Hyperacute therapy of acute ischemic stroke: intraarterial thrombolysis and mechanical revascularization strategies

Plasmin (Human) Administration in Acute Middle Cerebral Artery Ischemic Stroke: Phase 1/2a, Open-Label, Dose-Escalation, Safety Study

BACKGROUND

This phase 1/2a, open-label, multicenter, dose-escalation, safety study describes the first evaluation of plasmin as an intracranial thrombolytic treatment for acute ischemic stroke in the middle cerebral artery. The rationale for intrathrombus administration is that plasmin would bind fibrin inside the targeted clot, protecting it from circulating inhibitors.

METHODS

Plasmin was given in escalating doses within 9 hours of stroke onset, and treatment efficacy was determined in 5 patient cohorts (N = 40): cohort 1 (20 mg, .5 mL/min), cohort 2a (40 mg, .05 mL/min), cohort 2b (40 mg, .33 mL/min), cohort 3a (80 mg, .67 mL/min), and cohort 3b (80 mg, .33 mL/min).

RESULTS

Plasmin was generally safe at doses as high as 80 mg. No symptomatic intracranial hemorrhage was observed, and the rate of asymptomatic intracranial hemorrhage (12.5%) was consistent with that expected under supportive care. No relationship was observed between the plasmin dose and the incidence or severity of bleeding events, any particular serious adverse events, nor death. Changes in clinical chemistry, hematology, and coagulation parameters following plasmin treatment were unremarkable and unrelated to the dose. Plasmin administration resulted in successful reperfusion of the occluded vessel in 25% of patients across all cohorts, with no relationship between successful perfusion and total plasmin dose but a potential increase in reperfusion with slower infusion rates.

CONCLUSIONS

Plasmin treatment of the occluded middle cerebral artery within 9 hours of stroke onset was well tolerated and did notincrease adverse outcomes; however, successful recanalization was achieved in only a limited number of patients.

NADPH oxidase in stroke and cerebrovascular disease

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) was originally identified in immune cells as playing an important microbicidal role. In stroke and cerebrovascular disease, inflammation is increasingly being recognized as contributing negatively to neurological outcome, with NOX as an important source of superoxide. Several labs have now shown that blocking or deleting NOX in the experimental stroke models protects from brain ischemia. Recent work has implicated glucose as an important NOX substrate leading to reperfusion injury, and that NOX inhibition can improve the detrimental effects of hyperglycemia on stroke. NOX inhibition also appears to ameliorate complications of thrombolytic therapy by reducing blood-brain barrier disruption, edema formation, and hemorrhage. Further, NOX from circulating inflammatory cells seems to contribute more to ischemic injury more than NOX generated from endogenous brain residential cells. Several pharmacological inhibitors of NOX are now available. Thus, blocking NOX activation may prove to be a promising treatment for stroke as well as an adjunctive agent to prevent its secondary complications.

Good clinical outcome after ischemic stroke with successful revascularization is time-dependent

BACKGROUND

Trials of IV recombinant tissue plasminogen activator (rt-PA) have demonstrated that longer times from ischemic stroke symptom onset to initiation of treatment are associated with progressively lower likelihoods of clinical benefit, and likely no benefit beyond 4.5 hours. How the timing of IV rt-PA initiation relates to timing of restoration of blood flow has been unclear. An understanding of the relationship between timing of angiographic reperfusion and clinical outcome is needed to establish time parameters for intraarterial (IA) therapies.

METHODS

The Interventional Management of Stroke pilot trials tested combined IV/IA therapy for moderate-to-severe ischemic strokes within 3 hours from symptom onset. To isolate the effect of time to angiographic reperfusion on clinical outcome, we analyzed only middle cerebral artery and distal internal carotid artery occlusions with successful reperfusion (Thrombolysis in Cerebral Infarction 2-3) during the interventional procedure (<7 hours). Time to angiographic reperfusion was defined as time from stroke onset to procedure termination. Good clinical outcome was defined as modified Rankin Score 0-2 at 3 months.

RESULTS

Among the 54 cases, only time to angiographic reperfusion and age independently predicted good clinical outcome after angiographic reperfusion. The probability of good clinical outcome decreased as time to angiographic reperfusion increased (unadjusted p = 0.02, adjusted p = 0.01) and approached that of cases without angiographic reperfusion within 7 hours.

CONCLUSIONS

We provide evidence that good clinical outcome following angiographically successful reperfusion is significantly time-dependent. At later times, angiographic reperfusion may be associated with a poor risk-benefit ratio in unselected patients.

Intracarotid delivery of drugs: the potential and the pitfalls

The major efforts to selectively deliver drugs to the brain in the past decade have relied on smart molecular techniques to penetrate the blood-brain barrier, whereas intraarterial drug delivery has drawn relatively little attention. Meanwhile, rapid progress has been made in the field of endovascular surgery. Modern endovascular procedures can permit highly targeted drug delivery by the intracarotid route. Intracarotid drug delivery can be the primary route of drug delivery or it could be used to facilitate the delivery of smart neuropharmaceuticals. There have been few attempts to systematically understand the kinetics of intracarotid drugs. Anecdotal data suggest that intracarotid drug delivery is effective in the treatment of cerebral vasospasm, thromboembolic strokes, and neoplasms. Neuroanesthesiologists are frequently involved in the care of such high-risk patients. Therefore, it is necessary to understand the applications of intracarotid drug delivery and the unusual kinetics of intracarotid drugs.

Intra-arterial drug delivery: a concise review

The therapeutic potential of intra-arterial (IA) drug delivery to the brain has received limited attention in the last decade. In the 1980s, efforts to treat brain tumors with IA chemotherapy, the leading application of this technology, yielded modest results. Poor control of tissue drug concentrations and the potential risk of permanent neurologic injury further prevented the wider use of IA drugs. Yet, IA drugs were anecdotally used for treating a wide spectrum of brain diseases. Recent advances in endovascular technology and the increased safety of angiographic procedures now compel us to reevaluate IA drug delivery. This review describes the pharmacologic principles, applications, and pitfalls of IA drug delivery to the brain.

Perspectives on neuroprotective stroke therapy

After years of setbacks, the perspective of neuroprotective stroke therapy has revived in light of recent study results. We outline in this review how a neuroprotective candidate drug should be developed, beginning with a thorough preclinical evaluation according to the STAIR (Stroke Therapy Academic Industry Roundtable) criteria. Assessing the safety of the candidate drug in the relatively straightforward Phase IIA would be the first step into clinical development. While advancing into Phase IIB, the implementation of a responder analysis, the use of a surrogate biomarker as well as the use of Bayesian methodology should be considered to increase the likelihood of seeing any therapeutic sign. Clinical development in Phase III should consider that previously used dichotomized endpoints appropriate for evaluation of thrombolytic drugs are likely to be insufficient for assessing efficacy of neuroprotective drugs. Detection of a clinically relevant shift in the outcome measure appears to be a more relevant approach for the type of drug that achieves a reduction and not a reverse of the ischaemic lesion.