FKBP12 ligand-2 (compound d) is a high-affinity ligand that targets FKBP12. This compound is utilized to selectively enhance the binding of heterobifunctional molecules to BRD4, facilitating the intracellular accumulation of drugs through the "CellTrap" effect. It forms a ternary complex of FKBP12-ligand-BRD4, which inhibits BRD4, suppresses the expression of BRD4 target genes such as MYC, and induces tumor cell death. FKBP12 ligand-2 is applicable in selective cancer research based on the differential levels of presenter proteins within cells.