One common rationale used to support an obviousness argument is that the patented solution would have been “obvious to try.” The Supreme Court has stated that where “there are a finite number of identified, predictable solutions” for solving a problem and that “a person of ordinary skill has good reason to pursue the known options,” if that “leads to the anticipated success,” that “might show that it was obvious under § 103.” In a recent opinion upon appeal from the Patent Trial and Appeal Board (Board), Teva Pharmaceuticals, LLC v. Corcept Therapeutics, Inc., No. 21-1360 (Fed. Cir. 2021), the Federal Circuit confirmed that specific limitations in claim language necessarily shape the application of the “reasonable expectation of success” obviousness analysis.
Corcept developed a mifepristone tablet for treating Cushing’s syndrome. The U.S. Food and Drug Administration (FDA) approved Corcept’s application with certain stipulations. First, the FDA required Corcept to conduct a clinical trial to determine the safety of its tablet when co-administered with ketoconazole (a strong CYP3A inhibitor) and provided Corcept with a memorandum describing that the effects of co-administering mifepristone with strong CYP3A inhibitors was “unknown” and “may present a safety risk.” Additionally, the FDA approved the prescribing information for the tablet on its label. In relevant part, the label limited the “mifepristone dose to 300 mg per day when used with strong CYP3A inhibitors.” Corcept conducted the requested clinical trial and, based on data collected during that trial, filed for and was granted its ’214 patent. The claims of the ’214 patent are directed to a method of treating Cushing’s syndrome by co-administering a specific dosage (600 mg) of mifepristone and a strong CYP3A inhibitor (e.g., ketoconazole) to a patient.
Upon appeal of the Board’s decision that the challenger had failed to show obviousness of the claims of the ’214 patent, the Federal Circuit affirmed the Board, finding that obviousness could not be established absent a showing that the claimed solution would have been chosen from a finite number of identified, predictable solutions with a “reasonable-expectation-of-success.” Most notably, the Federal Circuit emphasized that “[t]he reasonable-expectation-of-success analysis must be tied to the scope of the claimed invention.” Because claim 1 of Corcept’s ’214 patent requires administration of a specific dosage (600 mg) of mifepristone, the Federal Circuit found that “the Board was required to frame its reasonable-expectation-of-success analysis around that specific dosage of mifepristone” such that establishing obviousness required a showing of “a reasonable expectation of success in achieving the specific invention claimed, a 600 mg dosage,” and that “[a]bsolute predictability is not required.” The Federal Circuit carefully reviewed the FDA’s required clinical testing, suggestions and approved label, finding that they did not suggest the outcome of testing the co-administration using a 600 mg dosage of mifepristone. Ultimately, the Federal Circuit held that “[b]ecause there was no expectation of success for any dosage over 300 mg per day, there was no expectation of success for the specific 600 mg per day dosage.”
The Federal Circuit’s decision is instructive of the idea that “obvious to try” or “invitation to experiment” (including, in this case, being legally required to experiment) does not necessarily equate to obviousness absent a necessary showing of a reasonable expectation of success tied to the claim limitations. Parties involved in an obviousness challenge under the “obvious to try” rationale should therefore remain cognizant of the fact that if one follows the prior art’s “obvious to try” measures and those measures fail to provide identified, predictable solutions and/or fail to provide a reasonable expectation of the resulting success, they may nevertheless result in a nonobvious invention. Put another way, merely showing that a solution would have been “obvious to try” or that a compelling “invitation to experiment” exists does not, in itself, end the obviousness inquiry; rather, it is critical to also establish that the experimental outcome (i.e., the specific claimed solution) was identifiable, predictable and reasonably expected to be successful.
 KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 421 (2007).
 Teva Pharmaceuticals, LLC v. Corcept Therapeutics, Inc., No. 21-1360, at *6 (Fed. Cir. 2021).
 Id. at *7.