Abstract Body: Introduction: Platelet glycoprotein (GP) Ibα is a key receptor for thrombosis. Under high shear conditions, GPIbα-VWF interactions are required for initiating platelet adhesion and vessel occlusion. GPIbα is also an important checkpoint for thrombo-inflammation in acute ischemic stroke. It has been considered as a desirable target against ischemic stroke for decades, but no anti-GPIbα drug has been successfully developed.
Methods: CA1001 was humanized from our unique mAb crossing different species, and manufactured under GMP-like conditions with 99.9% purity. The efficacy of CA1001 was assessed using various in vitro platelet functional assays with blood samples and in vivo models, including state-of-the-art intravital microscopy thrombosis and transient middle cerebral artery occlusion (tMCAO) models. Pharmacokinetics (PK), pharmacodynamics (PD), and a 14-day regulatory toxicology study were conducted in rats and rhesus monkeys.
Results: CA1001 specifically recognized platelet GPIbα from human, monkeys, rats, mice, rabbits and dogs. Using platelets from rhesus monkeys, healthy volunteers, and patients with peripheral artery disease, CA1001 dose-dependently inhibited ristocetin-induced platelet aggregation in vitro. Using laser injury and FeCl₃ injury intravital microscopy models, CA1001 inhibited thrombosis, prevented vessel occlusion, and importantly, promoted thrombus dissolution (thrombolysis) in vivo. In a 60-min tMCAO models, intravenous injection of CA1001 1 hour after tMCAO significantly reduced the cerebral infarct volume at 24 hours without increasing the risk of intracerebral hemorrhage. The PD studies showed that single bolus injection of CA1001 reached maximal anti-platelet effects within 5 minutes (0.25mg/kg in rats, 4mg/kg in monkeys) which was maintained following intravenous infusion. The extent and duration of the effect were dose-dependent. Plasma concentrations increased linearly with the dose received. In toxicology studies, CA1001 was well tolerated and safe without bleeding nor platelet count reduction. The No Obvious Adverse Event Level in rats and monkeys were 25mg/kg, and 100mg/kg respectively, which are 10 and 25 times the therapeutic targeted doses.
Conclusion: The first-in-class humanized anti-GPIbα Fab CA1001 has potent anti-thrombotic effects, consistent PK/PD properties and favorable safety and tolerability profiles warranting further clinical development in healthy volunteers and patients with acute ischemic stroke.