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For the first time in decades, a large randomized trial has shown meaningful progress against relapsed osteosarcoma — the most common malignant bone tumor in kids and young adults. The antibody-drug conjugate risvutatug rezetecan (Ris-Rez) cut the risk of disease progression by 67% compared to standard chemotherapy in the phase III ARTEMIS-011 trial. Experts are calling it "something we have not seen for years."
For decades, treatment options for relapsed or refractory osteosarcoma have been frustratingly limited — and survival rates have barely budged. That may be about to change. The phase III ARTEMIS-011 trial, presented at the 2026 ESMO Congress in Madrid, showed that the B7-H3-targeted antibody-drug conjugate (ADC) risvutatug rezetecan (Ris-Rez) dramatically outperformed standard chemotherapy in patients with heavily pretreated osteosarcoma.
The trial enrolled 122 patients (median age ~22 years, including adolescents as young as 12) across 24 sites in China. Patients were randomized 2:1 to Ris-Rez or gemcitabine plus docetaxel. The results were striking — and experts at ESMO called them historic for this disease.
By the Numbers:
Why it matters: Osteosarcoma primarily strikes children, adolescents, and young adults, and recurrent disease has had no standard of care for years. Ris-Rez already holds FDA Breakthrough Therapy Designation, and these phase III results could pave the way for regulatory approval — offering real hope to a patient population that has had very little.
