A high-throughput selection system for fast-acting covalent protein drugs
- Qiongxuan Fan
- Jiahao Mei
- Tian Li
- Chuanlong Zang
- Mengjiao Li
- Jing Tang
- You Xu
- Ge Yu
- Dandan Liu
- Kai Chen
- Bing Yang
- Jing Huang
- Ting Zhou
- Bobo Dang
2026-04-02
Covalent protein drugs offer therapeutic potential but are limited by slow target engagement and the absence of high-throughput selection platforms. Rapid covalent binding requires coordinated optimization of affinity, stability, and warhead geometry—an intrinsically multidimensional challenge. We develop a yeast display platform coupled with chemoselective modification that enables selection of fast-acting covalent proteins without increasing intrinsic warhead reactivity. Using this system, we engineered a covalent programmed death-ligand 1 (PD-L1) antagonistic nanobody with rapid crosslinking kinetics ( k obs = 0.18 min −1 , t 1/2 = 3.8 min) and improved tumor suppression compared with envafolimab and atezolizumab. Similarly, we engineered a fast-acting covalent interleukin-18 (IL-18) ( k obs = 0.54 min −1 , t 1/2 = 1.3 min) and a covalent miniprotein targeting the receptor binding domain (RBD) of SARS-CoV-2, demonstrating applicability across protein modalities.