Sanofi-Aventis filed a patent infringement suit against Barr Laboratories in the U.S. District Court for the District of New Jersey April 5 over the controlled-release version of the sleep aid zolpidem, Ambien CR , triggering a 30-month stay of FDA action on Barr's ANDA for a generic form of the drug.

Barr filed an ANDA with a Paragraph IV certification for generic Ambien CR 6.25 mg and 12.5 mg in December 2006. The company announced April 6 that it received notification of the application's acceptance in February.

In the suit filed by Sanofi, the company alleges that Barr's ANDA infringes on its patent, No. 6,514,531, related to the controlled-release technology of the drug. FDA's "Orange Book" lists the '531 patent as valid until Dec. 1, 2019, with pediatric exclusivity extending until June 1, 2020.

Sanofi claims Barr has infringed the patent by filing an ANDA and is requesting a permanent injunction restraining Barr from selling Ambien CR generics in the U.S.

Sales of Ambien CR in the U.S. were approximately $659 million for the 12 months ended in February, Barr said, citing IMS data.

Ambien CR was approved in September 2005 in 12.5 mg and 6.25 mg doses. An ANDA with a Paragraph IV certification was already filed for the 12.5 mg dose, according to FDA's certification list (¹ Also see "Ambien CR Paragraph IV Certification Filed" - Pink Sheet, 20 March, 2006.).

Generic launches of immediate-release Ambien are anticipated shortly; the patent for that formula, following a pediatric extension, is slated to expire April 21. FDA has granted several tentative approvals to ANDA holders for Ambien.

Since the approval of the extended-release formulation in 2005, which cleared FDA without limitations on duration of use, Sanofi has been aiming to switch patients from IR to CR to defend against the entry of generics (² Also see "Sanofi-Aventis Rebates Aim To Accelerate Switch To Ambien CR" - Pink Sheet, 3 August, 2006.).

New prescriptions of Ambien CR accounted for 16.2 percent of the sleep aid market for the week ended March 30, according to IMS data provided by Merrill Lynch, while new script share for Ambien was flat at 33.8 percent. In comparison, Sepracor's Lunesta (eszopiclone) new script share was 11.2 percent and Takeda's Rozerem (ramelteon) new script share was 2.8 percent.

In a separate patent-related announcement, Barr said April 9 that the U.S. Patent and Trademark Office has issued a notice of allowance for the reissuance of U.S. Patent 5,895,032 for its Seasonale (levonogestrel/ethinyl estradiol) extended-cycle oral contraceptive.

The announcement indicates that PTO will reissue the patent in the future, Barr said, noting it will then be listed in the FDA "Orange Book" with a patent expiration of 2017.

Barr filed its application seeking reissuance of the '032 patent with PTO in July 2004 after being notified that Watson Laboratories had filed an ANDA with a Paragraph IV certification asserting the patent was invalid. PTO rejected Barr's application three times, and the firm argued against the rejections each time. The PTO notice of allowance follows the company's third response and an additional supplement, Barr said.

Watson launched a generic version of Seasonale, marketed as Quasense , in September following FDA approval. Barr countered by launching an "authorized" generic of its own called Jolessa (³ Also see "Changing Of The Seasonale: Barr’s Extended-Cycle Contraceptive Goes Generic" - Pink Sheet, 7 September, 2006.).

Prescriptions of Seasonale were down 76.3 percent in the first quarter, according to IMS trend data provided by JP Morgan.

-Jessica Merrill (j.merrill@elsevier.com)

Sanofi Suit Triggers 30-Month Stay Of FDA Action On Barr’s Ambien CR ANDA

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