HPTN 035

Phase II/IIb Safety and Effectiveness Study of the Vaginal Microbicides BufferGel and 0.5% PRO2000/5 Gel (P) for the Prevention of HIV Infection in Women

Study Summary

What was HPTN 035?

A Phase II/IIb, four-arm, multisite, randomized controlled trial to evaluate the safety and effectiveness of two candidate vaginal microbicides, BufferGel and 0.5% PRO 2000/5 Gel (P), for the prevention of HIV infection in women.

Who participated in the study?

3,099 sexually active HIV-uninfected women from the following study sites: Blantyre, Malawi; Lilongwe, Malawi;; Durban, South Africa; Hlabisa, South Africa; Lusaka, Zambia; Harare, Zimbabwe; and Philadelphia, PA, USA

What happened during the study?

Study participants were randomly assigned to one of four groups: BufferGel, PRO 2000 Gel, placebo gel, and no gel. The Phase II portion of the study involved intensive safety evaluations among the first 799 women enrolled in the study. The Phase IIb portion involved the first 799 women and an additional 2,300 women.


PRO 2000 gel (0.5 percent dose) was 30 percent effective.

During the course of the study, 194 women acquired HIV. Of this total, 36 HIV infections occurred among participants who used PRO 2000, while 54 infections occurred among participants who used BufferGel, 51 infections occurred among participants who used placebo gel, and 53 infections occurred among participants who used no gel. Using these data as a basis for determining the effectiveness of the two candidate microbicides, the researchers found that BufferGel had no effect on HIV infection and that PRO 2000 had a 30 percent level of effectiveness in preventing HIV infection. Both gels were found to be safe.