FDA grants tirzepatide fast track status for obesity

The U.S. Food and Drug Administration granted Fast Track designation to tirzepatide for adults with obesity, or with overweight and a weight-related health condition, Eli Lilly announced on Oct. 6, 2022 ^[1]. Fast Track status is a program the FDA uses to speed the development and review of drugs meant to treat serious conditions and address an unmet medical need ^[1]. It does not mean the drug is approved. It means Lilly could start turning in finished pieces of its application before the whole package was ready, a process called a rolling submission ^[1].

At the time, tirzepatide was already on the market under the brand name Mounjaro, approved in May 2022 to help adults with type 2 diabetes control blood sugar ^[1][3]. It had not yet been approved for weight loss on its own. Lilly said it planned to build its obesity application mainly on two late-stage trials: SURMOUNT-1, which was already finished, and SURMOUNT-2, which was expected to wrap up by the end of April 2023 ^[1]. In SURMOUNT-1, nearly two-thirds of participants taking the highest dose lost at least 20% of their body weight ^[1]. Lilly said it aimed to finish its submission to the FDA soon after SURMOUNT-2 results came in, assuming they were positive ^[1].

Mike Mason, president of Lilly Diabetes, said in the announcement that obesity affects nearly 100 million Americans and drives significant health care costs, and that diet and exercise alone often are not enough for patients to reach their weight goals ^[1]. The company's broader SURMOUNT trial program had enrolled more than 5,000 people with obesity or overweight across six studies by that point, with results from three more trials expected in 2023 ^[1].

The fast track step came about 13 months before the FDA approved tirzepatide for chronic weight management under a new brand name, Zepbound, on Nov. 8, 2023 ^[4]. That approval relied on the SURMOUNT-1 and SURMOUNT-2 data referenced in the 2022 fast track announcement ^[4]. In SURMOUNT-1, people taking the highest studied dose, 15 mg, lost an average of 48 pounds, compared with 7 pounds on placebo ^[4]. In SURMOUNT-2, which included people with type 2 diabetes, those on the 15 mg dose lost an average of 15.7% of their body weight, or 34.4 pounds, compared with 3.3%, or 7 pounds, on placebo ^[4].

Why it matters for patients

Fast Track designation is a regulatory process step, not a signal that a drug works or is safe for a new use. It affects how the FDA reviews an application, not whether the agency will approve it. For patients following the news around weight-loss drugs, this kind of designation is a milestone that can shorten the calendar between finished clinical trials and a possible approval, but it carries no guarantee about the outcome.

At the time of this designation, tirzepatide was available only as Mounjaro, approved for type 2 diabetes, not specifically for weight loss in people without diabetes ^[1][3]. Anyone considering the drug for weight management before the Zepbound approval in November 2023 would have been using it off-label for that purpose, since the FDA had not yet reviewed or cleared it for chronic weight management ^[1][4].

What happens next

Following the October 2022 fast track designation, Lilly reported SURMOUNT-2 results in April 2023 showing weight reductions of up to 15.7% ^[3][4]. The FDA approved tirzepatide under the brand name Zepbound for chronic weight management on Nov. 8, 2023 ^[4]. Zepbound later gained a second approval, in December 2024, for moderate-to-severe obstructive sleep apnea in adults with obesity ^[4].