A Pilot Study of Exjade (Deferasirox) As Monotherapy in Higher Risk MDS or Acute Myeloid Leukemia

Although deferasirox use is established in clinical practice for iron overload, there have been a spate of case reports describing hematologic improvement attributed to use of this agent in myelodysplastic syndrome (MDS) patients (Guariglia et al, Leuk Res, 2011, 35 (5), 566-570). In addition, a post-hoc analysis was conducted assessing hematologic improvement in patients enrolled on the Evaluation of Patients' Iron Chelation with Exjade (EPIC) trial of deferasirox chelation therapy in low or intermediate-1 risk MDS. Erythroid, platelet, and neutrophil responses were observed in 21.5%, 13.0%, and 22.0% of 341 patients after a median of 109, 169, and 226 days, respectively (Gattermann, N et al, Haematologica, 2012, 97 (9), 1364-1371). There has even been a case report of a patient with acute monocytic leukemia who achieved a complete remission after deferasirox therapy (Fukushima et al, Anticancer Res, 2011, 31 (5) 1741-1744). Preclinical data has suggested potential mechanisms for hematologic improvement, including modulation of reactive oxygen species and activating the MAP kinase pathway (Callens et al, J Exp Med, 2010, 37 (4), 731-750), increased labile plasma iron leading to reactive oxygen species induction (Naka K et al, Antiox Redox Signal, 2008, 10 (11) 1883-1894), or inhibition of nuclear factor Kappa B (Messa et al, Haematologica, 95 (8) 1308-1316).

Given these intriguing findings, we performed a single-center, investigator-initiated pilot study of deferasirox in MDS International Prognostic Scoring System (IPSS) 1.5 or greater, intolerant of or with lack of response to hypomethylating agents, and acute myeloid leukemia (AML), either relapsed or refractory after treatment with a non-intensive regimen or newly diagnosed and not appropriate candidates for induction chemotherapy. As an inclusion criterion, baseline serum ferritin was > or = to 500 ng/mL. Prior therapy with iron chelating agents within the last 6 months was an exclusion criterion. Current therapy for AML or MDS, including hydroxyurea to control leukocytosis, was prohibited.

Thirteen patients consented to the study. There was one screen failure and one patient withdrew from the study after one day. Eleven patients received deferasirox at an initial dose of 10 mg/kg/day which was increased to 20 mg/kg/day if tolerating well. Three of 11 patients (27%) responded. One of the three responding patients achieved red blood cell (RBC) transfusion independence (no RBC transfusions for 6 weeks before death related to infectious complications), one improved bone marrow blasts from 57% to 30% after one month of therapy and the third patient improved bone marrow blasts from 13% to 8% after one month of therapy. The patient who achieved RBC transfusion independence did not achieve any other measures of response. The two patients who responded in the bone marrow did not achieve a concomitant hematologic response.

Of the 8 non-responding patients, one patient had stable disease and was on study for one year. One patient withdrew in the setting of neutropenic fever and mild transaminitis that was possibly attributable to deferasirox and was terminated from the study. One patient withdrew from the study due to personal choice and the remaining 5 patients came off study in the setting of complications from progressive disease.

Study drug was generally well tolerated. Grade 3 adverse events (AEs) included three patients with elevated creatinine (27%) and 2 patients with diarrhea (18%). One responding patient had a lower gastrointestinal bleed that was possibly attributable to deferasirox and was terminated from the study for this reason. One patient had grade 4 dry mouth immediately after drinking deferasirox slurry that resolved by 30 minutes after ingestion. No other significant AEs occurred that were possibly attributable to deferasirox.

In conclusion, deferasirox was generally well tolerated and showed modest activity as a single agent in higher risk MDS or non-proliferative acute myeloid leukemia. Further study of deferasirox in the phase II setting as monotherapy or in combination with other therapies such as hypomethylating agents (HMAs) or HMAs in combination with venetoclax is probably warranted.