Cotherapy with recombinant human insulin-like growth factor I and insulin improves glycemic control in type I diabetes

OBJECTIVE - To study the effects of 12 weeks of cotherapy with recombinant human IGF-I (rhIGF-I) and insulin on glycemic control in patients with type 1 diabetes. RESEARCH DESIGN AND METHODS - The study population consisted of 223 patients who ranged in age from 11-66 years and were randomized in a double-blind study to receive 12 weeks of treatment with twice-daily subcutaneous injections of placebo (n = 54), or rhIGF-I at a dose (A.M./P.M.) of 40/40 μg/kg (n = 56), 80/40 μg/kg (n = 57), or 80/60 μg/kg (n = 56), while continuing to receive standard insulin therapy. Patients were instructed to test blood glucose levels four times daily and adjust insulin doses to optimize blood glucose control. HbA(1c), insulin requirements, body weight, and parameters of the IGF-IGF-binding protein axis were assessed before and during treatment. RESULTS - All groups were comparable at baseline with respect to mean age, gender distribution, duration of diabetes, Hb(1c), and BMI. Cotherapy with rhIGF-I/insulin produced a mean decrease in HbA(1c) of 1.2%, compared with a 0.7% decrease in HbA(1c) for patients receiving intensified insulin therapy alone (P ≤ 0.01). Subjects receiving rhIGF- I/insulin cotherapy also decreased their daily insulin usage by 11-19%, compared with a 7% increase in insulin usage reported by the placebo group. Moreover, the incidence of hypoglycemia was similar in subjects treated with rhIGF-I/insulin cotherapy compared with those treated with insulin alone, despite the better glycemic control of the former group. The 40/40 dose of rhIGF-I was well tolerated. Higher doses of rhIGF-I did not further improve efficacy yet were associated with unacceptable levels of adverse events, including edema, jaw pain, and early worsening of retinopathy. CONCLUSIONS - These results demonstrate that rhIGF-I/insulin cotherapy improves glycemic control in patients with type 1 diabetes better than optimized insulin management alone; longer-term trials would be required to determine an acceptable benefit-risk profile.