Techniques: Antibody-based protease inhibitors

In vitro studies suggest insertion of disulfide-bridged peptide inhibitors of serine proteases into antibody CDR3 domains could generate protease inhibitors with high target affinity and specificity. The CDR3H loop of a human antibody against lysozyme was replaced with a ten-residue disulfide-bridged peptide inhibitor of human neutrophil elastase (NE; ELA-2), flanked by two seven-residue stalks derived from the bovine CDR3H loop. In vitro, the antibody bound NE with a Kd of 0.79 nM and inhibited NE activity with a Ki of 0.83 nM - compared with a Ki of 91.8 nM for the free peptide inhibitor - but did not inhibit the related serine proteases, trypsin and chymotrypsin, at concentrations up to 1 μM. Next steps include efficacy studies in vivo and PK studies to compare the half-life of the antibody with published values of Elafin. ...