Switching from TDF to TAF was associated with a 13% increase in the expected mean for ASCVD risk score (95% CI: 4%, 23%).
The benefits of switching from tenofovir disoproxil fumarate (TDF) to tenofovir alafenamide (TAF)-containing antiretroviral therapy (ART) are known and include preserved or improved renal function and bone mineral density in patients living with HIV (PLWH).
However, the effects of the switch on body mass index (BMI) and atherosclerotic cardiovascular disease (ASCVD) risk is unclear. That’s what investigators at Jefferson College of Pharmacy sought to do in a retrospective observational study of virologically suppressed adults living with HIV, which was presented at IDWeek 2019.
Adult patients on TDF for > 1 year with 2 consecutive HIV viral loads < 200 copies/mL in the year prior to a TAF switch were included in the study evaluating BMI and ASCVD risk score changes. Investigators collected and recorded body weight, BMI, cholesterol, ASCVD risk score, and other variables for the year prior to and following the switch. Besides a switch from TDF to TAF, no other ART regimen components were changed for patients included in the study.
Investigators used the Wilcoxon signed-rank test to compare unadjusted distributions of pre and post switch values, and constructed repeated measures generalized estimating equations to evaluate changes in BMI and ASCVD risk scores associated with switching from TDF to TAF. They were adjusted for predicters retained in the model if their p-values were < 005. Finally, the ASCVD risk scores skewed right, so the research team log-transformed the data prior to modeling.
A total of 110 patients were included in the analysis. In the unadjusted set, weight, BMI, total cholesterol, LDL, HDL, and ASCVD score had all significantly increased in the year following the switch (each p ≤ 0.01). Gender was the only factor retained in the adjusted BMI model, which showed that a switch from TDF to TAF resulted in an increase of 0.45 kg/m2 in the expected mean for BMI (95% confidence interval [CI]: 0.14, 0.76).
In the adjusted ASCVD model, age, gender, race, concomitant medications that can cause weight gain, and time since HIV diagnosis were all retained as covariates. Switching from TDF to TAF was associated with a 13% increase in the expected mean for ASCVD risk score (95% CI: 4%, 23%).
Jason Schafer, PharmD, MPH, BCPS AQ-ID, associate professor in the Department of Pharmacy Practice at Jefferson College of Pharmacy, Thomas Jefferson University, presenting author on the study, and the content editor of the HIV/AIDS section of Contagion®, explained the implications in an interview at IDWeek 2019 (see video).
“We observed significant increases in BMI and ASCVD risk in PLWH 1 year following a switch from TDF to TAF without changes in other ART regimen components,” investigators concluded “The mechanism of these metabolic changes is unclear and requires further study.”
The study, BMI and ASCVD Risk Score Changes in Virologically Suppressed Patients with HIV Switching from TDF to TAF Containing ART, was presented in an oral abstract session on Friday, October 4, 2019, at IDWeek in Washington, DC.