FDA Again Says Retatrutide Is a Drug; the Seventh Circuit Asks Whether Lilly Can Appeal at All

What is decided and what is not. The FDA’s October 2 decision is the agency’s own decision, reported below as the agency’s reasoning. Everything attributed to Lilly or to the government is a party’s argument in a supplemental brief. As of the date above, the Seventh Circuit had issued no ruling on jurisdiction or on the merits, and no outcome is predicted here.

What the FDA decided on October 2

The decision is a letter from the FDA to Lilly’s regulatory affairs office, titled “Issues Remanded to FDA.” It was not posted on an FDA page; the government attached a redacted copy to its October 8 filing in the Seventh Circuit, which is the copy read for this article. By its own account, it responds to the district court’s October 2025 order, which had told the agency to “identify, in a uniform fashion, the fundamental defining feature of ‘analogous’ proteins” and then revisit whether retatrutide is analogous to a protein.

The FDA’s answer is that two characteristics are critical. A product must contain one or more chains of alpha amino acids that together total more than 40 alpha amino acids, and the chain must have a specific, defined sequence. A product lacking them is not a protein, the agency says, and also is not “analogous” to one. Applying that test, the letter states that retatrutide is built on a chain of 39 alpha amino acids that does have a specific, defined sequence, plus a “side chain” of 8-amino-3,6-dioxaoctanoic acid (ADO), gamma-glutamate and a C20 fatty diacid moiety. The agency says that side chain is not a chain of alpha amino acids and so does not count toward the threshold. It concludes retatrutide is neither a protein nor an analogous product, so it is not a biological product, and “an application for retatrutide would need to be submitted under section 505” of the Federal Food, Drug, and Cosmetic Act.

The letter also states how the agency would count amino acids across more than one chain, using insulin’s A and B chains as the example of chains that associate as they do in nature. It says that analysis was not needed for retatrutide because retatrutide has a single alpha-amino-acid chain. In a footnote it adds that the FDA’s Center for Drug Evaluation and Research reviews retatrutide whether it is classed as a drug or as a biological product.

The Seventh Circuit's jurisdiction question

Per the appeals docket, No. 26-1301 was argued on September 24, 2026, before Chief Judge Brennan and Judges Easterbrook and Kirsch. The same day the court entered an order directing supplemental memoranda on appellate jurisdiction. The order asked the parties to cover “not only how appeals by private parties from remands to agencies have been treated in the Seventh Circuit but also how such appeals have been analyzed in the Supreme Court and other courts of appeals.” Memoranda were due October 8, and both sides filed that day.

The question exists because the district court’s judgment did two things. It upheld the FDA on the “protein” definition, and it vacated the FDA’s “analogous product” reasoning and remanded that question to the agency. Lilly appealed. Whether a private party may appeal immediately from a ruling that sends part of a case back to an agency is a separate matter from who is right on the amino-acid count.

What the government argues

In its supplemental letter brief, the government argues that a private party “cannot appeal a district court’s order remanding to an agency.” It says the Supreme Court has not decided the question outside Social Security cases and that other courts of appeals treat such remand orders as interlocutory for private parties. The government characterizes Seventh Circuit precedent as the outlier, writing that the court “appears to permit private parties to appeal most remand orders,” and argues that this extends to private litigants an exception meant for agencies.

It also relies on the October 2 decision. Under Lilly’s theory, the government argues, Lilly could maintain this appeal while also challenging the remand decision in district court and then appeal again, producing the “piecemeal” litigation the Supreme Court has cautioned against. Under the approach the government urges, Lilly would await the outcome of any challenge to the remand decision and file a single appeal.

What Lilly argues

Lilly’s supplemental brief argues that finality turns on the class of order, not on which party appeals, and that Seventh Circuit precedent already treats a remand order as appealable by a private party when it is appealable by the agency. It calls the case “a particularly poor vehicle for reconsidering settled Seventh Circuit law.”

On the October 2 decision, Lilly argues it “further confirms” jurisdiction. Its reasoning: the decision did not address the two issues actually on appeal, which are the protein definition and Lilly’s argument that a statutory 60-day provision (21 U.S.C. § 360bbb-2) made its recommendation take effect automatically. Lilly says that if it challenges the remand decision it would have to file a new suit. In a footnote, Lilly argues that the FDA “announced a nearly identical bright-line rule” on remand. That characterization is Lilly’s; the district court has not reviewed the October 2 decision.

Lilly also tells the court it plans to file its retatrutide application “no later than the first quarter of 2027” and needs to know which pathway, drug or biological product, to use. Its September 29 press release on the TRIUMPH-2 trial likewise says Lilly “plans to submit a Biologics License Application (BLA) in Q1 2027.” The FDA letter describes an application under section 505, the new-drug pathway.

What remains open

The Seventh Circuit has several ways to proceed that the parties’ filings describe: decide it has jurisdiction and reach the appeal’s questions, decide it lacks jurisdiction, or revisit its own precedent. The filings are the parties’ descriptions of those options, not a forecast. The materials read show no ruling as of this writing. Separately, nothing in the materials read shows whether Lilly has begun a new district-court challenge to the October 2 decision.

Background on the case, the district court’s holdings and why the label matters is in the earlier report on the appeal. That article preceded the argument and has not been rewritten here.

What this is, and isn’t

This is litigation and regulatory reporting. The FDA’s classification of retatrutide as a drug is a statement about which statutory pathway applies, not a safety, efficacy or approval determination. Retatrutide is investigational and is not approved for human use anywhere. Nothing here predicts how the Seventh Circuit will rule, and nothing here is legal advice or a usage recommendation. The FDA letter was read as a redacted exhibit; unredacted portions and any related agency materials were not available.

Sources

• FDA, Issues Remanded to FDA, letter to Eli Lilly and Company (Oct. 2, 2026) — primary: the FDA’s decision on remand, as redacted Exhibit 46-2 to the government’s October 8 filing.
• Order, No. 26-1301 (7th Cir. Sept. 24, 2026) — primary: the order directing supplemental memoranda on appellate jurisdiction.
• Supplemental Letter Brief for the Government (7th Cir. Oct. 8, 2026) — primary: the government’s position, attributed.
• Supplemental Brief of Appellant (7th Cir. Oct. 8, 2026) — primary: Lilly’s position, attributed.
• Docket, No. 26-1301 (7th Cir.) — primary: argument date, panel and filing dates.
• Lilly press release, Sept. 29, 2026 — company release (primary for what Lilly says it plans); the Q1 2027 application plan.