Addressing obviousness in the context of method of treatment claims using particular drug dosages, the US Court of Appeals for the Federal Circuit affirmed a Patent Trial & Appeal Board (Board) final written decision holding that Teva failed to prove obviousness because it failed to show a reasonable expectation of success. Teva Pharms., LLC v. Corcept Therapeutics, Inc., Case No. 21-1360 (Fed. Cir. Dec. 7, 2021) (Moore, C.J.)

Corcept filed a New Drug Application (NDA) for Korlym, a 300 mg mifepristone tablet administered to certain patients with Cushing’s syndrome. The US Food and Drug Administration (FDA) approved Corcept’s application but required a drug-drug interaction clinical trial to determine drug safety when co-administered with strong CYP3A inhibitors such as ketoconazole (Lee memorandum). Corcept conducted the drug-drug interaction study and received a patent relating to methods of treating Cushing’s syndrome by co-administering mifepristone and a strong CYP3A inhibitor based on the data from the Lee memorandum.

Teva sought a post-grant review of the patent after Corcept asserted it against Teva in district court. Teva argued that the patent would have been obvious in view of Korlym’s label and the Lee memorandum and submitted a supporting expert declaration. The Board held that Teva failed to prove that a skilled artisan would have had a reasonable expectation of success for safe co-administration of more than 300 mg of mifepristone with a strong CYP3A inhibitor, and thus failed to prove that the patent was obvious. Teva appealed, arguing that the Board erroneously required precise predictability rather than reasonable expectation of success in achieving the claimed invention and that the Board did not apply Federal Circuit prior art range precedents.

The Federal Circuit affirmed the Board’s decision. Turning first to a reasonable expectation of success, the Court explained that the analysis must be tied to the scope of the claimed invention. Because the patent required safe administration of a specific amount of mifepristone, the Board did not err in requiring Teva to show a reasonable expectation of success for a specific mifepristone dosage. Applying this correct standard, the Court found that the evidence supported that a skilled artisan would have had no expectation as to whether co-administering dosages of mifepristone above the 300 mg/day threshold set forth in the Korlym label would be successful. The Federal Circuit also agreed with the Board that Teva’s expert testimony supported a finding of no expectation of success in achieving the claimed invention based on inconsistent testimony before and after the institution.

Turning next to the applicability of Federal Circuit prior art range precedents, the Federal Circuit found that Teva had failed to prove that the general working conditions disclosed in the prior art encompassed the claimed invention. Substantial evidence supported the Board’s finding that there was no overlap in ranges because the prior art (Korlym label and industry publications) capped the range of co-administration dosages at 300 mg/day. The Court also noted that Teva’s reliance on mifepristone monotherapy dosages to create an overlap in the claimed ranges failed because the patent claims were limited to co-administration with a strong CYP3A inhibitor. The Court concluded that at best, the prior art directed a skilled artisan to try combining the prior art but failed to show a reasonable expectation of success in achieving the claimed invention.