A three judge panel of the Federal Circuit on November 18, 2014 affirmed the District of Delaware’s summary judgment decision that Warner Chilcott’s patents covering the osteoporosis drug Actonel were invalid for obviousness. Despite some uncertainty in the prior art regarding effective dosing of the drug, the Federal Circuit affirmed, stating that obviousness does not require absolute certainty or a guarantee of success.

Warner Chilcott licensed two patents from Hoffmann-La Roche (U.S. Patents 7,192,938 and 7,718,634) directed toward the use of risedronate to treat osteoporosis. After multiple companies submitted Abbreviated New Drug Applications seeking to sell generic versions of the drug, Warner Chilcott and Roche sued for patent infringement.

The claims at issue required three limitations: 1) oral administration of risedronate; 2) once per month; 3) at a dose of 150 mg. The district court found, and the Federal Circuit agreed, that as of the priority date of the asserted patents the FDA had approved several oral regimens of bisphosphonates, including risedronate. Similarly, the Federal Circuit agreed that the prior art taught once-monthly dosing of risedronate.

Regarding the 150 mg dosing limitation, Warner Chilcott and Roche argued that there was uncertainty regarding the safety and efficacy of such a once-monthly dose. Indeed, the Federal Circuit recognized that as of the priority date of the patents at issue the highest single dose of risedronate that actually had been tested in a patient was 50 mg. However, the Court pointed to several pieces of prior art suggesting that one could extrapolate from a known effective daily does to determine a monthly dose. Plaintiffs’ own expert also acknowledged that risedronate was known to exhibit linear bioavailability from 2.5mg to 50 mg, though scaling to higher doses was unknown. Under these facts, the Federal Circuit concluded that the District of Delaware did not err in granting summary judgment of invalidity, holding that there was a reasonable expectation of success in pursuing the 150 mg does. The Court noted: “obviousness does not require absolute certainty or a guarantee of success.”

This case serves as a reminder to ANDA litigants to think broadly when researching prior art. In light of the Federal Circuit’s instruction that obviousness does not require absolute certainty, simple statistical arguments, like linear extrapolations of dosing regimens, can be used to construct a powerful invalidity argument, even if the prior art does not precisely teach a particular claim limitation.