Original Article. Nephrology Dialysis Transplantation

Transcription

1 Nephrol Dial Transplant (1989)4: European Dialysis and Transplant Association-European Renal Association Nephrology Dialysis Transplantation Original Article Single-dose Pharacokinetics of Recobinant Huan Erythropoietin in Patients with Various Degrees of Renal Failure J. Kindler 1, K.-U. Eckardt 3, B. Eher 2, K. Jandeleit 1, A. Kurtz 3, A. Schreiber 3, P. Scigalla 2 and H.-G. Sieberth 1 'Departent of Internal Medicine II, RWTH Aachen, 2 Boehringer Mannhei GbH, FRG, and institute of Physiology, Zurich, Switzerland Abstract. The pharacokinetic profile of recobinant huan erythropoietin (rhuepo) was studied after a single intravenous dose of 150 U/kg in ten patients with various degrees of renal function: group I, creatinine clearance >80l/in, n = 2; group II, creatinine clearance l/in, w = 6; group III, creatinine clearance <3l/in (patients undergoing haeodialysis) n = 2. Erythropoietin concentrations in seru and urine saples obtained over 48 h were easured by RIA. rhuepo was cleared fro circulation in an exponential fashion, the half-life ranged fro 6.5 to 12.7 h (ean 9.03 h) and was not different between the groups. The apparent volue of distribution varied fro to I/kg (ean I/kg) this corresponds to 1.5 ties the plasa volue and was unrelated to kidney function. Renal clearance (groups I, II) accounted for less than 3% of total body clearance, both paraeters were unaffected by decreasing renal function. These results indicate that, in accordance with anial data, the eliination of rhuepo occurs ainly through non-renal echaniss. Key words: Recobinant huan erythropoietin; Pharacokinetics; Renal function Correspondence and offprint requests to: Professor Dr J. Kindler, Departent of Internal Medicine II, RWTH Aachen, PauwelsstraBe, D-5100 Aachen, FRG. Introduction Initial clinical experience with the use of recobinant huan erythropoietin (rhuepo) for the treatent of the anaeia of end-stage renal disease has been very encouraging, with correction of the anaeia in nearly all cases and iproveent of the well-being of patients on dialysis [1,2]. However, relatively little is known about the pharacokinetic behaviour of erythropoietin; this is due to a previous lack of sensitive and specific assay techniques for the horone. In recent preliinary pharacokinetic studies the plasa half-life of rhuepo in huans ranged between 4 h and 12 h [3-6]. The objective of the present study was to deterine the effect of decreasing renal function on the pharacokinetic profile of the horone after a single intravenous dose. Patients and Methods Ten subjects aged years, with a bodyweight between 61 and 115 kg, were divided into three groups according to their renal function: group I, creatinine clearance > 80 l/in per , n = 2; group II, creatinine clearance l/in per , n = 6; group III, creatinine clearance < 3 l/in per (patients undergoing haeodialysis), n = 2. The objectives and iplications of the study were explained and signed infored consent was obtained fro each subject, as specified in the declaration of Helsinki (Tokyo revision 1975). Table I deonstrates patient characteristics. Six of the eight patients with

2 346 J. Kindleretal Table 1. Patient deographic data Patient Sex Underlying disease Creatinine clearance (l/in/ ) Haeatocrit (Vol %) Erythropoietin (U/l) w w Chronic bronchitis Vasovagal syncope Chronic gloerulonephritis Chronic gloerulonephritis Chronic gloerulonephritis Chronic gloerulonephritis Chronic pyelonephritis Chronic gloerulonephritis Chronic pyelonephritis Chronic gloerulonephritis IS chronic renal failure had chronic gloerulonephritis, four of the ten patients suffered fro anaeia with a haeatocrit less than 33%. In all subjects the seru concentrations of erythropoietin were in the noral range (10-25 U/l). Especially in the two dialysis patients, the seru horone concentrations were inappropriately low for the degree of anaeia. The recobinant huan erythropoietin was dissolved in 2 l of sterile distilled water and subsequently adinistered as a single intravenous bolus injection to each patient in a dosage ranging fro 0 to 152 U/kg bodyweight. Venous blood saples (1 l) for assay of erythropoietin were obtained by venepuncture iediately before and 0.25, 0.5, 0.75, 1,2,3,4,5,6,8, 10,12, 18,24, 36, 40 and 48 h after adinistration. Blood speciens were collected in vacutainers and centrifuged, and the seru separated and frozen at C until analysis. Urine was collected during the 48-h period in all subjects except the two dialysis patients. The total volue of urine voided during the collection period was easured and ixed thoroughly. A 10-l aliquot fro each urine collection was reoved and stored frozen at C until analysis. Erythropoietin was estiated in seru and urine saples as described previously [7], using a radioiunoassay based on rhuepo as tracer and iunogen. The lower detection liit of the assay is 5 U Epo/l, the interassay coefficient of variation is 6.7% (51 estiations of a saple containing U Epo/l; ean ± SD). To eliinate differences in dosages the seru concentrations were corrected to a dosage of 150 U/kg bodyweight. Model-independent pharacokinetic paraeters, including tie-independent peak values were obtained directly fro the data. The further paraeters were calculated according to standard pharacokinetic equations [8], for exaple the areas under the concentration-tie curve (AUC) were calculated by the trapezoidal rule and the eliination rate constant k was obtained fro the slope of the approxiately log-linear part of the concentration-tie curve by linear regression. The data were best fitted by a two-copartent open odel. Group data were expressed as x +. Fig. 1. Seru concentration-tie profile after a single intravenous application of rhuepo in a dosage of 150 U/kg body weight to ten patients with various degress of renal function. (Upper panel: seilogarithic plot of seru concentration.) 48

3 Single-dose Pharacokinetics of rhu Epo in Varying Degrees of Renal Failure 347 Table 2. Pharacokinetic paraeters of recobinant huan erythropoietin (rhuepo) in patients with various degrees of renal function Patient Group AUC (U/h/l) 1,29 (h) v, (I/kg)».* (h) a (l/in/kg) (l/in/kg) Cljin ofcl > 80 l/in II l/in III < 3 l/in Total ean AUC = area under seru concentration-tie curve t,, = terinal half-life t, j, = half-life of the distribution phase V z =apparent volue of distribution Cl = total body clearance CL = renal clearance Results Figure 1 deonstrates the 48-h profiles of average seru erythropoietin concentrations for all ten patients after the single intravenous adinistration of the horone. The tie-independent peak values ranged between and U/l (ean U/l) and did not differ between groups. Recobinant huan erythropoietin was cleared fro circulation in a coplex anner. Using the seilogarithic plot of seru concentration (upper panel of Fig. 1), a biexponential decay curve was obtained. After an initial faster decline corresponding to the distribution phase, a slower decrease of seru erythropoietin concentration can be observed, which represents the eliination of the horone. When the early phase of the disappearance curve (reflecting ainly distribution and eliination effects) is excluded, the apparent seru halflife of rhuepo averaged 9.03 h (range h) and was unrelated to renal function (Table 2.) Figure 2 shows the coparative tie courses of ean seru concentrations of erythropoietin after a bolus injection of 150 U/kg bodyweight in the three patient groups. The areas under the seru Epo concentrationtie curves (AUC 0 _ 48 h) of all patients varied fro 219 to U/h per l (ean ) and were unrelated to kidney function. Pooling the data fro all subjects, the apparent volue of distribution of the injected horone averaged I/kg (range ), this corresponds to 1.5 ties of the x K End-stage renal failure - Moderate renal failure D a Noral renal function Hours Fig. 2. seru concentrations of rhuepo after a single intravenous adinistration of 150 U/kg bodyweight to patients with various degrees of renal function. plasa volue. The ean half-life of the distribution phase (t 1/2o ) was 1.93 h and did not correlate to kidney function. The average total body clearance of rhuepo in the whole study group was 0.09 l/in per kg (range ) and did not show any correlation with the creatinine clearance. No significant difference between the groups could be detected for renal clearance of rhuepo, which was found to be less than 3% of total body clearance (ean 1.86% of total clearance).

4 348 J. Kindler et al Discussion The ajority of previous studies on the pharacokinetic profile of erythropoietin has been carried out with ipure preparations using insensitive and highly variable bioassays for the deterination of plasa disappearance of erythropoietin in different anial species and in huans [9-12]. In recent years the developent of sensitive radioiunoassays for erythropoietin has provided an iportant tool for studies on the pharacokinetic behaviour of the horone [7]. Our results confir previous investigations [5,9-11,,14], that erythropoietin adinistered by pulse injection is cleared fro circulation in a ultiexponential fashion. After exclusion of the initial distribution phase of the disappearance curve an approxiate onoexponential decay curve of rhuepo was obtained. The seru half-life of the injected horone averaged 9.03 h and was unffected by renal function. Corresponding data were reported in noral healthy volunteers [6] and in patients on aintenance haeodialysis [4,5]. In these studies ean half-life of rhuepo after the first injection ranged between 8.6 h and 12 h and was unrelated to the dose of the horone. A significant decrease in half-life could be observed on continued treatent with rhuepo [4,5]. Anial data with 35 S-labelled and biologically active recobinant erythropoietin did not show any difference in the half-life of the horone in noral and uraeic rats with 12.8 h and 11.5 h respectively. However, in a pharacokinetic study in the rat with pure huan erythropoietin labelled with 125 I, the plasa half-life of the horone was significantly prolonged fro 3.5 h in noral rats to 4.4 h in anials with ligated renal pedicles under steady-state conditions []. Siilar data were obtained in dogs by use of 12S I-labelled purified recobinant erythropoietin (repo) [14]. The ean eliination half-life for 125 I-rEpo in intact dogs (9.0±0.6h) and anephric dogs (.8±1.4h) was significantly different (P < 0.05). Previous observations together with the results of the present investigation suggest that peripheral erythropoietin eliination occurs ainly through non-renal echaniss. In patients with noral and ipaired renal function the apparant volue of distribution of the injected horone approxiated to 1.5 ties the plasa volue. This finding indicates that rhuepo penetrates the extracellular space, even if the distribution volue of the horone was found to be saller than the latter. Confiration of the substantial extravascular distribution space was also obtained in different anial species and in huans [6,9-12,,14]. The total body clearance values of rhuepo obtained in this study were consistently low ( l/in per kg) and were not influenced by decreasing renal function. In contrast, Fu et al. reported a 30% decrease of eliination clearance of 12S I-rEpo after bilateral nephrectoy when copared with that of the intact dog. Thus species differences in the pharacokinetic profile of erythropoietin ust be considered likely. In coparison with the protein horones insulin, glucagon or prolactin [16-18], the etabolic clearance rate of erythropoietin in rats was found to be considerably less but was siilar to the etabolic clearane rate of glycoprotein horones as hoologous luteinizing and follicle stiulating horone{]. The renal handling of erythropoietin is still unclear. Although kidney hoogenates degraded 125 I-Epo in vitro [], the physicocheical characteristics of this glycoprotein horone probably ipede its degradation and eliination by the kidneys. In the present study, renal clearance of rhuepo accounted for less than 3% of total body clearance and did not depend on renal function. These data are in close agreeent with previous reports suggesting that in rats, dogs and huans the urinary excretion contributes only 4%-10% of the overall eliination rate of erythropoietin [11-]. In view of this finding it sees likely that peripheral erythropoietin disposal occurs ainly through the liver and possiby through erythropoietic tissue. In suary, this study deonstrates, that the peripheral etabolis of rhuepo is rearkably sluggish and depends ainly on extrarenal eliination echaniss. References 1. Winearls CG, Oliver DO, Pippard MJ, Reid C, Dowing MR, Cotes PM. Effect of huan erythropoietin derived fro recobinant DNA on the anaeia of patients aintained by chronic haeodialysis. Lancet 1986; 2: Eschbach JW, Egrie JC, Downing MR, Browne JK, Adason JW. Correction of the aneia of end-stage renal disease with recobinant huan erythropoietin: results of a Phase I and II clinical trial. N Engl J Med 1987; 316: Winearls CG, Cotes PM, Pippard M, Reid C, Oliver DO. Correction of anaeia in haeodialysis patients with recobinant erythropoietin - follow up and results of pharacokinetics, ferrokinetics and bone arrow culture studies. Xth International Congress of Nephrology. London July 1987, Abstracts, p Muirhead N, Keown PA, Slaugther D et al. Recobinant huan erythropoietin in the anaeia of chronic renal failure: a pharacokinetic study. Nephrol Dial Transplant 1988; 3: Egrie JC, Eschbach JW, McGuire T, Adason JW. Pharacokinetics of recobinant huan erythropoietin (rhuepo) adinistered to heodialysis (HD). Kidney Int 1988; 33: Urabe A, Tabaku F, Mizoguchi H et al. Effect of recobinant huan erythropoietin on the aneia of chronic renal failure. Int J Cell Cloning 1988; 6: Eckardt K-U, Kurtz A, Hirth P, Scigalla P, Wieczorek L. Bauer C. Evaluation of the stability of huan erythropoietin in saples for radioiunoassay. Klin Wochenschr 1988; 66: Coittee for pharacokinetic noenclature of the Aerican College of Clinical Pharacology, Philadelphia, Pennsylvania. Manual of sybols, equations and definitions in pharacokinetic. J Clin Pharacol 1982; 22: V. 9. Reisan KR, Dietrich DA, Ito K, Schaus JW. Influence of disappearance rate and distribution space on plasa concentration of erythropoietin in noral rats. J Clin Invest 1965; 65: Roh BL, Paulo LG, Thopson J, Fisher JW. Plasa disappearance of' "I-Iabeled erythropoietin in anesthetized rabbits. Proc Soc Exp Biol Med 1972; 141: Weintraub AH, Gordon AS, Bucker EL, Caiscoli JF, Contrera

5 Single-dose Pharacokinetics of rhuepo in Varying Degrees of Renal Failure JF. Plasa and renal clearance of exogenous erythropoietin in the dog. A J Physiol 1964; 7: Rosse WF, Waldann TA. The etabolis of erythropoietin in 16. patients with aneia due to deficient erythropoiesis. J Clin Invest 1964:43: Eanouel DS, Goldwasser E, Katz AJ. Metabolis of pure 17. huan erythropoietin in the rat. A J Physiol 1984; 247: F168-F Fu J-S. Lertora JJL, Brookins J, Rice JC. Fisher JW. Pharacokinetics of erythropoietin in intact and anephric dogs. J Lab Clin Med 1988; 111: Scigalla P, Hoelk G. Pahlke W. Pharacokinetics of recobinant 349 erythropoietin (repo) in noral and uraeic rats. Nephrol Dial Transplant 1987; 2: 389 Eanouel DS, Fang VS. Katz J. Prolactin etabolis in the rat: role of the kidney in degradation of the horone. (Renal Fluid Electrolyte Physiol 9) A J Physiol 1981; 240: F437-F445 Eanouel DS, Jaspan JB, Rubenstein AH, Huen AH-J, Fink E, Katz AJ. Glucagon etabolis in the rat. Contribution of the kidney to the atabolic clearance rate of the horone. J Clin Invest 1978:62:6- Katz AJ, Rubenstein AH. Metabolis of proinsulin, insulin and C-peptideintherat.yc/in/«( 1973; 52: Receivedfor publication Accepted