Mylan and Impax were the first generic drug companies to file substantially complete ANDAs for generic versions of Ditropan XL (oxybutynin chloride, extended release), an incontinence treatment with annual sales of about $400 million. Mylan was the first to file for the 5 mg and 10 mg dosage strengths and Impax was the first to file for the 15 mg strength.
As we previously reported, on September 6th the Court of Appeals for the Federal Circuit affirmed the invalidity of Alza's patent on Ditropan XL. Ordinarily, one would have expected the FDA to grant final approval of Mylan and Impax's ANDAs shortly thereafter (both companies had already received tentative approval), but in this case FDA review of a citizen petition caused final approval to be delayed for over two months.
On August 29, 2005, shortly before the district court invalidated Alza's patent on Ditropan XL, Ortho-McNeil filed a citizen petition asking the FDA to demand additional data from any companies filing ANDAs for generic Ditropan XL. Both Ortho-McNeil and Alza are subsidiaries of Johnson & Johnson. Ortho-McNeil's citizen petition asked FDA (1) to require that standard bioequivalence criteria be applied separately to oxybutynin and its active metabolite, desethyloxybutynin, to ensure that approved generic versions of Ditropan XL are both bioequivalent and clinically equivalent to the innovator product; (2) to apply bioequivalence criteria to the R- and S-enantiomers of oxybutynin and desethyloxybutynin; and (3) to require that all bioequivalence studies be conducted under both fasting and fed conditions.
On November 9th of this year, FDA responded to the citizen petition, granting it in part but denying most of its requests. On the same day, FDA granted final approval to Mylan and Impax for generic versions of Ditropan XL and the two companies launched their generic products immediately. Thus, FDA's delay in ruling on Ortho-McNeil's citizen petition appears to have resulted in an extra two months of market exclusivity for Alza.
Even worse for Mylan (and Impax too, presumably) is that FDA's delay in ruling on the citizen petition appears to have cost it two months of its 180-day exclusivity. While FDA's approval letter to Mylan asks Mylan to submit correspondence indicating when its exclusivity began to run, it seems pretty clear that Mylan's exclusivity began with the September 6th appeals court decision. Mylan filed its ANDA before enactment of the Medicare Modernization Act (MMA), and therefore the "court decision" trigger applies to Mylan's ANDA.
It seems particularly important for FDA to expedite its review of citizen petitions in situations such as this, where a portion of the 180-day marketing exclusivity period may be lost through no fault of the ANDA filer.