Effect of Long-Term Metreleptin Treatment on Glycemic Control in Rabson-Mendenhall Syndrome

Abstract Rabson-Mendenhall Syndrome is caused by mutations of the insulin receptor, resulting in extreme hyperinsulinemia and poorly controlled diabetes. We examined whether long-term treatment with metreleptin, a recombinant analog of the hormone leptin, improves glycemia in patients with Rabson-Mendenhall Syndrome. We measured HbA1c in 11 patients with Rabson-Mendenhall Syndrome treated with high-dose metreleptin (≥0.15 mg/kg/day) after 6, 12, 18, 24, 36, 48, and 60 months, and at last follow up in patients treated >60 months (mean 90 months). We measured HbA1c over a comparable time frame in 7 untreated patients with Rabson-Mendenhall syndrome. 5 of these patients were also in the treatment group and were studied prior to starting metreleptin treatment or after metreleptin withdrawal. 2 patients in the untreated cohort were never treated with high-dose metreleptin. We calculated change in A1c from baseline at each of these timepoints in both the treated and untreated groups. At baseline the treatment group had similar age (13.8±5.0 vs 11.3±5.3 years, P=0.35) and trended toward higher A1c (10.7%±1.5 vs 8.9%±2.3%, P=0.08). All analyses were therefore adjusted for baseline A1c. In the untreated group, A1c increased non-significantly over time (P=0.2). Least-square mean change in A1c from baseline was 0.2%±1.4%, 0.2%±1.6%, 0.8%±1.5%, 1.0%±1.5%, 1.8%±1.5%, 1.5%±1.5%, 0.9%±1.4%, and 2.4%±1.4%. at 6, 12, 18, 24, 36, 48, and ~90 months of follow-up. During high-dose metreleptin treatment, A1c decreased non-significantly over time (P=0.2). Least square mean change in A1c from baseline was -1.9%±1.7%, -1.4%±1.8%, -1.0%±1.7%, -1.1%±1.7%, -1.1%±1.7%, -1.5%±1.7%, -0.6%±1.7%, and -0.2%±1.7% at 0, 6, 12, 18, 24, 36, 48, and ~90 months of follow-up. Reductions in A1c after metreleptin were statistically significant at months 6 (p=0.009), 12 (p=0.03), and 48 (p=0.04). Over time, A1c was 1.4% higher in the untreated group vs. the metreleptin treated group (P=0.04). These results suggest that treatment with metreleptin may lower A1c over time in patients with Rabson-Mendenhall syndrome. Better glycemic control, as indicated by lower average HbA1c levels, may reduce the risk of diabetic complications over time.