FDA Approves the First New Herpes Antiviral Mechanism in Nearly 30 Years

Keypoints:

• The Food and Drug Administration (FDA) approved Hovilpri (pritelivir) on 9 October
• It treats herpes simplex virus lesions that resist standard antivirals in immunocompromised adults
• It is the first approved herpes therapy with a new mechanism of action in nearly 30 years
• In a Phase 3 trial of 101 adults, 62.7% healed completely within 28 days versus 34% on other therapies
• Asahi Kasei Therapeutics expects it to be available in the United States before the end of 2026

The FDA approved Hovilpri (pritelivir) 100 mg tablets for a hard-to-treat group. They are immunocompromised adults with herpes simplex virus (HSV) lesions on the skin or mucous membranes. The lesions must have failed to respond to acyclovir, valacyclovir or famciclovir. This applies with or without documented resistance. The drug was developed by AiCuris and is now owned by Asahi Kasei Therapeutics, which acquired the company in April 2026.

Herpes simplex is a lifelong infection. For most people it is manageable. For transplant recipients and people with blood cancers, outbreaks can be frequent, painful and resistant to existing drugs. That gap is what the approval targets.

The mechanism is the news. Older antivirals are nucleoside analogues, and the virus's own thymidine kinase enzyme must activate them. Pritelivir is a helicase-primase inhibitor. It blocks the viral proteins needed to unwind and copy the virus's DNA. It works against HSV-1 and HSV-2, including strains resistant to nucleoside analogues and foscarnet.

Trial results back it up. The pivotal PRIOH-1 Part C study was an open-label Phase 3 trial of 101 adults. Complete lesion healing within 28 days occurred in 62.7% of pritelivir patients. It occurred in 34% of those on investigator's choice therapy. Comparators included intravenous foscarnet and cidofovir. The FDA had granted Fast Track, Breakthrough Therapy and Priority Review status.

Practical details matter. Pritelivir is a tablet, which avoids the infusions that some alternatives require. It also has drug interactions, so pharmacists will play an important role. Asahi Kasei expects US availability before the end of 2026.

Will this mechanism reach people with less severe infections one day?