Third Circuit Affirms Summary Judgment for Pfizer in Zoloft MDL

A Third Circuit Court of Appeals panel recently upheld a lower court’s decision to dismiss plaintiffs’ claims at summary judgment in a multi-district litigation involving Zoloft, an anti-depressant manufactured by Pfizer. The MDL involved 315 plaintiffs alleging that Zoloft causes cardiac birth defects when taken during early pregnancy. The decision, which upheld an earlier ruling by the U.S. District Court for the Eastern District of Pennsylvania, has both good and bad aspects for defendants facing pharmaceutical product liability claims.

The plaintiffs introduced several expert witnesses in support of their claim that Zoloft is generally capable of causing cardiac birth defects (general causation). Among those experts was a statistician who utilized the “Bradford Hill” criteria to analyze the existing medical literature regarding the alleged causal link between Zoloft and cardiac birth defects. In conducting this analysis, the statistician relied upon a total of five studies — two that showed a significant association between Zoloft use and both cardiac defects and septal defects, and three more that showed a significant association between Zoloft use and septal defects alone. Pfizer filed a motion to exclude the statistician, and the District Court conducted a Daubert hearing.

After dismissing two of the five studies from consideration, the District Court expressed serious concerns with the three remaining studies. As an initial matter, although the three remaining studies produced consistent results, the District Court did not consider them to be “independent replications” because all three of the studies used overlapping data from Danish populations. Further, the court found that the plaintiffs’ statistician ignored another larger and more recent study — one which had incorporated virtually all of the data from the three remaining studies, but had reached a contradictory conclusion. For these and other reasons, the District Court precluded the plaintiffs’ statistician, finding that he failed to consistently apply the scientific methods he articulated, deviated from or downplayed certain well-established principles in his field, and inconsistently applied methods and standards to the data so as to support his a priori conclusion.

About four months after the plaintiffs’ statistician was excluded, the District Court granted Pfizer’s motion for summary judgment dismissing the plaintiffs’ claims in their entirety. On appeal, plaintiffs argued that: (1) the District Court erroneously created a new legal standard that a general causation opinion must be supported by replicated observational studies showing a statistically significant association between the drug and the alleged adverse effect to be considered “reliable” under Daubert; and (2) the District Court abused its discretion in excluding the statistician’s testimony.

Notably, the Third Circuit declined to adopt a bright-line rule regarding whether statistical significance is necessary to prove general causation. Rather, the court stated that “[a] causal connection may exist despite the lack of significant findings, due to issues such as random misclassification or insufficient power,” and that “[a] standard based on replication of statistically significant findings obscures the essential issue: a causal connection.”

Nonetheless, the Third Circuit still found that the District Court properly excluded the statistician’s testimony under Daubert. In doing so, the court emphasized that the District Court did not create a new legal standard for reliability, but instead “merely made a factual finding that teratologists generally require replication of significant results.” According to the panel, this finding had not prevented the District Court from considering other evidence of reliability; in fact, the District Court had also examined the statistician’s use of other techniques — including general trend analysis, reanalysis of other studies, and meta-analysis — but had simply rejected those techniques as unreliable.

All of this is generally good news. Indeed, whenever a court – state or federal – strikes plaintiffs’ experts under Daubert (or a state-law equivalent), that is good for defendants in these kinds of cases.

There are, however, some potentially troubling aspects of this decision, despite the court’s finding that the District Court did not abuse its discretion in excluding the statistician’s testimony. In particular, the court held that both the Bradford Hill criteria and “weight of evidence” analysis are generally reliable. While we certainly agree that use of Bradford Hill criteria can be appropriate, we are concerned with an overly broad recognition of the “weight of the evidence” methodology as generally reliable because, unlike Bradford Hill, “weight of the evidence” is more amorphous. We raise this concern because, for example, we disagree with the First Circuit’s recognition and allowance of the “weight of the evidence” methodology in the Milward v. Acuity Specialty Products Group, Inc. (639 F.3d 11) case. We previously discussed our concerns with an ill-defined “weight of the evidence” method in an article which can be found here.

The full text of the Third Circuit’s opinion can be found at the following citation: 2017 WL 2385279 (3rd Cir. 2017).

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