On October 10, 2026, local time, the U.S. FDA approved Hovilpri (pritelivir)
100 mg tablets for the treatment of mucocutaneous lesions caused by herpes
simplex virus (HSV) infection in immunocompromised adults; these lesions are
refractory to acyclovir, valacyclovir, or famciclovir (with or without
documented resistance).
Hovilpri is a novel helicase-primase inhibitor. It is the first FDA-approved HSV therapy with a new mechanism of action in nearly 30 years.
As an oral therapy, it provides a non-intravenous treatment option for eligible immunocompromised adults with refractory (with or without resistance) HSV infection. The FDA had granted Hovilpri Fast Track designation and Breakthrough Therapy designation, and its New Drug Application received Priority Review.
Researcher and Company Comments
Stacy Wheeler, CEO of Asahi Kasei Therapeutics U.S. and Europe, said: “Today’s approval brings the first FDA-approved treatment in nearly 30 years for refractory mucocutaneous HSV lesions with a new mechanism of action, representing an important advance for immunocompromised adults. Hovilpri provides a new oral treatment option for adult patients with persistent, difficult-to-treat disease.”
Genovefa Papanicolaou, MD, Clinical Director of the Infectious Diseases Service at Memorial Sloan Kettering Cancer Center, Professor at Weill Cornell College of Medicine, and a PRIOH-1 investigator, said: “In patients with hematologic malignancies or those undergoing stem cell transplantation, refractory HSV infections can be prolonged, painful, and difficult to treat, while existing intravenous treatments carry significant risks. In PRIOH-1, pritelivir showed superior lesion healing through Day 28 compared with investigator’s choice of treatment.”
Carl Kraus, Chief Medical Officer of Asahi Kasei Therapeutics, said: “Refractory HSV can be a serious clinical challenge in immunocompromised adults, a population with limited treatment options. The approval of Hovilpri reflects years of clinical research in refractory HSV and reinforces our commitment to advancing scientifically differentiated medicines for patients who remain difficult to treat. We thank patients, investigators, clinical teams, and the scientific community for making this milestone possible.”
About Herpes Simplex Virus (HSV)
HSV includes two types, HSV-1 and HSV-2, both of which can cause lifelong infection and currently cannot be cured. HSV-1 most commonly causes cold sores, and HSV-2 is the primary cause of genital herpes. Although many people infected with HSV never develop symptoms, the virus can reactivate and cause recurrent, painful lesions and, in some cases, complications. HSV represents a major global public health burden: in 2020, an estimated 3.8 billion people under age 50 (64% of the global population) were infected with HSV-1; approximately 520 million people aged 15–49 were infected with HSV-2. Immunocompromised patients have a particularly high disease burden, as their weakened immune systems place them at risk for more frequent, more severe, and refractory HSV infections.
About Pritelivir
Hovilpri is an oral HSV helicase-primase inhibitor indicated for the treatment of mucocutaneous lesions caused by HSV infection in immunocompromised adults whose lesions are refractory to acyclovir, valacyclovir, or famciclovir (with or without documented resistance). Hovilpri is active against HSV-1 and HSV-2, including strains resistant to nucleoside analogues and foscarnet. In the pivotal Phase III PRIOH-1 trial, Hovilpri demonstrated statistically significant superiority over investigator’s choice of treatment in lesion healing through Day 28. The most common adverse reaction with Hovilpri was headache.
U.S. Indication and Important Safety Information
Indication
Pritelivir tablets are indicated for the treatment of mucocutaneous lesions caused by HSV infection in immunocompromised adults whose lesions are refractory to acyclovir, valacyclovir, or famciclovir (with or without documented resistance).
Warnings and Precautions
Drug Interactions With Acid-Reducing Agents: Co-administration of Hovilpri with certain acid-reducing agents may reduce Hovilpri exposure, potentially resulting in reduced efficacy and the development of resistance. Avoid co-administration with certain proton pump inhibitors; separate dosing when Hovilpri is co-administered with H2-receptor antagonists and antacids.
Adverse Reactions: In clinical studies, the adverse reaction occurring in more than 5% of participants (all grades) in the Hovilpri group was headache, which occurred in 6% and 4% of participants in the Hovilpri and investigator’s choice groups, respectively.
Drug Interactions
Hovilpri is a breast cancer resistance protein (BCRP) inhibitor. Co-administration of Hovilpri with BCRP substrates may increase plasma concentrations of BCRP substrates, potentially increasing the risk of adverse reactions.
Co-administration with acid-reducing agents may increase gastric pH, reduce the systemic bioavailability of Hovilpri, and potentially reduce its efficacy or lead to resistance to Hovilpri. Avoid co-administration with esomeprazole or rabeprazole. Avoid co-administration with omeprazole or lansoprazole at daily doses exceeding 20 mg, or pantoprazole at daily doses exceeding 40 mg. Hovilpri should be taken at least 2 hours before or 12 hours after an H2-receptor antagonist. Hovilpri should be taken at least 2 hours before or 2 hours after an antacid.
