A Pilot Study of a Thrombopoietin-Receptor Agonist (TPO-R Agonist), Eltrombopag, in Patients With Low to Int-2 Risk Myelodysplastic Syndrome (MDS)

The myelodysplastic syndromes (MDS) are bone marrow disorders characterized by anemia, neutropenia, and thrombocytopenia. Patients with MDS are at risk for symptomatic anemia, infection, and bleeding, as well as a variable risk of progression to acute leukemia. With the exception of stem cell transplant, the standard treatments for MDS are rarely curative, and relapse rates are significant. MDS patients with cytopenias who fail standard therapies require regular blood or platelet transfusions which are expensive and inconvenient, and are at risk for serious bleeding complications.

Thrombopoietin (TPO) is the principal regulator of platelet production by megakaryocytes in the bone marrow. A 2nd generation TPO-agonist, eltrombopag (Promacta ) has been shown to increase platelets in thrombocytopenic patients with chronic immune thrombocytopenic purpura (ITP). Eltrombopag is administered orally, is well-tolerated, and is FDA approved for the treatment of thrombocytopenia in patients with chronic ITP who failed to respond to standard treatment.

Because the management of MDS patients with persistent cytopenias remains unsatisfactory and novel therapeutic approaches are needed, we propose a non-randomized, pilot, phase II study of eltrombopag in low to Int-2 risk MDS subjects with thrombocytopenia and anemia cytopenias who are either untreated or cytopenias that persist despite treatment with standard therapies to assess its utility in these settings.

Subjects will initiate study medication at an oral dose of 50 mg/day (25 mg/day for East Asians), which will be adjusted as clinically indicated to the lowest dose that maintains a stable platelet count greater than or equal to 20,000/microL above baseline while maximizing tolerability. Treatment response will be any increase in a cytopenia, in the lineage that fulfilled eligibility criteria for enrollment and will be defined as: (a) platelet count increases to 20,000/microL above baseline at 16 or 20 weeks , or stable platelet counts with transfusion independence for a minimum of 8 weeks in subjects who were previously transfusion dependent; (b) erythroid response for subjects with a pretreatment hemoglobin of less than 9 g/dL will be defined as an increase in hemoglobin by greater than or equal to 1.5g/dL without packed red blood cell (PRBC) transfusion support, or a reduction in the units of PRBC transfusions by at least 50% during the eight consecutive weeks prior to response assessment compared with the pretreatment transfusion number in the previous 8 weeks; (c) neutrophil response will be defined in those with a pretreatment absolute neutrophil count (ANC) of < 0.5 times 10(9)/L as at least a 100% increase or an absolute increase > 0.5 times 10(9)/L. Subjects meeting a response may remain on the extended access until they meet an off study criteria or the study is closed.

Subjects with response at 16 or 20 weeks may be consented for entry into the extended access part of the trial. In the event that a subject is transfused platelets for a count >10,000/microL without a medical indication during the study period, the subject may continue on study drug and the response assessment may be extended for an additional 4 weeks to week 20, at the discretion of the principal investigator. Subjects with evidence for a clinical response in any lineage at 16 weeks but not yet meeting full primary endpoint response criteria, and who are tolerating investigational treatment, may receive an additional 4 weeks of eltrombopag and be reassessed after 20 weeks. At that time, if they meet primary endpoint response criteria, they will be eligible to enter the extended access part of the study. If they do not meet primary endpoint response criteria, eltrombopag will be discontinued.