Amenamevir's Effective and Safe for Treatment of Recurrent Herpes Labialis Confirms Phase 3 Trial

Herpes labialis, a common viral infection caused by the herpes simplex virus (HSV-1), affects millions globally, causing painful lesions that can recur multiple times a year. Recurrent herpes labialis can be a source of significant discomfort and distress, especially when outbreaks are frequent. While antiviral medications like acyclovir and valacyclovir are commonly used to manage outbreaks, they typically require multiple doses over several days. Amenamevir (ASP2151) is a novel antiviral drug, a non-nucleoside analog, that works by inhibiting the activities of helicase and primase enzymes, which are crucial for the replication of herpes viral DNA.

Against the above background, Makoto Kawashima, Department of Dermatology, Tokyo Women's Medical University, Tokyo, Japan, and colleagues assessed the efficacy and safety of a single, patient-initiated dose of amenamevir for treating recurrent herpes labialis by conducting a phase 3, randomized, double-blind, placebo-controlled, multicenter study.

For this purpose, the researchers randomly assigned adult, immunocompetent patients with recurrent herpes labialis, who were able to recognize prodromal symptoms, to self-administer either amenamevir 1200 mg or a placebo. The treatment was initiated within six hours of prodromal symptom onset.

The primary efficacy endpoint was the time to complete healing of all herpes labialis lesions in the modified intention-to-treat population. Secondary endpoints included time to crusting of lesions, resolution of pain associated with herpes labialis, the proportion of patients with aborted lesions, and time to resolution of other subjective symptoms. The modified intention-to-treat population included 298 patients who self-initiated amenamevir and 307 patients who received the placebo, excluding those with aborted lesions.

The study led to the following findings:

• Amenamevir was superior to placebo for the primary endpoint, with a median time to healing of all lesions of 5.1 days for amenamevir versus 5.5 days for placebo (hazard ratio 1.24).
• Time to crusting of all lesions was significantly shorter with amenamevir compared to placebo.
• No significant differences were observed between the two groups for other secondary outcomes.
• Treatment-emergent adverse events were generally mild in both groups.
• Two moderate adverse events occurred, but they were unrelated to the study treatment.
• No severe adverse events were reported.

"A single patient-initiated dose of 1200 mg of amenamevir taken within 6 hours of the onset of prodromal symptoms significantly reduced the time to complete lesion healing in recurrent herpes labialis, when compared to a placebo, without any clinically significant safety issues," the researchers concluded.

Reference:

Kawashima, M., Watanabe, D., Fujio, K., & Komazaki, H. (2023). A phase 3, randomized, double-blind, placebo-controlled study evaluating a single, patient-initiated dose of amenamevir for recurrent herpes labialis. The Journal of Dermatology, 50(3), 311-318. https://doi.org/10.1111/1346-8138.16608