The US Food and Drug Administration (FDA) today approved a once-weekly extended-release formulation of exenatide injection (Bydureon, Amylin Pharmaceuticals) as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes.

It is the first once-a-week medication for type 2 diabetes on the market.

The approval comes roughly 2 and a half years after Amylin applied for FDA approval of the extended-release version of its twice-daily exenatide injection (Byetta). During that time, the manufacturer endured 2 rejections, with the agency asking it to supply more data on efficacy and safety — in particular, the drug’s effect on heart rate.

The agency still has its safety concerns. In approving the once-weekly medication, the FDA ordered Amylin to conduct a randomized, double-blind, placebo-controlled trial evaluating the drug’s effect on the incidence of major adverse cardiovascular events among patients with type 2 diabetes. The trial also must assess the risk for certain other adverse events, such as pancreatic cancer, renal disorders, and serious hypoglycemia, and the long-term effects on potential biomarkers of medullary thyroid carcinoma (MTC).

In addition, the company must conduct a number of studies with mice — and one that also includes mice, rat, and human thyroid C cells — that focus on MTC.

Two other precautionary strings are attached to the drug’s approval. The FDA required Amylin to create an MTC case series registry to monitor the annual incidence of the cancer in the United States for at least 15 years and identify any increase related to the introduction of extended-release exenatide. And Amylin must carry out a risk evaluation and mitigation strategy (REMS) “to ensure the benefits of the drug outweigh the risks of [MTC] and acute pancreatitis, including hemorrhagic and necrotizing pancreatitis.”

A boxed warning on the drug’s label explains why the FDA is worried about MTC. Extended-release exenatide “causes thyroid C-cell tumors at clinically relevant exposures in rats,” according to the boxed warning. “It is unknown whether Bydureon causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, as human relevance could not be determined by clinical or nonclinical studies.”

The boxed warning also states that the drug is contraindicated in patients with a personal or family history of MTC and in patients with multiple endocrine neoplasia syndrome type 2.

Extended-Release Exenatide Outperforms Twice-Daily Version

A clinical trial showed that after 24 weeks of treatment, patients taking extended-release exenatide lowered their hemoglobin A1c by 1.6 percentage points from baseline compared with a 0.9-percentage point reduction for patients taking the twice-daily version, Amylin stated in a press release.

The most common adverse effects that emerged in clinical trials were nausea (which usually decreased over time), hypoglycemia, vomiting, diarrhea, feeling jittery, dizziness, headache, dyspepsia, constipation, and asthenia.