Roxadustat (FG4592; ASP1517; AZD9941) in the Treatment of Anemia in Patients with Lower Risk Myelodysplastic Syndrome (LR-MDS) and Low Red Blood Cell (RBC) Transfusion Burden (LTB)

Background: Roxadustat (FG-4592) is an oral hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor that promotes coordinated erythropoiesis through HIF-mediated transcription. Transient, intermittent HIF activation by roxadustat mimics a physiological response that increases endogenous erythropoietin (EPO) production to near physiologic range and stimulates EPO receptor synthesis. In addition, roxadustat promotes iron metabolism by reducing serum hepcidin to allow absorption of iron from the gut and mobilize iron from cellular storage making more iron available for erythropoiesis. Roxadustat corrected and maintained hemoglobin (Hb) in chronic kidney disease patients in multiple Phase 3 trials irrespective of underlying inflammation. In these studies, roxadustat-treated patients required less IV iron to correct and maintain Hb compared to erythropoiesis-stimulating agent (ESA)-treated patients. MDS is characterized by symptomatic anemia and many patients require RBC transfusion and/or ESA treatment. As response to ESAs varies across sub-populations with limited durability, there is an unmet need for treatment of anemia in LR-MDS. This is the first study to evaluate the effect of roxadustat in treating anemia in primary MDS patients. Methods: This is a two-part study; an open-label (OL), dose-finding segment (N=24) followed by a randomized double-blind (DB) placebo-controlled segment (N=156, 3:2 ratio of roxadustat to placebo). The primary goal of the OL segment is to identify the starting roxadustat dose-level for the DB segment. A total 24 patients in the OL segment have been enrolled in three sequential cohorts with 8 patients in each starting dose cohort (1.5, 2.0, or 2.5 mg/kg). RBC transfusion has been allowed per institutional criteria. Eligible patients were very low, low or intermediate risk primary MDS patients based on the International Prognostic Scoring System Revised classification with <5% bone marrow blasts; had baseline Hb < 10.0 g/dL; were >18 years old; and had LTB defined as receiving 1-4 RBC units per 8 week period. Patients were ineligible if they used an ESA within 8 weeks of the study start; had endogenous EPO levels >400 mIU/mL, or had a del(5q) cytogenetic abnormality. Roxadustat was administered TIW with doses titrated every 8 weeks per a dosing algorithm based on Hb response and transfusion need. Data from the OL segment were evaluated to identify the starting dose for the DB segment (currently enrolling). The primary endpoint is transfusion independence (TI) for ≥56 consecutive days during the first 28 weeks of treatment. The proportion of patients who achieve ≥50% reduction in RBC transfusion over any 8 weeks compared to baseline (8 weeks prior to Day 1) and proportion of patients who achieve TI for ≥20 consecutive weeks are evaluated. Safety and tolerability are assessed by adverse event reporting, percentage of patients progressing to acute myeloid leukemia (AML), and clinical laboratory values. Results: Twenty-four transfusion dependent, LR-MDS patients were enrolled in the OL segment of this global Phase 3 trial. Nine patients (38%) achieved TI for at least 56 consecutive days within the first 28 weeks.Three of 9 patients started at 1.5 mg/kg dose, 1 patient started at 2.0 mg/kg dose and 5 patients started at 2.5 mg/kg dose. At the time of achieving TI, 7 of 9 patients (78%) were on 2.5 mg/kg dose, 1 patient (11%) was on 2.0 mg/kg dose (started with 1.5 mg/kg dose) and one patient (11%) was on 1.5 mg/kg dose. Four patients remained TI for >20 weeks (one at 1.5 mg/kg dose level and three at 2.5 mg/Kg dose-level). One additional patient achieved TI after the initial 28-week dosing period at a dose-level of 3.5 mg/kg (starting dose 2.0 mg/kg). A total of 14 patients (58%) achieved a ≥50% reduction in RBC units in any 8-week period compared to baseline (range of 2-4 RBC units in 8 weeks before dosing); 12 of these patients were at ≥ 2.5 mg/kg dose level when achieving a 50% reduction in transfusion without need for IV iron. The overall safety profile observed is consistent with the patient population under study. Six patients reported 8 treatment-emergent SAEs with none being fatal. No patient has progressed to AML. Full results from the OL segment of the study will be presented. Conclusion: Based on the observed response (TI and transfusion reduction) and safety profile in LR-MDS patients, 2.5 mg/kg was selected as the starting dose for the ongoing 156-patient DB portion of the trial.