The Food and Drug Administration approved Hovilpri, the brand name for pritelivir, on October 9, Asahi Kasei Therapeutics announced the same day. The approval covers mucocutaneous lesions caused by herpes simplex virus that are refractory, with or without documented resistance, to acyclovir, valacyclovir or famciclovir, in immunocompromised adults. This story was not covered in the editions of October 10 to 12 and is reported here with its original date stated plainly.
Pritelivir is a helicase-primase inhibitor, a mechanism that does not depend on activation by the viral thymidine kinase enzyme that standard nucleoside drugs require. That is why it can work against strains that have become resistant to the standard drugs. Asahi Kasei calls it the first FDA-approved treatment for refractory mucocutaneous HSV lesions with a novel mechanism of action in nearly 30 years. The drug was developed by AiCuris, which Asahi Kasei acquired in a deal reported at 920 million dollars earlier this year, and the application received Priority Review, Fast Track and Breakthrough Therapy designations.
The approval rests on Part C of the Phase 3 PRIOH-1 trial in immunocompromised adults with acyclovir-resistant mucocutaneous HSV. By day 28, 63 percent of Hovilpri-treated participants achieved complete lesion healing, against 34 percent on investigator’s choice treatment, an adjusted difference of 28.4 percentage points (95 percent confidence interval 9.6 to 47.3; p equals 0.0047). The dosing is a 400 milligram loading dose followed by 100 milligrams once daily.
The commercial footprint is narrow but real: refractory HSV is a persistent problem in stem-cell and solid-organ transplant recipients, people with HIV, and patients with malignancies or autoimmune disease, and the fallback options have been intravenous drugs such as foscarnet. An oral therapy changes where and how those patients are treated. Asahi Kasei expects Hovilpri to be available in the United States before the end of 2026.