A subdermal implant that delivers the HIV antiretroviral tenofovir alafenamide (TAF) has shown promise as an alternative to daily pre-exposure prophylaxis (PrEP) in an animal study. Researchers implanted the matchstick-sized device in beagle dogs and tested its ability to deliver TAF over a 40-day period. Truvada as PrEP is made up of two drugs, tenofovir disoproxil fumarate (TDF) and emtricitabine. TAF is an updated version of TDF that better targets cells and requires a smaller dose to be effective, thus lowering the risk of side effects to the kidneys and bones. The investigators found high levels of tenofovir in key blood cells during the first 35 days after implanting the device, levels 30 times higher than those estimated to be needed for PrEP to work well in humans. The study authors concluded that the implant “holds significant promise as a candidate for HIV prophylaxis in vulnerable populations.”