Trisenox® (arsenic trioxide) in Patients with Myelodysplastic Syndromes (MDS): Preliminary Results of a Phase I/II Study.

Introduction: Single-agent Trisenox^® (arsenic trioxide) induces high hematologic and molecular response rates leading to prolonged survival in patients with relapsed/refractory acute promyelocytic leukemia. Arsenic trioxide exhibits multifaceted mechanisms of action, including induction of tumor cell differentiation, apoptosis, and angiogenesis inhibition. Recent reports have documented the clinical activity of arsenic trioxide in MDS patients, leading to improvements in hematologic parameters and to transfusion independence or reduction. We report preliminary results of an ongoing European multicenter phase I/II study of arsenic trioxide in MDS patients. Patient eligibility includes all FAB categories with <30% blasts. Final results of the study will be reported.

Methods: Arsenic trioxide is given as a 1-hr IV infusion, loading dose of 0.30 mg/kg/day for 5 days, and maintenance with 0.25 mg/kg/day 2X a week for >15 weeks. Disease assessments are every 8 weeks, by modified IWG response criteria.

Patients: 105 patients have been enrolled: median age is 67 years (range 31–89), median time from diagnosis to 1st dose is 10.9 months (range 0.2–117.6). 101 patients have received drug and have been evaluated (78M/23F). 39 patients have IPSS lower-risk (LR: low and Int-1) and 62 have higher-risk (HR: high and Int-2) MDS. FAB categories are RA (9 patients), RARS (11), RAEB (62), RAEB-t (13), and CMML (6). 86 patients were transfusion dependent at baseline.

Results: Responses were observed in 27 evaluable patients (27%). They include 1 CR (1%), 20 major Hematologic Improvements (HI: 20%) and 6 minor HI (6%). Responses were seen across the 3 lineages: major HI-Erythroid: 11; major HI-Neutrophil: 8 (including 2 also HI-E); and major HI-Platelet: 6 (including 3 also HI-E). The hematologic improvement rate among LR patients was 9/39 (23%) and among HR patients, 18/62 (29%, including the CR). 14 patients became transfusion independent and an additional 7 patients had transfusions reduced by ≥50%. Responses were seen after 1–3 months of treatment, and median duration of response is 4+ months at this time. The true duration of response is not yet known, as 20 patients were still responding at their most recent assessments. Arsenic trioxide toxicity was manageable and mostly mild; 4 patients had treatment-related grade 3 febrile neutropenia and 1 patient each experienced grade 3 and grade 4 thrombocytopenia. One had grade 4 neutropenia; the only other grade 4 toxicity was 1 pulmonary edema. An additional 14 patients each had a different grade 3 event. QTc prolongation was reported in only 1 patient, who had 2 isolated episodes that were considered clinically insignificant and did not result in treatment delay. No patient had alopecia or severe nausea or vomiting.

Summary and Conclusions: These preliminary results indicate that arsenic trioxide is generally well tolerated, even by elderly patients, and that it induces responses in all three hematopoietic lineages, in similar proportions of patients with higher risk and with lower risk MDS. 14 of 86 transfusion-dependent patients became transfusion independent. Final results of the study will be presented.