First GLP-1/GIP Receptor Agonist OK’d for Type 2 Diabetes

The FDA approved first-in-class tirzepatide (Mounjaro) for patients with type 2 diabetes, the agency announced on Friday.

Tirzepatide, a glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide (GLP-1/GIP) agonist, is available at three dose levels (5 mg, 10 mg, and 15 mg), should be administered via injection once weekly, and is indicated as an adjunct to diet and exercise.

In five clinical trials in the SURPASS program, tirzepatide alone or as an add-on therapy proved better for HbA1c reduction versus long-acting insulin degludec or insulin glargine, the GLP-1 receptor agonist semaglutide (Ozempic), or placebo.

“Given the challenges many patients experience in achieving their target blood sugar goals, today’s approval of Mounjaro is an important advance in the treatment of type 2 diabetes,” said Patrick Archdeacon, MD, of the Division of Diabetes, Lipid Disorders, and Obesity at FDA’s Center for Drug Evaluation and Research, in a statement.

Compared with placebo, patients randomized to the maximum recommended dose of tirzepatide (15 mg) saw their HbA1c levels reduced by an absolute 1.6% when used as a stand-alone therapy, and by 1.5% when used in combination with a long-acting insulin. And when compared with active agents, patients on tirzepatide at the 15-mg dose had their HbA1c reduced by 1.0%, 0.9%, and 0.5% more than with insulin glargine, insulin degludec, or semaglutide, respectively.

Most participants in the trials had obesity, with a mean BMI of 32-34 across the studies at enrollment, but patients randomized to the GLP-1/GIP agonist experienced significantly more weight loss with the drug versus those assigned to placebo groups: a 15-lb greater reduction when tirzepatide was used as stand-alone therapy and a 23-lb greater reduction when combined with insulin.

And mean weight loss with tirzepatide at the maximum dose was 12 lb, 29 lb, and 27 lb greater than with semaglutide, insulin degludec, and insulin glargine, respectively.

FDA noted several adverse events observed in the SURPASS trials, including “nausea, vomiting, diarrhea, decreased appetite, constipation, upper abdominal discomfort and abdominal pain.”

The agency also cautioned that thyroid C-cell tumors have been observed in rat studies, though it remains unknown whether this is a risk in humans. Regardless, patients with a history of medullary thyroid cancer (or a family history) and those with multiple endocrine neoplasia syndrome type 2 should not be prescribed the GLP-1/GIP agonist.

Tirzepatide is not indicated for patients with type 1 diabetes, the agency pointed out, and has not been studied in those with a history of pancreatitis.