Hovilpri (pritelivir)

The FDA approved pritelivir (Hovilpri) on 9 October 2026 for immunocompromised adults, for the treatment of mucocutaneous lesions caused by herpes simplex virus (HSV) infection that is refractory, with or without documented resistance, to acyclovir, valacyclovir, or famciclovir. The oral regimen is 400 mg on day 1, then 100 mg once daily until the lesions have healed. Hovilpri received priority review, and the manufacturer reports Fast Track and Breakthrough Therapy designations. The pivotal evidence is PRIOH-1 Part C, a phase 3, randomized, open-label trial in which 101 participants were treated with pritelivir (51) or investigator's choice (50): intravenous foscarnet in 70% and otherwise cidofovir or topical imiquimod. In the prescribing information, all lesions healed within 28 days in 32 of 51 participants (63%) and 17 of 50 (34%) (adjusted difference 28.4; 95% CI 9.6 to 47.3; p = 0.0047), and healing up to day 42 was 82% and 42% (adjusted difference 40%; 95% CI 22.7 to 57.7). Adverse reactions were reported in 22% and 54% of participants, and discontinuations due to adverse drug reactions in 2% and 20%. The label lists no contraindications and one warning: certain acid-reducing agents may reduce pritelivir exposure.

Part C was open-label with investigator-assessed healing. As of October 2026, no full peer-reviewed publication of it was found, and the registry has no posted results. No evidence was found for time to lesion healing, recurrence, pain, or quality of life in Part C. The 95% CI of the day 28 difference includes zero among transplant recipients (50.0% and 39.3% healed) and participants with laboratory-confirmed acyclovir resistance (50.0% and 29.4%). The single-arm Parts D and F enrolled 35 participants refractory to acyclovir and foscarnet or foscarnet intolerant; lesions healed in 40% up to 28 days and 66% up to 42 days. The label reports pUL5 substitutions with reduced susceptibility in 4 phase 3 participants. Participants with ocular, central nervous system, or disseminated HSV disease were not enrolled. No published wholesale acquisition cost, budget impact model, cost-effectiveness analysis, or health technology assessment has been identified. Asahi Kasei estimates, from an internal investigation, approximately 15,000 people in the United States at second-line treatment, and a 2024 AiCuris presentation gives 27,200 severely immunocompromised people with acyclovir resistance. The manufacturer expects availability in the United States before the end of 2026.