Herpes in immunocompromised patients: FDA approves pill with new mechanism

The U.S. Food and Drug Administration has approved Hovilpri (pritelivir) tablets for adults with weakened immune systems who have skin or mucosal lesions caused by herpes simplex virus (HSV). The drug is intended for cases that have not responded to the standard treatments acyclovir, valacyclovir or famciclovir. According to the FDA, HSV-1 and HSV-2 cannot be cured, and immunocompromised patients may have more frequent or severe outbreaks that respond poorly to existing drugs because of resistance or intolerance. The approval was announced on Oct. 9 after a priority review.

Pritelivir is a helicase-primase inhibitor and works differently from acyclovir and related drugs. Its maker, Asahi Kasei Therapeutics, says it is the first FDA-approved HSV therapy with a novel mechanism in nearly 30 years. The drug was developed by AiCuris Anti-infective Cures AG, now part of Asahi Kasei Therapeutics. In the PRIOH-1 trial of 101 patients, all lesions had healed by day 28 in 63% of those taking Hovilpri, compared with 34% on other treatments.

Headache was the most common side effect in the trial, the FDA said. The tablets are expected to be available in the United States before the end of 2026; there is no information yet on approval in the EU. "In PRIOH-1, pritelivir demonstrated superior lesion healing compared with Investigator's Choice treatment up to day 28," said trial investigator Genovefa Papanicolaou of Memorial Sloan Kettering.