Asahi Kasei wins U.S. approval for oral Hovilpri in refractory herpes lesions

Asahi Kasei Therapeutics said the Food and Drug Administration approved Hovilpri (pritelivir) tablets for immunocompromised adults with mucocutaneous herpes simplex virus lesions that did not respond to acyclovir, valacyclovir, or famciclovir.

What the agency cleared

Asahi Kasei Therapeutics, the specialty pharmaceutical arm of Tokyo-based Asahi Kasei, said the Food and Drug Administration approved Hovilpri (pritelivir) 100 mg tablets for immunocompromised adults with mucocutaneous herpes simplex virus lesions that are refractory, with or without documented resistance, to acyclovir, valacyclovir, or famciclovir. The agency's own notice matches that indication and says Hovilpri received priority review.

In its release, Asahi Kasei Therapeutics calls Hovilpri a novel oral helicase-primase inhibitor and the first agency-approved herpes simplex therapy with a new mechanism of action in nearly 30 years. The company said the drug was developed by AiCuris Anti-infective Cures, which is now part of Asahi Kasei Therapeutics, and that it expects Hovilpri to be available in the United States before the end of 2026. The company also pointed readers to the full prescribing information, including interactions with certain acid-reducing medicines.

How the trial was framed

Approval rests on Prioh-1 Part C, a Phase 3 randomized, open-label, comparator-controlled superiority study (NCT 03073967). The Food and Drug Administration and the company both say 101 immunocompromised adults were randomized and treated. Participants had conditions such as blood cancers, stem-cell or solid-organ transplants, HIV infection, autoimmune or inflammatory disease, or other cancers.

Patients received oral pritelivir — a 400 mg loading dose on day 1, then 100 mg once daily — or an investigator's choice of available options, which the company lists as intravenous foscarnet, intravenous or topical cidofovir, or 5% topical imiquimod. Treatment ran up to 28 days, with an extension to 42 days if lesions were improving but not fully healed.

The primary endpoint was complete healing of all lesions by day 28. Both the agency and the company report 63% healed on Hovilpri versus 34% on investigator's choice. Asahi Kasei Therapeutics adds an adjusted treatment difference of 28.4% (95% confidence interval 9.6 to 47.3; p=0.0047). Observed response rates through day 42 were 82% versus 42%, the company said.

Safety and how the company positions it

The Food and Drug Administration says the most common adverse reaction was headache and points readers to the label for drug-interaction detail. The company reports adverse reactions in 22% of Hovilpri patients versus 54% on investigator's choice, discontinuations for adverse drug reactions of 2% versus 20%, and headache in 6% versus 4%.

Asahi Kasei Therapeutics frames Hovilpri as an oral option for a population that has often needed intravenous therapy when nucleoside analogues fail. Company executives Stacy Wheeler and Carl Kraus cast the clearance as a new oral choice for persistent, hard-to-treat disease in immunocompromised adults; a Prioh-1 investigator quoted in the release said refractory infections can be prolonged and painful in transplant and blood-cancer patients.

What the approval does not settle

U.S. list price, formulary coverage, and any change to Asahi Kasei's financial outlook were not in Friday's materials. Real-world uptake will still depend on specialty-pharmacy stocking, payer rules, and how clinics manage acid-reducing drug interactions called out on the label — none of which the approval notice settles.