Tylenol Autism Lawsuit Rehearing: PhRMA, Chamber and Manufacturers Urge Full Second Circuit to Step In

The amicus push behind the Tylenol autism lawsuit rehearing

The Tylenol autism lawsuit rehearing fight has drawn heavy reinforcements: five amicus filings, led by PhRMA, the U.S. Chamber of Commerce, and the National Association of Manufacturers, now urge the full U.S. Court of Appeals for the Second Circuit to revisit the July 13, 2026 panel decision that revived more than 500 federal cases claiming prenatal acetaminophen use causes autism and ADHD. The petition, filed September 10 by Kenvue and three retail co-defendants, is still pending, and until the court acts the cases cannot go back to U.S. District Judge Denise Cote in Manhattan for the next phase of the Multidistrict Litigation (MDL).

PhRMA's brief, described by Legal Newsline on October 14, puts the defense position in a single sentence: "The courtroom is not a laboratory, and Rule 702 exists to ensure that a jury is not asked to speculate about scientific questions." The brief is one of several filed under a Second Circuit order dated September 29 that expressly allowed friend-of-the-court submissions in support of rehearing. That order is itself a modest signal. Courts of appeals do not always invite amicus participation at the rehearing stage, and an order permitting it at least tells the bar that the petition is being read with some care.

The stakes run well beyond Tylenol. The July 13 opinion, written by Judge Guido Calabresi, is the most prominent appellate reading so far of the December 2023 amendments to Federal Rule of Evidence 702, and it went against the defense. Every MDL where General Causation turns on contested epidemiology, from GLP-1 drugs to hair relaxers, now has a Second Circuit precedent that plaintiffs can cite for the proposition that a judge may not exclude an expert simply because the judge reads the science differently. The defense bar and its trade-group allies want that precedent narrowed or erased before it spreads.

What follows sets out where the Tylenol autism lawsuit rehearing petition stands, who is backing it and why, what the panel actually held, how the Second Circuit has historically handled en banc requests, and what the next few months mean for claimants' counsel, defendants, and retailers.

Is the Tylenol autism lawsuit being reheard?

Not yet. Kenvue's petition asks for rehearing by the original three-judge panel or by the full court sitting en banc, and as of October 15, 2026 the Second Circuit has neither granted nor denied it; no public report shows the court has ordered the plaintiffs to file a response.

The petition was filed on Thursday, September 10, 2026, in the consolidated appeals docketed as Nos. 24-916, 24-1121, 24-2360, and 24-2594. According to Mealey's, the filers are Kenvue Brands LLC, formerly Johnson & Johnson Consumer Inc., along with Walgreen Co., Costco Wholesale Corp., and CVS Health Corp. Other retailers that sold store-brand acetaminophen are also defendants in the underlying cases; press coverage of the appeal has named Walmart and Target among them.

The petition's core claim, as Mealey's summarized it, is that the panel "effectively nullified the 2023 amendments" to Rule 702 by substituting its own reading of the science for Judge Cote's. The petitioners also make a fallback request. If the court will not reverse outright, they ask it at least to clarify that the July 13 decision does not automatically render the three reinstated experts admissible, and that Judge Cote retains authority on remand to test their opinions under the correct standard. That alternative ask matters more than it might seem: a clarification on that point would let the defense relitigate admissibility in the district court without the burden of overturning a precedential opinion.

The petition was not filed on the ordinary schedule. Federal Rule of Appellate Procedure 40, which since December 2024 governs both panel and en banc rehearing, sets a short default window after judgment. Kenvue and the retail defendants instead sought additional time over the summer; The Center Square reported that the company's appellate counsel in the case had retired and that new lawyers needed time to come up to speed. The September 10 filing followed that extension.

Who filed amicus briefs supporting rehearing in the Tylenol autism case?

Five amicus filings are reported in support of rehearing: one from the Atlantic Legal Foundation, a joint brief from the U.S. Chamber of Commerce and the American Tort Reform Association, one from the Pharmaceutical Research and Manufacturers of America (PhRMA), one from the National Association of Manufacturers, and one from Lawyers for Civil Justice. No amicus brief opposing rehearing has been reported.

The roster reads like a map of the institutional defense bar's interest in Rule 702. Each group is pressing a slightly different version of the same argument.

Amicus	Who it represents	Likely emphasis
PhRMA	Brand-name drug manufacturers	Scientific reliability; regulatory consensus that prenatal acetaminophen has not been shown to cause autism or ADHD
U.S. Chamber of Commerce and American Tort Reform Association	Business community and tort reform coalition	Systemic cost of weak gatekeeping in mass torts; uniformity with other circuits
National Association of Manufacturers	Industrial and consumer product manufacturers	Rule 702's reach beyond pharmaceuticals, into chemical and product cases
Lawyers for Civil Justice	Corporate defense lawyers and in-house counsel; long-time advocate of the 2023 amendment	Rulemaking history and the intent behind the 2023 text
Atlantic Legal Foundation	Public interest law firm focused on science in the courtroom	Methodology and the distinction between scientific dispute and unreliable inference

The "likely emphasis" column reflects each organization's stated mission and published advocacy on Rule 702; only PhRMA's brief has been quoted in public reporting so far.

According to Legal Newsline, PhRMA argues that allowing experts to tell a jury that acetaminophen use in pregnancy can lead to autism conflicts with Rule 702's reliability requirements, and that no major regulatory body or medical organization has concluded that such a causal link exists. Lawyers for Civil Justice's participation is especially pointed. The organization was among the most active proponents of the 2023 amendment during the federal rulemaking process, so its brief effectively asks the Second Circuit to honor a rule change that the group helped draft.

The absence of opposing amici is not surprising at this stage. Plaintiffs' organizations typically weigh in after the court requests a response or grants rehearing, and the plaintiffs' leadership in the MDL, which has included Ashley Keller of Keller Postman, Mikal Watts of Watts Guerra, and Mark Lanier of The Lanier Law Firm, has not been reported to have filed anything on the petition.

What did the Second Circuit decide in the Tylenol autism appeal?

On July 13, 2026, a unanimous Second Circuit panel held that Judge Cote exceeded her discretion when she excluded three of the plaintiffs' five general causation experts, vacated the summary judgment that had ended the litigation, and sent the cases back for further proceedings; it affirmed the exclusion of the other two experts and rejected the defendants' argument that federal drug law preempts the claims.

Judge Calabresi wrote for the panel, which also included Judges Gerard Lynch and Eunice Lee. The opinion's central line, widely quoted in coverage, is that the excluded analyses "constitute acceptable interpretations of scientific evidence where scientists may, and in fact do, disagree." In the panel's view, Judge Cote had resolved a genuine scientific dispute that belonged to the jury, rather than asking only whether each expert used a reliable method and applied it reliably.

The panel was careful to say what it was not deciding. It did not hold that acetaminophen causes autism or ADHD, and it did not hold that any plaintiff will win. Kenvue seized on that point the same day, calling the decision a "procedural ruling" that "does not change the fact that credible, independent science shows no proven link between acetaminophen and autism or ADHD," and saying it was "exploring all options." Kenvue shares fell about 2% that morning, to $19.28, according to CNBC.

The expert scorecard

The panel did not treat the experts as a bloc. It went expert by expert, and the split is the most useful way to understand both the ruling and the rehearing petition.

Expert	Institution (as reported)	Discipline in the MDL	District court (Dec. 2023)	Second Circuit (July 2026)
Dr. Andrea Baccarelli	Harvard T.H. Chan School of Public Health	Epidemiology	Excluded	Exclusion reversed
Dr. Eric Hollander	Albert Einstein College of Medicine	Psychiatry	Excluded	Exclusion reversed
Dr. Brandon Pearson	Columbia University	Toxicology / environmental health	Excluded	Exclusion reversed
Dr. Robert Cabrera	Not reported	Teratology and genetics	Excluded	Exclusion affirmed
Dr. Stan Louie	Not reported	Pharmacology	Excluded	Exclusion affirmed

Coverage of the two affirmed exclusions indicates the panel found that Dr. Cabrera had not adequately weighed and synthesized the Bradford Hill factors, and that Dr. Louie had not reliably explained his proposed dose and duration thresholds. Those affirmances matter for the petition. They show the panel did apply Rule 702 as a real screen, which cuts against the claim that it "nullified" the 2023 amendments, and they give the plaintiffs a ready answer to the argument that the panel simply deferred to any credentialed witness.

How many Tylenol autism lawsuits did the Second Circuit revive?

The July 13 decision revived more than 500 federal cases that Judge Cote had dismissed after excluding the plaintiffs' experts; some case trackers put the figure near 550. Reuters, which covered both the November 17, 2025 oral argument and the decision, used the "more than 500" formulation.

Did the panel address preemption?

Yes. The defendants argued that federal over-the-counter drug labeling rules made it impossible for them to add the warning the plaintiffs say was required, so the state-law Failure to Warn claims were preempted. The panel agreed with Judge Cote that they were not. As commentators have summarized it, the governing federal framework requires a general pregnancy warning but does not forbid a manufacturer from adding a stronger supplemental one. That holding, which the rehearing petition does not appear to be the main target of, means that Preemption (Products) will not end the litigation unless the full court or the Supreme Court revisits it.

The Rule 702 fight underneath the Tylenol autism lawsuit rehearing

To see why the defense bar has mobilized, start with the timing of Judge Cote's original ruling. Amended Rule 702 took effect on December 1, 2023. Judge Cote issued her exclusion opinion on December 18, 2023, about two and a half weeks later, making the acetaminophen MDL one of the first large mass torts decided under the new text. Defense commentators immediately held it up as a model of what the amendment was meant to accomplish. Judge Cote followed it in July 2024 by excluding a new causation expert offered by plaintiffs in later-filed cases.

The amended rule now reads, in relevant part, that an expert may testify "if the proponent demonstrates to the court that it is more likely than not that" the testimony rests on sufficient facts or data, is the product of reliable principles and methods, and "reflects a reliable application of the principles and methods to the facts of the case." The amendment made two changes. It wrote the preponderance standard into the text, and it tightened the last element so that the court, not the jury, must decide whether the expert's conclusion actually follows from the method. The Advisory Committee's stated concern was that many courts had been treating questions about the sufficiency of an expert's basis and the application of a method as matters of weight for the jury rather than admissibility for the judge.

Judge Cote's December 2023 opinion found that there was no generally accepted scientific conclusion that in utero acetaminophen exposure causes ASD or ADHD, and that the plaintiffs' experts had not reliably reached that conclusion either. Among other problems, she faulted the experts for how they handled confounding, including genetic and familial factors that sibling-controlled studies attempt to account for, and for a "transdiagnostic" approach that folded autism and ADHD findings together rather than analyzing each condition on its own evidence.

The Second Circuit panel did not reject the 2023 amendment. Its disagreement was about where the line falls between a judge testing an expert's method and a judge choosing between competing scientific interpretations. Where respected researchers have looked at the same body of studies and reached different conclusions, the panel reasoned, the gatekeeper's task is to keep out testimony that falls outside legitimate scientific discourse, not to pick the winning side of a live debate. Critics, including a widely circulated Volokh Conspiracy post on July 20 and the American Tort Reform Association's Judicial Hellholes blog, responded that this framing restores the "goes to weight, not admissibility" approach the amendment was written to end.

That is the question the petition puts to the full court, and it is why the amicus briefs speak in terms of uniformity. Several circuits have issued opinions since 2023 emphasizing the amended rule's demand for judicial scrutiny of application. If the Second Circuit's Tylenol opinion stands, plaintiffs in MDLs across the country will cite it as the leading appellate statement that the amendment did not authorize judges to resolve scientific disagreement, and defendants will argue it is an outlier. A circuit conflict on that framing is the kind of issue that can eventually interest the Supreme Court.

How often does the Second Circuit grant rehearing en banc?

Rarely. A Perkins Coie analysis counted only two appeals reheard en banc by the Second Circuit from the beginning of 2011 onward, against an average of about 12 per circuit across all federal courts of appeals in the same period, and a Paul Weiss study found the Second Circuit has granted fewer en banc petitions than any other circuit since 1979.

That history is the single most important fact for anyone forecasting the Tylenol autism lawsuit rehearing. The Second Circuit has a long institutional preference for resolving disagreements through statements accompanying a denial of rehearing, rather than through full-court rehearing. Judges who disagree with a panel often write separately to explain why, without converting the case into an en banc proceeding. A 2026 Morrison Foerster analysis, reprinted from the New York Law Journal, describes a modest uptick in en banc activity over the past five years, but the court still lags every other circuit.

Under the appellate rules, en banc rehearing is disfavored and is ordinarily reserved for two situations: when full-court consideration is needed to secure or maintain uniformity of the court's decisions, or when the case involves a question of exceptional importance. Kenvue's petition and its amici are framing the case as both. They argue that the panel's approach conflicts with how other circuits read amended Rule 702, and that the question of how much deference trial judges receive on expert reliability affects every complex case in the circuit.

Three realistic outcomes follow from that:

• Outright denial. The most likely result based on history. The mandate would then issue, and the cases would return to Judge Cote. Kenvue could then seek review in the Supreme Court.
• Denial with separate statements. Common in the Second Circuit for contested panel opinions. One or more judges might concur in or dissent from the denial, which would give a future certiorari petition useful material.
• Panel-level clarification. The original panel could amend its opinion, for example to address the petition's fallback request about whether Judge Cote may reexamine the reinstated experts on remand. This would not require full-court action and is the outcome the petition's alternative request is designed to make easy.

En banc rehearing itself, the outcome the amici are pressing for, would be a significant departure from the court's practice.

What happens to the Tylenol lawsuits while the rehearing petition is pending?

Everything is effectively paused at the appellate stage. A timely petition for rehearing stays the issuance of the Second Circuit's mandate, so the July 13 decision has not yet been formally sent back to the Southern District of New York, and Judge Cote cannot resume proceedings on the revived cases until the court rules on the petition and the mandate issues.

Under Federal Rule of Appellate Procedure 41, the mandate ordinarily issues seven days after the time to file a rehearing petition expires, or seven days after the court denies a timely petition. That means a denial in, say, November would put the cases back on Judge Cote's docket within about a week. A party planning to seek Supreme Court review can also ask the court of appeals to stay the mandate while a certiorari petition is prepared, which would extend the pause.

What happens once the cases do return is genuinely open. The panel reinstated three experts, but the remand still leaves Judge Cote to manage the next phase, which could include renewed or narrowed Daubert Challenge motions aimed at the reinstated experts' specific opinions, Specific Causation expert work for individual plaintiffs, and eventually case selection for any Bellwether Trial. The defense's fallback request in its petition is aimed squarely at this stage: if the panel confirms that Judge Cote may reexamine the reinstated experts, the defense keeps a path to a second exclusion ruling.

For individual claimants, the practical consequences are slower but real. The revived cases have been in limbo since the December 2023 exclusion ruling and the summary judgment that followed. Every additional month at the appellate stage pushes discovery, Plaintiff Fact Sheet (PFS) work, and any settlement discussion further out.

Timeline: the acetaminophen MDL from centralization to the amicus order

Date	Event
October 2022	Judicial Panel on Multidistrict Litigation (JPML) centralizes federal acetaminophen ASD-ADHD cases as MDL No. 3043 before Judge Denise Cote, S.D.N.Y.
December 1, 2023	Amended Federal Rule of Evidence 702 takes effect
December 18, 2023	Judge Cote excludes all five of plaintiffs' general causation experts; summary judgment for defendants follows
July 2024	Judge Cote excludes a new causation expert offered in later-filed cases
September 2025	Federal health officials announce steps toward a pregnancy label change for acetaminophen
October 2025	Kenvue asks the FDA to deny a citizen petition seeking a neurodevelopmental warning
November 3, 2025	Kimberly-Clark agrees to acquire Kenvue in a deal valued at about $48.7 billion
November 17, 2025	Second Circuit hears oral argument; panel questions whether the exclusions were proper
July 13, 2026	Second Circuit (Calabresi, Lynch, Lee) reinstates three experts, affirms two exclusions, rejects preemption, and revives more than 500 cases
Summer 2026	Defendants seek additional time to file a rehearing petition
September 10, 2026	Kenvue, Walgreen, Costco, and CVS petition for panel or en banc rehearing
September 29, 2026	Second Circuit order allows amicus briefs supporting rehearing
Mid-October 2026	PhRMA brief reported; five amicus filings in support of rehearing on file

The regulatory backdrop: FDA, Texas, and the Kimberly-Clark deal

The appellate fight is unfolding against an unusual regulatory and political backdrop that neither side can ignore.

In September 2025, federal health officials publicly linked prenatal acetaminophen use to autism and announced that the FDA would begin the process of changing the drug's labeling. Kenvue responded in October 2025 by asking the FDA to deny a citizen petition that sought a neurodevelopmental warning, and a second citizen petition followed in November 2025. More than a year later, the label has not changed. A Medical Daily review found that the current federal label record, last revised on May 27, 2026, still carries no neurodevelopmental warning, and the FDA has not published a timeline.

That gap cuts both ways in court. Plaintiffs point to the government's public statements as evidence that the association is taken seriously at the highest level. Defendants and their amici point to the absence of any completed label change, and to large studies such as an April 2026 Danish analysis reported by CNN that found no association, as evidence that regulators have not actually concluded that acetaminophen causes autism. PhRMA's brief leans on exactly that point.

Separately, Texas Attorney General Ken Paxton sued Johnson & Johnson and Kenvue in state court, alleging deceptive marketing of acetaminophen to pregnant women. That case proceeds under Texas consumer protection law and does not depend on the federal Rule 702 ruling, though any federal finding on scientific reliability is likely to be cited there.

The corporate overlay adds another variable. Kimberly-Clark agreed in November 2025 to acquire Kenvue in a cash-and-stock deal valued at about $48.7 billion, and Kimberly-Clark's 2026 securities filings describe the Second Circuit's July decision. Acetaminophen exposure is now a disclosed contingency for a larger combined company, which raises the stakes of how quickly and on what terms the federal cases are resolved.

What it means for practitioners

For MDL defense counsel

The petition and its amici are the defense bar's first coordinated effort to stop an appellate reading of amended Rule 702 that treats scientific disagreement as a jury question. Whatever the Second Circuit does, defense counsel in other MDLs should expect plaintiffs to cite the July 13 opinion in pending general causation briefing. The GLP-1 gastrointestinal-injury litigation, MDL No. 3094 before Judge Karen Spencer Marston in the Eastern District of Pennsylvania, heard closing arguments on its Rule 702 motions on October 13 and is in the Third Circuit, but out-of-circuit persuasive authority is still authority. Expert disclosures that distinguish the Tylenol experts on methodology, rather than on outcome, are the obvious response.

For plaintiffs' firms

The revived cases are not yet back in the district court, and the remand may come with a clarification that keeps Judge Cote's gatekeeping authority intact. Firms with Tylenol inventory should plan for a second round of Rule 702 litigation rather than a direct path to trial. The two affirmed exclusions also show where the panel drew lines: opinions that do not engage carefully with the Bradford Hill factors, or that propose dose and duration thresholds without a reliable basis, remain vulnerable. Intake decisions should account for the Statute of Limitations in each claimant's state, which the appellate pause does not toll.

For retailers and store-brand sellers

Walgreen, Costco, and CVS joined the petition because the revived claims run against sellers of store-brand acetaminophen as well as against Kenvue. Retail defendants have indemnity and supply-agreement questions that turn on the eventual allocation of any liability, and the timing of the mandate affects when those questions become live.

For transferee judges in other MDLs

District judges managing causation-heavy dockets now face competing signals. The 2023 amendment and its committee note tell them to scrutinize whether an expert's conclusion actually follows from the method. The July 13 opinion tells them, at least within the Second Circuit, that choosing between two scientifically respectable readings of the same studies is the jury's job. A careful opinion after this decision will likely do both explicitly: identify the methodological step being tested, explain why it is or is not reliably applied, and say in terms that the court is not resolving which side of a live scientific debate is correct. Opinions written that way are harder to attack on appeal under either framing, and the two affirmed exclusions in the Tylenol case show that the Second Circuit will still uphold exclusions grounded in specific methodological gaps, such as an unsupported dose threshold.

For litigation funders and the broader plaintiffs' bar

The Tylenol MDL has long been viewed as a test of whether amended Rule 702 would shut down mass torts built on observational epidemiology. The July 13 decision reopened that bet. Third-Party Litigation Funding decisions on GLP-1, hair relaxer, and other causation-heavy dockets will price in the probability that the Second Circuit's reading survives, which is why the en banc outcome matters well beyond the 500-plus revived cases.

Frequently asked questions

Is the Tylenol autism lawsuit being reheard?

Not yet. Kenvue and three retail defendants asked the Second Circuit on September 10, 2026 to rehear its July 13 ruling, five amicus filings support the request, and as of October 15, 2026 the court has not ruled.

How many Tylenol autism lawsuits are affected?

More than 500 federal cases in MDL No. 3043, which some trackers put near 550. Those cases were dismissed after Judge Cote excluded the plaintiffs' experts in December 2023 and were revived by the July 13, 2026 decision.

Did the court rule that Tylenol causes autism?

No. The Second Circuit decided only that three of the plaintiffs' experts used methods reliable enough to be heard by a jury. It expressly did not decide whether acetaminophen causes autism or ADHD, and no court has made that finding.

What happens if the Second Circuit denies rehearing?

The mandate would issue about seven days after the denial, unless stayed, and the cases would return to Judge Cote in the Southern District of New York for further proceedings. Kenvue could also petition the U.S. Supreme Court for certiorari.

Can I still file a Tylenol autism lawsuit?

New federal filings remain possible, but each claim is subject to the Statute of Limitations in the claimant's state, and the appellate pause does not stop that clock. Whether a particular claim is timely depends on state law and on when the claimant knew or should have known of the potential claim; that is a question for a licensed attorney in the relevant state.

Who is backing Kenvue's rehearing petition?

The Atlantic Legal Foundation, the U.S. Chamber of Commerce with the American Tort Reform Association, PhRMA, the National Association of Manufacturers, and Lawyers for Civil Justice have all filed amicus briefs supporting rehearing.