An observational cohort study of extended dosing (once every 2 weeks or once monthly) regimens with darbepoetin alfa in patients with chronic kidney disease not on dialysis: the EXTEND study

Background. Darbepoetin alfa (DA) has been shown to be an effective treatment of anaemia in patients with chronic kidney disease (CKD) not on dialysis (NoD). EXTEND is an observational study assessing the effectiveness of DA administered once biweekly (Q2W) or monthly (QM) in a general CKD-NoD population. Methods. Adult CKD-NoD patients starting DA Q2W/QM treatment in June 2006 or later were eligible. Retrospective and/or prospective data including haemoglobin levels and erythropoiesis-stimulating agent (ESA) dosing were collected for 6 months before and 12 months after DA initiation. Mean Hb levels were calculated every 3 months, and ESA dose was converted to a geometric mean weekly DA equivalent dose and summarized monthly. Results. Data from 4278 patients showed that patients receiving ESA treatment before DA Q2W/QM initiation had a mean (95% confidence interval) Hb level of 11.9 g/dL (11.8–12.0 g/ dL) at initiation and 11.6 g/dL (11.6–11.7 g/dL) at Months 10–12, with mean ESA dose of 22 lg/week (21–23 lg/week) prior to initiation, 16 lg/week (15–16 lg/week) at initiation and 16 lg/week (15–16 lg/week) at Month 12. In ESA-naive patients, Hb levels increased from 10.3 g/dL (10.2–10.3 g/dL) at initiation to 11.7 g/dL at Months 4–6 and were maintained at a mean level of 11.7 g/dL (11.7–11.8 g/dL) at Months 10– 12, with mean ESA dose of 16 lg/week (16–17 lg/week) at initiation and 16 lg/week (16–17 lg/week) at Month 12. In the 85% of patients receiving DA at extended intervals (Q2W or less frequently) at Month 12, 12 patients (0.3%) experienced DA-related adverse reactions. Conclusion. DA Q2W/QM was an effective treatment of anaemia in the general CKD-NoD patient population and a dose increase was not required in patients switching from a previous ESA regimen.