Pyrimethamine also has been widely studied for the treatment of advanced solid tumors such as lung cancer, ovarian cancer, triple negative breast cancer, and chronic lymphocytic leukemia based on the various mechanisms including signal transducer and activator of transcription 3 (STAT3) inhibition [15,16,17,18,19,20,21,22,23], differently from DX2 inhibition. Here, STAT3 is linked to B-cell chronic lymphocytic leukemia.