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Valacyclovir safely cut vertical CMV transmission

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Preventing congenital CMV remains a major unmet need

This small Israeli study is very important. The powerful finding of the study was buttressed by its placebo-controlled design and by its follow-up. The findings need replication in a larger study, but despite the small size of the current study the findings are noteworthy because of the desperate need for a safe and effective intervention to reduce the risk for maternal-fetal transmission of cytomegalovirus (CMV) when a woman has a first infection just before conception or early during pregnancy. Several years ago, the Institute of Medicine made prevention of prenatal CMV transmission (by vaccination) a major health priority based on the high estimated burden of congenital CMV infection, Addressing this still unmet need remains an important goal given the substantial disability that congenital CMV causes for thousands of infants born each year.

Janet A. Englund, MD, is a professor of pediatric infectious diseases at the University of Washington in Seattle and at Seattle Children’s Hospital. She had no relevant disclosures. She made these comments in an interview.



– Daily treatment with valacyclovir for at least 6 weeks safely cut the cytomegalovirus (CMV) vertical transmission rate from mothers to fetuses in women with a primary CMV infection during the three weeks before conception through their first trimester. That finding emerged from a randomized, controlled, single-center Israeli study with 92 women.

The rate of congenital fetal infection with CMV was 11% among neonates born to 45 women treated with 8 g/day of valacyclovir, compared with a 30% rate among the infants born to 47 women who received placebo, a statistically significant difference, Keren Shahar-Nissan, MD, said at an annual scientific meeting on infectious diseases. The results also showed that the valacyclovir regimen was well tolerated, with no increase compared with placebo in adverse events and with no need for dosage adjustment regardless of a 16 pill/day regimen to deliver the 8 g/day of valacyclovir or placebo that participants received.

Dr. Shahar-Nissan said that she and her associates felt comfortable administering this amount of valacyclovir to pregnant woman given previous reports of the safety of this dosage for both women and their fetuses. These reports included 20 pregnant women safely treated for 7 weeks with 8 g/day during the late second or early third trimester (BJOG. 2007 Sept;114[9]:1113-21); more than 600 women in a Danish nationwide study treated with any dosage of valacyclovir during preconception, the first trimester, or the second or third trimesters with a prevalence of births defects not significantly different from unexposed pregnancies (JAMA. 2010 Aug 25;304[8]:859-66); and a prospective, open-label study of 8 g/day valacyclovir to treat 43 women carrying CMV-infected fetuses starting at a median 26 weeks gestation and continuing through delivery (Am J Obstet Gynecol. 2016 Oct;215[4]:462.e1-462.e10).

The study she ran enrolled women seen at Helen Schneider Hospital for Women in Petah Tikva, Israel, during November 2015-October 2018 who had a serologically-proven primary CMV infection that began at any time from 3 weeks before conception through the first trimester, excluding patients with renal dysfunction, liver disease, bone-marrow suppression, or acyclovir sensitivity. Screening for active CMV infection is common among newly-pregnant Israeli women, usually at the time of their first obstetrical consultation for a suspected pregnancy, noted Dr. Shahar-Nissan, a pediatrician at Schneider Children’s Medical Center of Israel in Petah Tikva. About a quarter of the enrolled women became infected during the 3 weeks prior to conception, and nearly two-thirds became infected during the first 8 weeks of pregnancy.

The valacyclovir intervention appeared to be effective specifically for preventing vertical transmission of infection acquired early during pregnancy. In this subgroup the transmission rate was 11% with valacyclovir treatment and 48% on placebo. Valacyclovir seemed to have no effect on vertical transmission of infections that began before conception, likely because treatment began too late to prevent transmission.

“I think this study is enough” to convince the U.S. Food and Drug Administration to add this treatment indication to the labeling of valacyclovir, a drug that has been available in generic formulations for many years, Dr. Shahar-Nissan said in an interview. Before approaching the FDA, her first goal is publishing the findings, she added.

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