Failure to improve the effect of thrombolysis by memantine in a rat embolic stroke model

Kallmes D. Memantine for the treatment of ischemic stroke: experimental benefits and clinical lack of studies

Stroke is an important cause of mortality and disability worldwide. Immediately after stroke onset, the ischemic cascade initiates and deleteriously affects neural cells. Time to reperfusion therapy is a critical determinant of functional recovery in stroke patients. Although recent trials have shown the significant efficacy of endovascular thrombectomy, either alone or with intravenous tissue plasminogen activator, in improving the functional outcomes of stroke patients with large vessel occlusion, hours can pass before patients receive reperfusion therapy. Moreover, many patients do not meet the eligibility criteria to receive reperfusion treatments. Therefore, an adjunct and alternative agent that can protect ischemic neuronal tissue during the hyperacute phase until reperfusion therapy can be administered may prevent further brain damage and enhance functional recovery. Memantine is a US Food and Drug Administration approved drug for the treatment of Alzheimer’s disease. Memantine blocks overstimulated N-methyl-d-aspartate receptors and prevents neurotoxicity caused by massive glutamate release. Preclinical studies show that memantine decreases infarction volume and improves neurologic outcomes. However, few clinical studies have evaluated the safety and efficacy of memantine in stroke patients. This review article summarizes the current evidence for the role of memantine in the treatment of ischemic stroke and highlights areas for future research.

Memantine improves safety of thrombolysis for stroke

BACKGROUND AND PURPOSE

Despite side effects including N-methyl-d-aspartate-mediated neurotoxicity, recombinant tissue-type plasminogen activator (rtPA) remains the only approved acute treatment for ischemic stroke. Memantine, used for treatment of Alzheimer disease, is an antagonist for N-methyl-d-aspartate receptors. We investigated whether memantine could be used as a neuroprotective adjunct therapy for rtPA-induced thrombolysis after stroke.

METHODS

In vitro N-methyl-d-aspartate exposure, oxygen and glucose deprivation, and N-methyl-d-aspartate-mediated calcium videomicroscopy experiments were performed on murine cortical neurons in the presence of rtPA and memantine. The therapeutic safety of rtPA and memantine coadministration was evaluated in mouse models of thrombotic stroke and intracerebral hemorrhage. Ischemic and hemorrhagic volumes were assessed by MRI and neurological evaluation was performed by the string test and automated gait analysis.

RESULTS

Our in vitro observations showed that memantine was able to prevent the proneurotoxic effects of rtPA in cultured cortical neurons. Although memantine did not alter the fibrinolytic activity of rtPA, our in vivo observations revealed that it blunted the noxious effects of delayed thrombolysis on lesion volumes and neurological deficits after ischemic stroke. In addition, memantine rescued rtPA-induced decrease in survival rate after intracerebral hemorrhage.

CONCLUSIONS

Memantine could be used as an adjunct therapy to improve the safety of thrombolysis.

Preclinical stroke research--advantages and disadvantages of the most common rodent models of focal ischaemia

This review describes the most commonly used rodent models and outcome measures in preclinical stroke research and discusses their strengths and limitations. Most models involve permanent or transient middle cerebral artery occlusion with therapeutic agents tested for their ability to reduce stroke-induced infarcts and improve neurological deficits. Many drugs have demonstrated preclinical efficacy but, other than thrombolytics, which restore blood flow, none have demonstrated efficacy in clinical trials. This failure to translate efficacy from bench to bedside is discussed alongside achievable steps to improve the ability of preclinical research to predict clinical efficacy: (i) Improvements in study quality and reporting. Study design must include randomization, blinding and predefined inclusion/exclusion criteria, and journal editors have the power to ensure statements on these and mortality data are included in preclinical publications. (ii) Negative and neutral studies must be published to enable preclinical meta-analyses and systematic reviews to more accurately predict drug efficacy in man. (iii) Preclinical groups should work within networks and agree on standardized procedures for assessing final infarct and functional outcome. This will improve research quality, timeliness and translational capacity. (iv) Greater uptake and improvements in non-invasive diagnostic imaging to detect and study potentially salvageable penumbral tissue, the target for acute neuroprotection. Drug effects on penumbra lifespan studied serially, followed by assessment of behavioural outcome and infarct within in the same animal group, will increase the power to detect drug efficacy preclinically. Similar progress in detecting drug efficacy clinically will follow from patient recruitment into acute stroke trials based on evidence of remaining penumbra.