Phagocytic resistance plays a key role in tumor-mediated immune escape, so phagocytosis immune checkpoints are a potential target for cancer immunotherapy. CD47 is one of the important phagocytosis immune checkpoints; thus, blocking the interaction between CD47 and signal regulatory protein α (SIRPα) may provide new options for cancer treatment. Using computer-aided targeted epitope mammalian cell-displayed antibody library, we screened and obtained an engineered SIRPα variant fragment crystallizable fusion protein, FD164, with higher CD47-binding activity than wild-type SIRPα. Compared with wild-type SIRPα, FD164 has approximately 3-fold higher affinity for binding to CD47, which further enhanced its phagocytic effect in vitro and tumor suppressor activity in vivo. FD164 maintains the similar antitumor activity of the clinical research drug Hu5F9 in the mouse xenograft model. Furthermore, FD164 combined with rituximab can significantly improve the effect of single-agent therapy. On the other hand, compared with Hu5F9, FD164 does not cause hemagglutination, and its ability to bind to red blood cells or white blood cells is weaker at the same concentration. Finally, it was confirmed by computer structure prediction and alanine scanning experiments that the N⁴⁵, E⁴⁷, ⁵²TEVYVK⁵⁸, K⁶⁰, ¹¹⁵EVTELTRE¹²², and E¹²⁴ residues of CD47 are important for SIRPα or FD164 recognition. Briefly, we obtained a high-affinity SIRPα variant FD164 with balanced safety and effectiveness.

中文翻译：

---

从靶向表位哺乳动物细胞展示抗体库中选择和表征 FD164，一种具有平衡安全性和有效性的高亲和力信号调节蛋白 α 变体

吞噬抵抗在肿瘤介导的免疫逃逸中起着关键作用，因此吞噬免疫检查点是癌症免疫治疗的潜在靶点。CD47是重要的吞噬免疫检查点之一；因此，阻断 CD47 与信号调节蛋白α（SIRP α）之间的相互作用可能为癌症治疗提供新的选择。使用计算机辅助靶向表位哺乳动物细胞展示抗体库，我们筛选并获得了工程化的 SIRP α变体片段可结晶融合蛋白 FD164，其 CD47 结合活性高于野生型 SIRP α。与野生型 SIRP α相比, FD164 与 CD47 的结合亲和力高出约 3 倍，这进一步增强了其体外吞噬作用和体内肿瘤抑制活性。FD164 在小鼠异种移植模型中保持与临床研究药物 Hu5F9 相似的抗肿瘤活性。此外，FD164联合利妥昔单抗可以显着提高单药治疗的效果。另一方面，与Hu5F9相比，FD164不会引起血凝，在相同浓度下与红细胞或白细胞结合的能力较弱。最后通过计算机结构预测和丙氨酸扫描实验证实，N ⁴⁵ , E ⁴⁷ , ⁵² TEVYVK ⁵⁸ , K ⁶⁰ , ¹¹⁵CD47 的 EVTELTRE ¹²²和 E ¹²⁴残基对于 SIRP α或 FD164 识别很重要。简而言之，我们获得了具有平衡安全性和有效性的高亲和力 SIRP α变体 FD164。