Insulin Growth Factor-Receptor (IGF-1R) Antibody Cixutumumab Combined with the mTOR Inhibitor Temsirolimus in Patients with Refractory Ewing's Sarcoma Family Tumors

PURPOSE: Temsirolimus was combined with cixutumumab, a fully human IgG1 monoclonal antibody directed at the insulin growth factor-1 receptor (IGF-1R). EXPERIMENTAL DESIGN: Patients received cixutumumab, 6 mg/kg i.v. weekly, and temsirolimus, 25 to 37.5 mg i.v. weekly (4-week cycles), with restaging after 8 weeks. Median follow-up was 8.9 months. RESULTS: Twenty patients [17 with Ewing's sarcoma (EWS), 3 with desmoplastic small-round cell tumor (DSRCT)] were enrolled. Twelve patients (60%) were men with a median age of 24 years and six median prior systemic therapies in a metastatic setting. The most frequent toxicities were thrombocytopenia (85%), mucositis (80%), hypercholesterolemia (75%), hypertriglyceridemia (70%), and hyperglycemia (65%; mostly grade I-II). Seven of 20 patients (35%) achieved stable disease (SD) for more than 5 months or complete/partial (CR/PR) responses. Tumor regression of more than 20% (23%, 23%, 27%, 100%, 100%) occurred in five of 17 (29%) patients with EWS, and they remained on study for 8 to 27 months. One of six patients with EWS who previously developed resistance to a different IGF-1R inhibitor antibody achieved a CR. Four of the seven best responders developed grade III mucositis, myelosuppression, or hyperglycemia, which were controlled while maintaining drug dose. CONCLUSION: Cixutumumab combined with temsirolimus was well-tolerated and showed preliminary evidence of durable antitumor activity in heavily pretreated EWS family tumors.