United States: Lack Of Efficacy Data In Prior Art Defeats Invalidity Challenges

The US Court of Appeals for the Federal Circuit affirmed a district court decision that the asserted claims directed towards the anti-epileptic drug lacosamide were not invalid based on obviousness-type double patenting, obviousness or anticipation. UCB, Inc. v. Accord Healthcare, Inc., Case No. 2018 (Fed. Cir., May 23, 2018) (Stoll, J) (Prost, CJ, dissenting).

UCB owns a patent disclosing and claiming lacosamide, RE 38,551. Lacosamide belongs to a class of compounds known as functional amino acids (FAAs). In particular, lacosamide is an FAA with three chemical groups at positions R, R1 and R3. R is a benzyl group, R1 is a methyl group, and R3 is a nonaromatic methoxymethyl group. Lacosamide also contains only the R enantiomer.

UCB also holds an approved new drug application covering lacosamide, marketed as Vimpat, for the treatment of epilepsy. Several generic drug makers (appellants) filed an abbreviated new drug application seeking to market a generic version of lacosamide along with a Paragraph IV certification stating that the '551 patent is invalid or unenforceable, or that their proposed product will not infringe upon the '551 patent. 

Consequently, UCB sued appellants for patent infringement. Appellants stipulated to infringement of the '551 patent but raised three affirmative invalidity defenses:

  • Obviousness-type double patenting
  • Obviousness
  • Anticipation

The district court determined that the claims were not invalid based on these ground. The generic drug manufacturers appealed.

Appellants first argued that the asserted claims of the'551 patent were not patentably distinct from claims 44–47 of US Patent No. 5,654,301, which discloses a genus of chemical compounds and recites several different groups that can be placed at the R and R1 positions. The '301 patent does not, however, specifically disclose the chemical structure of lacosamide.

The Federal Circuit affirmed the district court's finding that the '551 patent was patentably distinct from the claims of the '301 patent. Unlike the claims of the '301 patent, the '551 patent requires (1) the R enantiomer with 90 percent purity, (2) an unsubstituted benzyl at R and (3) an unsubstituted methyl at R1. The Court agreed that "the trial evidence supports the district court's finding that there was no prior art that would have provided a person of ordinary skill reason to believe that unsubstituted benzyl and methyl would have been successful."

Chief Judge Prost's dissent faulted the district court for not considering LeGall in its primary double-patenting analysis. LeGall discloses a compound, 107e, which is the racemate version of the lacosamide compound—a mixture of both the R and S enantiomers. While LeGall does not provide any data regarding the anticonvulsant efficacy of 107e, it speculates that based on its structure, 107e "may have good anticonvulsant activity." The majority, however, disagreed, pointing to expert testimony at trial and to the district court's explanation that LeGall's reference to compound 107e lacked any data or discussion that would have motivated a person of ordinary skill in the art to use a nonaromatic compound such as a methoxymethyl at R3.

Appellants also argued that US Patent No. 5,378,729's disclosure of a genus of FAAs that would encompass lacosamide, as well as its disclosures that benzyl is "especially preferred" and that methyl is "most preferred" for this genus of compounds, itself renders the asserted claims obvious. The Court disagreed, finding that this disclosure did not provide any indication that out of the millions of possible choices, an unsubstituted benzyl at R and an unsubstituted methyl at R1 would have been selected in combination with a methoxymethyl group at R3 to arrive at lacosamide.

Next, the court addressed appellant's obviousness arguments. Appellants had asserted that claim 9 of the '551 patent would have been obvious based on LeGall alone or in combination with the '729 patent and Kohn 1991. The district court concluded that a person of ordinary skill in the art would not have selected any FAA, let alone the compounds disclosed in LeGall and Kohn 1991, as a lead compound. The Court agreed with the district court's finding that none of the prior art data cited showed any efficacy for lacosamide as an anticonvulsant. The class of compounds tested in LeGall showed little potency, and the compound disclosed in Kohn 1991 proved to be relatively unstable.

Finally, the Court affirmed the district court's finding that the racemate version of lacosamide (107e) disclosed in LeGall did not anticipate the asserted claims of the '551 patent directed towards the R enantiomer lacosamide, because the reference does not disclose separation into individual enantiomers, nor does it disclose any pharmaceutical data of the R enantiomer recited in claim 9 of the '551 patent.

Practice Note: Lack of relevant efficacy data and expert testimony that there was no reasonable expectation of success may help a patent survive obviousness type double patenting and obviousness invalidity challenges to species claims based on prior art patents disclosing a genus of chemical compounds.

Lack Of Efficacy Data In Prior Art Defeats Invalidity Challenges

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