Pritelivir Shifts Resistant Herpes Care from Intravenous to Oral

The FDA approved Hovilpri (pritelivir), a novel, oral antiviral for persistent herpes simplex virus sores in certain immunocompromised patients whose infections have not responded to available antiviral treatments.¹ The approval gives clinicians an oral option for a small, high-risk population that has largely relied on intravenous therapy when first-line treatment fails. It is also the first commercial milestone from their acquisition of Aicruis.

How Does Pritelivir Work Differently from Existing Antivirals?

Pritelivir blocks proteins the herpes virus needs to copy its genetic material, which stops the virus from multiplying.¹ Because of this mechanism, the treatment can work against some infections that have become resistant to older treatments.

That difference is the core of the approval.¹ Previous first-line drugs must be activated by a viral enzyme before they can block replication, and mutations that disrupt this activation step can cause resistance. For patients with weakened immune systems, such as transplant recipients, a resistant infection can leave few quality options.

The FDA based its decision on a late-stage trial of 101 participants.¹ Sores healed completely within 28 days in 62.7% of patients who received pritelivir, compared with 34% of those who received intravenous foscarnet, cidofovir, and imiquimod. Commonly reported side effects included headache, diarrhea, nausea, reduced appetite, vomiting, and dizziness.

What Manufacturing Choices Shaped Pritelivir’s Path To An Oral Tablet?

Developers evaluated maleate, sulfate, and mesylate salts before selecting a mesylate monohydrate form.² That form was chosen for its stability under forced degradation and its suitability for tableting. Because the compound is poorly soluble above roughly pH 2 to 3, solid-form selection was central to hitting the target bioavailability, which measured 73% in healthy volunteers. The 100 mg film-coated tablet was first made by fluid bed granulation and later moved to direct compaction, with scale-up guided by quality-by-design principles. The authors also described an optimized, green chemistry–based synthetic route intended for commercial production.

Why Does This Approval Matter?

Pritelivir shows the value of designing antivirals around known resistance mechanisms rather than improving on existing ones.¹ A drug that skips the viral activation step older agents depend on gives regulators and clinicians a clear reason to adopt it in patients whose disease is refractory.

The shift from intravenous to oral therapy also has practical consequences further down the line.¹ Foscarnet must be given by controlled intravenous infusion with frequent kidney and electrolyte monitoring, whereas an oral tablet removes the need for infusion access and could ease part of that treatment burden. That changes how the medicine is produced, packaged, and distributed, moving a portion of demand from sterile injectables toward oral dosage forms.

Asahi Kasei had estimated that pritelivir could serve about 15,000 US patients with weakened immune systems.¹ Small, specialized populations like this one often need flexible, smaller-batch manufacturing and dependable supply rather than large-volume capacity, a pattern that shapes decisions about in-house production versus outsourcing. As transplant and other immunocompromised populations grow, demand for agents that keep working when standard therapies fail is likely to increase, along with interest from developers and manufacturers in serving these focused markets.

References:

1. Das K. US FDA approves Asahi Kasei's drug for persistent herpes infections. Reuters. Published October 9, 2026. Accessed October 9, 2026. https://www.reuters.com/business/healthcare-pharmaceuticals/us-fda-approves-asahi-kaseis-drug-persistent-herpes-infections-2026-10-09/
2. Birkmann A, Bonsmann S, Kropeit D, et al. Discovery, chemistry, and preclinical development of pritelivir, a novel treatment option for acyclovir-resistant herpes simplex virus infections. J Med Chem. 2022;65:13614-13628. doi:10.1021/acs.jmedchem.2c00668