Ready to Launch: ADAPT Study Looks at Intermittent Dosing of PrEP

Investigators at the HIV Prevention Trials Network (HPTN) Annual Meeting Monday received an update on a study looking to ease the pill burden on those wishing to benefit from pre-exposure prophylaxis (PrEP).

Inspired by studies of non-human primates over the past seven years at the Centers for Disease Control and Prevention, the HPTN 067 "ADAPT" study (Alternate Dosing to Augment PrEP Tablet-taking) is a behavioral study looking at how adherence can be improved by lowering the frequency and potency of each dose, while achieving "comparable" efficacy in preventing HIV infection.

The primate studies, "... Encourage us that daily doses might not be necessary, and easier dosing that is better adaptable to people may be possible," said Bob Grant, MD, of the Gladstone Institute of Virology and Immunology in San Francisco, who presented on the study.  The idea of adapting PrEP regimens to the patients' needs was well-received by the audience, and Grant said it was a key concept to improving adherence, "especially in terms of  people whose lives are not defined by a disease they don't have."

The Phase II, randomized study of the antiretroviral oral truvada plus emtricitabine is currently completing enrollment of 180 HIV-uninfected men who have sex with men (MSM) and 180 women who have sex with men (WSM) at high-risk of acquiring HIV infection. Set to launch shortly, the trial is taking place at Silom Community Clinic in Bangkok for MSM and at Emavundleni Centre in Cape Town for WSM. After a six-week lead-in period including directly observed therapy to determine individual "steady state" pharmacokinetics, participants will be randomly placed in one of three groups:  those receiving daily dosing, those receiving time-driven dosing, and those receiving event-driven dosing.  Over the following 24 weeks study participants will self-administer, with one visit with investigators four weeks after dosing is completed.

Investigators hope to find that with the intermittent dosing participants will experience increased tolerance, increased convenience and a decrease in cost. Dosing pre- and post-sex might also provide guidance on when to start and stop PrEP, and motivate patients to plan for sex. They also plan to evaluate the potential influence of PrEP on sexual behavior and risk-taking. Study results are expected by early 2013.

Another trial worth noting is HPTN 068, set to last approximately four years, which will look at whether monthly cash transfers to young South African women in grades eight through 11 conditional on school attendance will affect HIV incidence among this population over time, as compared to those who are not randomized to receive cash transfers.

Meredith Mazzotta is with the Center for Global Health Policy.