Conference on Retroviruses and Opportunistic Infections (CROI)

Conference on Retroviruses and Opportunistic Infections (CROI)

March 06, 2019
3 min read

Discover trial: TAF noninferior to TDF for HIV PrEP

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SEATTLE — After several years of study, an HIV pre-exposure prophylaxis regimen containing tenofovir alafenamide was found to be noninferior to the traditional regimen with tenofovir disoproxil fumarate.

In 2016, the FDA approved emtricitabine plus tenofovir alafenamide (F/TAF) — marketed as Descovy (Gilead Sciences) — for the treatment of HIV. Studies have shown that TAF has a better safety profile than tenofovir disoproxil fumarate (TDF), the original formulation of tenofovir, and it can be administered at a lower dose.

Charles B. Hare, MD, an infectious disease specialist at the University of California, San Francisco, presented results from the phase 3 Discover study, which included more than 5,300 cisgender men who have sex with men and transgender women in North America and Europe. Researchers evaluated the two drugs for HIV pre-exposure prophylaxis (PrEP). Considered at “very high risk” for HIV, the participants were randomly assigned 1:1 to a daily regimen of F/TAF (200 mg/25 mg) or F/TDF (200 mg/300 mg), Hare said. Participants were followed for up to 96 weeks, and their adherence to the regimens were measured through pill counts and how much of the drug was detected in their blood.

Among the F/TAF arm, seven HIV infections were identified — an incidence rate ratio of 0.16 per 100 person-years. Among those in the F/TDF arm, 15 infections were found, translating to an incidence rate ratio of 0.34 per 100 person-years. This led researchers to conclude that F/TAF was noninferior to F/TDF.

“Both drugs actually performed quite well,” Hare said.

The safety of the two drugs were “comparable,” according to Hare. Discontinuation rates due to adverse events were 1.3% in the F/TAF arm and 1.8% in the F/TDF arm. The most common of these included anal chlamydia, oropharyngeal gonorrhea and rectal gonorrhea.

One pre-specified secondary analysis in a subset of patients showed an improvement in bone safety in patients taking F/TAF, according to Hare, and another pre-specified analysis showed “small but statistically significant differences that favored” F/TAF in terms of renal safety.

Hare said the overall rate of STIs was high in the study, with 57% of participants having at least one. High rates of rectal gonorrhea, chlamydia and syphilis were “persistent and maintained throughout the study,” suggesting that these “were the right participants to be enrolled in the study,” he added.

Notably, less than 10% of the study population was black, a limitation that Hare acknowledged.

“It would have been nice to have seen more African Americans in the study,” he said. – by John Schoen


Hare CB, et al. Abstract 104LB. Presented at: Conference on Retroviruses and Opportunistic Infections; March 4-7, 2019; Seattle.

Disclosure: Hare reports no relevant financial disclosures.