Substituting Exenatide for Insulin May Work for Some Type 2’s

For type 2 diabetes patients who were taking insulin plus oral antidiabetes drugs, the results from a small 16-week study suggest it may be feasible to substitute subcutaneous exenatide (Byetta) for insulin, especially among patients who have had a shorter disease duration, are taking relatively low insulin doses, and have better endogenous beta-cell function.

Dr. Stephen N. Davis of Vanderbilt University in Nashville, Tennessee, and colleagues conducted the pilot study with 49 patients (average age 53 years) who had an average disease duration of 11 years and were on insulin plus oral antidiabetes drugs at baseline. The subjects were randomized (2:1) to exenatide, which replaced insulin, or to continue on their current treatment. Patients randomized to exenatide self-injected 5 g bid for 4 weeks and 10 g bid for the remaining 12 weeks.
Under an intent-to-treat approach, patients who either completed at least 8 weeks of the study or discontinued exenatide because of loss of glycemic control were included in the analysis.

Maintenance of glycemic control was defined as a hemoglobin A1C increase of no more than 0.5%. The researchers note that because the study was not designed to compare exenatide with insulin, there were no specific glycemic goals for the insulin patients.

The mean overall A1C change in the exenatide group was +0.3% and in the insulin group was -0.1%. Eighteen of the 29 patients in the exenatide group achieved the predefined level of glycemic control. The majority (67%) of these 18 patients also had reductions in A1C from baseline.

The researchers, most of whom are affiliated with Byetta makers Amylin Pharmaceuticals, Inc. and Eli Lilly and Company, report that 27 of the 29 exenatide-treated patients lost weight (- 4.2 kg) during the study, while there was no substantial change in weight in the insulin-treated patients (+ 0.5 kg).

Finally, the researchers note that 79% of the exenatide group reported an adverse event compared with 56% of the insulin group.

In the editorial, Drs. Julio Rosenstock, of the Dallas Diabetes and Endocrine Center, and Vivian Fonseca, of Tulane University, New Orleans, emphasize that "our main mission when managing patients with diabetes is to improve glycemic control," and that other outcomes, such as weight loss, remain secondary.

"The overall effect on glycemic control was rather disappointing." They conclude that "this was clearly a negative trial, with a flawed study design and a conclusion that perhaps should have been stronger against substituting exenatide for insulin."
An accompanying editorial, however, is highly critical of the study, noting among other factors that "the insulin regimen used in this study was often non-physiological and that no attempt was made to optimize inslin therapy" before substituting exenatide.

Diabetes Care Nov. 2007;30:2767-2772.