Arsenic trioxide (As₂O₃) as a maintenance therapy for adult T cell leukemia/lymphoma

Adult T-cell leukemia-lymphoma (ATL) is an aggressive mature lymphoid proliferation associated with poor prognosis. Standard of care includes chemotherapy and/or the combination of zidovudine and interferon-alpha. However, most patients experience relapse less than 6 months after diagnosis. Allogeneic stem cell transplantation is the only curative treatment, but is only feasible in a minority of cases. We previously showed in a mouse model that Arsenic trioxide (As₂O₃) targets ATL leukemia initiating cells.

As₂O₃ consolidation was given in 9 patients with ATL (lymphoma n = 4; acute n = 2; and indolent n = 3), who were in complete (n = 4) and partial (n = 3) remission, in stable (n = 1) and in progressive (n = 1) disease. Patients received up to 8 weeks of As₂O₃ at the dose of 0.15 mg/kg/day intravenously in combination with zidovudine and interferon-alpha. One patient in progression died rapidly. Of the remaining eight patients, three with indolent ATL subtype showed overall survivals of 48, 53 and 97 months, and duration of response to As₂O₃ of 22, 25 and 73 months. The other 5 patients with aggressive ATL subtype had median OS of 36 months and a median duration of response of 10 months. Side effects were mostly hematological and cutaneous (one grade 3) and reversible with dose reduction of AZT/IFN and/or As₂O₃ discontinuation. The virus integration analysis revealed the regression of the predominant malignant clone in one patient with a chronic subtype.

These results suggest that consolidation with As₂O₃ could be an option for patients with ATL in response after induction therapy and who are not eligible for allogeneic stem cell transplantation.