Centers for Therapeutic Innovation, San Francisco, Pfizer Inc., 1700 Owens Street, San Francisco, CA 94158, USA.
Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94143, USA.
Structure. 2018 Feb 6;26(2):187-198.e4. doi: 10.1016/j.str.2017.12.010. Epub 2018 Jan 11.
Coagulation factor XIa is a candidate target for anticoagulants that better separate antithrombotic efficacy from bleeding risk. We report a co-crystal structure of the FXIa protease domain with DEF, a human monoclonal antibody that blocks FXIa function and prevents thrombosis in animal models without detectable increased bleeding. The light chain of DEF occludes the FXIa S1 subsite and active site, while the heavy chain provides electrostatic interactions with the surface of FXIa. The structure accounts for the specificity of DEF for FXIa over its zymogen and related proteases, its active-site-dependent binding, and its ability to inhibit substrate cleavage. The inactive FXIa protease domain used to obtain the DEF-FXIa crystal structure reversed anticoagulant activity of DEF in plasma and in vivo and the activity of a small-molecule FXIa active-site inhibitor in vitro. DEF and this reversal agent for FXIa active-site inhibitors may help support clinical development of FXIa-targeting anticoagulants.
凝血因子 XIa 是抗凝剂的候选靶点，它可以更好地将抗血栓功效与出血风险分离。我们报告了 FXIa 蛋白酶结构域与 DEF 的共晶结构，DEF 是一种人源单克隆抗体，可阻断 FXIa 功能并预防动物模型中的血栓形成，而不会增加可检测到的出血风险。DEF 的轻链封闭了 FXIa 的 S1 亚位点和活性位点，而重链则与 FXIa 的表面提供静电相互作用。该结构解释了 DEF 对 FXIa 及其酶原和相关蛋白酶的特异性、其依赖于活性位点的结合以及抑制底物切割的能力。用于获得 DEF-FXIa 晶体结构的无活性 FXIa 蛋白酶结构域逆转了 DEF 在血浆中和体内的抗凝活性，以及小分子 FXIa 活性位点抑制剂在体外的活性。DEF 和这种 FXIa 活性位点抑制剂的逆转剂可能有助于支持 FXIa 靶向抗凝剂的临床开发。
