FDA grants fast track status to tirzepatide for obesity

The FDA granted Fast Track designation to tirzepatide for chronic weight management in adults with obesity, or overweight with at least one weight-related condition, Eli Lilly said on Oct. 6, 2022 ^[1]. Tirzepatide is the drug in Mounjaro, which the FDA had approved on May 13, 2022, to improve blood sugar in adults with type 2 diabetes ^[1][3].

Fast Track is a procedural step, not an approval. The FDA gives the designation to drugs intended to treat serious conditions and fill an unmet medical need, with the aim of bringing promising medicines to patients sooner ^[1]. It let Lilly use a rolling submission for its new drug application, meaning the company could file completed sections for FDA review instead of waiting until the entire application was finished ^[1]. Barron's reported the move as Lilly getting one step closer to approval to market the drug for obesity in the U.S., and noted that investors had made Lilly's stock the best performing among its peers ^[2].

Lilly said the application would rest mainly on two Phase 3 trials. SURMOUNT-1, already complete, randomized 2,539 adults without type 2 diabetes who had obesity, or overweight with at least one of these conditions: high blood pressure, high cholesterol, obstructive sleep apnea or cardiovascular disease. Participants received 5 mg, 10 mg or 15 mg of tirzepatide or a placebo for 72 weeks at sites in the U.S., Argentina, Brazil, China, India, Japan, Mexico, Russia and Taiwan ^[1]. Lilly said nearly two-thirds of participants on the highest dose reduced their body weight by at least 20 percent ^[1].

SURMOUNT-2 was still running. It enrolled 938 adults with type 2 diabetes who had obesity or overweight, tested 10 mg and 15 mg of tirzepatide against placebo over 72 weeks, and was expected to finish by the end of April 2023 ^[1]. The broader SURMOUNT program began in late 2019 and has enrolled more than 5,000 people across six trials, four of them global. Results from SURMOUNT-2, -3 and -4 were anticipated in 2023 ^[1].

"We are pleased with the FDA's decision to grant Fast Track designation for tirzepatide, and we look forward to completing our rolling submission next year," said Mike Mason, president of Lilly Diabetes. He said obesity affects the health of nearly 100 million Americans ^[1].

Why it matters for patients

Fast Track does not change what a medicine is approved to treat. In October 2022, tirzepatide could be prescribed only as Mounjaro, for type 2 diabetes, not for weight management ^[1][3]. People with obesity or overweight could not get it for weight loss at that point, whatever the designation said.

Lilly also did not say what an obesity version would be called, what it would cost, or when it might reach pharmacies ^[1]. That information had not been disclosed. Barron's described the drug's commercial potential as possibly that of a megablockbuster, but that was a market view, not an approval or a coverage decision ^[2].

Tirzepatide is a once-weekly injection that activates the body's receptors for GIP and GLP-1, two natural gut hormones ^[1]. The weight results that later supported approval come from the two SURMOUNT trials. In SURMOUNT-1, people taking the 15 mg dose lost an average of 48 pounds and people taking the 5 mg dose lost an average of 34 pounds, compared with 7 pounds on placebo. In SURMOUNT-2, the 15 mg dose produced average weight reductions of 15.7 percent (34.4 pounds) and the 10 mg dose 13.4 percent (29.8 pounds), compared with 3.3 percent (7.0 pounds) on placebo ^[4].

What happens next

Lilly said it planned to start the rolling submission of its obesity application in 2022 and to complete it shortly after SURMOUNT-2 data were available ^[1]. The FDA approved Zepbound (tirzepatide) for chronic weight management on Nov. 8, 2023 ^[4]. On Dec. 20, 2024, the agency also approved it for moderate-to-severe obstructive sleep apnea in adults with obesity ^[4].

Whether Fast Track itself shortened the review has not been reported ^[1].