Development and in vitro characterization of humanized antibodies for blocking human TRPM4 channel

Transient receptor potential melastatin 4 (TRPM4) channel, a monovalent cation channel, plays a crucial role in various neurological disorders. We previously showed that TRPM4 activity can be blocked by our antibodies: M4P, which targets rat TRPM4 and M4M, against a similar antigenic epitope of human TRPM4. M4P and M4M demonstrated efficacy in mitigating stroke reperfusion injury. To facilitate human application, M4M was humanized through CDR grafting, resulting in human IgG1 antibodies (Ab1-6). These antibodies were evaluated for their binding affinity, surface staining, stability, and functional inhibition of the human TRPM4 channel. Ab6 (renamed as M4H) was selected and inhibited TRPM4 currents in human brain microvascular endothelial cells under ATP depletion conditions. Importantly, Ab6 (M4H) suppressed ATP depletion-induced cell swelling, indicating its potential for managing vascular injury in ischemic brain diseases. Future studies on animal models could advance the development of novel therapies of neurological disorders with vascular injury.