An exenatide lawsuit in Michigan is now legally possible for the first time in nearly three decades, but only for injuries occurring on or after February 13, 2024, when Michigan repealed the drug-manufacturer immunity statute that had blocked almost all such claims since 1995. Even with that door open, the federal litigation over Byetta and Bydureon ended in a defense victory in 2022 after the court found no reliable proof that the drugs cause cancer, and Michigan law still layers several protections around pharmaceutical defendants.
Why Michigan Claims Were Blocked Until 2024
From 1995 until early 2024, Michigan was the only state in the country that gave drug manufacturers what functioned as an absolute defense against product liability claims, provided the drug was FDA-approved and carried FDA-compliant labeling. The statute, MCL 600.2946(5), was enacted as part of the Michigan Product Liability Act (Public Act 249 of 1995) and dismissed high-profile cases outright, including the state attorney general’s $20 million Vioxx suit against Merck.1Michigan Legislature. Senate Fiscal Agency Analysis of Senate Bill 410
Because Byetta and Bydureon were FDA-approved and labeled in compliance with FDA requirements, any Michigan resident trying to sue over an exenatide injury during those years would have run directly into that immunity. It explains why no Michigan-specific exenatide lawsuit has been publicly documented.
The February 2024 Repeal
Michigan’s governor signed Senate Bill 410, sponsored by Senator Jeff Irwin, on December 7, 2023. The repeal took effect February 13, 2024.2Michigan Attorney General. AG Nessel Celebrates Bill Signing for Drug Immunity Repeal
The repeal is not retroactive. Michigan courts apply the law in effect on the date of the injury, not the date the lawsuit is filed. Injuries that occurred while the immunity was in force cannot support a new claim, and Senator Irwin acknowledged there is no mechanism for retroactive recovery on claims previously barred.3Tucker Ellis LLP. But Is It Retroactive? Michigan Repeal of Drugmaker Immunity Statute
What the Federal MDL Decided
Anyone considering an exenatide claim in Michigan has to reckon with what happened in federal court. More than 7,000 plaintiffs alleged that exenatide-based drugs caused pancreatic cancer, thyroid cancer, and pancreatitis. Their cases were consolidated in August 2013 into In re: Incretin-Based Therapies Products Liability Litigation, MDL No. 2452, in the U.S. District Court for the Southern District of California before Judge Anthony J. Battaglia.4Judicial Panel on Multidistrict Litigation. MDL-2452 Initial Transfer Order The MDL also covered claims against related incretin drugs Januvia and Victoza, with AstraZeneca, Amylin, Eli Lilly, Merck, and Novo Nordisk among the defendants.
The plaintiffs’ theory was failure to warn: they said manufacturers knew about cancer and pancreatitis risks but did not adequately disclose them. The manufacturers argued no concrete evidence established causation and that the FDA would not have approved the warnings plaintiffs said were missing.5FindLaw. Byetta Lawsuit Information
Judge Battaglia first dismissed the cases on preemption grounds in November 2015. The Ninth Circuit reversed unanimously in December 2017, finding the district court had misapplied preemption doctrine and improperly excluded evidence from Canadian regulators and animal studies.6U.S. Court of Appeals for the Ninth Circuit. In re Incretin-Based Therapies Products Liability Litigation, No. 15-56997
On remand, the court granted summary judgment for the defendants a second time on March 9, 2021, on two independent grounds. The court found “clear evidence” that the FDA would have rejected a pancreatic cancer warning because the agency had consistently called the causal link “indeterminate,” and it found no genuine dispute of material fact on general causation.7U.S. District Court, Southern District of California. Omnibus Order, Case No. 13-md-2452-AJB-MDD
Central to the causation ruling was the exclusion of every plaintiffs’ expert. Biostatisticians were excluded for relying on data the court called “dated,” “selective,” or “cherry-picked”; an oncology expert was excluded for lacking foundation on latency; a gastroenterologist was excluded after admitting counsel had taught him the alleged drug-cancer relationship; and a pathologist was excluded for applying human classification systems to non-human primates using methodology the court found unreliable.8Expert Institute. Judge Grants Defendants Motion for Summary Judgment in Diabetes Drug MDL, Excludes Plaintiffs Experts
The Ninth Circuit affirmed against Novo Nordisk in March 2022. The plaintiffs’ steering committee decided not to seek further review, and the MDL formally closed on November 9, 2022.9U.S. District Court, Southern District of California. MDL 2452 Closure Order
The Scientific Record a Michigan Plaintiff Would Face
The causation problem is not unique to the MDL plaintiffs; it reflects the state of the science. A 2012 retrospective cohort study of over 268,000 privately insured diabetes patients found no statistically significant association between exenatide and either hospitalization for acute pancreatitis or a pancreatic cancer diagnosis.10National Library of Medicine. Exenatide Therapy and the Risk of Pancreatitis and Pancreatic Cancer in a Privately Insured Population A 2019 meta-analysis of 12 randomized trials covering more than 36,000 patients likewise found no increased pancreatic cancer risk from GLP-1 receptor agonists as a class, though the authors noted mean follow-up was only about 1.7 years and longer studies would be needed to rule out very small risks.11Nature. GLP-1 Receptor Agonists and Pancreatic Cancer Risk Meta-Analysis
The Bydureon label carries a boxed warning that exenatide caused thyroid C-cell tumors in rats at clinically relevant doses, though whether the same risk applies to humans remains unknown.12U.S. Food and Drug Administration. BYDUREON Prescribing Information Pancreatitis is warned about on the label, following FDA action in 2007 and label strengthening over the next two years after postmarketing reports of severe hemorrhagic and necrotizing cases, some fatal.10National Library of Medicine. Exenatide Therapy and the Risk of Pancreatitis and Pancreatic Cancer in a Privately Insured Population
Michigan Rules That Still Apply After the Repeal
Even without the immunity statute, Michigan law gives pharmaceutical defendants several tools.
A rebuttable presumption of non-liability applies when the aspect of the product that caused the injury complied with federal or state safety standards at the time of sale.13Michigan Legislature. MCL 600.2946 For an FDA-approved, FDA-labeled drug, that presumption is a real hurdle, though unlike the old absolute immunity it can be overcome with evidence.
Michigan does not recognize strict liability in product defect cases. Claims must proceed under negligence, breach of warranty, or misrepresentation. Courts applying Michigan law also follow the learned intermediary doctrine, so a manufacturer’s duty to warn runs to the prescribing physician rather than to the patient.14Drug and Device Law Blog. Possible Learned Intermediary Showdown in Michigan
The statute of limitations for product liability is three years from the date of injury, and Michigan does not apply a discovery rule. The clock runs from when the injury occurs, not when the patient learns of it or connects it to a drug.15Drug and Device Law Blog. Michigan Product Liability Law: Retroactivity of New Law and Primer
Noneconomic damages are capped, with annually adjusted limits that stood at $569,000 or $1,016,000 depending on severity as of 2024.
How Narrow the Current Window Really Is
Two dates define the practical opening. The immunity repeal took effect February 13, 2024, so only injuries on or after that date can support a new claim. AstraZeneca discontinued both Byetta and Bydureon BCise in October 2024, citing business reasons.16UnitedHealthcare. Discontinuation of Bydureon BCise and Byetta That leaves a narrow band of new use during which an injury could have occurred, plus any lingering exposure from prescriptions filled before discontinuation.
A Michigan plaintiff whose injury falls inside that band still has to clear each of the remaining barriers: rebutting the presumption of non-liability for an FDA-compliant product, proving negligence or warranty rather than strict liability, establishing that the prescribing physician was inadequately warned, filing within three years of the injury itself, and — the issue that ended the federal MDL — producing expert testimony that survives scrutiny on general causation. Michigan’s damages cap would apply to any recovery.
The 2015 California state-court settlement of 84 Byetta and Bydureon cancer cases against AstraZeneca and Amylin was reached on undisclosed terms and did not repeat itself as the MDL moved toward its second dismissal.17Top Class Actions. Byetta Cancer Lawsuit Settlements No mass settlement followed the closure of the federal litigation, and no consolidated Michigan proceeding exists. Anyone weighing a claim should consult a Michigan product liability attorney about their specific injury date, prescription history, and medical record before the three-year clock runs.