Erythropoietin: physiologic basis for clinical applications

Correlation between Serum Erythropoietin and Cerebral Collateral Flow in Acute Ischemic Stroke Patient

BACKGROUND

Erythropoietin (EPO), which is associated with anemia, exerts neuroprotective effects in ischemic stroke. In cases of stenosis or narrowing of the main cerebral blood vessel, the prognosis is favorable if collateral blood circulation is well developed in acute stroke. Several studies have investigated the relationship between EPO administration and stroke outcomes. The present study investigated the correlation between serum EPO level and cerebral collateral circulation, which could result in favorable clinical outcomes.

METHODS

The study subjects were patients diagnosed with acute ischemic stroke who underwent initial brain magnetic resonance imaging between January 2020 and March 2022. Following brain computed tomography perfusion for collateral flow, serum EPO levels were measured. Collaterals were assessed according to the Mass system and divided into good collateral (GC) or poor collateral (PC) groups. Serum EPO levels were determined using a chemiluminescence immunoassay method. A correlation coefficient analysis was conducted to determine the correlation between serum EPO levels and GC. A receiver operating characteristic curve analysis determined the cutoff value of EPO for GC.

RESULTS

Serum EPO levels were significantly higher in the GC than that in the PC group (P<0.05). The cut-off level of serum EPO for a good outcome was 9.1 mIU/mL.

CONCLUSION

A high serum EPO (>9.1 mIU/mL) could be a marker of GC in patients with acute ischemic stroke that predicts good clinical outcomes.

Assessment of hemoglobin responsiveness to epoetin alfa in patients on hemodialysis using a population pharmacokinetic pharmacodynamic model

A population pharmacokinetic pharmacodynamic (PK/PD) model describing the effect of epoetin alfa on hemoglobin (Hb) response in hemodialysis patients was developed. Epoetin alfa pharmacokinetics was described using a linear 2-compartment model. PK parameter estimates were similar to previously reported values. A maturation-structured cytokinetic model consisting of 5 compartments linked in a catenary fashion by first-order cell transfer rates following a zero-order input process described the Hb time course. The PD model described 2 subpopulations, one whose Hb response reflected epoetin alfa dosing and a second whose response was unrelated to epoetin alfa dosing. Parameter estimates from the PK/PD model were physiologically reasonable and consistent with published reports. Numerical and visual predictive checks using data from 2 studies were performed. The PK and PD of epoetin alfa were well described by the model.

Simplifying anemia management in hemodialysis patients: ESAs administered at longer dosing intervals can enhance opportunities to provide patient-focused care

OBJECTIVE

To review issues and challenges in caring for hemodialysis patients with anemia of chronic kidney disease, specifically focusing on the effects of longer erythropoiesis-stimulating agent (ESA) dosing intervals on processes of care.

METHODS

PubMed searches were performed limited to the last 10 years to February 2011, focusing on articles in English that were 'clinical trials,' assessed processes of care, measured associations of hemoglobin (Hb) with outcomes, and explored/analyzed extended dosing intervals of ESAs in hemodialysis patients and recommendations for increasing the quality of care of these patients. Some limitations included the fact that a meta-analysis was not conducted; many studies were associative and therefore unable to prove causality; and none of the clinical trials directly compared the impact of more frequent or less frequent ESA dosing strategies on patient care and outcomes.

FINDINGS

Progress over the past several decades has been substantial; however, unmet needs remain and there is room for improvement in efficiencies of care. Many patients fail to meet Hb targets, and nephrology professionals' time is consumed with preparing, administering, and monitoring therapy. Direct interaction between patients and care providers has been lost as attention has shifted to 'cost-effective' (not necessarily patient-centered) ways to deliver care. Use of ESAs at longer dosage intervals represents one opportunity to improve efficiency of care. Newer ESAs have been developed for less frequent dosing. Once-monthly dosing decreases time spent administering/monitoring therapy and allows nephrology professionals to provide comprehensive renal care, wherein the patient rather than task-oriented processes becomes the primary focus.

CONCLUSIONS

A fragmented, uncoordinated care-delivery model heightens the urgency to systematically address issues related to delivery of care and improve efficiencies in anemia management as part of the patient-centered approach. ESAs designed for administration at longer intervals may effectively and reliably achieve Hb targets with once-monthly dosing, thereby decreasing time spent administering/monitoring therapy.

A phase I/II trial of high-dose erythropoietin in extremely low birth weight infants: pharmacokinetics and safety

OBJECTIVES

High-dose recombinant erythropoietin is neuroprotective in animal models of neonatal brain injury. Extremely low birth weight infants are at high risk for brain injury and neurodevelopmental problems and might benefit from recombinant erythropoietin. We designed a phase I/II trial to test the safety and determine the pharmacokinetics of high-dose recombinant erythropoietin in extremely low birth weight infants.

METHODS

In a prospective, dose-escalation, open-label trial, we compared 30 infants who were treated with high-dose recombinant erythropoietin with 30 concurrent control subjects. Eligible infants were <24 hours old, <or=1000 g birth weight, and <or=28 weeks of gestation and had an umbilical artery catheter in place. Each infant received 3 intravenous doses of 500, 1000, or 2500 U/kg at 24-hour intervals beginning on day 1 of age. Blood samples were collected at scheduled intervals to determine recombinant erythropoietin pharmacokinetics. Safety parameters were also evaluated. In the concurrent control group, only clinical data were collected.

RESULTS

Mean erythropoietin concentrations 30 minutes after recombinant erythropoietin infusion were 5973 +/- 266, 12291 +/- 403, and 34197 +/- 1641 mU/mL after 500, 1000, or 2500 U/kg, respectively. High-dose recombinant erythropoietin followed nonlinear pharmacokinetics as a result of decreasing clearance from the lowest dosage (17.3 mL/hour per kg for 500 U/kg) to the highest dosage (8.2 mL/hour per kg for 2500 U/kg). Steady state was achieved within 24 to 48 hours. Both 1000 and 2500 U/kg recombinant erythropoietin produced peak serum erythropoietin concentrations that were comparable to neuroprotective concentrations that previously were seen in experimental animals. No excess adverse events occurred in the recombinant erythropoietin-treated infants compared with control infants.

CONCLUSIONS

Early high-dose recombinant erythropoietin is well tolerated by extremely low birth weight infants, causing no excess morbidity or mortality. Recombinant erythropoietin dosages of 1000 and 2500 U/kg achieved neuroprotective serum levels.

Change in erythropoietin pharmacokinetics following hematopoietic transplantation

Pre-clinical studies have demonstrated that bone marrow ablation has a profound effect in decreasing erythropoietin (EPO) elimination. The study's objective was to determine in humans if EPO pharmacokinetics (PKs) are perturbed following bone marrow ablation. EPO PK studies were performed in eight subjects, aged 4 to 61 years, undergoing fully myeloablative hematopoietic stem cell transplantation. Serial PK studies using intravenous injection of recombinant human EPO (92+/-2.0 U/kg) (mean+/-SEM) were carried out during four periods of altered marrow integrity: baseline pre-ablation, post-ablation pre-transplant, early post-transplant pre-engraftment, and late post-transplant full engraftment. Compared with baseline, post-ablation pre-transplant and early post-transplant EPO PKs demonstrated declines in clearance increases in terminal elimination half-life of 36 and 95%, respectively. Clearance and half-life returned to baseline following full engraftment. The association of EPO elimination with decreased bone marrow activity in patients undergoing transplantation conclusively establishes the bone marrow as a key determinant of EPO elimination in humans.

Cloning of a cDNA encoding bovine erythropoietin and analysis of its transcription in selected tissues

A bovine cDNA encoding erythropoietin (Epo) was isolated by polymerase chain reaction (PCR) amplification and screening of a bovine kidney cDNA library. The sequenced cDNA has a length of 1312 bp and an open reading frame that encodes a predicted 192-amino-acid (aa) protein, including a putative signal sequence of 25 aa. A mature protein of 167 aa (18.4 kDa) results upon cleavage of the putative signal peptide. The deduced bovine mature Epo peptide exhibits 96, 88, 83, 82 and 79% sequence identity to that of sheep, swine, human, monkey and rat, respectively. The expression of the bovine Epo gene in tissues from a severely anemic calf, bovine fetus and a healthy steer was analysed by a competitive RT-PCR method. In kidneys of the severely anemic calf, Epo mRNA levels increased 60-fold relative to that from the kidneys of the healthy steer. Epo mRNA levels were threefold higher in the liver of the bovine fetus than that in its kidneys. Low levels of Epo transcripts were detected in RNA from spleen of the severely anemic calf and the bovine fetus. No Epo transcripts were detectable in spleen from the healthy steer.