Clinical Application of Recombinant Erythropoietin in Renal Dialysis Patients

Erythropoietin: an update on the therapeutic use in newborn infants and children

Recombinant human erythropoietin (epoetin) has become the most widely used cytokine in the world. Following the success of its use in patients with end-stage renal disease, the usefulness of epoetin in other anaemias was assessed, including paediatric patients, mainly newborns. The treatment or prevention of anaemia of prematurity with epoetin resulted in a significant reduction in the number of transfusions and donor exposure. A clear definition of which premature babies must receive therapy is yet to be established. Other indications in neonatal period include hyporegenerative and haemolytic anaemias. The potential for use of the nonhaematopoietic effects of epoetin in newborn infants is a novel and exciting issue. The role of epoetin as a tissue-protective factor for the CNS and intestinal mucosa is under exhaustive investigation. With the exception of chronic renal failure, in older children the efficacy of epoetin has not been evaluated as in adults. Although an impressive amount of studies were carried out during recent years in adult patients with cancer-related or HIV-infection-related anaemias, thus allowing clear conclusions to be established on its efficacy, only a few trials with a small number of patients have been reported in children. Up-to-date, results in paediatric patients suggest that epoetin therapy is as useful as in adult patients, but prospective, randomised trials including large number of patients are essential to achieve definitive conclusions.

Dose response to a single intramuscular injection of recombinant adeno-associated virus-erythropoietin in monkeys

BACKGROUND

Anemia is a significant problem in many disease states. Erythropoietin (Epo) has been used in the treatment of anemia associated with numerous chronic diseases. This study investigates the dose-response profiles of a single intramuscular (im) injection of a recombinant adeno-associated virus vector (rAAV) containing the Epo gene with the goal of achieving a sustained elevation of hematocrit (Hct).

METHODS

Cynomolgus (cm) monkeys were given single injections of different doses of rAAV-cm-Epo. The biological effect of Epo gene expression was monitored by determining the Hct levels and circulating hormone levels by ELISA. Antibody to the rAAV capsid protein was also measured over the 41-week period of the experiment.

RESULTS

Epo expression was noted only when 2 x 10(11) or more particles were injected. Epo was noted to be increased as soon as 1 week postinjection and was maximum in 6 to 8 weeks. This level of expression remained constant for nearly 20 weeks. Animals given the highest dose of rAAV developed a higher Hct over the first 8 weeks postinjection than those given an intermediate dose. However, the maximum levels of hemoglobin were the same. There was a weak correlation between amount of rAAV injected and capsid antibody response.

CONCLUSIONS

AAV vectors are able to transduce skeletal muscle and are capable of achieving sustained expression and systemic delivery of a therapeutic protein following a single im administration. Dose responses to rAAV-Epo are achievable, although a threshold inoculum of virus is necessary to produce an effect and the therapeutic window is narrow.

Thrombopoietin is synergistic with other hematopoietic growth factors and physiologic platelet agonists for platelet activation in vitro

Thrombopoietin (TPO) is the primary physiologic regulator of platelet production. The effect of TPO on platelet function, both alone and in combination with other hematopoietic growth factors, adenosine diphosphate (ADP), and epinephrine, was investigated using fluorescent-labeled antibodies to the activation-dependent antigen CD62 (P-selectin) and flow cytometry. TPO stimulated CD62 expression on normal human platelets, and this expression was completely inhibited by the soluble extracellular domain of the TPO receptor, MPL. The growth factors granulocyte colony-stimulating factor (G-CSF) and erythropoietin (EPO), but not interleukin-3 (IL-3) or stem-cell factor (SCF), also stimulated platelet activation. The combination of EPO, SCF, ADP, and epinephrine with TPO were synergistic for platelet CD62 expression. These data further support a role for TPO in modulating platelet function.