(Aaron Couture)

The road to victory for plaintiffs alleging that Pfizer’s antidepressant Zoloft causes birth defects has gotten steeper since a federal judge barred the testimony of one of their key expert witnesses.

After a week of Daubert hearings in April, U.S. District Judge Cynthia Rufe of the Eastern District of Pennsylvania ruled this week that Dr. Anick Bérard’s testimony would be excluded from trial.

Zoloft is a selective serotonin reuptake inhibitor (SSRI) that is sometimes prescribed to pregnant women. Mothers who took the drug while pregnant and had babies with birth defects filed the suit. Bérard had done studies that would have supported their argument that Zoloft had led to the birth defects.

“Dr. Bérard opines that SSRIs, in general, and Zoloft, in particular, cause a wide range of birth defects when used during pregnancy,” Rufe said in her opinion. “Other researchers in her field have concluded that the epidemiological research on which Dr. Bérard relies provides no conclusive evidence of an association between Zoloft and birth defects.”

Some of those other researchers actually recommend Zoloft as a first-line treatment for depression in pregnant women, the judge said.

“This does not represent a mere professional difference of opinion; Dr. Bérard’s opinions regarding Zoloft are only made possible by her departure from use of well-established epidemiological methods,” Rufe said.

Bérard is a professor at the University of Montreal who researches the effect of medications on pregnancy. The field is teratology and drugs that cause birth defects are called teratogens.

Since traditional epidemiological studies can’t ethically be done on pregnant women, those who study that group calculate risk to fetuses from drugs in other ways, Rufe explained.

The judge found that Bérard’s methods weren’t sturdy enough to pass muster for the court.

“The court is particularly concerned about the risk of reaching an erroneous conclusion using Dr. Bérard’s methodology,” Rufe said. “Dr. Bérard opines that, although one cannot assume teratogenicity from one weak association in one study, one can assume teratogenicity based upon multiple weak associations found across many studies.”

“However, an equally plausible conclusion from multiple studies finding only weak associations, not greater than one would expect by chance, is that the true association is weak; so weak that one cannot conclude that the risk is greater than that seen in the general population. This is, in fact, the conclusion most researchers in Dr. Bérard’s field have reached regarding the association between Zoloft and birth defects, even those cited by Dr. Bérard in support of her contrary opinion,” Rufe said.

The Daubert hearing—named for the 1993 U.S. Supreme Court case Daubert v. Merrell Dow Pharmaceuticals and which allows parties in the case to challenge expert testimony before the start of trial—focused mostly on Bérard, who was an important expert witness for the plaintiffs.

The defense, led by Quinn Emanuel Urquhart & Sullivan’s Mark Cheffo, characterized Bérard’s method for citing to scientific studies as flawed, arguing that she “cherry-picked” studies and disregarded ones that didn’t support her proposition that Zoloft can cause birth defects in babies born to women who took the drug while pregnant.

“The court finds that the expert report prepared by Dr. Bérard does selectively discuss studies most supportive of her conclusions, as Dr. Bérard admitted in her deposition, and fails to account adequately for contrary evidence, and that this methodology is not reliable or scientifically sound,” Rufe said in her opinion.

The judge later explained that “‘cherry-picking’ is always a concern, but is of heightened concern in this case, where many of Dr. Bérard’s conclusions and opinions were formulated by identifying trends in odds ratio estimates selected from the published literature, rather than being based upon replicated, statistically significant odds ratio estimates. The fact that her conclusions are drawn from trends she observed in a self-selected subset of supportive studies, not the totality of the epidemiological evidence, further underscores her problematic methodology.”

Pfizer released a statement following the entry of Rufe’s opinion, saying, “We are pleased the court found that the plaintiffs’ only epidemiology expert does not meet the necessary standards for reliable testimony and ordered her exclusion from the cases consolidated in the MDL. The ruling is significant as plaintiffs put their best science case forward, and after a full evidentiary hearing, the court determined that ‘her methods are not scientifically sound.’”

Joanne Matusko of NastLaw, who is on the legal team for the plaintiffs, couldn’t be reached for comment.

Saranac Hale Spencer can be contacted at 215-557-2449 or sspencer@alm.com. Follow her on Twitter @SSpencerTLI.

(Copies of the 24-page opinion in In re Zoloft, PICS No. 14-1035, are available from The Legal Intelligencer. Please call the Pennsylvania Instant Case Service at 800-276-PICS to order or for information.)