Abstract P217: Direct Myosin-2 Inhibition Restores Cerebral Perfusion in Cortical and Subcortical Regions Resulting in Functional Improvement After Ischemic Stroke

Abstract

Inefficient cerebral reperfusion is a major unresolved problem in ischemic stroke treatment because hypoxia-induced constriction of capillaries remains persistent even after recanalization by thrombolysis or thrombectomy. Capillary constriction is mediated by actomyosin contraction in precapillary smooth muscle cells (SMCs). We have developed and tested a formulation and administration technique to target the ischemic brain region and developed a promising small-molecule myosin-2 inhibitor (para-aminoblebbistatin (AmBleb) that mainly exerts its effect through direct inhibition of smooth muscle myosin-2 (SMM) in SMCs. The efficacy of SMM inhibition was tested in a rodent transient Middle Cerebral Artery Occlusion (tMCAO) stroke model. SMM was targeted by the direct administration of AmBleb into the ischemic region. AmBleb significantly accelerated the improvement of neurological deficits. Regional cerebral blood flow (rCBF) in the most important cortical and subcortical regions (e.g. motor- and somatosensory cortices, optic pathways, striatum, corpus callosum) showed drastic improvement in the AmBleb treated animals in line with the significant reduction of neurological deficits. We further optimized AmBleb and developed our lead compound MPH-222, which possesses significantly improved pharmacological properties than those of AmBleb. As observed with AmBleb, MPH-222 also fully relaxed isolated human and rat cerebral arterioles, and improved neurological functions of tMCAO operated rats characterized by significantly improved neurological deficits as well as enhanced locomotor symmetry. Moreover, as opposed to AmBleb, markedly lower MPH-222 dose was enough to achieve efficient concentrations in the ischemic region when catheter-based direct intra-arterial administration was applied. This result suggests that direct myosin inhibitor administration may be an optimal add-on therapy to thrombectomy. Funded by the Hungarian National Research, Development and Innovation Office (NVKP 16-1-2016-0051 and PIACI-KFI-2019-00488).