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Efficacy of Efavirenz in Different Racial Groups
Reported by Jules Levin
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Researchers from Bristol-Myers Squibb reported at the 6th Intl Congress on Drug Therapy (Glasgow, UK, Nov 17-21, 2002) study data and information in a poster on a comparison in response to efavirenz/AZT/3TC in Blacks and Caucasians. This study was undertaken because two years ago Scott Wegner presented data on 56 patients at the Resistance Workshop finding that Blacks did not respond as well as Caucasians to efavirenz. Researchers at the meeting did not believe this finding. Here are excerpts from the poster and data reported
Recently there have been multiple analyses evaluating the relationship between race and the efficacy of antiretroviral therapy. In a retrospective analysis of military personnel for whom access to care and socio-economic status were not confounding factors, no association between viral load and race or ethnicity was observed.1 Wegner et al observed racial differences in a time to virologic failure analysis specific to Efavirenz-based therapy. 2 Though patients from minority populations may present with more advanced HIV disease when compared with Caucasians, once in care, outcomes may not vary by race or ethnicity. The verification of these findings in other cohorts is warranted.
DMP Study 266-006 is an international multicenter, open-label, randomized
clinical trial comparing Efavirenz (EFV) + Zidovudine (ZDV) + Lamivudine (3TC),
Indinavir (IDV) + ZDV +3TC,and EFV + IDV in HIV-1 infected patients receiving
their first highly active antiretroviraltherapy (HAART) regimen.
The objective of the post hoc analysis presented here is to determine the
durability of response at 96 weeks by racial category (Black [B], Hispanic [H], and Caucasian [C]) with the HAART regimens used in DMP Study 266-006. Data on 1228 patients were analyzed for this study. About 400 patients were enrolled in each treatment arm of this study.
The authors evaluated response in two ways: Time to Virologic Failure (TVF), which is simply patients who achieved <50 copies/ml viral load and then experienced a rebound to >50 copies/ml. This included patients who discontinued from the study when viral load was >50 copies/ml. So these were patients who stayed on therapy and experienced viral load failure. Patients who discontinued therapy in study for any reason were not included in this analysis. Time to Treatment Failure (TTF) includes patients who had viral load >50 copies/ml after being <50 copies/ml, patients who had an AIDS-defining event (excluding Cd4 count <200 and herpes simplex virus), discontinued from the study for any reason, or never responded (i.e. never <50 copies/ml, TTF= 0 days).
Most of the patients receiving efavirenz/AZT/3TC were homosexual/bisexual (66%), 20% were heterosexual. The baseline CD4 counts and viral load were comparable across all treatment groups and racial groups, so the authors concluded that CD4 count or viral load before starting therapy did not affect the study findings. Kaplan-Meier survival estimates along with Boneferonni adjustment were used for multiple comparisons between races. This means the statisticians used the Kaplan-Meier estimates to estimate the outcomes of the patients in terms of the percent of patients who were viral failures (TVF) or treatment failures(TTF). They were able to compare between the races (Blacks vs Caucasians) using the Boneferonni statistical methods.
RESULTS
This analysis followed study patients for 96 weeks. The authors concluded that there were no significant differences between Blacks and Caucasians in response to efavrienz/AZT/3TC using either analysis, by TVF (viral failure) or TTF (treatment failure).
When looking only at TVF (time to viral failure) the authors found no difference between Blacks and Caucasians. When considering treatment failure (TTF), which considers study discontinuations, more Blacks discontinued efavirenz/AZT/3TC than Caucasians, but still there was no significant difference in Time To Treatment Failure between Blacks and Caucasians. Discontinuation due to adverse events was 5.9% for Caucasians and 10.9% for Blacks receiving efavirenz/AZT/3TC.
Kaplan-Meier estimates at 96 weeks were that 80.3% of Blacks and 77.3% of Caucasians who stayed on therapy and who achieved <50 copies/ml retained <50 copies/ml at week 96.
References
1. Brown AE, Malone JD, Zhou SYJ, Lane JR, Hawkes CA.Human Immunodeficiency Virus RNA levels in US adults: A comparison based upon race
and ethnicity.1997,176:795-797.
2. Wegner S, Vahey M, Dolan M, Wallace M, et al. Racial differences in clinical
efficacy of efavirenz-based antiretroviral therapy. Seattle,WA.Feb24-28,2002,
abstract poster428-W.
3. Swindells S, Cobos DG, Lee N, et al. Racial/ethnic differences in CD4 T-cell
count and viral load at presentation for medical care and in follow-up after HIV-1 infection. Vol16No13;1832-1834. J Infect Dis. 9th Conference on
Retroviruses and Opportunistic Infections AIDS 2002, Vol16No13; 1832-1834.
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