STEAP1 and Ewing sarcoma: AMG 509 (Xaluritamig) is an XmAb 2+1 T-cell contactor targeting STEAP1; it consists of two fragment antigen-binding domains that bind STEAP1, one anti-CD3 single-chain fragment variable domain, and one fragment crystallizable immunoglobulin domain, and specifically mediates T-cell-dependent cytotoxicity in PCa and Ewing’s sarcoma cells expressing high levels of STEAP1 [19,69].