In June 2023, the Supreme Court published its opinion in Amgen Inc. v. Sanofi. The Court unanimously affirmed the Federal Circuit’s holding that certain functional patent claims directed to a class of monoclonal antibodies were invalid for lack of enablement under 35 U.S.C. §112(a). After Amgen, innovators of these astounding medicines are caught between a rock and a hard place: The Court’s enablement standard is clear enough, but the current state of the art, saddled with inherent unpredictability, makes it operationally impossible for applicants to satisfy that standard when they attempt to claim more than a handful of discrete antibodies.

The upshot is an antibody patent singularity—applicants can enable, and thus claim, only the individual antibody structures they actually make, test, and disclose. And yet, a routine practice in the art called conservative replacement permits scientists to exploit known antibody structures to create literally noninfringing competitor antibodies whose properties may be identical to therapies already on the market. One way to counteract this decimation of the literal scope of antibody patents is through the doctrine of equivalents. Therapeutic antibody patent holders will likely assert infringement by equivalents of their narrowed claims against competing antibodies. Courts, however, lack a robust framework to guide the antibody equivalents analysis. Without such a framework, the analysis suffers and leads to undesirable outcomes that hamper innovation.

To prevent antibody innovation from stalling, the clinical properties of antibodies—not their molecular structures—should be the primary determinant of structural therapeutic antibody equivalents. Incorporating clinical data into the infringement inquiry hardly changes the analysis. It merely permits patent holders to assert infringement against other antibody therapeutics that perform the same function in the same way to achieve the same result. This analysis complies with the core tenets of patent law and the doctrine of equivalents. Furthermore, a clinical equivalents analysis counterbalances the obliteration of antibody claim scope resulting from Amgen, insures against the risk of subsidizing follow-on literally noninfringing copiers, and realigns industry incentives to promote innovation in a life-saving field.