Phase II Study of Ganitumab, a Fully Human Anti–Type-1 Insulin-Like Growth Factor Receptor Antibody, in Patients With Metastatic Ewing Family Tumors or Desmoplastic Small Round Cell Tumors

Purpose Ganitumab is a fully human monoclonal antibody against type-1 insulin-like growth factor receptor (IGF1R). An open-label phase II study was conducted to evaluate the efficacy and safety of ganitumab monotherapy in patients with metastatic Ewing family tumors (EFT) or desmoplastic small round cell tumors (DSRCT). Patients and Methods Patients ≥16 years of age with relapsed or refractory EFT or DSRCT received 12 mg/kg of ganitumab every 2 weeks. Objective response rate (ORR) was the primary end point. Secondary end points included clinical benefit rate (CBR = complete + partial responses + stable disease [SD] ≥ 24 weeks) and safety and pharmacokinetic profiles of ganitumab. The relationship between tumor response and EWS gene translocation status and IGF-1 levels was evaluated. Results Thirty-eight patients (22 with EFT; 16 with DSRCT) received one or more doses of ganitumab. Twenty-four patients (63%) experienced ganitumab-related adverse events. Grade 3 related events included hyperglycemia (n = 2), thrombocytopenia (n = 5), neutropenia (n = 2), leukopenia (n = 1), and transient ischemic attack (n = 1). There were no grade 4 or 5 treatment-related events. Of 35 patients assessed for response, two had partial responses (ORR, 6%) and 17 (49%) had SD. Four patients had SD ≥ 24 weeks, contributing to a CBR of 17%. The pharmacokinetic profile of ganitumab was similar to that observed in the first-in-human trial. Elevation of IGF-1 levels was observed postdose. EWS-Fli1 translocations were analyzed by RNA sequencing and fluorescent in situ hybridization, and novel translocations were observed in EFT and DSCRT. No apparent relationship between tumor response and IGF-1 levels or EWS gene translocations was observed. Conclusion Ganitumab was well tolerated and demonstrated antitumor activity in patients with advanced recurrent EFT or DSRCT.