Pharmacist Insights: Descovy and Truvada for HIV Pre-Exposure Prophylaxis

Clinical studies have shown similar efficacy between emtricitabine and tenofovir alafenamide (Descovy) and emtricitabine and tenofovir disoproxil fumarate (Truvada) for individuals at risk for HIV infection.

Clinical studies have shown similar efficacy between 2 pre-exposure prophylaxis (PrEP) drugs for individuals at risk for HIV infection.

Findings from the 96-week DISCOVER trial show that emtricitabine 200 mg and tenofovir alafenamide 25 mg tablets, F/TAF (Descovy, Gilead) is just as effective as emtricitabine 200 mg and tenofovir disoproxil fumarate 300 mg F/TDF (Truvada). F/TAF was initially approved in April 2016 and is currently indicated to reduce the risk of sexually acquired HIV-1 infection in adults at risk of HIV infection and adolescents weighing at least 35 kg in combination with other antiretroviral agents. F/TDF is a once-daily prescription medicine for adults and adolescents at risk of HIV who weigh at least 77 pounds.

The phase 3 DISCOVER clinical study evaluated the safety and efficacy of once-daily F/TAF for PrEP compared with F/TDF for PrEP in men and transgender women who have sex with men and are at risk for sexually acquired HIV infection. At both weeks 48 and 96, F/TAF demonstrated non-inferior efficacy to F/TDF for PrEP.

Moreover, F/TAF also showed favorable changes in key markers of renal and bone safety at week 96 compared with F/TDF for PrEP, according to the study.

The analysis showed significant differences in key markers of bone and renal safety in patients across different age groups. At week 96, there were statistically significant differences in measurements of renal safety favoring F/TAF in the overall trial population, as well as in older participants and in those with moderate renal impairment. Patients older than 50 years of age who received F/TAF showed a smaller decrease in median estimated glomerular filtration rate (eGFR) compared with those receiving F/TDF at week 96, according to the data.

Of the patients with moderate renal impairment, those who received F/TAF also had smaller changes in eGFR and markers of proximal tubular function. In this sub-group, eGFR increased by 3mL/min among those taking F/TAF and decreased by 1mL/min in those taking F/TDF.

Emtricitabine and tenofovir alafenamide are HIV nucleoside analogue reverse transcriptase inhibitors. Emtricitabine reaches maximal plasma concentration 3 hours after oral administration and has a median terminal elimination half-life of 10 hours. Tenofovir alafenamide reaches maximal plasma concentration 1 hour after oral administration. It has a median terminal elimination half-life of 0.51 hour, and its pharmacologically active metabolite, tenofovir diphosphate, has a half-life of 150 to 180 hours.

When taken consistently, the Centers for Disease Control and Prevention estimates that PrEP reduces the risk of HIV infection by up to 92%.