Combined Chelation Therapy with Deferasirox and Deferoxamine In Transfusion-Dependent Thalassemia

Abstract 4269

Therapeutic regimens that combine two iron chelators may enhance chelation efficiency by improving access to different tissue iron stores and control of the toxic labile iron pool. The combination of two chelators can reduce toxicity through averting the need for high doses of a single drug, but it is essential to establish the safety such regimens. We therefore explored the combined use of deferasirox (DSX) and deferoxamine (DFO) in patients with transfusion-dependent thalassemia who had failed standard chelation therapy with single drug. Patients were eligible if the liver iron concentration (LIC) >15 mg/g dry liver-weight or if iron-induced end organ injury was present. Subjects were monitored for hepatic and renal toxicity, visual or auditory changes, and the development of new complications from iron overload. The ability of the combined therapy to control systemic iron burden (serum ferritin and LIC) and myocardial iron overload (MRI T2*) was evaluated. We also measured changes in plasma levels of non-transferrin bound iron (NTBI) and labile plasma iron (LPI).

Fifteen subjects were enrolled in 3 groups: adults with LIC <15 mg/g dry liver-weight (group A), adults with LIC >15 mg/g (group B), and children 8–18 years with LIC >5 mg/g (group C). The duration of therapy was 52 weeks. DSX (20-30 mg/Kg) was administered daily and DFO (35-50 mg/Kg/infusion) was infused on 3–7 days/week (as 8–12 hour infusion) based upon the degree of iron overload present at baseline. At the initiation of the study, the mean daily dose of DFO was 16, 33, and 17 mg/Kg/day and mean DSX dose was 21, 25 and 22 mg/Kg/day for groups A, B and C, respectively. At the conclusion of the trial, the median LIC declined by 48% from 10.8 mg/g (3.9-34.8 mg/g) to 5.7 mg/g (1.0-24.0 mg/g, p=0.003). The median ferritin fell by 43% from 2030 ng/mL (1000-5230 ng/mL) to 1150 ng/mL (421-5260 ng/mL, p=0.008). Myocardial iron in the 3 subjects who had T2* <20 msec at study entry (range 6.5–19.5 msec at week 0) showed an average improvement of +2.43 msec following treatment (range 8.8–21.3 msec at week 52, p=0.027). All 3 subjects with left ventricular ejection fraction below 60% at baseline (47.5-58.1%) showed improvement at end of study (60.6-64.4%). There was progressive decline in median plasma NTBI level during the study from 3.26 μM (1.79-5.79 μM) at baseline to 2.38 μM (1.59-3.08 μM) at 12 months (p=0.008). DSX produced immediate and significant decline in plasma NTBI when administered during infusion of DFO. The median plasma NTBI measured on DFO alone was 2.46 μM (0.92-5.90 μM), which decreased to 1.96 μM (0-3.50 μM) following administration of the dose of DSX (p<0.001). A sustained control of the LPI fraction was also demonstrated throughout the study period. At baseline the median LPI was 0.87 μM (0-2.43 μM) which decreased to 0.05 μM (0-1.20 μM) during the study period (p=0.004).

No significant toxicity or unusual adverse events were observed with combined chelation therapy in this group of high-risk patients with thalassemia. Elevation of serum creatinine or ALT was not observed in any subject. One subject from group B died at 9 weeks from start of trial from sepsis. One subject interrupted DSX therapy because of abdominal pain. In all other cases the treatment was well tolerated and no dose adjustment or suspension of therapy was required on account of toxicity. Protocol-mandated modification of treatment (temporary cessation of DSX or DFO) occurred in three subjects owing to a marked fall in serum ferritin and LIC. These results suggest that simultaneous administration DSX and DFO is well tolerated and has low potential for toxicity. Combined chelation therapy appears to be effective in rapidly reducing systemic iron burden, lowering myocardial iron, and controlling plasma NTBI and LPI in patients at risk of developing end-organ damage.