Mending the Fence: Commercial Success & The Blocking Patent Defense in Pharmaceutical Litigation
AIPLA Quarterly Journal, 2026
In pharmaceutical litigation, the blocking patent defense is used increasingly to rebut a patent owner’s claim that a drug’s commercial success reflects the non-obviousness of an underlying patent. The proffered defense is often that the success of the at-issue patent is due to an earlier patent that likely deterred competitors from developing the at-issue patent before the patent owner actually did. Application of the defense in practice raises important questions about how courts should evaluate the impact of earlier patents on innovation and competition.
In the AIPLA Quarterly Journal, Analysis Group Managing Principal John Jarosz and Vice Presidents Andrea Hugill and Anna Gumen, together with Michael Chapman (Envision Economics), examine the role of the blocking patent defense and trends in its application.
The authors analyze how courts apply the defense and evaluate whether the application properly reflects real-world incentives for drug development. Drawing on economic analyses and empirical evidence, the authors explain that innovation can and often does proceed, despite the presence of an earlier “blocking” patent. They emphasize that the relevant inquiry is not simply whether a patent may have blocked innovation, but whether it actually did and to what degree it may have or did block innovation. In their view, the blocking inquiry should not be answered with a simple “yes” or “no” but instead requires evaluating the extent to which a patent influenced, or could influence, behavior in the relevant field.
The authors highlight the importance of evaluating real-world evidence on research and development, forward citations, and clinical trials. They note that, rather than relying solely on theoretical assumptions about deterrence, courts can and should consider whether innovation continued in practice. The article also presents a structured framework for incorporating real-world evidence to evaluate blocking patent claims.
The authors conclude that, while the blocking patent defense has gained traction in pharmaceutical litigation, its application is highly fact dependent. Determining whether a patent meaningfully constrained innovation requires a case-specific inquiry supported by concrete evidence, often requiring careful contextual interpretation. Particularly in cases involving pharmaceuticals, assessing the blocking patent defense can benefit from a nuanced, evidence-based approach that reflects how innovation and competition function in the industry.