Court weighs expert testimony in GLP-1 stomach injury lawsuits
The Rule 702 hearing will decide which scientific testimony about stomach injuries can reach a jury in a litigation that so far has produced no settlements and no verdicts.
A federal court in Philadelphia is scheduled to hear arguments the week of September 14, 2026, on whether the scientific experts behind thousands of GLP-1 stomach-injury lawsuits will be allowed to testify — a decision that will shape what evidence juries ever see [1].
The hearing concerns the admissibility of the plaintiffs' expert evidence under Federal Rule 702, which governs whether an expert's testimony is considered reliable enough to reach a jury [1]. It is before Judge Karen S. Marston in the U.S. District Court for the Eastern District of Pennsylvania [1]. Litigation trackers give the window as September 14–18 in one listing and September 10–18 in another. The exact start date has not been confirmed against the court docket.
The cases are consolidated in MDL 3094, created on February 2, 2024, which covers allegations that GLP-1 medications caused gastroparesis (often called stomach paralysis), intestinal obstruction or ileus [1]. A Judicial Panel on Multidistrict Litigation report covering August 2026 counted 3,928 stomach-injury lawsuits in the MDL [1]. As of August 31, 2026, 1,031 cases had been filed in the Eastern District of Pennsylvania, 101 of them in the previous 30 days [1].
The central pleading is a 264-page amended master long-form complaint filed on August 29, 2025, built around 16 counts, with failure-to-warn claims described as the litigation's core [1]. The defendants dispute the allegations, and none of them has been proven [1]. No case has settled or gone to trial, and no court or jury has found that these medications caused anyone's injury [1].
That is why the September hearing is described as the biggest test so far. In August 2025, the court excluded two of the plaintiffs' diagnostic experts and imposed a requirement that gastroparesis claims be supported by an objective gastric emptying study, while design-defect theories were narrowed, leaving the litigation primarily a failure-to-warn case [1]. Experts who survive a Rule 702 review can testify; those excluded cannot. The rulings from this hearing could strengthen or seriously weaken the stomach-injury track [1].
A separate track covers eye injuries. MDL 3163, created on December 15, 2025, involves about 200 lawsuits alleging non-arteritic anterior ischemic optic neuropathy (NAION), a sudden and usually permanent vision loss in one eye [1]. It grew from roughly 20 cases in about eight months [1]. The growth followed a 2024 Harvard study reporting elevated NAION risk in semaglutide patients and a June 2025 decision by European regulators to add NAION to the label as a "very rare" side effect [1]. Ozempic, Wegovy and Rybelsus (semaglutide) appear in both tracks; Mounjaro and Zepbound (tirzepatide) and Trulicity are currently part of the vision-loss track under the criteria the firm maintaining the tracker uses [1].
Why it matters for patients
The hearing does not change any medication's approval status, and no effect on supply or insurance coverage has been reported. What it can change is whether stomach-injury claims can be proven at trial at all. If the plaintiffs' experts are excluded, those cases become substantially harder to bring; if the experts are allowed, cases can move toward trial dates. Either way, no patient's claim has been decided, and no compensation has been paid, because there have been no settlements and no verdicts [1].
For anyone who has been diagnosed with a stomach injury, the August 2025 ruling matters directly: gastroparesis claims in the MDL now require objective confirmation through a gastric emptying study, and obstruction claims require objective testing [1]. A diagnosis recorded in medical records without that testing may not fit the current criteria [1]. The NAION track uses different criteria, including brand-name use of one of six medications and an actual NAION diagnosis with some permanent vision impairment [1].
What happens next
The expert-evidence hearing is scheduled for September 14–18, 2026, with some trackers listing a window that begins September 10 [1]. A date for the court's rulings has not been reported. No trial date has been set in either MDL, and no settlement has been announced [1]. The NAION track, which the tracker says has seen no dismissals so far, has not been tested by a comparable expert-admissibility hearing [1].
Sources
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