definiens: . Regulatory Prohibition shall mean, with respect to any [COMPANY] HCV Compound orNovartis HCV Product, including Alisporivir, proposed to be used with any Idenix HCV Compound or Idenix HCV Product inan HCV Combination Clinical Trial or a Drug - Drug Interaction Study, ( x ) any prohibition imposed by a Regulatory Authorityon the use of such [COMPANY] HCV Compound or [COMPANY] HCV Product with such Idenix HCV Compound or Idenix HCVProduct, or ( y ) any Clinical Hold on such [COMPANY] HCV Compound or [COMPANY] HCV Product ; provided, however, that, solelywith respect to Alisporivir, Regulatory Prohibition shall exclude any such prohibition that solely prohibits the use ofAlisporivir in 11combination only with a pegylated interferon ; i