A novel antibody against GPIbα inhibits platelet function and thrombosis without increasing bleeding.

Abstract

Glycoprotein Ibα (GPIbα), the initiation protein of arterial thrombosis, was selected as a target for developing new antiplatelet drugs to prevent and treat arterial thrombosis. However, no anti-GPIbα drug is used successfully in clinical. We used human platelets as an antigen to immunize mice and obtained mouse anti-human GPIbα antibody 9C9. The chimeric antibody 1A09 was constructed, and the antibody binding sites were validated, before employing 3D modeling. Following design of a humanized anti-GPIbα, a mouse-derived antibody was mutated into a human sequence to construct the humanized anti-GPIbα antibody SZ003. ELISA, western blot, platelet aggregation, and thrombus model experiments were used to test the specificity, affinity, safety, and thrombus inhibition effects. The experimental results showed that SZ003 bound to GPIbα, inhibited GPIbα-mediated platelet aggregation, and induced in vivo platelet clearance. Furthermore, SZ003-Fab inhibited GPIbα-mediated platelet aggregation and thrombosis but did not induce in vivo platelet clearance, prolong bleeding time in mouse tails, nor have cytotoxic effects on human platelets. The Fab fragment of anti-human GPIbα humanized antibody SZ003 effectively inhibited GPIbα receptor-mediated platelet activation and thrombosis in vivo without leading to thrombocytopenia and bleeding. Therefore, SZ003-Fab has clinical value as a novel antithrombotic drug to treat arterial thrombus-related diseases.