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US FDA approves Asahi Kasei’s drug for persistent herpes infections

By Thomson Reuters Oct 9, 2026 | 12:46 PM

Oct 9 (Reuters) – The US FDA on Friday approved Japan’s Asahi Kasei’s drug for persistent herpes simplex virus sores in ​certain patients with weakened immune systems ‌who have not responded to available antiviral treatments.

• The oral drug, called pritelivir, was developed by German drugmaker Aicuris, which Asahi Kasei acquired in April

• Pritelivir ‌blocks ​proteins the herpes virus needs ⁠to copy its genetic ⁠material, stopping it from multiplying and allowing the drug to work against some infections resistant to older treatments

• Older first-line drugs ​must be activated by a viral enzyme before blocking replication, and mutations that disrupt ⁠this activation can cause resistance

• ⁠The US Food and Drug ​Administration’s approval was based on a late-stage trial ​involving 101 participants, in which sores healed completely ‌within 28 days in 62.7% of patients who were given pritelivir, compared to 34% receiving other treatments

• The trial compared pritelivir with ⁠doctors’ choice of intravenous foscarnet, the main approved alternative, or cidofovir and imiquimod — older medicines used off-label

• ⁠The commonly ‌reported side effects in the ⁠trial included headache, diarrhea, nausea, reduced ​appetite, ‌vomiting and dizziness

• Asahi Kasei had ​previously estimated ⁠pritelivir could serve about 15,000 US patients with weakened immune systems, and generate peak annual sales of more than $400 million in the mid-to-late 2030s

(Reporting by Kunal Das in Bengaluru; Editing by ​Shilpi Majumdar)