The main goal of this study is to test a new medicine, Risvutatug Rezetecan also called Ris-Rez. We want to see if this medicine can help people with certain types of cancer, whether its safe to use, how well people tolerate it, and how their bodies handle the drug (how its absorbed and broken down). This research is for adolescents and adults who have either: Osteosarcoma, which is a type of bone cancer, or Soft Tissue Sarcoma, which is a type of cancer that starts in soft body tissues (like muscle, fat, or nerves). In both cancer types the cancer must have already been treated, but has come back or spread, and cant be removed by surgery
Participants must be ≥ 12 years of age.
Has histologically confirmed unresectable advanced or metastatic R/R OSA (Cohort 1) or unresectable advanced or metastatic STS (Cohort 2) that has progressed to at least one prior line of systemic therapy.
Has documented disease progression on the last line of systemic treatment as confirmed by radiological imaging
Has an ECOG performance status of 0 or 1, or Lansky PS/Karnofsky PS ≥ 70% for adolescent participants, with no deterioration in the 2 weeks prior to first dose/randomization.
Has received any prior therapy with an Antibody-drug-conjugates (ADC) with a TOPO1-inhibitor payload.
Has known sensitivity to study intervention components or excipients or other allergy that, in the opinion of the investigator or medical monitor, contraindicates participation in the study.
Has severe, uncontrolled or active cardiovascular disorders.
Known active infectious diseases requiring systemic treatment or known Human immunodeficiency virus (HIV).