MDL 3163 authorizes early motion practice on causation and preemption
A federal court overseeing eye-injury lawsuits tied to GLP-1 drugs ordered early rulings on whether the drugs cause NAION vision loss and whether FDA approval blocks such claims, mirroring a fight already underway in the stomach-injury litigation.
On July 2, 2026, the judge overseeing the multidistrict litigation for NAION vision-loss claims issued Case Management Order 12, opening the first round of substantive motions on two questions: whether GLP-1 medications can generally cause NAION, a rare form of sudden vision loss, and whether federal drug approval preempts state-law injury claims [1]. The order applies to MDL 3163, a consolidated set of federal lawsuits alleging that semaglutide or tirzepatide products caused NAION [1].
MDL 3163 was created on December 15, 2025, after Eli Lilly asked to consolidate the eye-injury cases, over plaintiffs' objection [1]. It started with roughly 20 cases and had grown to 200 by August 2026 [1]. The same federal judge, Karen S. Marston of the Eastern District of Pennsylvania, also oversees the much larger MDL 3094, which consolidates gastroparesis and stomach-injury lawsuits against the same drugmakers and has 3,928 pending cases as of August 2026 [1]. That older docket has already been litigating causation and preemption for months, with expert-evidence hearings on general causation scheduled for September 14 through 18, 2026 [1]. CMO 12 puts the NAION docket on a similar track, but on its own separate timeline [1].
As of the source's reporting date, no court has ruled on either issue in MDL 3163 — there have been no dismissals, no rulings on expert testimony, no bellwether trial schedule, and no settlements in that docket [1]. The regulatory record differs by country: the European Union added NAION as a "very rare" side effect to its drug label in June 2025, and Australia made a similar change in July 2026, but the U.S. label had not changed as of August 7, 2026 [1].
Why it matters for patients
General causation and preemption are foundational legal questions. General causation asks whether the science supports the idea that a drug class can cause a specific injury at all, before any single patient's case is even considered. Preemption asks whether FDA's approval and labeling decisions shield the manufacturer from state lawsuits. If judges rule against plaintiffs on either question, many individual NAION claims could be narrowed or dismissed before ever reaching a jury [1].
For patients who have taken these drugs and experienced sudden vision loss in one eye, or who are considering starting a GLP-1 medication, this order does not change anything about safety or approval status today. No court has found that any GLP-1 drug causes NAION, and no settlements exist in this litigation [1]. The gap between the EU and Australian labels, which now list NAION as a very rare risk, and the unchanged U.S. label is also worth understanding for anyone weighing information about these drugs, since it shows regulators in different countries have reached different conclusions so far based on the same body of evidence [1].
What happens next
MDL 3094's Rule 702 hearing on general causation for stomach injuries runs September 14 through 18, 2026, and its outcome may offer an early signal of how the same judge could approach similar causation arguments in the NAION docket [1]. No hearing date for the CMO 12 motions in MDL 3163 has been reported yet, and there is no bellwether trial schedule in either MDL [1].
Sources
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