Hovilpri (Pritelivir): New Herpes Drug FDA Approved in 2026

Almost every herpes pill sold in the US works the same way. Acyclovir was approved in 1982, and valacyclovir (Valtrex) and famciclovir are improved versions of the same idea. They work well for most people, which is why so little changed for decades. Pritelivir is different because it attacks the virus from a completely different angle, and in October 2026 it became the first herpes drug with a new mechanism of action approved in nearly 30 years (source). Here is what it is, who it is for, and what it means for the rest of us.

What pritelivir is

Pritelivir is an antiviral pill, sold as Hovilpri 100 mg tablets. It was developed by the German company AiCuris, which is now part of Asahi Kasei Therapeutics (source). It belongs to a class called helicase primase inhibitors. That is a mouthful, so here is the plain version. To copy itself, the herpes virus has to unzip its DNA and prepare it for copying. The helicase primase complex is the tool that does that job. Pritelivir jams that tool, so the virus cannot copy itself.

The road to approval was quick. In April 2026 the FDA accepted the application with Priority Review, after earlier granting Breakthrough Therapy designation (source). In October 2026 the FDA approved it (source).

How it differs from Valtrex and acyclovir

The key difference is how the drug gets switched on. Acyclovir, valacyclovir and famciclovir are all inactive until an enzyme made by the virus itself, called thymidine kinase, turns them on (source). That works brilliantly until the virus changes that enzyme. When it does, the drug never switches on and stops working. That is the most common way herpes becomes resistant.

Pritelivir does not need the virus to switch it on. It blocks a different target altogether, so a virus that has learned to dodge acyclovir has no defence against it.

	Hovilpri (pritelivir)	Valacyclovir (Valtrex)	Acyclovir
Drug class	Helicase primase inhibitor	Nucleoside analogue	Nucleoside analogue
Needs the virus to switch it on?	No	Yes	Yes
Works on acyclovir resistant herpes?	Yes	No	No
Who it is for	Immunocompromised adults, treatment resistant	Most people with HSV-2	Most people with HSV-2
Status in the US	FDA approved October 2026	Approved, cheap generic	Approved since 1982

What the Phase 3 trial showed

The main trial is called PRIOH-1 (source). It enrolled 101 people with weakened immune systems, including transplant recipients, people with cancer and people with HIV, whose herpes had not cleared on standard treatment. They were randomly given either pritelivir or whatever treatment their doctor would normally choose, which for resistant herpes usually means foscarnet or cidofovir, two older drugs that are given by drip and can be hard on the kidneys.

By day 28, all lesions had healed in 63% of people on Hovilpri, compared with 34% on the other treatments (source). With treatment allowed to continue to day 42, the response rate reached 82% for Hovilpri against 42% for the comparison group (source). Side effects were less common on Hovilpri than on the comparison drugs, 22% against 54%, and the most common one was headache, in 6% of patients (source).

For this group, that is a big deal. These are people who had run out of good options, and the backup drugs are unpleasant. A pill that heals about twice as many of them matters a lot.

Who Hovilpri is for, and who it is not for

The FDA approved it for one specific use: adults with weakened immune systems whose herpes sores on the skin or mucous membranes have not responded to acyclovir, valacyclovir or famciclovir, with or without proven resistance (source). In plain terms:

• Who it is approved for: transplant recipients, people having chemotherapy, people with advanced HIV, and other adults with a weakened immune system whose herpes will not heal on the standard drugs.
• Who it is not approved for: the average person with HSV-2 who has occasional outbreaks, or who takes daily Valtrex and does well on it.

Resistance to acyclovir is rare in people with healthy immune systems and far more common in people whose immune systems are weakened (source). So for most readers of this site, the drug they already have still works. If you think your outbreaks are not responding to treatment, raise it with a doctor, because there are tests that can check for resistance.

When you can get it

When	What happened or happens
April 2026	FDA accepts the application with Priority Review
October 2026	FDA approves pritelivir as Hovilpri 100 mg tablets
By the end of 2026	Expected to be available in the US, most likely through specialists and hospitals first
Later, if at all	Any use in everyday HSV-2 would need new trials in that group

No price had been announced at the time of writing. Drugs for small, serious patient groups usually cost far more than generic valacyclovir, so do not expect it to be cheap. It is a prescription drug, so the route to it is a doctor, usually a specialist who is already treating the underlying condition.

What it means for everyone else with HSV-2

Directly, not much yet. Indirectly, quite a lot. Hovilpri is the first helicase primase inhibitor approved in the US, and it proves to regulators and drug companies that this class works in people. A related drug, amenamevir, has been sold in Japan since 2017, mainly for shingles.

That matters because the most exciting drugs in the herpes pipeline are in the same class. Assembly Biosciences is developing once a week helicase primase pills, and one of them cut HSV-2 shedding by 94% in a small trial (source). Those are aimed at ordinary people with recurrent genital herpes. Hovilpri’s approval makes that path easier. You can follow all of these on our vaccine and cure tracker.

What to do in the meantime

For almost everyone, the best treatment is still the one that has existed for years. Daily valacyclovir reduces outbreaks and, in a large trial, cut the risk of passing HSV-2 to a partner by about 48% (source). It is on the CDC’s list of recommended treatments (source) and costs little as a generic. Our valacyclovir guide covers doses and cost, and the antiviral comparison covers the other options.

Related: Vaccine and cure tracker | Antiviral comparison | Valacyclovir guide | Treatment options