Patent issues, natural product drug

The series of litigations continued over other issues, inciuding the nature of crystal modifications (Zenith v. Bristol-Myers Squibb 1992). Zenith prepared and formulated a hemihydrate of cefadroxil, for which it submitted an ANDA to the FDA. Bristol-Myers (now Bristol-Myers Squibb) contended that the FDA should require a much more extensive new drug application (NDA) for the hemihydrate, rather than approve it within the framework of the FDA monograph for the monohydrate. BM also alleged that the Zenith product converted to the monohydrate, thereby infringing the 657 patent. Bristol-Myers theory of infringement was that the Zenith product converts to... 

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