RecruitingPhase 2ProcedureTesting the Effectiveness of the Anti-cancer Drug, Mirdametinib, in Treating Relapsed, Refractory Chronic Lymphocytic LeukemiaThis phase II trial tests the effect of mirdametinib in treating patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) that has come back after a period of improvement (relapsed) or that has not responded to previous treatment (refractory). Mirdametinib, a methyl ethyl ketone (MEK) inhibitor, works by blocking the action of an abnormal protein that signals cancer cells to multiply. This may help slow or stop the spread of cancer cells. Giving mirdametinib may be effective in treating patients with relapsed or refractory CLL or SLL.