EGFR- and HER3-targeted bispecific antibody-drug conjugate demonstrates anti-tumor activity in metastatic castration-resistant prostate cancer

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Abstract

Metastatic castration-resistant prostate cancer (mCRPC) remains lethal with limited treatment options. Antibody–drug conjugates (ADCs) have emerged as a transformative class across multiple solid tumors, yet their clinical application in prostate cancer has been limited. Izalontamab brengitecan (Iza-bren; BL-B01D1) is a bispecific ADC targeting EGFR and HER3 that has demonstrated activity in other malignancies. Here, we evaluated its therapeutic potential in prostate cancer. Multi-omics analyses revealed frequent EGFR and HER3 expression in CRPC adenocarcinoma but not in neuroendocrine subtypes. BL-B01D1 exerted potent, target-dependent cytotoxicity in prostate cancer cell lines, xenografts, and patient-derived organoids (PDOs). We highlight a representative mCRPC patient with high EGFR/HER3 expression who achieved a rapid and durable clinical and radiologic response to BL-B01D1, concordant with matched PDO sensitivity. Mechanistic studies identified ABCG2 upregulation as a driver of acquired resistance, with genetic or pharmacologic inhibition restoring BL-B01D1 sensitivity. Importantly, tumor tissue obtained at progression after BL-B01D1 treatment confirmed ABCG2 upregulation, validating a clinically relevant resistance mechanism. These findings support BL-B01D1 as a promising therapeutic strategy in mCRPC and nominate ABCG2 as a rational target for overcoming resistance.

Authors

Bangwei Fang, Xiaomeng Li, Ying Lu, Weiwei Ma, Hualei Gan, Tingwei Zhang, Qi Liu, Beihe Wang, Zixian Wang, Yi Zhu, Hai Zhu, Sa Xiao, Xiaojie Bian, Gonghong Wei, Dingwei Ye, Yao Zhu