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Executive Summary

BENZOYL PEROXIDE IS "NOT LIKELY" TO ENHANCE OR PRODUCE TUMORS in human skin, Andrew Sivak, VP-Life Sciences Section of Arthur D. Little, Inc., concluded in a report prepared for Rich-Vicks and submitted to FDA. "The marked differences in behavior and structure between human and mouse skin taken together with the absence of any demonstration of tumor promotion in human skin by any chemical agent provides adequate support for the view that benzoyl peroxide is not likely to act as an enhancer or producer of tumors in human skin," Sivak stated. Sivak's report was prepared in light of studies in the literature on the tumor promotion (Slaga and Odukoya) and carcinogenicity (Kurokawa) of benzoyl peroxide in mice. Sivak noted that in 1981, "Slaga "reported that benzoyl peroxide could promote epidermal tumors in mouse skin initiated with the potent chemical carcinogen 7,12-dimethylbenz(a)anthracene (DMBA), although benzoyl peroxide itself had no complete carcinogenic or tumor initiating activity." At about the time of Slaga's initial report, Sivak said "there began to appear a series of papers from a number of different laboratories relating free radical and/or active oxygen formation to tumor promotion in mouse skin and the action of mouse skin tumor promoters in certain cell culture systems." Sivak stated that "while this association has been made, the mechanistic role of these active species and whether they directly contribute to tumor promotion in mouse skin is unknown at the present time." Rich-Vicks met with FDA July 29 to discuss the safety of benzoyl peroxide and the studies that have been done regarding tumor promotion and carcinogenicity. FDA reached no conclusions on the ingredient, but suggested that the data discussed be submitted to the agency. Benzoyl peroxide is classified as a Category I ingredient in the tentative final monograph for OTC acne products. Summarizing his findings, Sivak said: "Studies that showed that benzoyl peroxide in an acetone vehicle could promote mouse skin tumors following initiation with potent aromatic hydrocarbon carcinogens have raised questions about the safety of benzoyl peroxide based on the premise that there may be risk of skin tumor promotion in humans. However, no skin tumor promotion was found in mice initiated with ultraviolet-B light, a human carcinogen, and promoted with benzoyl peroxide in more realistic hydroalcoholic and aqueous gel vehicles, although croton oil was an effective promoter." Sivak said one study, by Kurokawa, found both promoting activity with DMBA initiation and complete carcinogenic activity in Sencar mice. However, Sivak asserted that "the observation of tumors with benzoyl peroxide alone in the Sencar mice can be the result of promotion of spontaneously initiated cells." Sivak stated that Kuokawa agreed in a personal communication to him that this interpretation "is the likely explanation for the tumors that arose."

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