ORAL ZOVIRAX ADDITIONAL PRIMATE STUDIES TO ASSESS GONADAL TOXICITY

ORAL ZOVIRAX ADDITIONAL PRIMATE STUDIES TO ASSESS GONADAL TOXICITY were recommended by FDA's Anti-Infective Drugs Advisory Cmte. at its meeting Oct. 28. Burroughs Wellcome noted that it could address the effect of Zovirax (acyclovir) on hormonal levels and menstrual cycles, as well as gonadal function, in a primate study. The cmte. voted 7 to 3, however, against requiring additional studies for evaluation of gonadal toxicity in humans (males and females) who are being treated with suppressive regimens of oral acyclovir. Cmte. member Stephen Straus, MD, Natl. Institutes of Health, suggested that "the ongoing retrospective post-marketing surveillance studies be given an opportunity to see what kind of data they collect." However, cmte. member Itzhak Brook, MD, Armed Forces Institute of Radiobiology, recommended that additional studies in the female be done if continuing animal studies produce leads that should be further investigated. The cmte. was called upon by FDA to determine whether Burroughs Wellcme has adequately addressed the issues of possible gonadal and genetic toxicity in post-marketing surveillance studies conducted since oral Zovirax was approved in February. Cmte. member Ronica Kluge, MD, University of Texas/Galveston, commented that "the one major thing that has not been completely addressed . . . is follow-up over time." She also recommendd that the progeny of parents who have been on the drug be followed for a longer period of time and that use of acyclovir in nursing mothers be examined. Asked by the cmte. how long Burroughs Wellcome planned to follow the progeny of acyclovir treated pregnancies obtained through individual registries, Burroughs Wellcome Pharmacoepidemiology Product Surveillance Dept. Head Hugh Tilson, MD, noted that the individual registry follows patients only to completion of pregnancy. Cmte. chairwoman Sarah Cheeseman, MD, University of Massachusetts Medical School, commented: "That sounds like throwing away a tremendous resource." She said it might be worth watching the children through early childhood. Tilson responded that such follow-up would methodologically be possible "with the proviso that with a very high loss to follow-up we'd be hard pressed to say much about that population, particularly over time." He stated, however, that it would be more practical to conduct follow-up through health maintenance organizations, as the firm is currently doing. Burroughs Wellcome has granted an award to the Boston Drug Collabrative Surveillance Program, and has letters of agreement with the Kaiser Permanente Medical Group and Tennessee Medicaid for monitoring unexpected events and perinatal outcome.