The U.S. Food and Drug Administration (FDA) has approved HOVILPRI (pritelivir) tablets for the treatment of mucocutaneous lesions caused by herpes simplex virus (HSV) infection in immunocompromised adults whose infections have not responded to standard antiviral treatments.
The approved indication covers patients whose HSV infections are refractory, with or without documented resistance, to acyclovir, valacyclovir, or famciclovir. These infections can cause persistent lesions affecting the skin and mucosal surfaces, including the lips, nostrils, eyes, and genital areas.
HOVILPRI offers a new oral treatment option for eligible patients with weakened immune systems who have limited alternatives when conventional antiviral therapy fails. The FDA granted priority review to the application
The approval was supported by results from the pivotal Phase 3 PRIOH-1 trial, Part C, which evaluated pritelivir in immunocompromised adults with mucocutaneous HSV infections that had not responded to standard antiviral treatments.
A total of 101 adults participated in the randomized, open-label, comparator-controlled trial. Participants received either HOVILPRI or the investigator's choice of available treatments. The primary endpoint was the proportion of participants who achieved complete healing of all lesions within the treatment period of up to 28 days.
Key findings included
- 63% of patients receiving HOVILPRI achieved complete lesion healing by Day 28.
- 34% of patients receiving comparator treatments achieved complete lesion healing by Day 28.
- By Day 42, observed complete lesion-healing rates were 82% with HOVILPRI and 42% with comparator treatments.
The Day 28 results represented an adjusted treatment difference of 28.4 percentage points, with a 95% confidence interval of 9.6 to 47.3 and a p-value of 0.0047.
Treatment could continue for up to 42 days when lesions were improving but had not completely healed by Day 28.
Pritelivir is an oral helicase-primase inhibitor that works through a mechanism distinct from that of commonly used nucleoside analogue antivirals. Medicines such as acyclovir require activation by the viral thymidine kinase enzyme before they can inhibit viral replication. Certain viral mutations can reduce susceptibility to these medicines, contributing to treatment failure in some patients.
Pritelivir targets the herpes virus helicase-primase complex, which is involved in viral DNA replication. Its different mechanism of action is particularly relevant for patients whose infections do not respond to conventional antiviral therapy.
According to Asahi Kasei Therapeutics, HOVILPRI represents the first FDA-approved HSV therapy with a novel mechanism of action in nearly 30 years. In Part C of the PRIOH-1 trial, adverse reactions were reported in 22% of participants receiving HOVILPRI, compared with 54% receiving investigator-selected comparator treatments. Discontinuations due to adverse drug reactions occurred in 2% of patients in the HOVILPRI group and 20% in the comparator group.
Headache was the most common adverse reaction reported with HOVILPRI, occurring in 6% of treated patients, compared with 4% in the comparator group. The FDA also advises healthcare professionals to consult the prescribing information for potential drug interactions.
The approved indication is specifically for immunocompromised adults with mucocutaneous HSV lesions that are refractory to acyclovir, valacyclovir, or famciclovir, with or without documented resistance.
The trial included patients with a range of underlying conditions, including hematologic malignancies or disorders, hematopoietic stem-cell transplantation, HIV infection, autoimmune or inflammatory diseases, other malignancies, and solid-organ transplantation.
The approval does not mean that HOVILPRI is intended for every person with herpes simplex infection. It is intended for the defined population with difficult-to-treat lesions and weakened immune systems.
HSV infection remains incurable, and the virus can reactivate after periods of inactivity. The new medicine is intended to treat the specified lesions rather than eliminate the virus from the body.
Asahi Kasei Therapeutics stated that HOVILPRI is expected to become available in the United States before the end of 2026. The company has not established, in the announcement, a confirmed commercial launch date.
The approval marks a significant development in the treatment of refractory HSV infections, particularly for immunocompromised patients who may otherwise face prolonged disease and limited treatment options.
