Lilly files the Mounjaro new drug application

Eli Lilly and Company submitted a new drug application for tirzepatide injection, later marketed as Mounjaro, on September 14, 2021. The Food and Drug Administration recorded receipt of the filing on September 15, 2021, according to the agency's approval letter for NDA 215866 ^[1]. The application asked the FDA to approve tirzepatide as an add-on to diet and exercise to improve blood sugar control in adults with type 2 diabetes ^[1].

The filing marked the formal start of the FDA's review of a new molecule that combines two hormone-mimicking actions in one drug. The agency's letter, issued about eight months later, confirms the application was reviewed under section 505(b) of the Federal Food, Drug, and Cosmetic Act and that Lilly submitted amendments during the review period ^[1]. The FDA ultimately approved the application, though the approval letter itself is dated well after the original filing ^[1].

As part of the review, the FDA decided not to convene an outside advisory committee, stating that no issues required outside expert input ^[1]. The agency did, however, attach several conditions to approval. Lilly must complete a pediatric study in patients ages 10 to 17, expected to finish in December 2027 with a final report due by September 2028 ^[1]. The company also agreed to run a 15-year registry study tracking cases of medullary thyroid carcinoma in the United States, with a final report not due until June 2040, and a separate study measuring how much tirzepatide passes into breast milk, originally slated for completion by July 2024 ^[1].

The approved product carries a shelf life of 24 months when stored at 2 to 8 degrees Celsius, according to the FDA's dating period specification based on the stability data submitted with the application ^[1].

Why it matters for patients

A new drug application is the formal request a company makes before the FDA will allow a medicine to be sold. The September 2021 filing did not itself put tirzepatide on pharmacy shelves; it opened the review process that the FDA later completed with a full approval for use in adults with type 2 diabetes ^[1]. Patients considering the drug should understand that the approved use covers glycemic control alongside diet and exercise, not other purposes, based on the labeling described in the approval letter ^[1].

The long-term studies attached to the approval, including the multi-decade thyroid carcinoma registry, exist because tirzepatide works on hormone pathways that regulators wanted monitored over time ^[1]. These studies will continue collecting data for years, and their findings could eventually affect how the drug's safety profile is understood, though results are not yet available from the source reviewed here.

The pediatric study requirement also matters for families of younger patients, since the drug's safety and effectiveness in ages 10 to 17 had not been established at the time of adult approval and remained under study with a completion date years in the future ^[1].

What happens next

Based on the FDA's own letter, the pediatric study in patients ages 10 to 17 is expected to be completed by December 2027, with a final report due by September 2028 ^[1]. The medullary thyroid carcinoma registry study is scheduled to run with interim reports every year through 2039, and a final report is due by June 2040 ^[1]. The lactation study looking at tirzepatide levels in breast milk was originally expected to be completed by July 2024, according to the timetable Lilly submitted to the FDA in April 2022 ^[1]. The sources here do not describe intermediate results from any of these ongoing studies.