Anti-HIV Drug Efficacy: Are There Sex Differences?

Bishoy Faltas, MD

Current antiretrovial therapy is, on average, equally effective in both sexes and thus can be used in a similar way to treat HIV-infected men and women.

There are an estimated 15.5 million women living with HIV worldwide, representing nearly half of the HIV-positive population.1 However, women are frequently under-represented in randomized clinical trials (RCTs) of antiretroviral drugs. This makes it difficult to determine whether women achieve  virologic outcomes similar to those of men because any sex-related analyses typically lack sufficient statistical power. To help address the disparity, which has important public health implications, the FDA’s Division of Antiviral Products created a database that includes 20,328 HIV-positive patients who were participants in 40 randomized controlled trials (RCTs) that were included in 18 new drug applications submitted to the agency between 2000 and 2008. All trials included were conducted for at least 48 weeks.

Soon and colleagues2 used this database to address the question of whether sex differences exist in the effectiveness of antiretrovirals. Results were published in AIDS Patient Care and STDs. The investigators conducted a meta-analysis of the 40 RCTs in the FDA database that included 7 drug classes and 16 single-agent or fixed-dose combination antiretroviral drugs. The percentage of females enrolled in each of the RCTs varied widely, ranging from 8% to 68%. Overall, approximately 20% of the included patients in the database were women.2 Researchers evaluated the percentage of subjects with HIV RNA loads less than 50 copies/mL at 48 weeks.

The results showed that, on average, antiretroviral drugs were equally effective in men and women.2 The meta-analyses odds ratio with co-variate adjustment did not show any statistically significant sex differences in efficacy. The authors conducted 20 subgroup analyses by age, region, and ethnicity, however, and found several statistically significant sex differences favoring males. One of these analyses showed a statistically significant difference for Caucasian subjects in the treatment-naive population (P = .001) favoring males.2

The analyses of the FDA database comprise one of the most comprehensive reviews of antiretroviral drug efficacy-by-sex data currently available. The results demonstrate, based on a very large dataset, that antiretroviral therapy is, on average, equally effective in both sexes and thus can be used in a similar way to treat HIV-infected men and women.

1. Napravnik S, Poole C, Thomas JC, et al. Gender difference in HIV RNA levels: a meta-analysis of published studies. J Acquir Immune Defic Syndr. 2002;31:11-19. (Abstract)
2. Soon GG, Min M, Struble KA, et al. Meta-analysis of gender differences in efficacy outcomes for HIV-positive subjects in randomized controlled clinical trials of antiretroviral therapy (2000-2008). AIDS Patient Care and STDs. 2012;26:444-453. doi:10.1089/apc.2011.0278. (Abstract)