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In an Opinion and Order issued yesterday, the U.S. District Court for the District of Delaware found in favor of ANDA applicants Mylan (MYL), Barr (BRL) and Anchen in the Amrix (Cyclobenzaprine HCl extended-release capsules) Paragraph IV litigation. The decision follows a bench trial that took place last autumn. The decision is somewhat surprising, because on April 8, just before the 30-month stay was set to expire and while the parties were still waiting for an opinion from the court, the court enjoined the defendants from lauching generic versions of Amrix until the court issued its opinion.

The patents-in-suit were U.S. Patent Nos. 7,387,793, which claims extended-release formulations of cyclobenzaprine HCl, and 7,544,372, which claims methods of relieving muscle spasms by administering the formulations. The defendants argued that the asserted claims of the patents-in-suit are invalid for obviousness over prior art multiparticulate extended-release drug formulations, "when combined with the known PK parameters of immediate-release cyclobenzaprine as disclosed in the prior art."

The plaintiffs, Eurand (EURX), Cephalon (CEPH) and Anesta AG, argued that "before the patents-in-suit, no dosage form of cyclobenzaprine existed that provided a therapeutically effective plasma concentration over a period of 24 hours, nor did PK values for said formulation exist." They further argued that not every element of the asserted claims was described in the prior art and, thus, the patents could not be obvious.

The court, however, disagreed, noting that "not every limitation of a claimed invention need be found in the prior art," but instead gaps can be filled by the knowledge of a person of ordinary skill in the art. Moreover, the court found that the claimed PK profile was disclosed in the prior art, "and optimization of this immediate release profile into an extended release form was routine for one of ordinary skill in the art."

The court concluded:

It would have been obvious to one of skill in the art at the time of the invention to try and create an extended release formulation of cyclobenzaprine mirroring the PK properties of the immediate release formulation. If an extended release formulation matches the AUC and Cmax of the already approved immediate release formulation, a person of ordinary skill in the art can generally expect that the extended release formulation will have approximately the same effect in the body as the immediate release formulation. Such a motivation is taught by the FDA, in its direction that an extended release dosage form should have the same AUC and Cmax of an already approved immediate release formulation. Additionally, it would have been obvious to one of skill in the art to use the invention's claimed drug delivery system, as it had already proven effective with a drug that was related to cyclobenzaprine and shared many of its properties.

Therefore, a person or ordinary skill in the art would have been motivated to take a group of known elements to create an extended release version of cyclobenzaprine, and to have a reasonable expectation of success in doing so. The patents-in-suit "claim a structure already known in the art that is altered by the mere substitution of one element for another known in the field, and the combination did no more than yield a predictable result." KSR. Therefore, the invention was obvious.

In addition to finding the asserted claims invalid for obviousness, the court found the claims not invalid for failure to comply with the best mode requirement; and found the patents not unenforceable due to inequitable conduct. The court also found that Mylan and Barr infringe the claims, but Anchen does not.

Mylan previously announced in a press release that it was the first to file a patent challenge relating to Amrix, and thus believes that it is entitled to 180-day exclusivity. Mylan's ANDA was granted final approval on April 18, following expiration of the 30-month stay. It remains to be seen when Mylan will launch its generic Amrix product.

Source: District Court Delivers Good News to Mylan, Barr in Amrix Litigation