,15 Given its established safety profile from the initial phase I trial17 and ongoing phase II trials in adult patients with advanced solid tumors, PRL3-zumab was administered to a pediatric patient with multiply relapsed metastatic PAX7-FKHR fusion-positive rhabdomyosarcoma on a compassionate basis after diagnosis of a fifth relapse and disease progression. Here, PTP4A3 is linked to rhabdomyosarcoma.