Late last month, the U.S. District Court for the District of Delaware (J. Farnan) upheld the validity of Proctor & Gamble's (PG) U.S. Patent No. 5,583,122, which claims risedronate sodium, the active ingredient in Actonel. Teva (TEVA) had challenged the '122 patent in a paragraph IV certification in its ANDA. P&G's U.S. sales of Actonel, which is indicated for the prevention and treatment of osteoporosis, were approximately $1 billion last year.
Teva alleged that the '122 patent is invalid as obvious in light of U.S. Patent No. 4,761,406, entitled "Regimen for Treating Osteoporosis." Alternatively, Teva alleged that the '122 patent is invalid for obviousness-type double patenting in view of the '406 patent. Specifically, Teva argued that the structural similarities between risedronate, claimed in the '122 patent, and 2-pyr EHDP, disclosed and claimed in the '406 patent, render claims 4, 16 and 23 of the '122 patent obvious.
The Federal Circuit has held that "structural similarity between claimed and prior art subject matter, proved by combining references or otherwise, where the prior art gives reason or motivation to make the claimed compositions, creates a prima facie case of obviousness." Takeda. In addition to structural similarities, the Federal Circuit has also required a showing of "adequate support in the prior art" for the change in structure. Id. Clarifying these principals further, the Federal Circuit has held that a prima facie case of unpatentability requires a "showing that the prior art would have suggested making the specific molecular modifications necessary to achieve the claimed invention." Id.
Reviewing the evidence adduced at trial in light of these legal principles, the Court concludes that Teva has not established by clear and convincing evidence that "the prior art would have suggested making the specific molecular modifications necessary" to achieve risedronate. To begin, the Court is unpersuaded that a person of ordinary skill in the art would have selected 2-pyr EHDP as the "lead compound" out of the numerous compounds disclosed in the '406 patent.
The court further concluded, even if Teva can establish a prima facie case of obviousness, Proctor & Gamble has demonstrated sufficient evidence of unexpected results regarding resedronate's potency and toxicity to rebut such a prima facie showing." Finally, the court determined that Teva had not proven double patenting, as "the same type of analysis is used for an obviousness-type double patenting inquiry as for a Section 103 obviousness inquiry."
The '122 patent won't expire until December 2013. Teva immediately announced its intention to appeal the district court's decision to the Federal Circuit.