FDA has again concluded that Eli Lilly’s retatrutide should be regulated as a drug rather than a biologic, handing Lilly another loss in a classification dispute that has now moved between the agency, a federal district court and the Seventh Circuit.
The October 2 decision came on remand after a district court ordered FDA to reconsider part of its earlier analysis. Six days later, Lilly and the government filed competing supplemental briefs with the Seventh Circuit over a threshold question that could determine what happens next: whether Lilly’s current appeal can proceed at all.
The dispute is unfolding as Lilly separately moves against sellers of unauthorized retatrutide, creating two parallel fights around a molecule that has not yet reached the market through an FDA approval.
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FDA reaches the same answer
Lilly asked FDA in January 2024 to classify retatrutide as a biological product that would be reviewed under a biologics license application. FDA rejected that request, finding that retatrutide was neither a “protein” nor an “analogous product” to a protein.
Lilly challenged the decision in federal court. The district court later sent part of the issue back to FDA, directing the agency to better explain the defining characteristics of an “analogous product” to a protein before applying that standard to retatrutide. The court also left open the possibility that FDA could reach the same ultimate conclusion.
On remand, FDA did exactly that. The agency identified two characteristics it says must be present, at minimum, for an active ingredient to qualify as analogous to a protein, including an alpha-amino-acid polymer totaling more than 40 alpha amino acids and a specific, defined sequence.
Retatrutide, FDA says, falls short on the first requirement. The molecule contains a chain of 39 alpha amino acids, and FDA does not count its additional side-chain components toward the threshold in the way Lilly argues they should be counted.
The agency therefore concluded again that retatrutide is neither a protein nor an analogous product to a protein, and is not a biological product. Under FDA’s position, a marketing application for retatrutide would proceed under Section 505 of the Federal Food, Drug and Cosmetic Act rather than through the BLA pathway.
FDA also rejected Lilly’s separate argument involving a statutory 60-day deadline. Lilly has argued that its recommended classification should have taken effect after the original agency decision was found deficient, while FDA says it responded within the required 60-day period and that the statute does not provide for automatic classification when a timely agency decision is later vacated by a court.
The next fight may be over jurisdiction
The October 2 decision is an FDA determination, not a new ruling from the Seventh Circuit. The appeals court heard oral argument on September 24 and then asked the parties to submit additional briefing on whether it has jurisdiction over Lilly’s appeal.
The government argues that it does not. DOJ says remand orders to administrative agencies generally are not immediately appealable by private parties because further agency proceedings remain available, and Lilly can challenge FDA’s new October 2 decision in district court before returning to the appeals court.
DOJ’s concern is that allowing the current appeal to proceed could produce piecemeal litigation. Lilly could litigate the existing appeal, separately challenge FDA’s new remand decision and potentially return to the Seventh Circuit a second time.
Lilly argues that existing Seventh Circuit precedent allows the appeal and that the issues now before the court are not the same issues FDA reconsidered on remand. In particular, Lilly continues to press its argument that the district court should not have simply remanded the matter because of the statutory 60-day provision governing product-designation requests.
Lilly also argues that the October 2 decision strengthens the case for jurisdiction because FDA has completed the remand proceedings. The company says FDA’s new analysis effectively recreates the type of bright-line rule that triggered the district court’s concerns in the first place, now requiring an analogous product to meet both the greater-than-40-alpha-amino-acid threshold and a defined-sequence requirement.
The Seventh Circuit has not yet ruled on the appeal.
The fight is getting bigger than classification
The regulatory dispute is occurring against a much broader fight around retatrutide. Lilly has been pursuing sellers it says are offering unauthorized versions of the investigational drug before FDA has approved a commercial product.
That distinction is becoming increasingly important as retatrutide use spreads outside clinical trials. Products labeled as retatrutide are already being sold through research and gray-market channels, even though Lilly remains the sponsor developing the molecule and no FDA-approved retatrutide product is available to patients.
Recent reports around research-grade products have also raised questions about whether the concentration listed on some vials accurately reflects the amount of drug inside. That matters when adverse events associated with those products are discussed alongside Lilly’s clinical-trial safety data, because an inaccurately dosed or otherwise unverified product is not equivalent to retatrutide manufactured and administered under a clinical trial protocol.
For patients, the latest FDA decision does not mean retatrutide has been rejected as an obesity drug. The fight is over its regulatory classification, while the separate clinical-development program continues.
It also does not mean Lilly has lost its appeal. FDA has now ruled against the company again at the agency level, but the Seventh Circuit still has to decide whether it will hear Lilly’s current challenge and, if it does, how it will resolve the underThe bigger story is that retatrutide now exists in two very different worlds. One is a late-stage investigational drug moving through Lilly’s clinical and regulatory program, while the other is an already-established market of products being sold under the retatrutide name before an approved Lilly version exists.
FDA and Lilly are fighting over what retatrutide legally is. For patients already encountering the molecule outside clinical trials, the more immediate question may be what is actually inside the vial.
