Antibody-mediated depletion of human CLEC-2 in a novel humanised mouse model

Platelet C-type lectin-like receptor 2 (CLEC-2) has been proposed as a potential anti-thrombotic target as genetic or antibody-mediated receptor deficiency prevents occlusive thrombus formation in mice. This occurs through interaction with an unknown ligand as the endogenous ligand podoplanin is not present in the vasculature. However, the CLEC-2-podoplanin interaction does have an important role in tumour metastasis. There are currently no methods to test potential human therapeutics targeting CLEC-2, such as antibodies, in vivo . We have therefore generated and characterised a humanised CLEC-2 mouse (hCLEC-2 KI ) and developed a novel monoclonal anti-human CLEC-2 antibody, HEL1, for in vivo testing. hCLEC-2 KI mice were phenotypically normal and had comparable platelet glycoprotein receptor expression, activation and aggregation to wildtype platelets. hCLEC-2 KI mice had both comparable bleeding and vessel occlusion times to WT mice. Challenging hCLEC-2 KI mice with HEL1 or a second monoclonal anti-hCLEC-2 antibody, AYP1, resulted in transient thrombocytopenia as well as CLEC-2 depletion for more than 2 weeks but had no effect on haemostasis. This illustrates the power of the humanised CLEC-2 mouse model in evaluating novel therapeutics in vivo , including antibodies that target CLEC-2, as well as the limited effect on haemostasis when targeting CLEC-2.