Lubeluzole for acute ischaemic stroke

Cerebrolysin for acute ischaemic stroke

BACKGROUND

Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from porcine brain, which has potential neuroprotective properties. It is widely used in the treatment of acute ischaemic stroke in Russia, Eastern Europe, China, and other Asian and post-Soviet countries. This is an update of a review first published in 2010 and last updated in 2020.

OBJECTIVES

To assess the benefits and harms of Cerebrolysin or Cerebrolysin-like agents for treating acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Trials Register, CENTRAL, MEDLINE, Embase, Web of Science Core Collection, with Science Citation Index, and LILACS in May 2022 and a number of Russian databases in June 2022. We also searched reference lists, ongoing trials registers, and conference proceedings.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing Cerebrolysin or Cerebrolysin-like agents started within 48 hours of stroke onset and continued for any length of time, with placebo or no treatment in people with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Three review authors independently applied the inclusion criteria, assessed trial quality and risk of bias, extracted data, and applied GRADE criteria to the evidence.

MAIN RESULTS

Seven RCTs (1773 participants) met the inclusion criteria of the review. In this update we added one RCT of Cerebrolysin-like agent Cortexin, which contributed 272 participants. We used the same approach for risk of bias assessment that was re-evaluated for the previous update: we added consideration of the public availability of study protocols and reported outcomes to the selective outcome reporting judgement, through identification, examination, and evaluation of study protocols. For the Cerebrolysin studies, we judged the risk of bias for selective outcome reporting to be unclear across all studies; for blinding of participants and personnel to be low in three studies and unclear in the remaining four; and for blinding of outcome assessors to be low in three studies and unclear in four studies. We judged the risk of bias for generation of allocation sequence to be low in one study and unclear in the remaining six studies; for allocation concealment to be low in one study and unclear in six studies; and for incomplete outcome data to be low in three studies and high in the remaining four studies. The manufacturer of Cerebrolysin supported three multicentre studies, either totally, or by providing Cerebrolysin and placebo, randomisation codes, research grants, or statisticians. We judged two studies to be at high risk of other bias and the remaining five studies to be at unclear risk of other bias. We judged the study of Cortexin to be at low risk of bias for incomplete outcome data and at unclear risk of bias for all other domains. All-cause death: Cerebrolysin or Cortexin probably result in little to no difference in all-cause death (risk ratio (RR) 0.96, 95% confidence interval (CI) 0.65 to 1.41; 6 trials, 1689 participants; moderate-certainty evidence). None of the included studies reported on poor functional outcome, defined as death or dependence at the end of the follow-up period, early death (within two weeks of stroke onset), quality of life, or time to restoration of capacity for work. Only one study clearly reported on the cause of death: cerebral infarct (four in the Cerebrolysin and two in the placebo group), heart failure (two in the Cerebrolysin and one in the placebo group), pulmonary embolism (two in the placebo group), and pneumonia (one in the placebo group). Non-death attrition (secondary outcome): Cerebrolysin or similar peptide mixtures may result in little to no difference in non-death attrition, but the evidence is very uncertain, with a considerable level of heterogeneity (RR 0.72, 95% CI 0.38 to 1.39; 6 trials, 1689 participants; very low-certainty evidence). Serious adverse events (SAEs): Cerebrolysin probably results in little to no difference in the total number of people with SAEs (RR 1.16, 95% CI 0.81 to 1.66; 3 trials, 1335 participants; moderate-certainty evidence). This comprised fatal SAEs (RR 0.90, 95% CI 0.59 to 1.38; 3 trials, 1335 participants; moderate-certainty evidence) and an increase in the total number of people with non-fatal SAEs (RR 2.39, 95% CI 1.10 to 5.23; 3 trials, 1335 participants; moderate-certainty evidence). In the subgroup of dosing schedule 30 mL for 10 days (cumulative dose 300 mL), the increase was more prominent (RR 2.87, 95% CI 1.24 to 6.69; 2 trials, 1189 participants). Total number of people with adverse events: Cerebrolysin or similar peptide mixtures may result in little to no difference in the total number of people with adverse events (RR 1.03, 95% CI 0.92 to 1.14; 4 trials, 1607 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

Moderate-certainty evidence indicates that Cerebrolysin or Cerebrolysin-like peptide mixtures derived from cattle brain probably have no beneficial effect on preventing all-cause death in acute ischaemic stroke. Moderate-certainty evidence suggests that Cerebrolysin probably has no beneficial effect on the total number of people with serious adverse events. Moderate-certainty evidence also indicates a potential increase in non-fatal serious adverse events with Cerebrolysin use.

Mitochondria in Cell-Based Therapy for Stroke

Despite a relatively developed understanding of the pathophysiology underlying primary and secondary mechanisms of cell death after ischemic injury, there are few established treatments to improve stroke prognoses. A major contributor to secondary cell death is mitochondrial dysfunction. Recent advancements in cell-based therapies suggest that stem cells may be revolutionary for treating stroke, and the reestablishment of mitochondrial integrity may underlie these therapeutic benefits. In fact, functioning mitochondria are imperative for reducing oxidative damage and neuroinflammation following stroke and reperfusion injury. In this review, we will discuss the role of mitochondria in establishing the anti-oxidative effects of stem cell therapies for stroke.

Lubeluzole Repositioning as Chemosensitizing Agent on Multidrug-Resistant Human Ovarian A2780/DX3 Cancer Cells

In a previous paper, we demonstrated the synergistic action of the anti-ischemic lubeluzole (Lube S) on the cytotoxic activity of doxorubicin (Dox) and paclitaxel in human ovarian cancer A2780 and lung cancer A549 cells. In the present paper, we extended in vitro the study to the multi-drug-resistant A2780/DX3 cell line to verify the hypothesis that the Dox and Lube S drug association may potentiate the antitumor activity of this anticancer compound also in the context of drug resistance. We also evaluated some possible mechanisms underlying this activity. We analyzed the antiproliferative activity in different cancer cell lines. Furthermore, apoptosis, Dox accumulation, MDR1 downregulation, ROS, and NO production in A2780/DX3 cells were also evaluated. Our results confirm that Lube S improves Dox antiproliferative and apoptotic activities through different mechanisms of action, all of which may contribute to the final antitumor effect. Moderate stereoselectivity was found, with Lube S significantly more effective than its enantiomer (Lube R) and the corresponding racemate (Lube S/R). Docking simulation studies on the ABCB1 Cryo-EM structure supported the hypothesis that Lube S forms a stable MDR1-Dox-Lube S complex, which hampers the protein transmembrane domain flipping and blocks the efflux of Dox from resistant A2780/DX3 cells. In conclusion, our in vitro studies reinforce our previous hypothesis for repositioning the anti-ischemic Lube S as a potentiating agent in anticancer chemotherapy.

The Development of Novel Drug Treatments for Stroke Patients: A Review

Acute ischemic stroke is a critical condition that can result in disability and death. The consequences of this medical condition depend on various factors, including the size of the stroke, affected brain region, treatment onset, and the type of treatment. The primary objective of stroke treatment is to restart ischemic penumbra tissue perfusion and reduce infarct volume by sustaining blood flow. Recent research on the condition’s pathological pathways and processes has significantly improved treatment options beyond restoring perfusion. Many studies have concentrated on limiting injury severity via the manipulation of molecular mechanisms of ischemia, particularly in animal research. This article reviews completed and ongoing research on the development of acute ischemic stroke drugs. This study focuses on three main categories of antithrombotic drugs, thrombolytic drugs, and neuroprotective agents. The paper outlines findings from animal and clinical trials and explores the working mechanisms of these drugs.

Oxidative Stress in Ischemia/Reperfusion Injuries following Acute Ischemic Stroke

Recanalization therapy is increasingly used in the treatment of acute ischemic stroke. However, in about one third of these patients, recanalization is followed by ischemia/reperfusion injuries, and clinically to worsening of the neurological status. Much research has focused on unraveling the involved mechanisms in order to prevent or efficiently treat these injuries. What we know so far is that oxidative stress and mitochondrial dysfunction are significantly involved in the pathogenesis of ischemia/reperfusion injury. However, despite promising results obtained in experimental research, clinical studies trying to interfere with the oxidative pathways have mostly failed. The current article discusses the main mechanisms leading to ischemia/reperfusion injuries, such as mitochondrial dysfunction, excitotoxicity, and oxidative stress, and reviews the clinical trials with antioxidant molecules highlighting recent developments and future strategies.

Cerebrolysin for acute ischaemic stroke

BACKGROUND

Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from porcine brain that has potential neuroprotective properties. It is widely used in the treatment of acute ischaemic stroke in Russia, Eastern Europe, China, and other Asian and post-Soviet countries. This is an update of a review first published in 2010 and last updated in 2017.

OBJECTIVES

To assess the benefits and harms of Cerebrolysin for treating acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE, Embase, Web of Science Core Collection, with Science Citation Index, LILACS, OpenGrey, and a number of Russian databases in October 2019. We also searched reference lists, ongoing trials registers, and conference proceedings.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing Cerebrolysin, started within 48 hours of stroke onset and continued for any length of time, with placebo or no treatment in people with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria, assessed trial quality and risk of bias, extracted data, and applied GRADE criteria to the evidence.

MAIN RESULTS

Seven RCTs (1601 participants) met the inclusion criteria of the review. In this update we re-evaluated risk of bias through identification, examination, and evaluation of study protocols and judged it to be low, unclear, or high across studies: unclear for all domains in one study, and unclear for selective outcome reporting across all studies; low for blinding of participants and personnel in four studies and unclear in the remaining three; low for blinding of outcome assessors in three studies and unclear in four studies. We judged risk of bias to be low in two studies and unclear in the remaining five studies for generation of allocation sequence; low in one study and unclear in six studies for allocation concealment; and low in one study, unclear in one study, and high in the remaining five studies for incomplete outcome data. The manufacturer of Cerebrolysin supported four multicentre studies, either totally, or by providing Cerebrolysin and placebo, randomisation codes, research grants, or statisticians. We judged three studies to be at high risk of other bias and the remaining four studies to be at unclear risk of other bias. All-cause death: we extracted data from six trials (1517 participants). Cerebrolysin probably results in little to no difference in all-cause death: risk ratio (RR) 0.90, 95% confidence interval (CI) 0.61 to 1.32 (6 trials, 1517 participants, moderate-quality evidence). None of the included trials reported on poor functional outcome defined as death or dependence at the end of the follow-up period or early death (within two weeks of stroke onset), or time to restoration of capacity for work and quality of life. Only one trial clearly reported on the cause of death: cerebral infarct (four in the Cerebrolysin and two in the placebo group), heart failure (two in the Cerebrolysin and one in the placebo group), pulmonary embolism (two in the placebo group), and pneumonia (one in the placebo group). Serious adverse events (SAEs): Cerebrolysin probably results in little to no difference in the total number of people with SAEs (RR 1.15, 95% CI 0.81 to 1.65, 4 RCTs, 1435 participants, moderate-quality evidence). This comprised fatal SAEs (RR 0.90, 95% CI 0.59 to 1.38) and an increase in the total number of people with non-fatal SAEs (RR 2.15, 95% CI 1.01 to 4.55, P = 0.047, 4 trials, 1435 participants, moderate-quality evidence). In the subgroup of dosing schedule 30 mL for 10 days (cumulative dose 300 mL), the increase was more prominent: RR 2.86, 95% CI 1.23 to 6.66, P = 0.01 (2 trials, 1189 participants). Total number of people with adverse events: four trials reported on this outcome. Cerebrolysin may result in little to no difference in the total number of people with adverse events: RR 0.97, 95% CI 0.85 to 1.10, P = 0.90, 4 trials, 1435 participants, low-quality evidence. Non-death attrition: evidence from six trials involving 1517 participants suggests that Cerebrolysin results in little to no difference in non-death attrition, with 96 out of 764 Cerebrolysin-treated participants and 117 out of 753 placebo-treated participants being lost to follow-up for reasons other than death (very low-quality evidence).

AUTHORS' CONCLUSIONS

Moderate-quality evidence indicates that Cerebrolysin probably has little or no beneficial effect on preventing all-cause death in acute ischaemic stroke, or on the total number of people with serious adverse events. Moderate-quality evidence also indicates a potential increase in non-fatal serious adverse events with Cerebrolysin use.

Pre-clinical to Clinical Translational Failures and Current Status of Clinical Trials in Stroke Therapy: A Brief Review

In stroke (cerebral ischemia), despite continuous efforts both at the experimental and clinical level, the only approved pharmacological treatment has been restricted to tissue plasminogen activator (tPA). Stroke is the leading cause of functional disability and mortality throughout worldwide. Its pathophysiology starts with energy pump failure, followed by complex signaling cascade that ultimately ends in neuronal cell death. Ischemic cascade involves excessive glutamate release followed by raised intracellular sodium and calcium influx along with free radicals' generation, activation of inflammatory cytokines, NO synthases, lipases, endonucleases and other apoptotic pathways leading to cell edema and death. At the pre-clinical stage, several agents have been tried and proven as an effective neuroprotectant in animal models of ischemia. However, these agents failed to show convincing results in terms of efficacy and safety when the trials were conducted in humans following stroke. This article highlights the various agents which have been tried in the past but failed to translate into stroke therapy along with key points that are responsible for the lagging of experimental success to translational failure in stroke treatment.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebrovascular disease. However, the sedative effects of GABA receptor agonists have limited their wider application in people with acute stroke, due to the potential risk of stupor. This is an update of a Cochrane Review first published in 2013, and previously updated in 2014 and 2016.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (accessed May 2018), the Cochrane Central Register of Controlled Trials (CENTRAL) 2018, Issue 4 (accessed May 2018), MEDLINE (from 1949 to May 2018), Embase (from 1980 to May 2018), CINAHL (from 1982 to May 2018), AMED (from 1985 to May 2018), and 11 Chinese databases (accessed May 2018). In an effort to identify further published, unpublished, and ongoing trials we searched ongoing trial registers, reference lists, and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for people with acute stroke (within 12 hours after stroke onset), with the primary outcomes of efficacy and safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy, and assessed the risk of bias. We used the GRADE approach to assess the quality of the evidence.

MAIN RESULTS

We included five trials with 3838 participants (acute ischemic or hemorrhagic stroke patients, 3758 analyzed). Most of the participants recruited had acute ischaemic stroke, with limited data available from participants with other stroke subtypes, including total anterior circulation syndrome (TACS). The methodological quality of the included trials was generally good, with an unclear risk for selection bias only. For death and dependency at three months, pooled results did not find a significant difference for chlormethiazole versus placebo (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.96 to 1.11; four trials; 2909 participants; moderate-quality evidence) and for diazepam versus placebo (RR 0.94, 95% CI 0.82 to 1.07; one trial; 849 participants; moderate-quality evidence). The most frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95; two trials; 2527 participants; moderate-quality evidence) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46; two trials; 2527 participants; moderate-quality evidence).

AUTHORS' CONCLUSIONS

This review provides moderate-quality evidence that fails to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of people with acute stroke. More well-designed RCTs with large samples of participants with total anterior circulation syndrome are required to determine if there are benefits for this subgroup. Somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Cerebrolysin for acute ischaemic stroke

BACKGROUND

Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from pigs' brain tissue, which has potential neuroprotective and neurotrophic properties. It is widely used in the treatment of acute ischaemic stroke in Russia, Eastern Europe, China, and other Asian and post-Soviet countries.

OBJECTIVES

To assess the benefits and risks of cerebrolysin for treating acute ischaemic stroke.

SEARCH METHODS

In May 2016 we searched the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE, Embase, Web of Science Core Collection, with Science Citation Index, LILACS, OpenGrey, and a number of Russian Databases. We also searched reference lists, ongoing trials registers and conference proceedings, and contacted the manufacturer of cerebrolysin, EVER Neuro Pharma GmbH (formerly Ebewe Pharma).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing cerebrolysin, started within 48 hours of stroke onset and continued for any time, with placebo or no treatment in people with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied inclusion criteria, assessed trial quality and risk of bias, and extracted data.

MAIN RESULTS

We identified six RCTs (1501 participants) that met the inclusion criteria.We evaluated risk of bias and judged it to be unclear for generation of allocation sequence in four studies and low in two studies; unclear for allocation concealment in five studies and low in one study; high for incomplete outcome data (attrition bias) in five studies and unclear in one study; unclear for blinding; high for selective reporting in four studies and unclear in two; and high for other sources of bias in three studies and unclear in the rest. The manufacturer of cerebrolysin, pharmaceutical company EVER Neuro Pharma, supported three multi-centre studies, either totally, or providing cerebrolysin and placebo, randomisation codes, research grants, or statisticians.None of the included trials reported on poor functional outcome defined as death or dependence at the end of the follow-up period or early death (within two weeks of stroke onset).All-cause death: we extracted data from five trials (1417 participants). There was no difference in the number of deaths: 46/714 in cerebrolysin group versus 47/703 in placebo group; risk ratio (RR) 0.91 95% confidence interval (CI) 0.61 to 1.35 (5 trials, 1417 participants, moderate-quality evidence).Serious adverse events (SAEs): there was no significant difference in the total number of SAEs with cerebrolysin (RR 1.16, 95% CI 0.81 to 1.67). This comprised no difference in fatal SAEs (RR 0.90, 95% CI 0.59 to 1.38) and an increase in the number of people with non-fatal SAEs (20/667 with cerebrolysin and 8/668 with placebo: RR 2.47, 95% CI 1.09 to 5.58, P = 0.03) (3 trials, 1335 participants, moderate-quality evidence).Total number of people with adverse events: three trials reported on this. There was no difference in the total number of people with adverse events: 308/667 in cerebrolysin group versus 307/668 in placebo group; RR 0.97 95% CI 0.86 to 1.09, random-effects model (3 trials, 1335 participants, moderate-quality evidence).

AUTHORS' CONCLUSIONS

The findings of this Cochrane Review do not demonstrate clinical benefits of cerebrolysin for treating acute ischaemic stroke. We found moderate-quality evidence of an increase in non-fatal SAEs with cerebrolysin use but not in total SAEs.

Cerebrolysin for acute ischaemic stroke

BACKGROUND

Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from pigs' brain tissue, which has potential neuroprotective and neurotrophic properties. It is widely used in the treatment of acute ischaemic stroke in Russia, Eastern Europe, China, and other Asian and post-Soviet countries.

OBJECTIVES

To assess the benefits and risks of cerebrolysin for treating acute ischaemic stroke.

SEARCH METHODS

In May 2016 we searched the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE, Embase, Web of Science Core Collection, with Science Citation Index, LILACS, OpenGrey, and a number of Russian Databases. We also searched reference lists, ongoing trials registers and conference proceedings, and contacted the manufacturer of cerebrolysin, EVER Neuro Pharma GmbH (formerly Ebewe Pharma).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing cerebrolysin, started within 48 hours of stroke onset and continued for any time, with placebo or no treatment in people with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied inclusion criteria, assessed trial quality and risk of bias, and extracted data.

MAIN RESULTS

We identified six RCTs (1501 participants) that met the inclusion criteria.We evaluated risk of bias and judged it to be unclear for generation of allocation sequence in four studies and low in two studies; unclear for allocation concealment in five studies and low in one study; high for incomplete outcome data (attrition bias) in five studies and unclear in one study; unclear for blinding; high for selective reporting in four studies and unclear in two; and high for other sources of bias in three studies and unclear in the rest. The manufacturer of cerebrolysin, pharmaceutical company EVER Neuro Pharma, supported three multi-centre studies, either totally, or providing cerebrolysin and placebo, randomisation codes, research grants, or statisticians.None of the included trials reported on poor functional outcome defined as death or dependence at the end of the follow-up period or early death (within two weeks of stroke onset).All-cause death: we extracted data from five trials (1417 participants). There was no difference in the number of deaths: 46/714 in cerebrolysin group versus 47/703 in placebo group; risk ratio (RR) 0.91 95% confidence interval (CI) 0.61 to 1.35 (5 trials, 1417 participants, moderate-quality evidence).Serious adverse events: two trials reported on this outcome, with 90% confidence cerebrolysin increased the risks of serious adverse events by at least one third compared to placebo: 62/589 in cerebrolysin group versus 46/600 in placebo group; RR 1.37 90% CI 1.01 to 1.86 (2 trials, 1189 participants, moderate-quality evidence).Total number of people with adverse events: three trials reported on this. There was no difference in the total number of people with adverse events: 308/667 in cerebrolysin group versus 307/668 in placebo group; RR 0.97 95% CI 0.86 to 1.09, random-effects model (3 trials, 1335 participants, moderate-quality evidence).

AUTHORS' CONCLUSIONS

The findings of this Cochrane Review do not demonstrate clinical benefits of cerebrolysin for treating acute ischaemic stroke. We found moderate-quality evidence suggesting that serious adverse events may be more common with cerebrolysin use in acute ischaemic stroke.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebrovascular disease. However, the sedative effects of GABA receptor agonists have limited their wider application in people with acute stroke, due to the potential risk of stupor. This is an update of a Cochrane review first published in 2013, and previously updated in 2014.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (accessed March 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) 2016, Issue 3, part of the Cochrane Library (accessed March 2016), MEDLINE (from 1949 to March 2016), Embase (from 1980 to March 2016), CINAHL (from 1982 to March 2016), AMED (from 1985 to March 2016), and 11 Chinese databases (accessed March 2016). In an effort to identify further published, unpublished, and ongoing trials we searched ongoing trials registers, reference lists, and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for people with acute stroke (within 12 hours after stroke onset), with the primary outcomes of efficacy and safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy, and assessed the risk of bias.

MAIN RESULTS

We included five trials with 3838 participants (3758 analyzed). The methodological quality of the included trials was generally good, with an unclear risk for selection bias only. Four trials (N = 2909) measured death and dependency at three months for chlormethiazole versus placebo; pooled results did not find a significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.96 to 1.11). One trial (N = 849) measured this outcome for diazepam versus placebo (RR 0.94, 95% CI 0.82 to 1.07). The most frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95; two trials; N = 2527) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46; two trials; N = 2527).

AUTHORS' CONCLUSIONS

This review provides moderate-quality evidence that fails to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of people with acute stroke. More well-designed RCTs with large samples of participants with total anterior circulation syndrome are required to determine if there are benefits for this subgroup. Somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Cerebrolysin for acute ischaemic stroke

BACKGROUND

Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from pigs' brain tissue, which has potential neuroprotective and neurotrophic properties. It is widely used in the treatment of acute ischaemic stroke in Russia, China, and other Asian and post-Soviet countries.

OBJECTIVES

To assess the benefits and risks of Cerebrolysin for treating acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (October 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (November 2014), MEDLINE (1966 to November 2014), EMBASE (1974 to November 2014), Web of Science Core Collection, with Science Citation Index (1940 to November 2014), LILACS (1982 to December 2014), OpenGrey (1980 to December 2014), and a number of Russian Databases (1998 to December 2014). We also searched reference lists, ongoing trials registers and conference proceedings, and contacted the manufacturer of Cerebrolysin, EVER Neuro Pharma GmbH (formerly Ebewe Pharma).

SELECTION CRITERIA

Randomised controlled trials comparing Cerebrolysin started within 48 hours of stroke onset and continued for at least two weeks with placebo or no treatment in people with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied inclusion criteria, assessed trial quality and risk of bias, and extracted data.

MAIN RESULTS

We included one trial involving 146 participants. We evaluated risk of bias and judged it to be high for generation of allocation sequence, low for allocation concealment, high for incomplete outcome data (attrition bias), unclear for blinding, high for selective reporting and high for other sources of bias. The manufacturer of Cerebrolysin, pharmaceutical company Ebewe, provided Cerebrolysin and the placebo, as well as the randomisation codes. There was no difference in the number of deaths (6/78 in Cerebrolysin group versus 6/68 in placebo group; risk ratio (RR) 0.87, 95% confidence interval (CI) 0.29 to 2.58) or in the total number of adverse events (16.4% versus 10.3%; RR 1.62, 95% CI 0.69 to 3.82) between the treatment and control groups.

AUTHORS' CONCLUSIONS

Routine administration of Cerebrolysin to people with acute ischaemic stroke cannot be supported by the available evidence from RCTs.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebral ischemia. However, the sedation effects of GABA receptor agonists have limited their wider application in acute stroke patients due to the potential risk of stupor.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (February 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 5), MEDLINE (1949 to June 2014), EMBASE (1980 to June 2014), CINAHL (1982 to June 2014), AMED (1985 to June 2014) and 11 Chinese databases (June 2014). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers, reference lists and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for acute stroke patients (within 12 hours after stroke onset), with the outcomes of death or dependency, functional independence and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the methodological quality.

MAIN RESULTS

We included five trials with 3838 patients. The methodological quality of the included trials was generally good, with low risk of bias. Four trials measured death and dependency at three months in chlormethiazole versus placebo without significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.95 to 1.11). One trial measured this outcome between diazepam and placebo (RR 0.94, 95% CI 0.82 to 1.07). In the subgroup analysis of total anterior circulation syndrome (TACS), a higher percentage of functional independence was found in the chlormethiazole group (RR 1.33, 95% CI 1.09 to 1.64). The frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46).

AUTHORS' CONCLUSIONS

This review does not provide the evidence to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of patients with acute ischemic or hemorrhagic stroke. Chlormethiazole appeared to be beneficial in improving functional independence in patients with TACS according to the subgroup analysis, but this result must be interpreted with great caution. More well-designed RCTs with large samples of TACS would be required for further confirmation. However, somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Oxidative Stress and the Use of Antioxidants in Stroke

Transient or permanent interruption of cerebral blood flow by occlusion of a cerebral artery gives rise to an ischaemic stroke leading to irreversible damage or dysfunction to the cells within the affected tissue along with permanent or reversible neurological deficit. Extensive research has identified excitotoxicity, oxidative stress, inflammation and cell death as key contributory pathways underlying lesion progression. The cornerstone of treatment for acute ischaemic stroke remains reperfusion therapy with recombinant tissue plasminogen activator (rt-PA). The downstream sequelae of events resulting from spontaneous or pharmacological reperfusion lead to an imbalance in the production of harmful reactive oxygen species (ROS) over endogenous anti-oxidant protection strategies. As such, anti-oxidant therapy has long been investigated as a means to reduce the extent of injury resulting from ischaemic stroke with varying degrees of success. Here we discuss the production and source of these ROS and the various strategies employed to modulate levels. These strategies broadly attempt to inhibit ROS production or increase scavenging or degradation of ROS. While early clinical studies have failed to translate success from bench to bedside, the combination of anti-oxidants with existing thrombolytics or novel neuroprotectants may represent an avenue worthy of clinical investigation. Clearly, there is a pressing need to identify new therapeutic alternatives for the vast majority of patients who are not eligible to receive rt-PA for this debilitating and devastating disease.

Preclinical evaluation of marketed sodium channel blockers in a rat model of myotonia discloses promising antimyotonic drugs

Although the sodium channel blocker mexiletine is considered the first-line drug in myotonia, some patients experiment adverse effects, while others do not gain any benefit. Other antimyotonic drugs are thus needed to offer mexiletine alternatives. In the present study, we used a previously-validated rat model of myotonia congenita to compare six marketed sodium channel blockers to mexiletine. Myotonia was induced in the rat by injection of anthracen-9-carboxylic acid, a muscle chloride channel blocker. The drugs were given orally and myotonia was evaluated by measuring the time of righting reflex. The drugs were also tested on sodium currents recorded in a cell line transfected with the human skeletal muscle sodium channel hNav1.4 using patch-clamp technique. In vivo, carbamazepine and propafenone showed antimyotonic activity at doses similar to mexiletine (ED50 close to 5mg/kg); flecainide and orphenadrine showed greater potency (ED50 near 1mg/kg); lubeluzole and riluzole were the more potent (ED50 near 0.1mg/kg). The antimyotonic activity of drugs in vivo was linearly correlated with their potency in blocking hNav1.4 channels in vitro. Deviation was observed for propafenone and carbamazepine, likely due to pharmacokinetics and multiple targets. The comparison of the antimyotonic dose calculated in rats with the current clinical dose in humans strongly suggests that all the tested drugs may be used safely for the treatment of human myotonia. Considering the limits of mexiletine tolerability and the occurrence of non-responders, this study proposes an arsenal of alternative drugs, which may prove useful to increase the quality of life of individuals suffering from non-dystrophic myotonia. Further clinical trials are warranted to confirm these results.

Molecular Dissection of Cyclosporin A's Neuroprotective Effect Reveals Potential Therapeutics for Ischemic Brain Injury

After the onset of brain ischemia, a series of events leads ultimately to the death of neurons. Many molecules can be pharmacologically targeted to protect neurons during these events, which include glutamate release, glutamate receptor activation, excitotoxicity, Ca²⁺ influx into cells, mitochondrial dysfunction, activation of intracellular enzymes, free radical production, nitric oxide production, and inflammation. There have been a number of attempts to develop neuroprotectants for brain ischemia, but many of these attempts have failed. It was reported that cyclosporin A (CsA) dramatically ameliorates neuronal cell damage during ischemia. Some researchers consider ischemic cell death as a unique process that is distinct from both apoptosis and necrosis, and suggested that mitochondrial dysfunction and Δψ collapse are key steps for ischemic cell death. It was also suggested that CsA has a unique neuroprotective effect that is related to mitochondrial dysfunction. Here, I will exhibit examples of neuroprotectants that are now being developed or in clinical trials, and will discuss previous researches about the mechanism underlying the unique CsA action. I will then introduce the results of our cDNA subtraction experiment with or without CsA administration in the rat brain, along with our hypothesis about the mechanism underlying CsA’s effect on transcriptional regulation.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebral ischemia. However, the sedation effects of GABA receptor agonists have limited their wider application in acute stroke patients due to the potential risk of stupor.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (January 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 1), MEDLINE (1949 to March 2012), EMBASE (1980 to March 2012), CINAHL (1982 to March 2012), AMED (1985 to March 2012) and 11 Chinese databases (March 2012). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers, reference lists and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for acute stroke patients (within 12 hours after stroke onset), with the outcomes of death or dependency, functional independence and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the methodological quality.

MAIN RESULTS

We included five trials with 3838 patients. The methodological quality of the included trials was generally good, with low risk of bias. Four trials measured death and dependency at three months in chlormethiazole versus placebo without significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.95 to 1.11). One trial measured this outcome between diazepam and placebo (RR 0.94, 95% CI 0.82 to 1.07). In the subgroup analysis of total anterior circulation syndrome (TACS), a higher percentage of functional independence was found in the chlormethiazole group (RR 1.33, 95% CI 1.09 to 1.64). The frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46).

AUTHORS' CONCLUSIONS

This review does not provide the evidence to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of patients with acute ischemic or hemorrhagic stroke. Chlormethiazole appeared to be beneficial in improving functional independence in patients with TACS according to the subgroup analysis, but this result must be interpreted with great caution. More well-designed RCTs with large samples of TACS would be required for further confirmation. However, somnolence and rhinitis are frequent adverse events related to chlormethiazole.

The failure of animal models of neuroprotection in acute ischemic stroke to translate to clinical efficacy

The discrepancy in results regarding neuroprotective agents in animal experiments compared to clinical trials is a major problem. While many neuroprotective agents have been proven effective in a variety of animal ischemic stroke models, none have been shown to work in phase III clinical trials. This review retrospectively summarizes the neuroprotectants selected for human randomized controlled trials (RCT) and explores the reasons behind the clinical translational failure of these agents. Here, we suggest that there are many factors (model selection, anesthetic choice, physiological monitoring, model success criteria, embolus property, reperfusion damage, infarction area, therapeutic time window, drug penetration, blood concentration, gender difference, and outcome evaluation) responsible for this phenomenon. Ultra-early treatment using a "home run" drug and multi-target therapy may be the most promising for future consideration.

Cerebrolysin for acute ischaemic stroke

BACKGROUND

Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from pigs' brain tissue which has proposed neuroprotective and neurotrophic properties. It is widely used in the treatment of acute ischaemic stroke in Russia and China.

OBJECTIVES

To assess the benefits and risks of cerebrolysin for treating acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (February 2009), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2009), MEDLINE (1966 to February 2009), EMBASE (1974 to February 2009), LILACS (1982 to February 2009), Science Citation Index (1940 to February 2009), SIGLE Archive (1980 to March 2005), and a number of relevant Russian Databases (1988 to February 2009). We also searched reference lists, ongoing trials registers and conference proceedings.

SELECTION CRITERIA

Randomised controlled trials comparing cerebrolysin with placebo or no treatment in patients with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Three review authors independently applied the inclusion criteria, assessed trial quality and extracted the data.

MAIN RESULTS

We included one trial involving 146 participants. There was no difference in death (6/78 in the cerebrolysin group versus 6/68 in the placebo group; risk ratio (RR) 0.87, 95% confidence interval (CI) 0.29 to 2.58) or in the total number of adverse events (16.4% versus 10.3%; RR 1.62, 95% CI 0.69 to 3.82) between the treatment and control groups.

AUTHORS' CONCLUSIONS

There is not enough evidence to evaluate the effect of cerebrolysin on survival and dependency in people with acute ischaemic stroke. High-quality and large-scale randomised controlled trials may help to gain a better understanding of the potential value of cerebrolysin in acute ischaemic stroke.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.

Methodological quality of animal studies on neuroprotection in focal cerebral ischaemia

BACKGROUND

The recurrent failure of apparently promising neuroprotective drugs to improve outcome in trials of patients with acute ischaemic stroke may partially be explained by over-optimistic conclusions about efficacy as a result of methodological shortcomings in preclinical studies. We assessed the methodological quality of animal studies of five different neuroprotective agents that have been tested in 21 clinical trials including a total of more than 12,000 patients with acute ischaemic stroke.

METHODS

We performed a literature search restricted to full publications on the effects of clomethiazole, gavestinel, lubeluzole, selfotel, or tirilazad mesylate on infarct volume or functional outcome in animal models of acute focal cerebral ischaemia. We used a rating scale to assess the methodological quality of the included studies. One point was attributed to each of 10 items. A score of 4 to 6 points was considered "medium" and a score above 7 "high."

RESULTS

A total of 45 articles were included. The median score on the methodological quality index was 3; 18 studies had a medium score and one a high score. Randomised treatment allocation was mentioned in 19 studies (42 %), blinded administration of study medication in 10 (22 %), and blinded outcome assessment in 18 (40 %). The study drug was administered at a median of 10 min (range, -60 to 360 min) after the onset of ischaemia.

CONCLUSION

The evidence for neuroprotective efficacy that formed the basis for initiating the 21 trials was obtained in animal studies with a methodological quality that would, in retrospect, not justify such a decision. More rigorous preclinical study methodology may lead to more reliable and reproducible results.

Role of nitric oxide after brain ischaemia

Ischaemic stroke is the second or third leading cause of death in developed countries. In the last two decades substantial research and efforts have been made to understand the biochemical mechanisms involved in brain damage and to develop new treatments. The evidence suggests that nitric oxide (NO) can exert both protective and deleterious effects depending on factors such as the NOS isoform and the cell type by which NO is produced or the temporal stage after the onset of the ischaemic brain injury. Immediately after brain ischaemia, NO release from eNOS is protective mainly by promoting vasodilation; however, after ischaemia develops, NO produced by overactivation of nNOS and, later, NO release by de novo expression of iNOS contribute to the brain damage. This review article summarizes experimental and clinical data supporting the dual role of NO in brain ischaemia and the mechanisms by which NO is regulated after brain ischaemia. We also review NO-based therapeutic strategies for stroke treatment, not only those directly linked with the NO pathway such as NO donors and NOS inhibitors but also those partially related like statins, aspirin or lubeluzole.

Clinical trials for cytoprotection in stroke

To date, many cytoprotective drugs have reached the stage of pivotal phase 3 efficacy trials in acute stroke patients. (Table 1) Unfortunately, throughout the neuroprotective literature, the phrase "failure to demonstrate efficacy" prevails as a common thread among the many neutral or negative trials, despite the largely encouraging results encountered in preclinical studies. The reasons for this discrepancy are multiple, and have been discussed by Dr. Zivin in his review. Many of the recent trials have addressed deficiencies of the previous ones with more rigorous trial design, including more specific patient selection criteria (ensure homogeneity of stroke location and severity), stratified randomization algorithms (time-to-treat), narrowed therapeutic time-window and pharmacokinetic monitoring. Current trials have also incorporated biologic surrogate markers of toxicity and outcome such as drug levels and neuroimaging. Lastly, multi-modal therapies and coupled cytoprotection/reperfusion strategies are being investigated to optimize tissue salvage. This review will focus on individual therapeutic strategies and we will emphasize what we have learned from these trials both in terms of trial design and the biologic effect (or lack thereof) of these agents.

Excitatory amino acid antagonists for acute stroke

BACKGROUND

Focal cerebral ischaemia causes release of excitatory amino acid (EAA) neurotransmitters, principally glutamate, with resultant over-stimulation of EAA receptors and downstream pathways. Excess glutamate release is a pivotal event in the evolution of irreversible ischaemic damage in animal models of ischaemia, and drugs that modulate glutamate action either by inhibiting its release, or blocking post-synaptic receptors, are potent neuroprotective agents. Many clinical trials with EAA modulating drugs have been conducted, none individually demonstrating efficacy.

OBJECTIVES

To synthesise all the available data on all different classes of EAA modulators and to evaluate evidence of effects on outcome systematically.

SEARCH STRATEGY

Relevant trials were identified in the Specialised Register of Controlled Trials (last searched May 2001). In addition, MEDLINE and EMBASE online searches for the terms "neuroprotection" (and its variants), "neuroprotective agent", for all individual drugs and drug classes included in the review, hand searches of conference proceedings from European, International, American Heart Association and Princeton conferences on Stroke, American Neurological Association and American Academy of Neurology meetings from 1992-2001, and direct contact with individual investigators and pharmaceutical companies.

SELECTION CRITERIA

Trials were included if they were randomised, controlled studies giving agents with pharmacological properties that included modification of release of EAAs, or blockade of EAA receptors, in stroke within 24h of onset. Efficacy analysis was restricted to trials with a parallel group design: dose escalation studies were excluded. Intention-to-treat analyses were performed on all data. Outcome had to be reported in terms of death or dependence 1-12 months after the acute event.

DATA COLLECTION AND ANALYSIS

Data were available for 36 of 41 relevant trials identified, involving 11,209 subjects. Data were unavailable for 632 participants (517 in trials fulfilling criteria for efficacy analysis). Seven trials did not report disability data, which were available for 29 trials involving 10,802 subjects. Twenty one of these trials, involving 10,342 subjects, were parallel group studies included in the primary efficacy analysis. Efficacy analysis included data derived from 9 trials not primarily designed to assess efficacy (1022 subjects). The primary (efficacy) end-point was the proportion of patients dead or disabled at final follow-up (defined by Barthel Index<60 at 3 months by preference). Mortality was a secondary end-point. Drugs were considered as individual agents, and also grouped principally into categories of ion channel modulators (glutamate release inhibition) and NMDA antagonists.

MAIN RESULTS

There was no significant heterogeneity of outcome amongst individual drugs, or of drug classes either for the primary efficacy analysis (death or dependence) or for mortality at final follow-up. For the primary efficacy analysis, odds of death or dependence were 1.03 [95% confidence interval 0.96-1.12], and for mortality 1.02 [0.92-1.12]. Neither ion channel modulators (death or dependence 1.02 [0.90-1.16]) nor NMDA antagonists (death or dependence 1.05 [0.95-1.16]) differed from the principal analysis including all compounds. Trends for increased mortality with three NMDA antagonists were seen - selfotel (OR 1.19 [0.81-1.74]), aptiganel (OR 1.32 [0.91-1.93]) and gavestinel (OR 1.12 [0.95-1.32]) - but this did not achieve significance for the NMDA antagonists considered as a class (1.09 [0.96-1.23]). Aptiganel was also associated with a trend towards worse functional outcome (OR 1.20 [0.88-1.65]) although this was not the case for either of the other two compounds. No statistically significant detriment of psychotomimetic NMDA antagonists was found, although a trend towards higher mortality in this sub-group was seen (OR 1.25 [0.96-1.64]).

REVIEWER'S CONCLUSIONS

There was no evidence of significant benefit or harm from drugs modulating excitatory amino acid action. Reductio]).

REVIEWER'S CONCLUSIONS

There was no evidence of significant benefit or harm from drugs modulating excitatory amino acid action. Reduction of death or dependence by 8% or more has been excluded for gavestinel and lubeluzole, which contribute most of the data for this review. However, mechanistic understanding of neuroprotection is too poor to extrapolate from these two failed development plans to all glutamate modulators. Further clinical trials of neuroprotective agents remain justified, since confidence limits around estimates of effect remain wide for most agents, and cannot reliably exclude benefit. Although numbers of patients are too small to confirm or refute a trend towards increased mortality with some NMDA antagonists, further commercial development of these agents is exceedingly unlikely.