Specific, chemically modified aptamers (X-Aptamers) were identified against two immune checkpoint proteins, recombinant Programmed Death 1 (PD-1) and Programmed Death Ligand 1 (PD-L1). Selections were performed using a bead-based X-Aptamer (XA) library containing several different amino acid functional groups attached to dU at the 5-position. The binding affinities and specificities of the selected XA-PD1 and XA-PDL1 were validated by hPD-1 and hPD-L1 expression cells, as well as by binding to human pancreatic ductal adenocarcinoma tissue. The selected PD1 and PDL1 XAs can mimic antibody functions in in vitro assays.

中文翻译：

---

PD1 / PD-L1 X-适体的选择

针对两种免疫检查点蛋白，重组的程序性死亡1（PD-1）和程序性死亡配体1（PD-L1），鉴定了经过化学修饰的特异性适体（X-适体）。使用基于珠的X-适体（XA）文库进行选择，该文库包含在5位连接到dU的几个不同的氨基酸官能团。选定的XA-PD1和XA-PDL1的结合亲和力和特异性通过hPD-1和hPD-L1表达细胞以及与人胰腺导管腺癌组织的结合来验证。所选的PD1和PDL1 XA可以模拟体外测定中的抗体功能。