In a study appearing in the December 20 issue of JAMA, Anna Wald, M.D., M.P.H., of the University of Washington & Fred Hutchinson Cancer Research Center, Seattle, and colleagues compared the medications pritelivir and valacyclovir for reducing genital herpes simplex virus shedding and lesions in persons with recurrent genital herpes.

Image/Gerd Altmann
Image/Gerd Altmann

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 percent), likely because these drugs neither completely inhibit genital viral shedding (when the virus is active and potentially transmissible to sexual partners). Alternative agents to treat HSV infections are needed.

For this crossover study, 91 participants (adults with 4 to 9 annual genital HSV-2 recurrences) were randomly assigned, 45 to receive pritelivir first, a different class of medication for genital herpes, and 46 to receive valacyclovir first. Participants took the first drug 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 U.S. Food and Drug Administration placed the trial on clinical hold based on findings in a concurrent nonclinical toxicity study, and the sponsor terminated the study.

Of the 91 randomized 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 percent of swabs during pritelivir treatment compared with 5.3 percent during valacyclovir treatment. Genital lesions were present on 1.9 percent of days in the pritelivir group vs 3.9 percent 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 percent of participants in the pritelivir group and 69 percent of participants in the valacyclovir group.

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