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Pritelivir provides greater virus suppression than valacyclovir in patients with recurrent genital herpes, according to a study published in the December 20 issue of JAMA.

The treatment for genital herpes simplex virus (HSV) infections relies on the nucleoside analogues acyclovir, valacyclovir, or famciclovir administered either for each recurrence or daily to prevent recurrences.

In addition, valacyclovir, when taken daily has been shown to reduce the risk of HSV-2 transmission to susceptible partners. However, the protection is only partial (approximately 50%), likely because these drugs do not completely inhibit genital viral shedding. Alternative agents to treat HSV infections are needed.

In the current crossover study, Anna Wald, MD, University of Washington Fred Hutchinson Cancer Research Center, Seattle, Washington, and colleagues randomised 91 adults with 4 to 9 annual genital HSV-2 recurrences to receive pritelivir first (n = 45) or valacyclovir first (n = 46) for 28 days followed by 28 days of washout before taking the second drug for 28 days.

Throughout treatment, the participants collected genital swabs 4 times daily for HSV testing. The US Food and Drug Administration (FDA) placed the trial on clinical hold based on findings in a concurrent nonclinical toxicity study, and the sponsor terminated the study.

Of the 91 randomised participants, 56 had completed both treatment periods at the time of the study’s termination.

In intent-to-treat analyses, HSV shedding was detected in 2.4% of swabs during pritelivir treatment compared with 5.3% during valacyclovir treatment. Genital lesions were present on 1.9% of days in the pritelivir group versus 3.9% in the valacyclovir group.

The frequency of shedding episodes did not differ by group. Quantity of virus shed was decreased significantly during pritelivir treatment compared with valacyclovir treatment.

The frequency of pain was reduced in the pritelivir group compared to the valacyclovir group.

Treatment-emergent adverse events occurred in 62% of participants in the pritelivir group and in 69% of participants in the valacyclovir group.

“Further research is needed to assess longer-term efficacy and safety,” the authors wrote.

SOURCE: JAMA