Asahi Kasei Therapeutics' HOVILPRI approved for refractory mucocutaneous HSV in immunocompromised adults

Approval and indication

The FDA approved HOVILPRI (pritelivir) 100 mg tablets for treatment of mucocutaneous lesions caused by herpes simplex virus (HSV) that are refractory, with or without documented resistance, to acyclovir, valacyclovir, or famciclovir in immunocompromised adults.

Mechanism

Pritelivir is an oral helicase‑primase inhibitor with a mechanism of action distinct from nucleoside analogue therapies. It is active against both HSV‑1 and HSV‑2, including strains resistant to nucleoside analogues and foscarnet.

Clinical evidence

The approval was supported by the randomized, open‑label Phase 3 PRIOH‑1 Part C registrational trial in 101 immunocompromised adults. By Day 28, complete lesion healing occurred in 63% of pritelivir‑treated participants versus 34% receiving Investigator's Choice, an adjusted treatment difference of 28.4% (95% CI: 9.6, 47.3; p=0.0047). By Day 42 observed response rates were 82% versus 42% (adjusted difference 40.0%, 95% CI: 22.7, 57.7). The regimen used a 400 mg loading dose on Day 1 followed by 100 mg once daily.

Safety and cautions

Adverse reactions were reported in 22% of pritelivir patients compared with 54% for Investigator's Choice; discontinuations due to adverse drug reactions were 2% versus 20%. The most common adverse reaction was headache (6% with pritelivir, 4% with Investigator's Choice). Pritelivir is a BCRP inhibitor and concomitant use with certain acid‑reducing agents can reduce pritelivir exposure; specific proton pump inhibitors should be avoided and H2‑antagonists/antacids staggered per prescribing information.

Regulatory pathway and availability

Pritelivir received FDA Fast Track and Breakthrough Therapy designations and the NDA was granted Priority Review. HOVILPRI is expected to be available in the United States before the end of 2026.