AIDS 2008 Abstract - Abacavir/lamivudine (ABC/3TC) shows robust virologic responses in ART-naïve patients for baseline (BL) viral loads (VL) of </font><font face='symbol'>³</font><font face='verdana,arial,helvetica,san-serif'>100,000c/mL and <100,000c/mL by endpoint used in ACTG5202

Abacavir/lamivudine (ABC/3TC) shows robust virologic responses in ART-naïve patients for baseline (BL) viral loads (VL) of ³100,000c/mL and <100,000c/mL by endpoint used in ACTG5202

Presented by Keith Pappa, United States.

K. Pappa¹, J. Hernandez², B. Ha¹, M. Shaefer², C. Brothers², Q. Liao³

¹GlaxoSmithKline, Infectious Diseases MDC, U.S. HIV Collaborative Studies, Research Triangle Park, NC, United States, ²GlaxoSmithKline, Infectious Diseases MDC, U.S. HIV, Research Triangle Park, NC, United States, ³GlaxoSmithKline, MDC BDS-Infectious Diseases, U.S., Research Triangle Park, NC, United States

Background: ACTG5202 is an ongoing randomized trial in 1858 ART-naïve pts evaluating open-label efavirenz (EFV) or ritonavir-boosted atazanavir (ATV/r) combined with ABC/3TC or tenofovir/emtricitabine (TDF/FTC). A recent review of ACTG5202 by the DSMB noted greater risk of virologic failure and adverse events in ABC/3TC-treated pts compared to TDF/FTC-treated pts with BL VL³100,000 c/mL. An analysis was performed of other clinical trials using ABC/3TC-containing regimens using the efficacy endpoint defined in ACTG5202 to assess impact of BL VL on virologic response.
Methods: 48-wk efficacy data in 2940 ART-naïve pts were analyzed by BL VL strata (<100,000 and ³100,000c/mL) from 6 clinical trials. The efficacy endpoint using Kaplan-Meier analysis was time to virologic failure (defined as confirmed VL ³1,000c/mL at or after 16 wks and before 24 wks, or VL ³200c/mL at or after 24 wks). The safety endpoint was defined as time to onset of first grade 3/4 sign, symptom, or lab toxicity at least 1 grade higher than BL. Tabled below are the Kaplan-Meier estimates of the probability of reaching the safety endpoint.
Results: By 48 wks, 87%-95% of subjects did not experience virologic failure. The safety endpoint outcome was similar in both strata.

[Table 1]

Conclusions: Using the efficacy and safety endpoint defined in ACTG5202, this analysis of 6 clinical trials showed that the efficacy of ABC/3TC-containing regimens was robust in ART-naïve pts irrespective of BL VLs.