Data from a randomized, double-blind clinical study found that the use of pritelivir led to a lower percentage of swabs with herpes simplex virus (HSV) detection over 28 days vs. valacyclovir. Full findings from the study are published in JAMA.

A group of researchers, led by Anna Wald, MD, MPH,from the University of Washington & Fred Hutchinson Cancer Research Center, Seattle, WA, aimed to determine if pritelivir was more effective than valacyclovir in suppressing genital HSV-2 shedding in patients with frequent recurrences. Current herpes infection treatment includes nucleoside analogues whereas pritelivir is a novel HSV helicase-primase inhibitor that has shown to reduce genital shedding and lesions. 

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Dr. Wald and coauthors conducted a crossover study (n=91) in healthy adults with recurrent genital herpes (4-9 annual HSV-2 recurrences) from October 2012 to July 2013. They compared daily oral doses of pritelivir 100mg with valacyclovir 500mg. Study patients took the first drug for 28 days followed by 28 days of washout prior to taking the second drug for 28 days. Genital swabs were collected 4 times daily for testing. 

The primary endpoint was within-participant genital HSV shedding while receiving pritelivir vs. valacyclovir. Data from the intent-to-treat analyses showed that HSV shedding was seen in 2.4% of swabs during pritelivir treatment vs 5.3% during valacyclovir treatment (relative risk [RR] 42, 95% CI: 0.21-0.82; P=0.01). Of the swabs containing HSV, the mean quantity of HSV was higher during valacyclovir treatment than during pritelivir treatment (difference -0.1, 95% CI: -0.6 to 0.5; P=0.83). 

Genital lesions were seen 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=0.04). The authors noted, however, that the frequency of shedding did not differ by group, with 1.3 per person-month for pritelivir vs. 1.6 per person-month for valacyclovir (RR 0.80, 95% CI: 0.52-1.22; P=0.29). 

Pritelivir use resulted in a reduced percentage of swabs with HSV detection over 28 days vs. valacyclovir use. More studies are needed to establish long-term safety and efficacy, Dr. Wald noted.

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