On August 26, the FDA approved use of Promacta® (eltrombopag), produced by GlaxoSmithKline (GSK), for use in patients with severe aplastic anemia (SAA) who have had an insufficient response to immunosuppressive therapy and are not candidates for a hematopoietic stem cell transplant. Eltrombopag, works by helping to increase production of blood cells.
According to Cynthia Dunbar, M.D., Head, Molecular Hematopoiesis Section, Hematology Branch, Division of Intramural Research, National Heart Lung and Blood Institute of the National Institutes of Health, the approval of eltrombopag as a treatment for SAA is significant because “This is the first new drug approved for aplastic anemia since ATG, and it is the first drug ever approved to treat refractory aplastic anemia. Once a day treatment with this oral, well-tolerated drug leads to clinically significant responses in approximately 40 percent of patients, the majority multi-lineage [neutrophil, red cell, and platelets]. In some patients with normalized marrow function, eltrombopag can be discontinued and the responses persist long-term, up to three years or more in some patients treated on the original trial.”
When asked which patients are likely to be affected by the FDA approval of eltromobopag for SAA, Dr. Dunbar noted, “Those patients with severe aplastic anemia that have not responded or had suboptimal responses to at least one treatment cycle with antithymocyte globulin (ATG) and cyclosporine. The FDA has approved eltrombopag for the treatment of these refractory patients. It is important to note that this new labeling indication for eltrombopag involves dosing different from that employed for immune thrombocytopenic purpura (ITP), the only prior labeled indication for eltrombopag, and that the duration of treatment required before concluding whether eltrombopag is effective or not is quite prolonged, also in contrast to ITP. [Severe aplastic anemia] patients in our completed study leading to the FDA approval were just beginning to show responses after 3-4 months of treatment, and maximal responses often took up to 12 months.”
What impact does this have on patients with SAA and paroxysmal nocturnal hemoglobinuria (PNH)? “In the initial study, we excluded patients with active PNH, and/or with PNH clone size greater than 50 percent” said Dunbar. “We were treating patients with cytopenias due to marrow failure, not anemia due to PNH red blood cell destruction. Patients with PNH clones smaller than 50 percent were treated, and their clone sizes tended to remain approximately the same.”
Read more on our website about some of the research studies on eltrombopag for severe aplastic anemia.