Objective: This study investigated whether the growth hormone receptor antagonist pegvisomant could produce regression of diabetic retinal neovascularization.
Design: A prospective, single-group, open-label, phase IIa multicenter trial was conducted.
Participants: Twenty-five patients with diabetes mellitus (13 with type 1 and 12 with type 2) and proliferative diabetic retinopathy aged 21 years or older were enrolled.
Methods: Patients received an initial loading dose of 100 mg pegvisomant by subcutaneous injection, followed by self-administered injections of 20 mg daily for 12 weeks. The treatment period was followed by a 12-week period during which patients were observed off treatment.
Main outcome measure: The effect of treatment on diabetic retinopathy was evaluated from fundus photographs that were graded at a central reading center.
Results: Regression of retinopathy was not observed in any patient. At the end of the treatment period, the extent of neovascularization in the study eye was unchanged in 16 patients (9 of 13 with type 1 and 7 of 12 with type 2) and had progressed in 9 patients (4 of 13 with type 1 and 5 of 12 with type 2). The maximum reduction from baseline per patient in the insulin-like growth factor-I (IGF-I) serum level averaged 55%; 17 (68%) of the 25 patients had a greater than 50% reduction in IGF-I. After treatment was discontinued, IGF-I levels returned to baseline.
Conclusions: This study did not find evidence that pegvisomant could produce regression of diabetic retinal neovascularization.