Products Liability Law Daily Lack of admissible expert epidemiological testimony dooms Zoloft birth defect plaintiffs
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Wednesday, April 6, 2016

Lack of admissible expert epidemiological testimony dooms Zoloft birth defect plaintiffs

By John W. Scanlan, J.D.

All cases pending in federal multidistrict litigation brought by patients against Pfizer, Inc., alleging that its Zoloft antidepressant medication caused birth defects when taken by pregnant women were dismissed with prejudice by the MDL court. Without admissible expert testimony on the epidemiological evidence, the plaintiffs lacked sufficient evidence to establish general causation (In re: Zoloft (Sertraline Hydrochloride) Products Liability Litigation, April 5, 2016, Rufe, C.).

At initial discovery hearings in MDL No. 2342, the Plaintiffs Steering Committee (PSC) proffered the testimony of four expert witnesses on the issue of general causation. The court excluded the opinions of its expert on epidemiology, Dr. Amick Bérard, finding that they were not based on a scientifically valid methodology and that she had failed to address epidemiological studies that were inconsistent with her opinion [see Products Liability Law Daily’s June 30, 2014 analysis]. In a later opinion, the court also partially excluded the opinions of the PSC’s other three causation experts: Dr. Robert Cabrera (a teratologist), Dr. Michael Levin (a molecular developmental biologist), and Dr. Thomas Sadler (an embryologist), ruling that they could not testify that Zoloft caused birth defects in humans but could testify as to the existence of plausible biological mechanisms by which altered concentrations of serotonin could cause birth defects [see Products Liability Law Daily’s August 13, 2014 analysis]. The court denied reconsideration of its opinion excluding Dr. Bérard’s testimony [see Products Liability Law Daily’s January 27, 2015 analysis], but allowed the PSC to introduce the testimony of biostatistics professor Nicholas Jewell, Ph.D., to testify on general causation with regard to cardiac defects [see Products Liability Law Daily’s January 9, 2015 analysis]. However, Jewell’s report and testimony were later excluded because the court found he had not consistently applied the scientific methods he articulated, deviated from well-established principles in his field, and inconsistently applied methods and standards to support his a priori opinion [see Products Liability Law Daily’s December 4, 2015 analysis].

Pfizer then moved for summary judgment, arguing that the PSC was unable to establish causation on any of its claims without the testimony of its experts. The PSC asserted that there was still sufficient evidence of causation, including adverse event reports, internal Pfizer documents finding an association between Zoloft and cardiac events, evidence of biological plausibility from Dr. Levin and Dr. Sadler, differential diagnosis performed by pediatric cardiologist Ra-Id Abdulla, M.D., and an expert opinion by former FDA Commissioner Dr. David A. Kessler, M.D.

Expert testimony. The court reaffirmed its ruling that Dr. Levin and Dr. Sadler may not testify that conventional doses of Zoloft can cause birth defects in humans. While the PSC asserted that these opinions would be offered only with respect to two of the cases, they were inadmissible with respect to any plaintiff. Because animal studies cannot overcome the contrary results of human epidemiological evidence, the opinions could not support general causation. The court said that it would not permit the circumvention of its prior ruling and also would not sanction the PSC’s tactics in submitting the reports, withdrawing them when challenged, and then resubmitting them to oppose the summary judgment motion.

The court also observed that Dr. Abdulla had not treated either of the minor plaintiffs and had not been designated an expert on general causation. Furthermore, his testimony offered nothing new to the discussion of epidemiological studies that Professor Jewell and Dr. Bérard could not reliably interpret, and his specific causation opinion assumed that general causation had been established. There was too great of an analytical gap between his data and his opinion because his differential diagnosis opinion could not "rule-in" Zoloft as a potential cause of birth defects.

Finally, the court would not allow Dr. Kessler to testify regarding general causation because he had not been identified as an expert on general causation and because he failed to create a material issue on it. His testimony did not address the strengths and limitations of the various epidemiological studies, and there was no evidence that he had reconciled the existence of studies that did not show a statistically significant risk using a scientifically reliable methodology.

Non-expert evidence of causation. Case studies and adverse event reports were insufficient to create a material issue of fact on general causation. These reports and studies represented anecdotal data, not scientific methodology, and paled in comparison to epidemiological studies to the contrary.

In addition, internal Pfizer documents could not establish causation. Reviews of published studies were not the type of documents that experts would typically rely upon in a causation analysis because the studies themselves would be a better source of information. Discussions by Pfizer employees about associations between Zoloft and birth defects may be relevant to Pfizer’s knowledge and actions if Zoloft is found to cause birth defects but are not themselves evidence of causation.

The case is No. 12-MD-2342 (MDL No. 2342).

Attorney: Mark P. Robinson, Jr. (Robinson Calcagnie Robinson Shapiro Davis, Inc.) and Dianne M. Nast (Nastlaw LLC) for plaintiffs. Pamela J. Yates (Kaye Scholer LLP), James E. Hooper, Jr. (Wheeler Trigg O’Donnell LLP) and Robert C. Heim (Dechert LLP) for Pfizer Inc. and Greenstone LLC.

Companies: Pfizer Inc.; Greenstone LLC

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