenofovir DF (TDF) and efavirenz (EFV) to lamivudine/zidovudine (CBV) and EFV in antiretroviral therapy (ART)-naïve patients (pts). A week 48 resistance analysis (RA) is presented. Baseline (BL) genotyping was performed on plasma HIV from all pts (ITT population n=509). BL NNRTI-R pts (n=22) were excluded from the modified ITT population (mITT, n=487). Pts meeting RA criteria (HIV RNA >400 c/mL at week 48 or early discontinuation) were genotyped and phenotyped at failure (ViroLogic).

RESULTS: 35/487 pts met RA criteria at week 48 (TDF/FTC, n=12/244; CBV, n=23/243, p=0.055). NNRTI-R was the most common resistance that developed (TDF/FTC, n=9/244; CBV, n=16/243; p=0.16). 2/244 patients in the TDF/FTC arm versus 7/243 patients in the CBV developed M184V/I (p=0.11). One CBV pt developed a thymidine analogue mutation (TAM). No pt developed K65R. Among 22 pts with BL NNRTI-R, 20 had NNRTI-R only; 2 also had TAMs, one with M184V. No pt had M184V/I alone or K65R at BL. Significantly more pts with BL NNRTI-R met week 48 RA criteria compared to pts without NNRTI-R (35/487, 7.2% vs 9/22, 41%. p<0.0001). 7/9 (78%) patients then developed M184V/I; 4/9 (44%) developed additional NNRTI-R. No pt with BL NNRTI-R developed TAMs or K65R.

CONCLUSIONS: Resistance development occurred less frequently in the TDF/FTC arm of study 934 compared to the CBV arm (3.7% versus 7%, mITT). Fewer pts on TDF/FTC developed M184V and no pt developed K65R through 48 weeks. A significantly greater proportion of pts with BL NNRTI-R met RA criteria and then developed further NNRTI-R and/or M184V. The effectiveness in ART-naïve HIV patients of combination regimens including an NNRTI would be improved by the use of genotyping prior to starting therapy.

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050724
Clinical | TuPp0305 | Damian Mccoll
6.3 679 6.3 Phase III/IV trials

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