A Chinese phase 3 trial of Bristol Myers Squibb’s antibody-drug conjugate has hit its dual primary survival endpoints, providing further validation of the Big Pharma’s $800 million bet on the candidate.
BMS paid SystImmune $800 million upfront in 2023 for ex-China rights to the EGFR×HER3 bispecific ADC, izalontamab brengitecan (iza-bren). The deal, which marked BMS’ entry into the ADC space, covered a drug candidate with the potential to tackle cancer cell proliferation and survival by blocking EGFR and HER3 while simultaneously delivering a cytotoxic payload to tumor cells.
Since then, phase 3 studies run by SystImmune’s parent company, Sichuan Biokin Pharmaceutical, have hit primary endpoints, leading to filings for approval in forms of esophageal and throat cancers in China. Biokin reported a third late-stage win Thursday.
The latest data come from a phase 3 trial that gave iza-bren to people with unresectable locally advanced or metastatic triple-negative breast cancer (TNBC). Participants’ cancers had previously progressed after taxane therapy. TNBC patients who had previously received certain other drugs, including ADCs, were excluded from the trial.
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At a prespecified interim analysis, progression-free and overall survival were significantly better on iza-bren than on physician’s choice of chemotherapy, achieving the trial’s dual primary endpoints. No data from the trial are publicly available, with the companies holding the results back for an upcoming medical meeting.
The implications of the phase 3 victory for BMS are unclear. While Biokin targeted the post-taxane population, BMS’ phase 2/3 TNBC trial is enrolling first-line patients who are ineligible for anti-PD-1/L1 checkpoint inhibitors such as Merck & Co.’s Keytruda. EGFR and HER3 are often overexpressed in TNBC, an aggressive tumor that lacks the receptors and proteins that enable treatment of other breast cancers.
Merck is targeting some similar biology with its Daiichi Sankyo-partnered, HER3-directed ADC patritumab deruxtecan. The Big Pharma began a phase 3 study of the drug candidate in hormone receptor-positive, HER2-negative unresectable locally advanced or metastatic breast cancer last year. BioNTech started a phase 1/2 trial of an EGFR×HER3 bispecific ADC in advanced solid tumor patients in August.
