# A Novel Human Anti-FV mAb as a Potential Tool for Diagnostic and Coagulation Inhibitory Approaches

## TL;DR

A new human antibody targeting Factor V shows promise for both anticoagulant therapy and diagnostic use.

## Contribution

A novel human monoclonal antibody (D9) with high specificity for Factor V is developed and characterized.

## Key findings

- D9 binds Factor V with low nM affinity and minimal cross-reactivity with other coagulation factors.
- D9 prolongs activated partial thromboplastin time (aPTT), indicating anticoagulant potential.
- D9 could serve as a diagnostic and research tool due to its high specificity.

## Abstract

Cardiovascular diseases, including thrombosis, are the leading cause of mortality worldwide. The generation of monoclonal antibodies (mAb) targeting specific coagulation factors could provide more targeted and safer anticoagulant therapies. Factor V (FV) is a critical cofactor in the prothrombinase complex, which catalyzes the conversion of prothrombin to thrombin, a key enzyme in the coagulation cascade. We isolated a novel human antibody specific to FV by using phage display technology. The selection occurred by panning a large repertoire of phages expressing human antibody fragments (scFv) in parallel on the purified recombinant protein in its native form (FV) or activated by proteolytic maturation (Factor Va (FVa)). Through ELISA screening, we identified the clone with the highest binding affinity for both targets, and it was successfully converted into IgG1. The novel human mAb, called D9, was found capable of binding to Factor V with a low nM affinity both by ELISA and BLI assays, whereas its cross-reactivity with some other coagulation factors was found null or very poor. Furthermore, when tested in blood clotting tests, it was found able to prolong activated partial thromboplastin time (aPTT). Thus, D9 could become not only a potential therapeutic agent as a specific anticoagulant but also a precious tool for diagnostic and research applications.