Pfizer's response to the approval of Sandoz' Omnitrope could signal the extent to which industry gauges the legality of approving follow-on biologics under the 505(b)(2) pathway.

"We are reviewing FDA's actions to determine if further action is warranted or appropriate," Pfizer said in response to the approval. "It would be scientifically and legally improper for FDA to rely on clinical and manufacturing information for Genotropin as a basis for approving Sandoz' somatropin product."

Omnitrope (somatropin [rDNA orgin]) cleared FDA May 30 as the first follow-on recombinant human growth hormone to be approved under the 505(b)(2) pathway, referencing Pfizer's Genotropin.

One avenue for Pfizer would be to take legal action against FDA to invalidate Omnitrope's marketing authorization. Alternatively, the firm could bring action against Sandoz asserting violation of Pfizer's intellectual property.

Among the issues Pfizer lays out in its 2004 citizen petition arguing against approval of Omnitrope is whether it was appropriate for FDA to accept clinical trial data on Omnitrope; studies of Omnitrop did not employ active controls. The petition also raises questions regarding preclinical testing (see chart: " ¹ Show Me The Monkey; Pfizer Wants More Animal Studies ").

If Pfizer decides against fighting approval of the drug, it would signal that industry views FDA's position as within the scope of current law and regulations.

In the meantime, Pfizer will likely attempt to prevent Sandoz from obtaining a therapeutic equivalence rating for its hormone product, which Sandoz said it will seek (² Also see "Sandoz To Seek Omnitrope Therapeutic Equivalence With Genotropin" - Pink Sheet, 5 June, 2006., p. 6).

ViroPharma, marketer of Lilly's Vancocin , filed a supplement May 31 to a citizen petition laying out legal arguments against FDA's decision to loosen bioequivalence testing standards for the Clostridium difficile medication, specifically waivers for in vivo studies for generics.

Abbott also challenged the agency's bioequivalence standards for levothyroxine drug products in a 2003 citizen petition, arguing that such tests could not support approval of generic Synthroid (³ [A#00660260001], p. 3).

If Sandoz is successful in securing a substitutability rating, Pfizer could also take the fight to the state pharmacy board level, a strategy employed by DuPont when its franchise product Coumadin (warfarin) became subject to generic competition (⁴ Also see "DuPont/Barr Enter Into Legal Truce With Five Product Promotion Accord" - Pink Sheet, 24 January, 2000., p. 30).

Pfizer’s Omnitrope Options Include Approval Challenge, Substitutability Fight

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