Wednesday 29 April, 2009

Darifenacin hydrobromide (Enablex) ER 7.5 mg and 15 mg tablets: Watson confirmed patent challenge

Generic player Watson Pharma confirmed (in a press release Here ) that it has filed ANDA with Para IV certification against innovator Novartis’s urinary incontinence medication Darifenacin hydrobromide (Enablex) extended-release 7.5 mg and 15 mg. Darifenacin, which is chemically (S)-2-[1-[2-(2,3-dihydrobenzofuran-5-yl)ethyl] pyrrolidin-3-yl] -2,2-diphenyl-acetamide is a M-3 Muscarinic acetylcholine receptor inhibitor.


Following patents are listed in Orange Book for this product:


US5096890 (Assignee; Pfizer, Expiry: Mar 13, 2015): Which covers 3-substituted pyrrolidine derivatives like Darifenacin as product

US6106864 (Assignee; Pfizer, Expiry: Aug 21, 2016): which covers a pharmaceutical dosage form adapted for administration to the gastrointestinal tract of a patient, comprising darifenacin, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable adjuvant, diluent, or carrier; characterized in that the dosage form is adapted to release in the lower gastrointestinal tract at least 10% by weight of the darifenacin, or the pharmaceutically acceptable salt thereof.

Earlier, Watson filed it’s ANDA (possibly, on latest ANDA filing date i.e Dec 22, 2008) and sent innovator Para IV notice w.r.t ‘864 patent.

Further, after the receipt of Para IV notice letter, innovator Novartis filed suit against Watson on April 24, 2009 in the U.S. District Court of Delaware seeking to prevent Watson from commercializing its products prior to expiration of ‘864, accordingly, Watson’s ANDA approval process would be delayed by 30 months as per Hatch-Waxman provisions.

Possibly, Watson is first Para IV filer for this product, accordingly, Watson will be eligible for 180 days lucrative exclusivity.


Earlier, innovator got final approval to market this product on Dec 22, 2004.

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