FDA approves Hovilpri for immunocompromised adults with unresponsive HSV lesions

The FDA has approved Hovilpri (pritelivir) tablets for adults with weakened immune systems who have mucocutaneous lesions caused by herpes simplex virus (HSV) infection and have not responded to other therapies. The FDA page on the approval is current as of October 9, 2026. It names the therapies the patients did not respond to: acyclovir, valacyclovir or famciclovir.

What the FDA approved

The approval covers immunocompromised patients, meaning adults with weakened immune systems, as the FDA page puts it. It applies to those with HSV infection who have mucocutaneous lesions and have not responded to acyclovir, valacyclovir or famciclovir. The FDA said Hovilpri received priority review for this indication.

The FDA said patients with compromised immune systems can have more frequent and serious HSV outbreaks. The FDA said these outbreaks can respond poorly to available treatments, because the virus is resistant to the medications or because patients cannot tolerate side effects.

The trial behind the approval

The FDA said it evaluated the efficacy of Hovilpri in a randomized, open-label, comparator-controlled, superiority trial. The trial is PRIOH-1, Part C, a Phase 3 trial registered as NCT03073967. It enrolled immunocompromised participants with mucocutaneous HSV infection who did not respond to treatment with acyclovir, valacyclovir or famciclovir.

Participants received Hovilpri or the trial investigator's choice of available treatments. Treatment lasted up to 28 days, until all mucocutaneous lesions healed. The period was extended up to 42 days if lesions were improving but not completely healed after 28 days.

A total of 101 immunocompromised adults were randomly assigned and treated, according to the FDA. They had a wide range of immunosuppressive clinical conditions, including one or more of the following:

hematologic malignancy or disorder
hematopoietic stem-cell transplantation
HIV infection
autoimmune or inflammatory diseases
non-hematologic malignancies
solid-organ transplantation

The trial registry record lists AiCuris Anti-infective Cures AG as the sponsor. It describes Hovilpri dosing as pritelivir 100 mg once daily, after a loading dose of 400 mg as the first dose. The comparator group received the investigator's choice of foscarnet, cidofovir or imiquimod, as nationally approved.

What the trial found

The primary outcome was the proportion of participants with all lesions healed during the treatment period of up to 28 days. By 28 days, the FDA said, all lesions were healed in 63% of patients receiving Hovilpri, compared with 34% of patients receiving one of the other medications.

The trial registry record lists the same measure in different words. It counts participants cured, meaning all lesions healed as assessed by the investigator, during the treatment period of up to 28 days. The record describes Part C as designed to show superiority of pritelivir against the investigator's choice.

Safety

The FDA said the most common adverse reaction was headache. It also said the prescribing information describes certain drug interactions with Hovilpri.