A novel anti-HER2/EGFR bispecific antibody-drug conjugate demonstrates promising antitumor efficacy and overcomes resistance to HER2- or EGFR-targeted ADCs.

HER2 and EGFR are frequently co-expressed in various tumors. While antibody-drug conjugates (ADCs) targeting HER2, such as T-DM1 and T-Dxd, have shown remarkable antitumor effects in clinical responses, their effectiveness is constrained by drug resistance. EGFR amplification or high expression is one of the factors that lead to resistance against HER2-targeted ADCs. Likewise, the amplification of HER2 may lead to the development of resistance to EGFR-targeted therapies. To overcome these challenges, we, therefore, developed a bispecific antibody (B2C4) that targets HER2 and EGFR. B2C4 exhibited strong binding affinity and internalization activity in tumor cells with high expression of HER2 and EGFR, as well as in those with high expression of either target. B2C4 was then conjugated with vc-MMAE to create a bispecific ADC (B2C4-MMAE) with an average DAR of 4.05. By effectively engaging both arms of the bispecific ADC, B2C4-MMAE demonstrated significant antitumor activity in tumor cells and animal models that were unresponsive HER2- or EGFR-targeted ADCs. B2C4-MMAE could serve as an alternative therapeutic option for tumors that are resistant to single-target treatments. Additionally, B2C4-MMAE exhibited potential in treating tumors resistant to T-Dxd, underscoring its promise as a treatment for challenging cases.