In the pivotal PRIOH-1 study, all lesions healed during treatment in 63% of patients receiving Hovilpri. The rate was 34% among patients given an investigator’s choice of available treatments.
The FDA approved Hovilpri, or pritelivir, on October 9, 2026. It is a 100 mg tablet for adults with weakened immune systems whose HSV sores on the skin or mucous membranes have not responded to nucleoside analogue therapies. The named treatments include acyclovir. Valacyclovir and famciclovir are also among them.
The indication covers sores on the lips and nostrils. It also includes lesions affecting the eyes or genitals. Asahi Kasei says confirmed resistance is not required. Hovilpri is the first-in-class oral helicase-primase inhibitor, an alternative to intravenous antivirals for refractory infections, according to this account of its mechanism.
The FDA indication is limited to immunocompromised adults with refractory HSV skin or mucosal lesions; it is not an approval for routine treatment of recurrent cold sores or genital herpes in people with healthy immune systems.
What the trial showed
PRIOH-1 enrolled 101 immunocompromised adults. Treatment lasted up to 28 days, with an extension to 42 days for patients whose lesions were improving but had not fully healed by day 28.
Participants had weakened immunity for different reasons. Some had received haematopoietic stem cell transplants or had cancer. Others had HIV infection, autoimmune diseases or a solid organ transplant. Contemporary OB/GYN describes the phase 3 study as a comparative superiority trial. It was randomized and open-label.
The FDA decision was based on part C of the phase 3 PRIOH-1 trial, registered as NCT03073967. AiCuris developed pritelivir before its acquisition by Asahi Kasei was completed in 2026; Hovilpri is the first commercial asset for Asahi Kasei associated with the program.
The healing-rate difference matters clinically, but the open-label design leaves a limit: the reported figures do not show how Hovilpri would compare in a blinded trial. Asahi Kasei says it is the first FDA-approved HSV therapy with a novel mechanism of action in nearly 30 years.
AiCuris gives Asahi Kasei a new drug asset
HSV-1 and HSV-2 cause common infections, including cold sores and genital herpes. After an initial infection, the virus can lie dormant and reactivate. In people with weakened immune systems, recurrences can produce lesions that release contagious virus particles.
Asahi Kasei acquired German biotech AiCuris for $920 million in April. AiCuris is now a wholly owned subsidiary. It also developed Prevymis, or letermovir, which MSD markets to prevent cytomegalovirus infection in HSCT patients. AiCuris is developing AIC468 to prevent and treat BK virus infections in kidney transplant recipients. The deal echoes Shionogi’s acquisition of a company with a newly approved therapy, though the diseases and assets differ, as detailed in this account of the Shionogi deal.
Asahi Kasei expects to launch Hovilpri in the US before the end of the year. It has not disclosed a price. The company already sells Cresemba, or isavuconazonium sulfate, and Exacin, or isepamicin. Asahi Kasei says AiCuris will help it pursue pharmaceutical sales of around $1.9 billion by its 2030 fiscal year.
