Cherry-Picking Epidemiological Data Proves Fruitless For Zantac MDL Plaintiffs

JurisdictionUnited States,Federal
Law FirmWinston & Strawn LLP
Subject MatterLitigation, Mediation & Arbitration, Trials & Appeals & Compensation
AuthorRand Brothers, Michael L. Lavetter and Spencer W. Churchill
Published date22 March 2023

The plaintiffs in the Zantac MDL faced a challenge that is common in products liability cases: How to handle evolving science and conflicting epidemiological data. Predictably, the plaintiffs hired experts to weave favorable epidemiological data into opinions supporting their allegation that Zantac, a heartburn medication also known as ranitidine, had the potential to degrade into a known carcinogen, NDMA. But when the U.S. District Court for the Southern District of Florida found that these experts had not adequately addressed countervailing epidemiological data'among other shortcomings, as detailed in our recent posts on other aspects of the Zantac decision'it excluded their opinions and granted summary judgment against the more-than-2,450 plaintiffs because they had no admissible evidence of general causation.1 The Court's thorough and well-reasoned analysis illustrates that, while cherry-picking data may seem to give plaintiffs an advantage in the short term, it can ultimately open a path to summary judgment for watchful defendants in pharmaceutical cases.

At the forefront of the Court's analysis was an appreciation of the evolving state of the science during the litigation. The initial complaints in the Zantac litigation relied heavily on scientific data from a testing laboratory's citizen petition.2 But the Court noted that FDA later found the testing underpinning the petition to be invalid.3 For instance, a study overseen by Stanford University and initially relied on heavily by the plaintiffs was subsequently retracted by its authors.4 Moreover, none of the many epidemiological studies focusing on ranitidine conducted in 2020 and 2021, after the voluntary recall of ranitidine products, found an association or a causal link between ranitidine and cancer.5

This conflict in the science set up a dilemma for the plaintiffs, who found their theory of the case at odds with the more recent epidemiological studies. Thus, the plaintiffs chose two distinct approaches to prove their case: (1) retaining an expert to test ranitidine for NDMA and (2) introducing the opinions of "epidemiologists who based their opinions, not on the conclusions of any ranitidine-based study author, but instead (for the most part) upon the raw data found in studies that analyzed NDMA-rich food and NDMA-rich air."6

The Court rejected the plaintiffs' experts' experiments and analysis as unreliable under Federal Rule of Evidence 702 and Daubert v. Merrell Dow Pharmaceuticals, Inc....

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