Introduction: After vascular occlusion, there are two major zones of injury: the infarct core that rapidly dies, and the surrounding penumbra, which is hypoxic and at risk for infarction. Restoring blood flow by vascular recanalization (ie. endovascular +/- IV tPA) to prevent the penumbra from infarcting has become the new standard of care for acute ischemic stroke patients presenting with salvageable tissue. However, not all patients benefit from recanalization. Regardless of successful or partial reperfusion, secondary hypoxic events within the rescued penumbra can cause selective neuronal loss (SNL) that may account for suboptimal clinical recovery. OMX is a breakthrough oxygen delivery protein tuned to release oxygen specifically in hypoxic tissue and reduce hypoxia to prevent SNL within the reperfused penumbra.
Methods: To mimic the clinical situation whereby occlusion is followed by gradual reperfusion after spontaneous or therapeutic thrombolysis, we used the endothelin-1 induced middle cerebral artery occlusion (MCAO) model. OMX was administered intravenously up to 2h post-MCAO. Short and long-term histological and behavioral outcomes were used to assess hypoxia, apoptosis, gliosis, SNL, infarct volume and sensorimotor functions.
Results: Despite reperfusion, hypoxic tissue persists and progressively infarcts in vehicle-treated rats. However, OMX-treated rats showed no infarct expansion over 7d, indicating that OMX prevents infarction of the majority of hypoxic tissue. OMX reduces hypoxia and caspase 3/9 activity in a dose-dependent manner and significantly prevents SNL and gliosis. When administered post-MCAO, OMX significantly improves both sensory and motor functions (∼30-80% improvement, *p<0.05) in aged rats up to 28d post-MCAO. Moreover, extensive toxicology studies demonstrate that OMX is well tolerated in multiple species and can be used safely in combination with tPA.
Conclusions: OMX is a promising therapeutic candidate that can be administered in combination with reperfusion therapies to stabilize the at-risk hypoxic tissue and ameliorate long-term clinical outcomes in stroke patients.