BIONEWS
Risvutatug rezetecan, an antibody drug conjugate targeting a protein on the surface of several solid tumors, just won its second phase 3 in roughly a month.
Children and young adults with osteosarcoma, a rare bone cancer with almost no treatment options after two rounds of chemotherapy, just got a late-stage trial win from a GSK-partnered drug developed by China's Hansoh Pharmaceutical.
The drug, risvutatug rezetecan, is an antibody-drug conjugate, a guided-chemotherapy class that pairs a tumor-targeting antibody with a cell-killing payload. It targets B7-H3, a protein common on several solid tumors. In a China-based phase 3 trial, the drug met its primary endpoint of extending progression-free survival versus chemotherapy in patients with relapsed or progressive osteosarcoma who had been through at least two prior lines of systemic therapy.
GSK said consistent benefit was seen across secondary endpoints including overall survival, and no new safety signals were identified. Hansoh is preparing a regulatory submission in China on the topline. The trial won, the numbers are not public.
Osteosarcoma is rare, with a reported incidence of about 3.4 cases per million people per year. It skews young, hitting children, adolescents, and young adults in active bone. The current standard is surgery plus multi-agent chemotherapy, and for patients who relapse or progress after two prior lines, the menu of effective options thins out fast. GSK chief executive Luke Miels, on the Q2 earnings media call, called the readout a moment that helps kids with cancer.
The topline is the second phase 3 win for risvutatug rezetecan in roughly a month. The B7-H3 antibody-drug conjugate class had made its case earlier in small-cell lung cancer, where risvutatug rezetecan is in a phase 3 in second-line disease and was granted Orphan Drug Designation in Japan. GSK has telegraphed additional phase 3 trials in genitourinary cancers starting later this year, per chief scientific officer Tony Wood on the April earnings call.
Daiichi Sankyo and Merck's rival B7-H3 ADC, ifinatamab deruxtecan, had the FDA accept a filing in second-line small-cell lung cancer in April and is in phase 3 in prostate and esophageal cancers. The two B7-H3 programs will, together, test whether the target is class-agnostic or indication-specific.
The China-only filing and the undisclosed endpoint numbers put real limits on the readout. Clinicians and investors cannot yet tell whether the magnitude of the PFS or OS benefit, or the safety profile in detail, supports broad use or only a narrow subgroup. The global study, Embold Sarcoma-202, is a phase 1b/2 in previously treated unresectable advanced or metastatic sarcomas that enrolled its first patients last month and runs alongside soft-tissue sarcoma cohorts. A global pivotal in osteosarcoma has not been announced.
Hansoh's China filing needs a target action date from the National Medical Products Administration. GSK will have to decide whether to add an osteosarcoma arm to a global phase 3 in the same class or open one separately. The FDA decision on ifinatamab deruxtecan in second-line small-cell lung cancer lands in the same window.