Study to Assess Darbepoetin Alfa Dosing for the Correction of Anemia in Pediatric Patients With Chronic Kidney Disease

Time to First Hemoglobin Value ≥ 10.0 g/dL

The time from study Day 1 to the day a participant first achieved hemoglobin ≥ 10.0 g/dL for participants who achieved hemoglobin ≥ 10.0 g/dL.

Time frame: 24 weeks

Hemoglobin Concentration Over Time

Time frame: Baseline and Weeks 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25.

Weight-adjusted Darbepoetin Alfa Dose at Time of Achieving First Hemoglobin ≥ 10.0 g/dL

The darbepoetin alfa dose at the time a participant achieved a first hemoglobin level ≥ 10.0 g/dL, divided by the participant's weight measured at the closest study week prior to the dosing, post dialysis.

Time frame: 24 weeks

Darbepoetin Alfa Weight-Adjusted Dose Over Time

Arithmetic means are provided; Withheld doses are counted as 0 μg.

Time frame: Day 1 (initial dose) and Weeks 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25.

Change From Baseline at Week 13 and Week 25 in Parent-reported Pediatric Quality of Life Inventory (PedsQL) Scores

The PedsQL is a health-related quality of life (HRQOL) questionnaire that can be used to measure quality of life in children ≥ 2 years old. The 23-item PedsQL 4.0 includes physical functioning (8 items), emotional functioning (5 items), social functioning (5 items), and school functioning (5 items). Separate questionnaires for ages 2 to 4 (toddler), 5-7, 8-12, and 13-18 years are used for parent proxy-reporting, which assesses parents' perceptions of their child's HRQOL. The instructions ask how much of a problem each item has been during the past 1 month; each item is answered on a 5-point scale: 0 = never a problem; 1 = almost never a problem; 2 = sometimes a problem; 3 = often a problem; 4 = almost always a problem. Scores from the 4 subscales, the total score, and the psychosocial composite score were generated using standard algorithms. Each item's score in the questionnaire was converted to a 0 to 100 scale (with higher scores indicating better HRQOL).

Time frame: Baseline, Week 13 and Week 25 (or end of study visit if earlier than Week 25)

Change From Baseline at Week 13 and Week 25 in Child Self-reported Pediatric Quality of Life Inventory (PedsQL) Scores

The PedsQL child self-reported questionnaire was used in children \> 5 years old. The 23-item PedsQL 4.0 includes physical functioning (8 items), emotional functioning (5 items), social functioning (5 items), and school functioning (5 items). Separate questionnaires for ages 5-7, 8-12, and 13-18 years was used for child self-reporting. The instructions asked how much of a problem each item has been during the past 1 month; each item is answered on a 5-point scale for ages 8 to 18 (0 = never a problem; 1 = almost never a problem; 2 = sometimes a problem; 3 = often a problem; 4 = almost always a problem), or simplified to a 3-point scale for ages 5 to 7 (0 = not at all a problem; 2 = sometimes a problem; 4 = a lot of a problem). Scores from the 4 subscales, the total score, and the psychosocial composite score were generated using standard algorithms. Each item's score in the questionnaire was converted to a 0 to 100 scale (with higher scores indicating better HRQOL).

Time frame: Baseline, Week 13 and Week 25 (or end of study visit if earlier than Week 25)

Number of Participants With Treatment-emergent Adverse Events

A serious adverse event (SAE) is defined as an adverse event that meets at least one of the following serious criteria: • is fatal, • is life threatening, • requires in-patient hospitalization or prolongation of existing hospitalization, • results in persistent or significant disability/incapacity, • is a congenital anomaly/birth defect, and/or • other significant medical hazard. The investigator assessed whether the adverse event was related to the investigational product (IP). Events of interest included hypertension, ischemic heart disease, cardiac failure, cerebrovascular disorders, convulsions, embolic and thrombotic events, embolic and thrombotic events: venous, embolic and thrombotic events: arterial, embolic and thrombotic events: vessel type unspecified and mixed arterial and venous, dialysis vascular access thrombosis, antibody-mediated pure red cell aplasia, hypersensitivity, lack of efficacy-effect, and malignancies.

Time frame: 25 weeks

Hemoglobin Serial Rate of Change (ROC) Over Time

Calculated using the serial method as the change in hemoglobin from the previous non-missing hemoglobin level divided by number of days in between, and then multiplied by 7.

Time frame: Weeks 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25.

Number of Participants With Hemoglobin > 12.0, > 13.0, and > 14.0 g/dL During the Study

Time frame: 25 weeks

Maximum Increase in Hemoglobin Over Any 2 Week Period

The maximum increase between any 2 non-missing hemoglobin measurements over any 2-week period from Day 1.

Time frame: 25 weeks

Change From Baseline in Systolic Blood Pressure Over Time

Time frame: Baseline and Weeks 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25.

Change From Baseline in Diastolic Blood Pressure Over Time

Time frame: Baseline and Weeks 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25.

Number of Participants Who Developed Anti-erythropoiesis Antibodies

Participants who were negative for anti-erythropoiesis antibodies at Baseline (pre-dose) and who developed anti-erythropoiesis antibodies during the study. Serum samples were tested using Amgen's Surface Plasmon Resonance Immunoassay (SPRIA) method.

Time frame: 25 weeks

Darbepoetin Alfa Serum Concentrations for Participants Less Than 6 Years of Age

Serum concentrations of darbepoetin alfa were measured by an enzyme-linked immunosorbent assay (ELISA).

Time frame: Weeks 1, 2, and 3 before the investigational product dose and 2 days after the first investigational product dose