Adults with weakened immune systems whose herpes sores do not heal with standard antiviral medicines now have a new treatment they can take by mouth. The U.S. Food and Drug Administration approved Hovilpri (pritelivir) on Oct. 9, according to the agency’s list of novel drug approvals.
The drug is approved to treat adults with weakened immune systems who have skin or mucous membrane sores caused by herpes simplex virus that have not responded to other therapies. Patients take a higher dose on the first day and then one tablet daily.
Most people with herpes manage outbreaks with familiar pills such as acyclovir or valacyclovir. But in people with HIV, organ or stem cell transplants, cancer or autoimmune disease, sores can last for weeks and resist those drugs, leaving options that often require IV treatment and close lab monitoring.
Aicuris, the drug’s developer, said in April that pritelivir would become the first new herpes treatment in more than two decades if approved. Stacy Wheeler, chief executive of Asahi Kasei Therapeutics for the U.S. and Europe, said: “HOVILPRI offers a new oral treatment option for adult patients with a persistent, difficult-to-treat disease.” Both statements come from the drugmakers rather than independent reviewers.
Who Qualifies for the New Pill
Hovilpri is approved only for immunocompromised adults whose herpes sores on the skin or mucous membranes are refractory, meaning they did not improve with standard antivirals. It is not approved for routine cold sores or genital herpes in otherwise healthy people.
The drug was developed by Aicuris and is being brought to market by Asahi Kasei, which completed its acquisition of Aicuris this year. The company expects the drug to be available in the U.S. before the end of 2026, and no price has been announced. Asahi Kasei has estimated that about 15,000 U.S. patients could be eligible, according to Reuters reporting carried by KSL.
Because it is a new specialty medicine without a set price, insurance coverage and prior authorization rules are not yet known. Patients who may qualify can ask their infectious disease specialist or transplant team whether the drug is appropriate once it becomes available.
A Different Way to Block the Virus
Acyclovir and related drugs work only after a viral enzyme called thymidine kinase activates them. When the herpes virus develops mutations in that enzyme, the drugs can stop working.
Pritelivir works differently. It is a helicase-primase inhibitor, which blocks a separate set of viral proteins the virus needs to copy its genetic material, and it does not depend on thymidine kinase, according to Contagion Live’s report on the approval. The approved regimen is 400 milligrams on the first day, followed by 100 milligrams once daily.
The current backup treatments carry real burdens. The CDC’s herpes treatment guidelines note that foscarnet and cidofovir can damage the kidneys and “require intensive laboratory monitoring” along with input from an infectious disease specialist.
Dr. Genovefa Papanicolaou, clinical director of the infectious disease service at Memorial Sloan Kettering Cancer Center and an investigator in the main trial, said refractory herpes infections in patients with blood cancers or stem cell transplants can be “prolonged, painful, and difficult to treat.”
Trial Results and Their Limits
The approval rests largely on the Phase 3 PRIOH-1 trial, sponsored by Aicuris. In its controlled portion, 101 patients were randomly assigned to pritelivir or to an investigator’s choice of existing treatments, including IV foscarnet, IV or topical cidofovir, or topical imiquimod, according to an Aicuris announcement on the trial.
By day 28, all sores had healed in 63% of patients taking pritelivir, compared with 34% in the comparison group. Side effects linked to treatment were reported in 22% of pritelivir patients versus 54% of those on standard treatments, and fewer pritelivir patients stopped treatment because of side effects. Headache was the most common side effect. Among patients who continued treatment through day 42, the company reported healing in 82% of pritelivir patients compared with 42% in the comparison group.
The trial was open-label, meaning patients and doctors knew which treatment was being given, which can influence how results are judged. The comparison group received several different treatments rather than one standard drug. The study was company-funded, and a full peer-reviewed report has not yet been published.
Pritelivir also interacts with some common heartburn medicines. Esomeprazole and rabeprazole should be avoided, other proton pump inhibitors should be limited, and doses should be separated from antacids and H2 blockers. Patients should review all their medicines with a pharmacist or prescriber before starting.
Next Steps for Patients and Caregivers
People with weakened immune systems should contact their care team if herpes sores last longer than usual, spread, or keep returning despite treatment. Sores that do not heal can become infected and are a sign that treatment may need to change.
Patients should not stop or change prescribed antivirals on their own. Testing for drug resistance and choosing a new treatment are decisions for a clinician, often an infectious disease specialist. Sudden fever, confusion, severe headache, eye pain or vision changes, or trouble breathing in someone with a herpes infection and a weakened immune system need urgent medical care.
The drug received Breakthrough Therapy designation and Priority Review during development. The next details to watch are pricing, insurance coverage, and launch timing. MedicalDaily will update this report as that information becomes available.
Key Questions Answered
What is Hovilpri?
Hovilpri, or pritelivir, is an oral antiviral tablet approved by the FDA on Oct. 9, 2026, for certain hard-to-treat herpes simplex infections.
Who can use Hovilpri?
Adults with weakened immune systems whose herpes sores on the skin or mucous membranes have not responded to standard antiviral medicines.
How is it different from acyclovir?
It blocks the virus’s helicase-primase complex and does not need the viral enzyme that acyclovir relies on, so it may work when that enzyme has mutated.
How well did it work in the trial?
All sores healed by day 28 in 63% of patients on pritelivir, compared with 34% of those on other treatments.
What are the limitations of the evidence?
The trial was open-label and company-sponsored, and the comparison group received several different treatments.
When will Hovilpri be available and how much will it cost?
The company expects availability in the U.S. before the end of 2026. Pricing has not been announced.
Does Hovilpri interact with other medicines?
Yes. It interacts with some heartburn medicines, including certain proton pump inhibitors, so patients should review all medicines with a pharmacist or prescriber.
Published by Medicaldaily.com
