People who switch from the old version of the antiretroviral (ARV) tenofovir to the new iteration may be inclined to gain weight.

The Food and Drug Administration (FDA) recently approved a slate of new combination tablets from Gilead Sciences in which the pharmaceutical company replaced the drug tenofovir disoproxil fumarate (TDF) with tenofovir alafenamide fumarate (TAF). As a standalone pill, TAF, known by the brand name Vemlidy, is also approved for the treatment of hepatitis B virus (HBV).

TDF is associated with bone and kidney toxicities, and research indicates that TAF is safer than TDF on those measures. However, a recent review of various studies found that this safety benefit might only be realized when someone switches from TDF to TAF while taking a boosting agent—either Norvir (ritonavir) or Tybost (cobicistat)—with each drug.

Publishing their findings in the journal Infection, researchers conducted a retrospective analysis of data regarding people receiving ARV treatment for HIV from a hospital in Munich between July 2015 and June 2017.

During that period, 310 individuals were switched from an ARV regimen containing TDF to a regimen containing TAF. A total of 129 of them met the inclusion criteria for the study, including having sufficient weight measurements. Also during this period, 711 people in the clinic were treated with TDF but did not switch regimens. Out of this group, 112 of them met the study’s inclusion criteria.

A total of 360 days after switching to TAF, the cohort members increased their body weight by an average of 3.17 percent, compared with no statistically significant shift in weight in the comparison group continuously taking TDF.

To read the study abstract, click here.