Early last year, the In re: Incretin-Based Therapies MDL court held that the plaintiffs’ warnings claims were preempted, excluded plaintiffs’ general causation experts, and granted summary judgment to all defendants on dual preemption and causation grounds. In re: Incretin-Based Therapies Prods. Liab. Litig., 524 F. Supp. 3d 1007 (S.D. Cal. 2021). For context, that was the second time the defendants won summary judgment; the Ninth Circuit had reversed an earlier preemption victory in an opinion that predated the Supreme Court’s decision in Albrecht. In re Incretin-Based Therapies Prods. Liab. Litig., 721 F. App’x. 580 (9th Cir. 2017). Now, however, the Ninth Circuit has affirmed summary judgment as to one defendant (Novo Nordisk A/S (“Novo”)). In re: Incretin-Based Therapies Prod. Liab. Litig., 2022 WL 898595 (9th Cir. Mar. 28, 2022).
Plaintiffs in the Incretin MDL had alleged that a variety of diabetes medications cause pancreatic cancer and that the defendants failed to adequately warn of that risk. As the district court noted and the Ninth Circuit confirmed, such claims require expert witness testimony on the issue of general causation. Although plaintiffs proffered numerous experts – including two biostatisticians, a cellular biologist, a chemical toxicologist, a gastroenterologist, and a pathologist – they offered only one medical causation expert, an oncologist. The district court excluded all of these experts, noting as to the oncologist that he claimed to base his opinions on a “weight of the evidence” methodology but had not actually weighed all of the relevant evidence. Specifically, he had failed to independently analyze a number of available clinical trials and other sources that had found no causal relationship. Indeed, the expert confirmed in his deposition testimony that he had not performed any independent epidemiological data analysis for his report; instead, he “blindly” accepted the analyses of plaintiffs’ nonmedical experts, who themselves were excluded for conducting a “selective review” and inconsistently determining whether to include data in their analyses. Moreover, the oncologist had failed to explain in sufficient detail how he applied his methodology, for example, how he determined the weight to assign to the evidence. Additionally, the court noted that, despite years of research on the subject, the plaintiffs’ oncology expert was “alone” in concluding that incretin-based therapies cause or contribute to pancreatic cancer. Thus, the court granted summary judgment not only because the claims were preempted but also because they lacked expert support on general causation.
The Ninth Circuit affirmed in a short and straightforward opinion, focusing solely on the exclusion of the oncologist and the resulting lack of expert testimony to support general causation. First, the appellate court approved the district court’s emphasis on the oncologist’s failure to review the multiple studies that had found no causal relationship between the active ingredient in Novo’s product and the development of pancreatic cancer. Likewise, echoing the district court’s comment that the oncologist’s failure to explain his methodology undercut his reliability, the Ninth Circuit reiterated that “an expert must provide sufficient explanation for their methodology such that someone else using the same data and methods would be able to replicate the results.” Furthermore, the Ninth Circuit held that the district court had properly considered the fact that the oncologist was “alone” in concluding that Novo’s product caused or contributed to pancreatic cancer.
Importantly, the Ninth Circuit rejected an argument for admission of the oncologist’s opinion based on Wendell v. GlaxoSmithKline, 858 F.3d 1227 (9th Cir. 2017). Wendell had held that “when an expert establishes causation based on a differential diagnosis, the expert may rely on his or her extensive clinical experience as a basis for ruling out a potential cause of the disease.” But the oncologist in Incretin was not relying on a differential diagnosis or opining on specific causation. Moreover, as the Incretin court noted, “nothing in Wendell absolves expert witnesses of the general and longstanding requirement that they explain their methods with enough detail that their results can be replicated.” In short, Wendell does not authorize experts to opine on general causation – or specific causation, for that matter – simply because they have experience and claim to have performed a literature review. They must show their work, and that work must pass muster.
The recent Incretin opinion did not reach the preemption issue, thus declining to add to the still-sparse body of Ninth Circuit law applying Albrecht (presently consisting of just two opinions). However, the Ninth Circuit’s reminder that an expert who purports to apply a “weight of the evidence” methodology may not simply ignore adverse evidence is encouraging. So, too, is its reiteration that experts must do more than merely cite their credentials and claim to have interpreted literature through the lens of experience before offering opinions.