Did clinical trials in which erythropoietin failed to reduce acute myocardial infarct size miss a narrow therapeutic window?

Asialo-rhuEPO as a Potential Neuroprotectant for Ischemic Stroke Treatment

Neuroprotective drugs to protect the brain against cerebral ischemia and reperfusion (I/R) injury are urgently needed. Mammalian cell-produced recombinant human erythropoietin (rhuEPOM) has been demonstrated to have excellent neuroprotective functions in preclinical studies, but its neuroprotective properties could not be consistently translated in clinical trials. The clinical failure of rhuEPOM was thought to be mainly due to its erythropoietic activity-associated side effects. To exploit its tissue-protective property, various EPO derivatives with tissue-protective function only have been developed. Among them, asialo-rhuEPO, lacking terminal sialic acid residues, was shown to be neuroprotective but non-erythropoietic. Asialo-rhuEPO can be prepared by enzymatic removal of sialic acid residues from rhuEPOM (asialo-rhuEPOE) or by expressing human EPO gene in glycoengineered transgenic plants (asialo-rhuEPOP). Both types of asialo-rhuEPO, like rhuEPOM, displayed excellent neuroprotective effects by regulating multiple cellular pathways in cerebral I/R animal models. In this review, we describe the structure and properties of EPO and asialo-rhuEPO, summarize the progress on neuroprotective studies of asialo-rhuEPO and rhuEPOM, discuss potential reasons for the clinical failure of rhuEPOM with acute ischemic stroke patients, and advocate future studies needed to develop asialo-rhuEPO as a multimodal neuroprotectant for ischemic stroke treatment.

Why is it worth testing the ability of zinc to protect against ischaemia reperfusion injury for human application

Ischaemia (interruption in the blood/oxygen supply) and subsequent damage induced by reperfusion (restoration of blood/oxygen supply) ultimately leads to cell death, tissue injury and permanent organ dysfunction. The impact of ischaemia reperfusion injury (IRI) is not limited to heart attack and stroke but can be extended to patients undergoing surgeries such as partial nephrectomy for renal cancer, liver resection for colorectal cancer liver metastasis, cardiopulmonary bypass, and organ transplantation. Unfortunately, there are no drugs that can protect organs against the inevitable peril of IRI. Recent data show that a protocol incorporating specific Zn formulation, dosage, number of dosages, time of injection, and mode of Zn delivery (intravenous) and testing of efficacy in a large preclinical sheep model of IRI strongly supports human trials of Zn preconditioning. No doubt, scepticism still exists among funding bodies and research fraternity on whether Zn, a naturally occurring metal, will work where everything else has failed. Therefore, in this article, we review the conflicting evidence on the promoter and protector role of Zn in the case of IRI and highlight factors that may help explain the contradictory evidence. Finally, we review the literature related to the knowledge of Zn's mechanism of action on ROS generation, apoptosis, HIF activation, inflammation, and signal transduction pathways, which highlight Zn's likelihood of success compared to various other interventions targeting IRI.

Zinc preconditioning protects against renal ischaemia reperfusion injury in a preclinical sheep large animal model

Ischaemia-reperfusion injury (IRI) during various surgical procedures, including partial nephrectomy for kidney cancer or renal transplantation, is a major cause of acute kidney injury and chronic kidney disease. Currently there are no drugs or methods for protecting human organs, including the kidneys, against the peril of IRI. The aim of this study was therefore to investigate the reno-protective effect of Zn²⁺ preconditioning in a clinically relevant large animal sheep model of IRI. Further the reno-protective effectiveness of Zn²⁺ preconditioning was tested on normal human kidney cell lines HK-2 and HEK293. Anaesthetised sheep were subjected to uninephrectomy and 60 min of renal ischaemia followed by reperfusion. Sheep were preconditioned with intravenous injection of zinc chloride prior to occlusion. Serum creatinine and urea were measured before ischaemia and for 7 days after reperfusion. HK-2 and HEK293 cells were subjected to in vitro IRI using the oxygen- and glucose-deprivation model. Zn²⁺ preconditioning reduced ischaemic burden determined by creatinine and urea rise over time by ~ 70% in sheep. Zn²⁺ preconditioning also increased the survival of normal human kidney cells subjected to cellular stress such as hypoxia, hydrogen peroxide injury, and serum starvation. Overall, our protocol incorporating specific Zn²⁺ dosage, number of dosages (two), time of injection (24 and 4 h prior), mode of Zn²⁺ delivery (IV) and testing of efficacy in a rat model, a large preclinical sheep model of IRI and cells of human origin has laid the foundation for assessment of the benefit of Zn²⁺ preconditioning for human applications.

A novel adenylyl cyclase type 5 inhibitor that reduces myocardial infarct size even when administered after coronary artery reperfusion

We developed a novel adenylyl cyclase type 5 (AC5) inhibitor, C90, that reduces myocardial infarct size even when administered after coronary reperfusion. This is key, since it is not practical to administer a drug to a patient with myocardial infarction before revascularization, and is one reason why so many prior drugs, which reduced infarct in experimental animals, failed in clinical trials. C90 is the most potent AC5 inhibitor, as exhibited by its IC50 value for AC5 inhibition, which was 5 times lower than the next most potent AC5 inhibitor. C90 reduced cAMP in response to forskolin in wild type mice by 42%, but no longer reduced cAMP in response to forskolin in mice with disruption of AC5, indicating that the mechanism of C90 was specific for AC5 inhibition. Compared with vehicle treatment, C90 reduced infarct size by 64% at a dose of 0.6 mg/kg. Thus, C90 is a novel, selective and potent AC5 inhibitor that reduces infarct size, when delivered after coronary artery reperfusion, rendering it potentially clinically useful. It also reduces beta-adrenergic receptor signaling, which will provide additional benefit to patients with coronary artery disease or heart failure.

Effect of Erythropoietin in patients with acute myocardial infarction: five-year results of the REVIVAL-3 trial

BACKGROUND

Erythropoietin (EPO) has been suggested to promote cardiac repair after MI. However, the randomized, double-blind, placebo controlled REVIVAL-3 trial showed that short term high dose EPO in timely reperfused myocardium does not improve left ventricular ejection fraction after 6 months. Moreover, the study raised safety concerns due to a trend towards a higher incidence of adverse clinical events as well as a increase in neointima formation after treatment with EPO. The present study therefore aimed to assess the 5-year clinical outcomes.

METHODS

After successful reperfusion 138 patients with STEMI were randomly assigned to receive epoetin beta (3.33×10⁴ U, n = 68) or placebo (n = 70) immediately, 24 and 48 h after percutaneous coronary intervention. The primary outcome of the present study- the combined incidence of MACE 5 years after randomization - occurred in 25% of the patients assigned to epoetin beta and 17% of the patients assigned to placebo (RR 1.5; 95% CI 0.8-3.5; p = 0.26). Target lesion revascularization was required in 15 patients (22.1%) treated with epoetin-ß and 9 patients (12.9%) treated with placebo (p = 0.15). Analysis of patients in the upper and lower quartile of baseline hemoglobin as an indirect estimate of endogenous erythropoietin levels revealed no significant impact of endogenous erythropoietin on efficiency of exogen administered epoetin-ß in terms of death and MACE.

CONCLUSION

These long-term follow-up data show that epoetin beta does not improve clinical outcomes of patients with acute myocardial infarction.

TRIAL REGISTRATION

URL www.clinicaltrials.gov ; Unique identifier NCT00390832; trial registration date October 19th 2006.

Novel cardioprotective and regenerative therapies in acute myocardial infarction: a review of recent and ongoing clinical trials

Following the original large-scale randomized trials of aspirin and β-blockade, there have been a number of major advances in pharmacological and mechanical treatments for acute myocardial infarction. Despite this progress, myocardial infarction remains a major global cause of mortality and morbidity, driving a quest for novel treatments in this area. As the understanding of mitochondrial dynamics and the pathophysiology of reperfusion injury has evolved, the last three decades have seen advances in ischemic conditioning, pharmacological and metabolic cardioprotection, as well as biological and stem-cell therapies. The aim of this review is to provide a synopsis of adjunctive cardioprotective and regenerative therapies currently undergoing or entering early clinical trials in the treatment of patients with acute myocardial infarction.

Erythropoietin Reduces Post-PCI Arrhythmias in Patients With ST-elevation Myocardial Infarction

BACKGROUND

Arrhythmia is the foremost cause of sudden death after myocardial infarction (MI). Animal models have recently shown that erythropoietin (EPO) can reduce the incidence of arrhythmia after MI.

METHODS

We investigated the effects of administrating 33,000 IU EPO on the occurrence of post-MI arrhythmia in 40 patients with ST-elevation MI who were randomly assigned in either EPO or placebo groups. Arrhythmias were blindly documented using full 12-lead configuration during 24 hours after percutaneous coronary intervention (PCI) by a cardiologist. Afterward, CK-MB, hematologic, and hemodynamic data were examined within 2 weeks after MI.

RESULTS

A comparison made between the 2 groups showed significant differences in the incidence of arrhythmias (20% in EPO group and 35% in placebo group, P = 0.043). However, no significant differences in type of arrhythmias were observed between the groups. There was no significant difference between levels of CK-MB in the 2 groups during 24 hours (P = 0.186). Hematologic and hemodynamic data showed no significant changes 2 weeks after PCI.

CONCLUSION

High-dose administration of EPO in patients with ST-elevation MI who have been treated by primary PCI and standard antiplatelet therapy reduces the occurrence of arrhythmias. For clinical interpretation of the results, further well-designed trials are required.

Erythropoietin action in stress response, tissue maintenance and metabolism

Erythropoietin (EPO) regulation of red blood cell production and its induction at reduced oxygen tension provides for the important erythropoietic response to ischemic stress. The cloning and production of recombinant human EPO has led to its clinical use in patients with anemia for two and half decades and has facilitated studies of EPO action. Reports of animal and cell models of ischemic stress in vitro and injury suggest potential EPO benefit beyond red blood cell production including vascular endothelial response to increase nitric oxide production, which facilitates oxygen delivery to brain, heart and other non-hematopoietic tissues. This review discusses these and other reports of EPO action beyond red blood cell production, including EPO response affecting metabolism and obesity in animal models. Observations of EPO activity in cell and animal model systems, including mice with tissue specific deletion of EPO receptor (EpoR), suggest the potential for EPO response in metabolism and disease.

Long term effects of epoetin alfa in patients with ST- elevation myocardial infarction

PURPOSE

The HEBE III trial showed that epoetin alfa administration in patients with a first ST-elevation myocardial infarction (STEMI) did not improve left ventricular function at 6 weeks after primary percutaneous coronary intervention (PCI). The long term effects of erythropoiesis- stimulating agents on cardiovascular morbidity and mortality are unknown, therefore we evaluated clinical events at 1 year after PCI.

METHODS

A total of 529 patients with a first STEMI and successful primary PCI were randomized to standard optimal medical treatment (N = 266) or an additional bolus of 60,000 IU epoetin alfa administered intravenously (N = 263) within 3 h after PCI. Analyses were performed by intention to treat.

RESULTS

At 1 year after STEMI, 485 patients had complete follow-up. The rate of the composite end point of all-cause mortality, re-infarction, target vessel revascularization, stroke and/or heart failure was 6.4 % (N = 15) in the epoetin alfa group and 9.6 % (N = 24) in the control group (p = 0.18). Thromboembolic events were present in 1.3 % (N = 3) of patients in the epoetin alfa group and 2.4 % (N = 6) in the control group. There was no evidence of benefit from epoetin alfa administration in subgroups of patients.

CONCLUSIONS

Administration of a single bolus of epoetin alfa in patients with STEMI does not result in a reduction of cardiovascular events at 1 year after primary PCI. There was a comparable incidence of thromboembolic complications in both treatment groups, suggesting that epoetin alfa administration is safe at long term.

Erythropoietin and the heart: physiological effects and the therapeutic perspective

Erythropoietin (Epo) has been thought to act exclusively on erythroid progenitor cells. The identification of Epo receptor (EpoR) in non-haematopoietic cells and tissues including neurons, astrocytes, microglia, immune cells, cancer cell lines, endothelial cells, bone marrow stromal cells, as well as cells of myocardium, reproductive system, gastrointestinal tract, kidney, pancreas and skeletal muscle indicates that Epo has pleiotropic actions. Epo shows signals through protein kinases, anti-apoptotic proteins and transcription factors. In light of interest of administering recombinant human erythropoietin (rhEpo) and its analogues for limiting infarct size and left ventricular (LV) remodelling after acute myocardial infarction (AMI) in humans, the foremost studies utilising rhEpo are reviewed. The putative mechanisms involved in Epo-induced cardioprotection are related to the antiapoptotic, anti-inflammatory and angiogenic effects of Epo. Thus, cardioprotective potentials of rhEpo are reviewed in this article by focusing on clinical applicability. An overview of non-haematopoietic Epo analogues, which are a reliable alternative to the classic EpoR agonists and may prevent undesired side effects, is also provided.

High-dose erythropoietin during cardiac resuscitation lessens postresuscitation myocardial stunning in swine

We investigated the metabolic and functional myocardial effects of erythropoietin (EPO) administered during resuscitation from cardiac arrest using an open-chest pig model of ventricular fibrillation and resuscitation by extracorporeal circulation, after having reported in rats a reversal of postresuscitation myocardial dysfunction associated with activation of mitochondrial protective pathways. Ventricular fibrillation was induced in 16 male domestic pigs and left untreated for 8 minutes, after which extracorporeal circulation was started and maintained for 10 additional minutes, adjusting the extracorporeal flow to provide a coronary perfusion pressure of 10 mmHg. Defibrillation was accomplished and the extracorporeal flow was adjusted to secure a mean aortic pressure of 40 mmHg or greater during spontaneous circulation for up to 120 minutes. Pigs were randomized 1:1 to receive EPO (1200 U/kg) or 0.9% NaCl before starting extracorporeal circulation. Severe postresuscitation myocardial dysfunction developed in both groups. However, recovery of myocardial function-comparing baseline with 120 minutes postresuscitation-was better in pigs treated with EPO than NaCl, as shown for left ventricular ejection fraction (from 45 ± 8% to 36 ± 9% in EPO, not significant; and from 46 ± 8% to 26 ± 8% in NaCl, P < 0.001) and for peak systolic pressure/end-systolic volume (from 2.7 ± 0.8 mmHg/mL to 2.4 ± 0.7 mmHg/mL in EPO, not significant; and from 3.0 ± 1.1 mmHg/mL to 1.8 ± 0.6 mmHg/mL, P < 0.001 in NaCl). The EPO effect was associated with significantly higher myocardial O2 consumption (12 ± 6 mL/min/unit of tissue vs 6 ± 2 mL/min/unit of tissue, P < 0.017) without effects on myocardial lactate consumption. Thus, EPO administered during resuscitation from ventricular fibrillation lessened postresuscitation myocardial stunning-an effect that could be useful clinically to help promote postresuscitation hemodynamic stability.