The present invention provides compounds of any one of Formulae (A), (I-11), (II), and (V) (e.g., compounds of Formula (A-1)-(A-18)), and methods for treating Waldenström's macroglobulinemia (WM) and other B cell neoplasm in a subject using the compounds. The methods comprise administering to a subject in need thereof an effective amount of the compounds. Also provided are methods to treat B cell neoplasms using the compounds in combination with inhibitors of Bruton's tyrosine kinase (BTK), interleukin-1 receptor-associated kinase 1 (IRAK1), interleukin-1 receptor-associated kinase 4 (IRAK4), bone marrow on X chromosome kinase (BMX), phosphoinositide 3-kinase (PI3K), transforming growth factor b-activated kinase-1 (TAK1), and/or a Src family kinase.