Recurrent Extracranial Malignant Solid Neoplasm

This phase I/II trial tests the safety, best dose, and effectiveness of CBX-12 in the treatment of pediatric patients (ages 12 months to 30 years) with rhabdomyosarcoma, Ewing sarcoma, or other extracranial solid tumors that have come back after a period of improvement (relapsed) or that do not respond to treatment (refractory). CBX-12 is a conjugate drug made of a peptide linked to a drug called exatecan. Upon administration, the peptide portion of CBX-12 gets inserted into the membrane of tumor cells and then exatecan is released into the tumor cells. Exatecan inhibits deoxyribonucleic acid replication in tumors cells, leading to tumor cell death. CBX-12 may be a safe and effective treatment option for pediatric patients with relapsed or refractory rhabdomyosarcoma, Ewing sarcoma, or other solid tumors.