The purpose of this study is to learn more about how treatment with an experimental drug called xaluritamig works in children, adolescents and young adults with Ewing sarcoma (EWS) that has come back after treatment (relapsed) or has not responded to treatment (refractory). EWS is a rare type of cancer that usually starts in the bones or soft tissues around the bones. The study aims to evaluate the safety (side effects) of xaluritamig, find the highest safe dose, and see how the patient’s Ewing sarcoma responds. Xaluritamig binds to STEAP1, a protein that is overexpressed in Ewing sarcoma; it is designed to help the immune system to recognize and attack cancer cells by bringing cancer-fighting immune cells directly to the Ewing sarcoma. Participants will receive xaluritamig as an intravenous (IV) infusion. Study procedures also include physical examination, blood and urine sample collection, radiology scans, bone and tumor biopsy, and questionnaires. This study has 2 parts. In the first part of the study, participants in different subgroups based on age will receive a xaluritamig dose selected from other studies that have already tested xaluritamig. In the second part, more participants will receive the dose selected in Part 1; researchers aim to gather more information about side effects and look for early signs that xaluritamig may help treat EWS.
20200034: A Phase 1b Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of Xaluritamig in Adult, Adolescent and Pediatric Participants With Relapsed or Refractory Ewing Sarcoma *^