The addition of ViiV Healthcare’s investigational attachment inhibitor fostemsavir to an optimized antiretroviral (ARV) background regimen fully suppressed HIV in a majority of people with highly drug-resistant virus two years into a recent study.

The study, presented at the International AIDS Society Conference on HIV Science in July, included 272 people who had taken numerous ARVs and were on a failing regimen. However, they still had at least one approved ARV from one or two drug classes that remained fully active against their virus. They were randomized to receive either 600 milligrams of fostemsavir twice daily or a placebo. They all stayed on their failing ARV regimen for the first eight days of the study, after which they received fostemsavir plus a background ARV regimen optimized to work as well as possible.

Another 99 people whose virus was not susceptible to any approved ARVs were put in the nonrandomized cohort. They immediately received fostemsavir plus an optimized background regimen, which could include other investigational drugs.

At 96 weeks into the study, 60% of the randomized cohort and 37% of the nonrandomized group had a fully suppressed viral load. The average CD4 count rose by 205 and 119, respectively.

“Heavily treatment-experienced adults have complex needs arising from immune suppression, treatment failures and antiretroviral resistance, along with safety and tolerability issues associated with various antiretroviral regimens,” notes Max Lataillade, DO, MPH, vice president and head of clinical development at ViiV. “Fostemsavir is saving lives.”