Rare Cancer Affects 3 in 1 Million; GSK ADC Outperforms Chemotherapy in Phase 3

An antibody-drug conjugate (ADC) being jointly developed by GSK and its Chinese partner Hansol Pharmaceutical demonstrated superior efficacy to existing chemotherapy in a phase 3 trial in relapsed osteosarcoma.

According to biopharmaceutical news outlet Fierce Biotech on the 28th local time, Hansol Pharmaceutical said it had met the primary endpoint in a Chinese phase 3 trial of the B7-H3-targeted ADC risvutatug rezetecan.

The trial compared risvutatug rezetecan with chemotherapy in patients with osteosarcoma whose disease had relapsed or progressed after two or more systemic therapies. The results showed that the risvutatug rezetecan group had a statistically significant extension in progression-free survival (PFS) compared with the chemotherapy group.

The treatment also showed consistent improvement in key secondary endpoints, including overall survival (OS), and no new safety concerns were identified. Luke Mills, GSK's chief executive officer (CEO), said of the results, "Helping children with cancer is always deeply meaningful."

Osteosarcoma is a bone cancer that primarily develops in children and adolescents. It is a rare cancer that occurs in approximately 3.4 people per 1 million annually worldwide, and treatment options are limited when the disease relapses.

Hansol Pharmaceutical plans to submit a marketing authorization application to Chinese regulatory authorities based on these results. The success is also viewed as a positive development for GSK's global Embold Sarcoma-2020 trial, which is being conducted in multiple sarcomas, including osteosarcoma.

Risvutatug rezetecan previously succeeded in a phase 3 trial in patients with small cell lung cancer (SCLC). GSK considers the drug a key asset and plans additional phase 3 trials to expand its indications to cancers including genitourinary cancers.

In the B7-H3-targeted ADC market, Daiichi Sankyo and Merck's (MSD) ifinatamab deruxtecan is currently furthest along, undergoing U.S. Food and Drug Administration (FDA) review for an indication in small cell lung cancer.