Metaxalone (Skelaxin): New York court invalidated two important patents of innovator

King Pharma announced that the U.S. District Court for the Eastern District of New York in the case of King Pharma v. Eon Labs, Case No. 04-cv-5540 (DGT), issued a summary Judgement opinion by invalidating two important patents relating to SKELAXIN® (Metaxalone).
Following patents are listed in Orange Book for this product:
US6407128 (Expiry: Dec 3, 2021): Which covers a method of increasing the oral bioavailability of metaxalone to a patient receiving metaxalone therapy comprising administering to the patient a therapeutically effective amount of metaxalone in a pharmaceutical composition with food.
US6683102 (Expiry: Dec 3, 2021) : A method of using metaxalone in the treatment of musculoskeletal conditions comprising: providing the patient with a therapeutically effective amount of metaxalone; and informing the patient that the administration of metaxalone with food results in an increase in at least one of C(max) and AUC(last) of metaxalone compared to administration without food.
US7122566 (Expiry: Feb 6, 2026): A method of using metaxalone for treating a patient's condition, comprising providing a patient with metaxalone; and informing the patient or a medical care worker that metaxalone affects activity of a cytochrome p450 isozyme, and that administration of metaxalone with a substance that affects activity of a cytochrome p450 isozyme can affect plasma concentration, safety, efficacy or any combination thereof of metaxalone, the substance, or both.

Eon filed ANDA with Para IV in 2003 for this product. Subsequently, innovator sued Eon for the infringement of ‘128 and ‘102 patents in New York Eastern District Court.
As per court’s summary judgment opinion, the ‘128 and ‘102 patents, which basically cover improved bioavailability of Mataxolone with food were held invalid and obvious in the light of following prior art disclosure:
1) Fathie et al (Article I) published in Current therapeutic research (1964),
2) Fathie et al (Article II) published in Clinical Medicine (1965)
3) Morey et al published in Journal of Osteopathic Association (1963)
4) Albanese et al published in Nurses Drug References (1982)
5) Abrams et al published in Clinical Drug Therapy (1995)
6) Dent et al published in Current Therapeutic Research (1975)
The above prior art disclosure discuss use of Metaxalone 400 mg and 800 g tablets with food.
The Company plans to appeal the Order, which was issued in response to Eon’s motion for summary judgment without the benefit of a hearing.

Furthermore, the Order is unrelated to the Company’s pending litigation against Sandoz, Inc., successor to Eon, in the U.S. District Court for the District of New Jersey regarding’566 patent. Importantly, Sandoz does not currently have an Abbreviated New Drug Application approved by the U.S. Food and Drug Administration to market a generic version of SKELAXIN®.

Innovator got approval for its NDA on 800mg tablets on Aug 30, 2002

Innovator is already in litigation with Mutual Pharmaceutical and Sandoz. However, innovator has settled its litigation with Core pharma in January, 2008 as reported earlier by this blog Here

King Pharmaceutical Settle lawsuit with Core on metaxalone

King Pharma had ended a patent infringement lawsuit filed against CorePharma related to its drug Skelaxin (metaxalone). SKELAXIN® is a muscle relaxant with a low chance of drowsiness or side effectsAll the claims, including Core's counterclaims, were dismissed without prejudice in a New York federal court.After the dismissal was announced in a filing with the Securities and Exchange Commission. Under the terms of a termination agreement King entered with Core on Jan. 2, King will grant Core a nonexclusive license to make and sell a 400 mg metaxalone product, in what amounts to a generic form of Skelaxin.The license will be effective on Jan. 1, 2012, or six months after a third party sells a generic form of Skelaxin, whichever occurs first.The lawsuit was first filed on March 7, 2003. Other suits were filed against Eon Labs Inc. and Mutual Pharmaceutical Co., both of whom King said had filed to make a generic form of Skelaxin.