Efficacy and safety of paricalcitol in children with stages 3 to 5 chronic kidney disease.

BACKGROUND: Elevated intact parathyroid hormone (iPTH) levels can contribute to morbidity and mortality in children with chronic kidney disease (CKD). We evaluated the pharmacokinetics, efficacy, and safety of oral paricalcitol in reducing iPTH levels in children with stages 3-5 CKD. METHODS: Children aged 10-16 years with stages 3-5 CKD were enrolled in two phase 3 studies. The stage 3/4 CKD study characterized paricalcitol pharmacokinetics and compared the efficacy and safety of paricalcitol with placebo followed by an open-label period. The stage 5 CKD study evaluated the efficacy and safety of paricalcitol (no comparator) in children with stage 5 CKD undergoing dialysis. RESULTS: In the stage 3/4 CKD study, mean peak plasma concentration and area under the time curve from zero to infinity were 0.13 ng/mL and 2.87 ng•h/((or ng×h/))mL, respectively, for 12 children who received 3 µg paricalcitol. Thirty-six children were randomized to paricalcitol or placebo; 27.8% of the paricalcitol group achieved two consecutive iPTH reductions of ≥30% from baseline versus none of the placebo group (P = 0.045). Adverse events were higher in children who received placebo than in those administered paricalcitol during the double-blind treatment (88.9 vs. 38.9%; P = 0.005). In the stage 5 CKD study, eight children (61.5%) had two consecutive iPTH reductions of ≥30% from baseline, and five (38.5%) had two consecutive iPTH values of between 150 and 300 pg/mL. Clinically meaningful hypercalcemia occurred in 21% of children. CONCLUSIONS: Oral paricalcitol in children aged 10-16 years with stages 3-5 CKD reduced iPTH levels and the treatment was well tolerated. Results support an initiating dose of 1 µg paricalcitol 3 times weekly in children aged 10-16 years.

Collagen XVIII mutation in Knobloch syndrome with acute lymphoblastic leukemia.

Knobloch syndrome (KNO) is caused by mutations in the collagen XVIII gene (COL18A1) and patients develop encephalocele and vitreoretinal degeneration. Here, we report an El Salvadorian family where two sisters showed features of KNO. One of the siblings also developed acute lymphoblastic leukemia. DNA sequencing of COL18A1 revealed a homozygous, 2-bp deletion (c3514-3515delCT) in exon 41, which leads to abnormal collagen XVIII and deficiency of its proteolytic cleavage product endostatin. KNO patients with mutations in COL18A1 may be at risk for endostatin-related conditions including malignancy.

Low doses of pamidronate to treat osteopenia in children with severe cerebral palsy: a pilot study.

The aim of this study was to test the efficacy of low doses of pamidronate in increasing bone mineral density (BMD) in non-ambulatory children and adolescents with cerebral palsy (CP). Twenty-three non-ambulatory children and adolescents (12 females, 11 males; mean age 10y [SD 5y], range 4y 1 mo-17 y 11 mo) with severe spastic quadriplegic CP and low BMD were recruited from a multidisciplinary clinic. Severity of CP was graded at Level IV (n=10) and Level V (n=13) using the Gross Motor Function Classification System. Patients received intravenous pamidronate (4.12 mg/kg/y, maximum 45 mg/d) every 4 months. Lumbar spine and femoral neck BMD were measured at baseline and after 4 and 12 months. Twelve months after the first dose of pamidronate there was a significant increase in lumbar spine and femoral neck BMD (p<0.01 for both sites) and z scores compared with baseline values (p<0.01 for both sites). Mean BMD z scores increased 1.6 points for femoral neck and 1.9 points for lumbar spine after 12 months of pamidronate treatment. Serum intact parathyroid hormone increased significantly and cross-linked N-teleopeptide of type I collagen decreased significantly at 12 months. No significant side effect was noted. Low doses of pamidronate are well tolerated and significantly increase BMD in non-ambulatory children and adolescents with CP.

Darbepoetin alfa for the treatment of anemia in pediatric patients with chronic kidney disease.

Darbepoetin alfa, an erythropoiesis-stimulating glycoprotein, has proved efficacious in the treatment of anemia of chronic kidney disease (CKD) in adult subjects. However, little information is available from pediatric populations. We conducted an open-label, non-inferiority, 28-week study comparing the efficacy of darbepoetin alfa with that of recombinant human erythropoietin (rHuEpo) in pediatric subjects with CKD. Subjects, aged 1-18, who were receiving stable rHuEpo treatment (n=124) were randomized (1:2) to either continue receiving rHuEpo or convert to darbepoetin alfa, with doses titrated to achieve and maintain hemoglobin (Hb) levels between 10.0 and 12.5 g/dl. Darbepoetin alfa was considered to be non-inferior to rHuEpo if the lower limit of the two-sided 95% confidence interval (CI) for the difference in the mean change in Hb between the two treatment groups was above -1.0 g/dl. The adjusted mean change in Hb between the baseline and the evaluation period for the rHuEpo and darbepoetin alfa groups was -0.16 g/dl and 0.15 g/dl, respectively, with a difference of 0.31 g/dl (95% CI: -0.45, 1.07) between the means. These results, and the comparable safety profiles, demonstrate that darbepoetin alfa is non-inferior to rHuEpo in the treatment of anemia in pediatric patients with CKD.

Experience with autogenous arteriovenous access for hemodialysis in children and adolescents.

The National Kidney Foundation's DOQI-NKF recommendation to construct an autogenous arteriovenous access (AAVA) for chronic hemodialysis whenever possible can be a challenge in the pediatric population. This report reviews recent surgical experience in this patient subgroup. From March 1999 to April 2004, 47 consecutive children requiring permanent vascular access had construction of AAVA. There were 16 girls and 31 boys, with a mean age of 14.6 years (range 5-20). The surgeon preoperatively mapped veins with ultrasound in all patients. Access sites were radial-cephalic (n = 16), upper arm brachial-cephalic (n = 15), transposed upper arm brachial-basilic (n = 7), and transposed femoral vein (n = 9). An operating microscope was used to construct three radial-cephalic accesses in individuals with small arteries. Three forearm cephalic veins were transposed (one at the original surgical procedure and two postoperatively). Five upper arm cephalic veins were transposed (three at the original surgical procedure and two postoperatively). Femoral vein accesses were constructed for either exhausted access in the upper extremities (n = 7) or patient preference (n = 2). Primary patency at 1 and 2 years was 100% and 96%, respectively. Secondary patency at 1 and 2 years was 100%. One individual with a radial-cephalic AAVA and severe radial artery calcification required an inflow procedure. Thirty-five accesses are currently in use (functionally patent), eight are in individuals with successful renal transplants, and two are maturing; one individual declines using the access. Two accesses are secondarily patent (thrombosed and repaired 12 and 29 months after construction, respectively), and one access thrombosed after 27 months (abandoned). Construction of an AAVA is possible in virtually all pediatric age individuals if attention is given to preoperative vein mapping, selective use of an operating microscope, and creation of a transposed femoral vein when upper extremity access is neither possible nor desired.

Iron therapy in the pediatric hemodialysis population.

Iron therapy maintains iron stores and optimizes the response to recombinant human erythropoietin (r-HuEPO) in patients with end-stage renal failure. Information is limited, however, regarding the preferential route of iron administration in pediatric patients receiving hemodialysis. Therefore, we prospectively randomized 35 iron-replete patients (aged >1 to <20 years) to receive up to 16 weeks of maintenance i.v. ( n=17) or daily oral ( n=18) iron. Eligible patients had received hemodialysis for >2 months, had a baseline transferrin saturation [TSAT] >20%, and were receiving maintenance r-HuEPO. Treatment arms were evenly distributed with respect to baseline demographic and clinical characteristics, with no statistically significant differences in baseline hemoglobin (Hb), hematocrit (Hct), reticulocyte Hb content (CHr), serum ferritin (SF), TSAT, or r-HuEPO dose. In the 35 patients, i.v. iron dextran and not oral iron was associated with a significant increase (138.5 to 259.1 ng/ml, P=0.003) in SF. A comparison of the change in SF between the i.v. iron group and the oral iron group was also significant ( P=0.001). Whereas only i.v. iron was associated with a significant decrease in the dose of r-HuEPO (234.0 to 157.6 U/kg per week, P=0.046) and an increase of the CHr (29.2 to 30.1 pg, P=0.049), these changes were not significantly different from those experienced by patients in the oral iron group. In both groups, the Hct remained stable and in neither group was there a significant change in the TSAT. In summary, although both oral and i.v. iron maintained patients in an iron-replete state in this short-term study, only i.v. therapy allowed for a significant improvement in iron stores.

Safety and pharmacokinetics of ascending single doses of sirolimus (Rapamune, rapamycin) in pediatric patients with stable chronic renal failure undergoing dialysis.

Sirolimus (Rapamune, rapamycin) has been shown to be an effective and safe immunosuppressive drug in adult kidney transplant patients when administered concomitantly with cyclosporine (CsA) and steroids. This study reports on a phase 1 assessment of the drug's tolerance, safety, and pharmacokinetic parameters in pediatric patients. The safety and pharmacokinetic profiles of ascending single doses of sirolimus oral solution were investigated in 32 clinically stable pediatric patients on chronic hemodialysis (n = 26) or peritoneal dialysis (n = 6). Patients were divided into two age groups (5-11 and 12-18 yr), and each patient received either a single dose of sirolimus (1, 3, 9, or 15 mg/m(2)) or placebo. Whole blood and plasma samples were collected from each patient for the determination of sirolimus pharmacokinetic parameters. Safety assessments were based on reports of adverse events and results of scheduled physical examinations, vital sign measurements and clinical laboratory tests. The younger patients (5-11 yr) showed statistically significant increases in whole blood sirolimus t(max) (p < or = 0.05) and weight-normalized CL/F (p<0.05) when compared with older patients (12-18 yr). There were no differences in terminal t(1/2), V(ss)/F, dose-normalized peak concentration (C(max)) and AUC, or the B/P. The whole blood sirolimus mean t(max) and weight-normalized CL/F in younger patients were increased by approximately 41.5% and 30%, respectively. Whole blood sirolimus concentrations exhibited less than proportional increases with ascending doses, which may have been caused by the large inter-subject variability in CL/F, small number of subjects, and a potentially inherent decrease in sirolimus bioavailability in younger pediatric patients. Adverse events occurred in all dose and age groups, with headache and stomach pain being the most frequently observed events. No deaths or serious adverse events were reported, and no patient withdrew from the study because of an adverse event. Based on an inter-study analysis, weight-normalized CL/F in the current population of younger pediatric dialysis patients (5-11 yr, 544 +/- 463 mL/h/kg, n = 7) was increased by 90% (p < or = 0.05) compared with healthy adults (19-36 yr, 287 +/- 111 mL/h/kg, n = 25). These results suggest that younger pediatric patients might require an increased maintenance dose of sirolimus to achieve whole blood exposures similar to those in healthy adults. Sirolimus is well tolerated as a single dose of 1, 3, 9, or 15 mg/m(2).

Pharmacokinetics of darbepoetin alfa in pediatric patients with chronic kidney disease.

Darbepoetin alfa is a novel erythropoiesis-stimulating protein with a two- to threefold longer half-life than recombinant human erythropoietin (epoetin) in adult patients with chronic kidney disease (CKD). This randomized, open-label, crossover study was conducted to determine the pharmacokinetic profile of darbepoetin alfa in pediatric patients with CKD. Twelve patients 3-16 years of age with CKD were randomized and received a single 0.5 micro g/kg dose of darbepoetin alfa administered intravenously (IV) or subcutaneously (SC). After a 14- to 16-day washout period, patients received an identical dose of darbepoetin alfa by the alternate route. After IV administration, the mean clearance of darbepoetin alfa was 2.3 ml/h per kg, with a mean terminal half-life of 22.1 h. After SC administration, absorption was rate limiting, with a mean terminal half-life of 42.8 h and a mean bioavailability of 54%. Comparison of these results with those from a previous study of darbepoetin alfa in adult patients indicated that the disposition of darbepoetin alfa administered IV or SC is similar in adult and pediatric patients, although absorption may be slightly more rapid in pediatric patients after SC dosing. The mean terminal half-life of darbepoetin alfa in this study was approximately two- to fourfold longer than that previously reported for epoetin in pediatric patients.