Iron Chelation with Deferasirox (Exjade^®) Improves Iron Burden in Patients with Myelodysplastic Syndromes (MDS)

INTRODUCTION: The majority of patients (pts) with MDS require red blood cell transfusions, which can result in iron overload and its clinical sequelae. The US03 trial is designed to evaluate the long-term efficacy and safety of the once-daily, oral iron chelator, deferasirox (DFX), in pts with lower-risk MDS. In this ongoing study 93/176 pts have now completed 12 months of treatment.

METHODS: US03 is a Phase II, open-label, 3-year trial in pts with Low- or Int-1 IPSS-risk MDS and transfusional iron overload (serum ferritin [SF] 1000 μg/L and >20 units RBC transfusions), with serum creatinine (SCr) 2-fold the upper limit of normal (ULN). Initial DFX dose was 20 mg/kg/day and could be increased to 40 mg/kg/day based on tolerability and response. SF was monitored monthly; labile plasma iron (LPI), the reactive species of non-transferrin-bound iron, was assessed quarterly.

BASELINE FEATURES: 176 pts were enrolled at 45 centers. Mean age: 70 years (range 21–90); 105 men and 71 women; IPSS Low risk (n=47; 27%); Int-1 (n=126; 72%); other (n=3; 2%). Mean baseline iron status was: SF, 3397 μg/L (863–36,280); LPI, 0.4 μmol/L (0.0–3.6). Forty-one percent of pts had elevated LPI at baseline (≥0.5 μmol/L). Mean number of lifetime prior transfusions: 63; mean duration of transfusions: 3.5 years (0–34). MDS therapy at study entry included azacitidine, hydroxyurea, lenalidomide, thalidomide or decitabine in 25 pts, and growth factors in 48 pts. Calculated creatinine clearance was normal (>80 mL/min) in 77 pts and abnormal (abn) in 99: mildly abn (51– 80 mL/min) in 71; moderately abn (30–50 mL/min) in 25; severely abn (<30 mL/min) in 3.

RESULTS: Over 12 months, the mean dose of DFX was 21 mg/kg/day, and the mean transfusion rate was 3.4 units/month. Mean SF±SEM (μg/L) values at baseline, 3, 6, 9 and 12 months were 3397±233 (n=176), 3057±144 (n=143), 2802±128 (n=126), 2635±148 (n=109) and 2501±139 (n=93), respectively. In pts with elevated baseline LPI, sustained suppression of mean LPI to the normal range was achieved after 3 months of treatment. The figures show reductions (±SEM) in SF, and in LPI in pts with baseline LPI ≥0.5 μmol/L. Hematological improvement by IWG 2000 criteria was achieved in 8 pts (5%): erythroid response in 5 (major 3; minor 2); platelet in 1 (major); neutrophil in 1 (major); and combined platelet and neutrophil in 1.

SAFETY: Of 173 pts, 18 (10%) discontinued DFX because of suspected adverse events (AEs), and an additional 5 (3%) because of serious AEs (SAEs). The most common AEs were diarrhea (n=9), rash (n=3) and nausea (n=2), while the most common SAEs were rash (n=2) and diarrhea (n=1). Of 147 pts with normal baseline SCr, 26 (18%) increased >ULN on at least two occasions (3.0 mg/dL max SCr). There were 9/172 (5%) and 22/168 (13%) new onset cases of grade 3–4 thrombocytopenia and neutropenia, respectively, none suspected to be related to DFX; 7 and 11 of these pts, respectively, were receiving other MDS treatment therapies, including lenalidomide, decitabine, hydroxyurea and azacitidine. There were 17 deaths (10%), due to sepsis/infection (n=8), disease progression (n=4), intracranial bleed (n=2), cardio-respiratory arrest (n=2) and renal failure (n=1), all thought to be unrelated to DFX.

CONCLUSIONS: In these heavily iron-overloaded pts, DFX was generally well tolerated. New onset cytopenias were consistent with the underlying disease. A 2-year extension phase of this study will assess the long-term safety and efficacy of DFX as well as the clinical impact on cardiac, hepatic and endocrine function.

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