New Drugs and Clinical Trials · asia
Phase 3 Breakthrough in Later-Line Osteosarcoma Treatment: B7-H3 ADC Delays Disease Progression in Chinese Trial
In osteosarcoma that has recurred or progressed after at least two lines of treatment, risvutatug rezetecan has defeated chemotherapy for the first time in a randomized Phase 3 trial; a regulatory filing in China is expected to move forward, but the magnitude of benefit, maturity of survival data, and full safety data have yet to be disclosed.
Once osteosarcoma recurs after multiple lines of treatment, options capable of altering the course of the disease are extremely limited. Hansoh Pharma announced that the B7-H3-targeted antibody-drug conjugate (ADC) risvutatug rezetecan (Riz-Rez; development code HS-20093) met the primary endpoint in the Phase 3 ARTEMIS-011 trial, significantly prolonging progression-free survival compared with chemotherapy, with a clinically meaningful magnitude of improvement.
ARTEMIS-011 is a randomized, open-label, multicenter trial conducted in China that enrolled patients with osteosarcoma that had recurred or progressed after failure of at least two lines of systemic therapy. According to the ClinicalTrials.gov registration, a total of 117 participants aged 12 years or older were randomized 2:1 to receive HS-20093 at a dose of 12.0 mg/kg once every three weeks or gemcitabine in combination with docetaxel.
Hansoh has not yet disclosed the median progression-free survival, hazard ratio, or response rate for either group. It is therefore currently possible only to confirm that the trial crossed its prespecified statistical threshold, but not to assess how much additional disease-control time patients gained on average. The company said that investigator-assessed progression-free survival and overall survival results were both consistent with the direction of the primary analysis. However, the announcement did not specify whether the overall survival data were mature or whether the difference reached statistical significance.
Regarding safety, both Hansoh and GSK, which holds the ex-China rights, said that no new safety signals were identified, but details on serious adverse events, discontinuation rates, or dose adjustments have not yet been disclosed. For patients who have received multiple lines of treatment and may still be adolescents, these data will be an important part of determining whether the efficacy can translate into practical treatment value.
### Background
B7-H3 is expressed at higher levels on the surface of multiple tumor types and is regarded as a delivery marker that ADCs can exploit. HS-20093 previously produced positive results in a Phase 3 trial in small cell lung cancer; this osteosarcoma trial advances the signal into another cancer type with few treatment options. The US FDA has granted the drug Breakthrough Therapy designation for relapsed or refractory osteosarcoma, and GSK is also evaluating its performance in patients with sarcoma through the global late Phase 1/Phase 2 EMBOLD Sarcoma-202 study.
Hansoh plans to communicate with the National Medical Products Administration regarding a biologics license application in China, with ARTEMIS-011 serving as the principal supporting evidence. GSK holds exclusive development and commercialization rights outside mainland China, Hong Kong, Macau, and Taiwan. However, whether this single-country Chinese study—with a limited sample size and an open-label design—can directly support regulatory decisions in other markets will depend on the full data, population representativeness, and results from global trials.