FDA
expands approval of Promacta
Eltrombopag (Promacta,
GlaxoSmithKline), an oral thrombopoietin receptor agonist, already had been
approved for treatment of thrombocytopenia in patients with chronic hepatitis
C, as well as those with chronic immune thrombocytopenia who demonstrated insufficient
response to immunoglobulins, corticosteroids or splenectomy.
In patients with severe
aplastic anemia, bone marrow does not make sufficient numbers of white blood
cells, red blood cells and platelets. Eltrombopag increases the production of
blood cells by inducing the proliferation and differentiation of bone marrow stem
cells.
The FDA had granted
eltrombopag breakthrough therapy designation for this indication in January,
and it granted priority review status in April.
The FDA based its approval
in part on results of a phase 2 study conducted by the National Heart, Lung and
Blood Institute at NIH. The single-arm, open-label trial included 43 patients
with severe aplastic anemia who had insufficient response to immunosuppressive
therapy.
Results showed 17 patients
(40%) demonstrated hematologic response in at least one lineage — red blood
cells, white blood cells or platelets — after week 12. During the study’s
extension phase, eight patients demonstrated multi-lineage response. Four of
them tapered off treatment but maintained the response throughout a median follow-up
of 8.1 months (range, 7.2-10.6).
Ninety-one percent of
patients had been platelet transfusion-dependent at baseline. Among responders,
the median platelet transfusion-free period was 200 days (range, 8-1,096).
Eighty-six percent of patients had been red blood cell transfusion-dependent at
baseline. Among responders, the median red blood cell transfusion-free period was
208 days (range, 15-1,082).
The most frequently
reported adverse events in eltrombopag-treated patients were nausea (33%),
fatigue (28%), cough (23%), diarrhea (21%) and headache (21%).
“FDA approval of Promacta
addresses a significant treatment need for this very rare but serious blood
disorder in those who have failed current treatment options,” Paolo Paoletti,
MD, GlaxoSmithKline’s president of oncology, said in a press release. “Through
collaboration with the National Institutes of Health, whose studies demonstrate
the potential for Promacta to achieve a hematologic response in at least one
lineage — red blood cells, platelets or white blood cells — patients now have a
treatment option where one didn’t previously exist.”
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