The present disclosure provides a pharmaceutical composition for treating and/or preventing SWI/SNF complex-dysfunction cancer. More specifically, according to the present disclosure, a compound represented by formulae (1) to (23) (the formulae are as set forth in the specification) or a pharmaceutically acceptable salt thereof can have a therapeutic and/or prophylactic effect on SWI/SNF complex-dysfunction cancer. A pharmaceutical composition, which is for treating and/or preventing cancer and contains a CBP/P300 inhibitor, can be provided. The cancer may be SWI/SNF complex-dysfunction cancer. The SWI/SNF complex-dysfunction cancer may be BAF complex-dysfunction cancer. The BAF complex-dysfunction cancer may be SMARC-deficient cancer, ARID-deficient cancer, or SS18-SSX fusion cancer. The SMARC-deficient cancer may be SMARCB1-deficient cancer, SMARCA2-deficient cancer, SMARCA4-deficient cancer, or SMARCA2/A4-deficient cancer.