Eli Lilly fights to classify weight-loss drug retatrutide as a biologic

On September 24, Eli Lilly and the Food and Drug Administration will present oral arguments before the 7th Circuit Court of Appeals in the dispute over the classification of retatrutide, Lilly’s experimental weight-loss peptide. The legal question hinges on whether the molecule meets the FDA’s definition of a protein, which would qualify it as a biologic and grant 12 years of statutory exclusivity, shielding it from compounding and biosimilar competition.

The FDA has argued that retatrutide does not satisfy the strict protein definition, while Lilly contends it is either a protein or analogous to one, and that the agency missed a statutory deadline for a decision. A district-court ruling sent the matter back to the FDA, and Lilly now claims the agency’s inaction triggers automatic biologic designation. Trade groups for compounding facilities oppose the move, calling it a “money grab.” The decision will influence the drug’s price, patient access, and the broader regulatory environment for new obesity treatments.