Biochemical Reagents, iBAP-II, BAP1 deubiquitinase inhibitor, CAS 1013813-81-4, 98% by HPLC/NMR (Conforms), Inhibitor of the H2AK119 deubiquitinase BAP1 (IC50 0.092 ug/ml). It is selective for BAP1 over UCHL5, USP5,7,8, TNFAIP3-catalytic domain, USP2-catalytic domain, Otubain-1, and Ataxin3. iBAP-II disrupted the BAP1/ASXL3/BRD4 axis via induction of protein degradation of the ASXL3 scaffold protein in the small cell lung cancer lines NCI-H1963, NCI-H748, and NCI-H1882. It also suppressed expression of the master transcription factor ASCL1 in NCI-H1963 small cell lung cancer cells. iBAP-II significantly delayed disease progression in a small cell lung cancer xenograft mouse model.