The FDA shot down AstraZeneca’s Farxiga (dapagliflozin) as an adjunct treatment to insulin for type 1 diabetes patients in a complete response letter to the company on Monday.

The once-daily oral medication is a selective SGLT2 inhibitor, one of a group of prescription drugs cleared by the agency for use in conjunction with dieting and exercise to lower blood sugar in adults with type 2 diabetes.

“The safety and efficacy of SGLT2 inhibitors have not been established in patients with type 1 diabetes, and FDA has not approved them for use in these patients,” the agency said.