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Original Investigation
December 20, 2016

Effect of Pritelivir Compared With Valacyclovir on Genital HSV-2 Shedding in Patients With Frequent RecurrencesA Randomized Clinical Trial

Author Affiliations
  • 1University of Washington & Fred Hutchinson Cancer Research Center, Seattle
  • 2AiCuris Anti-infective Cures GmbH, Wuppertal, Germany
  • 3Westover Heights Clinic, Portland, Oregon
  • 4University of Texas Health Science Center & Center for Clinical Studies, Houston
  • 5Indiana University School of Medicine, Indianapolis
JAMA. 2016;316(23):2495-2503. doi:10.1001/jama.2016.18189
Key Points

Question  Is pritelivir more effective than valacyclovir for suppression of genital herpes simplex virus 2 (HSV-2) shedding in patients with frequent recurrences?

Findings  In this double-blind, randomized crossover study of 91 adults with recurrent genital herpes, the percentage of genital swabs with HSV detected over 28 days was significantly lower during use of pritelivir than use of valacyclovir (2.4% vs 5.3%).

Meaning  Pritelivir may be more effective for suppression of genital HSV-2 infection than valacyclovir, but further research is needed to assess longer-term efficacy and safety.


Importance  Current therapy of herpes infections relies on nucleoside analogues. Pritelivir is a well-tolerated novel herpes simplex virus (HSV) helicase-primase inhibitor that reduced genital shedding and lesions.

Objective  To compare the efficacy of pritelivir with valacyclovir for suppression of genital HSV-2 infection.

Design, Setting, and Participants  A phase 2, randomized, double-blind, crossover clinical trial at clinical research centers in 4 US cities (October 2012-July 2013) compared daily oral doses of 100 mg of pritelivir with 500 mg of valacyclovir. The planned sample size was 98 adults, allowing for detection of a 50% reduction in viral shedding between the study treatments. Healthy adults with 4 to 9 annual genital HSV-2 recurrences were eligible. Ninety-one participants were randomized: 45 to receive pritelivir and 46 to receive valacyclovir first when the US 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.

Interventions  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 testing by HSV polymerase chain reaction assays.

Main Outcomes and Measures  The primary end point was within-participant genital HSV shedding while receiving pritelivir compared with valacyclovir. Secondary end points included the quantity of HSV in positive swabs and the frequency of genital lesions and shedding episodes.

Results  Of the 91 randomized participants (median age, 48 years; 57 women [63%]), 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% (173 of 7276 ) of swabs during pritelivir treatment compared with 5.3% (392 of 7453) during valacyclovir treatment (relative risk [RR], 0.42; 95% CI, 0.21 to 0.82; P = .01). In swabs with HSV, the mean quantity of HSV was 3.2 log10 copies/mL during pritelivir treatment vs 3.7 log10 copies/mL during valacyclovir treatment (difference, −0.1; 95% CI, −0.6 to 0.5; P = .83). Genital lesions were present on 1.9% of days in the pritelivir group vs 3.9% in the valacyclovir group (RR, 0.40; 95% CI, 0.17-0.96; P = .04). The frequency of shedding episodes did not differ by group, with 1.3 per person-month for pritelivir and 1.6 per person-month for valacyclovir (RR, 0.80; 95% CI, 0.52 to 1.22; P = .29). Treatment-emergent adverse events occurred in 62.3% of participants in the pritelivir group and 69.2% of participants in the valacyclovir group.

Conclusions and Relevance  Among adults with frequently recurring genital HSV-2, the use of pritelivir compared with valacyclovir resulted in a lower percentage of swabs with HSV detection over 28 days. Further research is needed to assess longer-term efficacy and safety.

Trial Registration  clinicaltrials.gov Identifier: NCT01658826