The pathophysiology of HCL is now better understood, opening the way for new therapies including combined chemoimmunotherapy, immunotoxins targeting CD22 (moxetumomab pasudotox), BRAF inhibitors (vemurafenib, dabrafenib), MEK inhibitors (trametinib, cometinib), and BTK inhibitors (ibrutinib). The gene discussed is BRAF; the disease is hairy cell leukemia.