The FDA has approved fostemsavir for adult patients with HIV who have tried multiple medications and whose HIV infection cannot be successfully treated with other antiretroviral (ARV) therapies due to resistance, intolerance, or safety concerns. The application was granted fast track, priority review, and breakthrough therapy designations. Fostemsavir is a novel HIV-1 attachment inhibitor that blocks the virus from attaching to host immune system CD4+ T-cells.
Approval was supported by the phase III BRIGHTE study, a partially randomized, double-blind, placebo-controlled study of 371 adults with HIV who exhibited multidrug resistance. The primary endpoints were safety and efficacy.
Per study protocol, 272 patients in the randomized cohort received either blinded fostemsavir 600 mg twice daily or placebo, in addition to their current ARV regimen, for 8 days; they then continued to receive open-label fostemsavir and an investigator-selected optimized background therapy (OBT). After 8 days, patients randomized to fostemsavir showed superior adjusted mean decline in HIV-1 RNA viral load compared with those who received placebo (decline of 0.79 vs. 0.17 log10 copies/mL, respectively). After 96 weeks, 60% of the fostemsavir cohort achieved undetectable HIV viral load and clinically meaningful improvements in CD4+ T-cell count.
Investigators also reported results from a nonrandomized cohort of 99 participants with no active AVR agents available at screening who were treated with open-label fostemsavir 600 mg twice daily plus OBT. In this group, 37% of subjects achieved undetectable HIV viral load at weeks 24 and 96.
The most common adverse events observed in more than 5% of participants were nausea, fatigue, and diarrhea. Fostemsavir is approved as an extended-release tablet dosed at 600 mg.