India’s leading Para IV challenger – Dr. Reddy’s Laboratories (DRL) has finally zeroed down to settle its pending Para IV patent litigation with GlaxoSmithKline (GSK) over the blockbuster anti-migraine drug, Imitrex, generically known as Sumatriptan Succinate which is worth around US $ 890 million in sales in the U.S. market. GSK, under the terms of agreement, has agreed to grant an authorized generic (AG) status to DRL for its Imitrex tablets in the U.S. market which would eventually allow DRL to launch its authorized generic in the last quarter of 2008 ahead of the expiration of the pediatric exclusivity on the U.S. Patent # 5,037,845. After Merck’s blockbuster drugs, Zocor & Proscar, Imitrex is third in a row to fall in DRL expanding authorized generic portfolio. As far as DRL is concerned, it is undoubtly a win situation, both on strategic and financial frontier. This settlement strategically gives DRL an advantage over other generic manufacturers and financially reduces DRL’s legal burden of fighting expensive patent litigations. But what made GSK to go about settling it?

Sumatriptan Succinate and Orange Book Status

Sumatriptan.gifSumatriptan succinate is broadly covered by the U.S. Patent No. 4,816,470 (the genus patent) within the Markush Structural Formula I and in particular claimed by the U.S. 5,037,845 (the species patent). The genus patent was subject to 35 U.S.C. § 156 and received an extension of the patent term for the period of 275 days, extending the original expiration date from March 28, 2006 to December 28, 2006. Both genus and species patents also received additional six months pediatric exclusivity, extending patent validity period till June 28, 2007 (genus patent) and February 06, 2009 (species patent). In addition to genus and species patents, Orange Book also lists three more U.S. patents for pharmaceutical compositions and method of treating migraine running out patent protection from September 2012 to July 26, 2016 (including six months pediatric exclusivity). These patents are as follows.

U.S. Patent # 5,863,559 (the ‘559) directed to a pharmaceutical composition for oral administration comprising a compressed film-coated tablet comprising a tablet core containing 25 to 200mg of 3-[2-(dimethylamino)ethyl]-N-methyl-1H-indole-5-methanesulphonamide succinate (1:1) salt as active ingredient, and a pharmaceutically acceptable carrier or excipient and a film coating on said tablet core wherein the film coating is applied to the tablet core in an amount of from 2 to 5% w/w of the tablet.

U.S. Patent # 6,020,001 (the ‘001 patent) directed to a pharmaceutical composition for oral administration comprising a film-coated tablet containing 3-[1-(dimethylamino)ethyl]-N-methyl-1H-indole-5-methanesulphonamide succinate (1:1) salt as active ingredient, and a pharmaceutically acceptable carrier or excipient.

U.S. Patent # 6,368,627 (the ‘627 patent) directed to a method of treating or prophylactically treating a human suffering from migraine which comprises oral administration of a pharmaceutical composition comprising a film-coated solid dosage form of 3-[2-dimethylamino)ethyl]-N-methyl-1H-indole-5-methanesulfonamide or a pharmaceutically acceptable salt or solvate therefore as active ingredient.

DRL Eyes Sumatriptan!

In December 2003, DRL filed an abbreviated new drug application (ANDA) with U.S. FDA seeking marketing approval for its generic version of Imitrex tablet, along with Para IV certification on four of the five O.B. listed patents for Imitrex tablets. After receiving notification for DRL, GSK subsequently sued DRL and filed patent infringement lawsuit in the U.S. District Court for the Southern District of New York alleging patent infringement of the species patent. Later six other generic companies also filed ANDAs for Imitrex but of those only Cobalt Pharmaceuticals certified Para IV certification for the species patent, challenging its validity. GSK filed infringement suit against Cobalt in the U.S. District Court for the Southern District of New York. In February 2005, GSK also filed a patent infringement suit against Spectrum Pharmaceutical in the U.S. District Court for the District of Delaware, alleging infringement of the species patent. However, Spectrum filed ANDA for marketing approval for sumatriptan injection.

GSK’s Unexpected Move

In the meantime, GSK made a surprising and unexpected move by filing Disclaimer and Dedication with the USPTO for the ‘559, ‘001 and ‘627 patents under 35 U.S.C. § 253 and thereby dedicating to the public the entire term of the said patents. The dedication was filed on August 16, 2004 and subsequently notified in Official Gazette on November 02, 2004.

It is expressly provided under 37 CFR § 1.321(a) that “a patentee owning the whole or any sectional interest in a patent may disclaim any complete claim or claims in a patent. In like manner any patentee may disclaim or dedicate to the public the entire term, or any terminal part of the term, of the patent granted. Such disclaimer is binding upon the grantee and its successors or assigns.” This is furthermore a right that is guaranteed by U.S. patent statute as provided under 35 U.S.C. § 253 that “a patentee, whether of the whole or any sectional interest therein, may, on payment of the fee required by law, make disclaimer of any complete claim, stating therein the extent of his interest in such patent. Such disclaimer shall be in writing, and recorded in the Patent and Trademark Office; and it shall thereafter be considered as part of the original patent to the extent of the interest possessed by the disclaimant and by those claiming under him. In like manner any patentee or applicant may disclaim or dedicate to the public the entire term, or any terminal part of the term, of the patent granted or to be granted.”

GSK also asked the U.S. FDA to delist the ‘559 and ‘627 patents from the Orange Book but the FDA refrained from delisting the said patents in the light of petitions filed by Ranbaxy and Ivax against the delisting of Orange Book listed patents for Simvastatin. Moreover, referring USPTO ‘Patent Maintenance Fees’ section, the ‘627 patent has already expired on April 10, 2006 due to non-payment of maintenance fees.

Who Played Smart Enough?

Considering that GSK already dedicated the ‘559, ‘001 and ‘627 patents to the public under 35 U.S.C. § 253 and likely to run-out patent protection for its species patent in February 06, 2009, it seems to be that GSK has made a smarter move than DRL. By allowing DRL to launch Imitrex as an authorized generic in the last quarter of 2008, GSK has well avoided a DRL attack on the validity of the species patent.

Today’s post comes from Varun Chhonkar, Senior Officer – Patents with J.B. Chemicals & Pharmaceuticals Ltd., Mumbai, India (varun.chhonkar[at]jbcpl.com). © Varun Chhonkar.

  Print This Post Print This Post  

Comments are closed.