Oncogenic mutations in the extracellular domain (ECD) of cell-surface receptors could serve as tumor-specific antigens that are accessible to antibody therapeutics. Such mutations have been identified in receptor tyrosine kinases including HER2. However, it is challenging to selectively target a point mutant, while sparing the wild-type protein. Here we developed antibodies selective to HER2 S310F and S310Y, the two most common oncogenic mutations in the HER2 ECD, via combinatorial library screening and structure-guided design. Cryogenic-electron microscopy structures of the HER2 S310F homodimer and an antibody bound to HER2 S310F revealed that these antibodies recognize the mutations in a manner that mimics the dimerization arm of HER2 and thus inhibit HER2 dimerization. These antibodies as T cell engagers selectively killed a HER2 S310F-driven cancer cell line in vitro, and in vivo as a xenograft. These results validate HER2 ECD mutations as actionable therapeutic targets and offer promising candidates toward clinical development.

细胞表面受体细胞外结构域 （ECD） 中的致癌突变可以作为抗体治疗药物可获得的肿瘤特异性抗原。已在包括 HER2 在内的受体酪氨酸激酶中发现此类突变。然而，选择性地靶向点突变体，同时保留野生型蛋白是具有挑战性的。在这里，我们通过组合文库筛选和结构引导设计开发了对 HER2 S310F 和 S310Y （HER2 ECD 中最常见的两种致癌突变）具有选择性的抗体。HER2 S310F 同型二聚体和与 HER2 S310F 结合的抗体的低温电子显微镜结构显示，这些抗体以模拟 HER2 二聚化臂的方式识别突变，从而抑制 HER2 二聚化。这些抗体作为 T 细胞接合器在体外选择性地杀死 HER2 S310F 驱动的癌细胞系，并在体内作为异种移植物杀死。这些结果验证了 HER2 ECD 突变是可操作的治疗靶点，并为临床开发提供了有前途的候选药物。