Efficacy of vemurafenib in hairy-cell leukemia

The BR A F V600E mutation is present in nearly all cases of hairy-cell leukemia. 1 This finding has led to the introduction of BRAF inhibitors for the treatment of chemotherapy-re - sistant hairy-cell leukemia, and patients have had a good response to the oral inhibitor vemu - rafenib. 2-4 Constitutive phosphorylation of both extracellular signal-regulated kinase (ERK) and mitogen-activated protein–ERK kinase (MEK) has been considered to be a direct consequence of BRAF activation, with BRAF inhibition result - ing in cell death through suppression of this pathway in hairy-cell leukemia. However, data to support this theory are limited, since most pa - tients present with pancytopenia. [Opening paragraph]