受体酪氨酸激酶 FGFR3 在膀胱癌中经常发生突变，是一个经过验证的治疗靶点。尽管泛 FGFR 酪氨酸激酶抑制剂 (TKI) 已显示出临床疗效，但毒性和获得性耐药性限制了这些药物的益处。虽然基于抗体的疗法可以提供比 TKI 更好的选择性，但传统的配体阻断抗体通常是组成型活性受体酪氨酸激酶的无效抑制剂。此外，FGFR3 多种致癌变异体的存在给抗体介导的阻断带来了额外的挑战。在这里，我们开发了一种四价 FGFR3×FGFR3 双特异性抗体，它比我们生产的任何常规 FGFR3 抗体更有效地抑制 FGFR3 点突变体和融合蛋白。双特异性抗体的每个臂通过顺式结合模式接触 FGFR3 的两个不同表位。该抗体可阻断最常见的 FGFR3 致癌变异（S249C 胞外域突变）的二聚化，并抑制对泛 FGFR TKI 耐药的 FGFR3 变异的功能。该抗体在抑制 FGFR3 驱动的肿瘤模型的生长方面非常有效，其疗效与 FDA 批准的 TKI erdafitinib 相当。因此，这种双特异性抗体可能为广泛且高度选择性地抑制致癌 FGFR3 变体提供有效的方法。意义：广泛抑制功能获得性 FGFR3 变体的双特异性抗体的开发提供了一种针对具有致癌性 FGFR3 点突变和融合的肿瘤的治疗策略，这是抗体阻断的特别困难的情况。©2024由美国癌症研究协会出版。

The receptor tyrosine kinase FGFR3 is frequently mutated in bladder cancer and is a validated therapeutic target. Although pan-FGFR tyrosine kinase inhibitors (TKI) have shown clinical efficacy, toxicity and acquired resistance limit the benefit of these agents. While antibody-based therapeutics can offer superior selectivity than TKIs, conventional ligand-blocking antibodies are usually ineffective inhibitors of constitutively active receptor tyrosine kinases. Furthermore, the existence of multiple oncogenic variants of FGFR3 presents an additional challenge for antibody-mediated blockade. Here, we developed a tetravalent FGFR3×FGFR3 bispecific antibody that inhibited FGFR3 point mutants and fusion proteins more effectively than any of the conventional FGFR3 antibodies that we produced. Each arm of the bispecific antibody contacted two distinct epitopes of FGFR3 through a cis mode of binding. The antibody blocked dimerization of the most common FGFR3 oncogenic variant (S249C extracellular domain mutation) and inhibited the function of FGFR3 variants that are resistant to pan-FGFR TKIs. The antibody was highly effective in suppressing growth of FGFR3-driven tumor models, providing efficacy comparable to that of the FDA-approved TKI erdafitinib. Thus, this bispecific antibody may provide an effective approach for broad and highly selective inhibition of oncogenic FGFR3 variants. Significance: Development of a bispecific antibody that broadly inhibits gain-of-function FGFR3 variants provides a therapeutic strategy to target tumors with oncogenic FGFR3 point mutations and fusions, a particularly difficult case for antibody blockade.©2024 The Authors; Published by the American Association for Cancer Research.