Work

Antibody-mediated VWF targeting reconstitutes ADAMTS13 metalloproteinase activity and prevents thrombocytopenia in mice

Year: 2026

Type: preprint

Abstract: ADAMTS13 (a multidomain metalloproteinase) cleaves von Willebrand factor (VWF), thereby preventing the accumulation of ultra-large VWF multimers that promote platelet-rich thrombus formation. Severe ADAMTS13 deficiency causes thrombotic thrombocytopenic purpura (TTP). In immune-mediated TTP (iTTP), anti-ADAMTS13 autoantibodies inhibit ADAMTS13 activity, often by targeting non-catalytic domains that mediate substrate recognition. We developed ADAMTS13 mimetics by fusing the ADAMTS13 metalloproteinase domain to anti-human VWF A2 domain antibodies, aiming to replace native substrate-recognition domains with antibody-mediated substrate targeting while removing major autoantibody-targeted ADAMTS13 domains. The resulting mimetics bound to the recombinant VWF A2 domain and showed proteolytic activity toward both the recombinant VWF A2 domain and FRETS-VWF73 substrate. Kinetic analysis showed that the mimetics had not only lower k cat values than ADAMTS13 but also lower K m values, thereby maintaining overall catalytic efficiency. Importantly, ADAMTS13 mimetics retained VWF A2-cleaving activity in the presence of a spacer domain-directed anti-ADAMTS13 autoantibody both in vitro and in vivo . In an iTTP mouse model, ADAMTS13 mimetics prevented recombinant VWF-induced thrombocytopenia, whereas the parental anti-VWF A2 domain antibody did not. Platelet-preserving activity was also observed in ADAMTS13-deficient mice. In further analyses, some mimetics showed reduced binding to a conformationally restricted VWF A2 domain, resulting in reduced cleavage activity. Antibody binding correlated with platelet recovery in the iTTP mouse model, suggesting that epitope accessibility and antibody-mediated positioning contribute to in vivo activity. These findings demonstrate that antibody-mediated substrate targeting can reconstitute the VWF-cleaving activity of the ADAMTS13 metalloproteinase domain and suggest that ADAMTS13 mimetics represent a potential therapeutic approach for iTTP.

Source: bioRxiv (Cold Spring Harbor Laboratory)

DOI: 10.64898/2026.09.11.750821