A three-panel judge has upheld a motion for summary judgment in favor of GlaxoSmithKline (GSK), dismissing hundreds of lawsuits alleging that the manufacturer’s anti-nausea drug Zofran caused a number of adverse health effects for pregnant women including birth defects. In a 35-page opinion, U.S. Circuit Judge William J. Kayatta Jr. explains the panel’s rationale for dismissing the hundreds of cases making up the multi-district litigation (MDL). 

The crux of the MDL plaintiffs’ arguments was that Zofran should have been labeled with a warning that taking the drug while pregnant could increase the risk of pregnancy. They based these claims on studies that the plaintiffs believe would have forced the FDA to label the drug as a risk to pregnant people. GSK argued that these claims were preempted by the FDA’s labeling and motioned for summary judgment. In 2019, the judge in charge of the MDL, U.S. District Judge F. Dennis Saylor IV, dismissed the motion for summary judgment but following the 2019 Supreme Court decision, Merck v. Albrecht, reversed his decision, according to Law360.

Officially, Zofran (ondansetron hydrochloride) is not approved for use in pregnancy. Instead, the medication is prescribed as an anti-nausea drug for patients going through chemotherapy, radiation, or post-operation nausea. However, the order notes that Zofran is used to treat pregnancy-related nausea as an “off-label” usage. GSK was the manufacturer of Zofran from 1991 until it sold the manufacturing rights to Novartis in 2015.

In the panel’s opinion, the court reviewed the history of Zofran’s approval beginning in 1990 with the drug’s New Drug Application approval process. The court record shows that GSK conducted and submitted four animal reproductive studies to the FDA as proof of Zofran’s safety and efficacy. The four that were chosen were all performed in the United Kingdom on rabbits and rats. In these studies, researchers found no causal link between Zofran and birth defects and stated that the rates of birth defects that were detected were within the normal range in both the test and control groups. After the FDA did an internal review of the studies, the agency found that the drug was not teratogenic (causing birth defects), and Zofran was approved.

There were some studies that were conducted by GSK in the late 1980s in Japan that were not submitted to the FDA. These studies, which were three rabbit and rat studies conducted “parallel” to the United Kingdom studies, were performed to meet Japanese regulatory requirements. According to the panel, these Japanese studies were the focus of the plaintiffs’ appeal, arguing that the Japanese studies did show that Zofran caused birth defects, and therefore would have resulted in the FDA reclassifying Zofran. However, the panel notes that while there were instances of birth defects in the Japanese studies, the defects were not causally linked to Zofran. 

With no compelling evidence that these studies would have swayed the FDA, Judge Kayatta Jr. writes, “The district court granted summary judgment in favor of GSK, finding that federal law preempted plaintiffs' state law claims because there was clear evidence that the Food and Drug Administration (FDA) would have rejected the warning that plaintiffs allege is required under state law. We affirm the district court's grant of summary judgment.” 

With this rejection, the last opportunity for the MDL to proceed is to appeal to the Supreme Court.