P-glycoprotein (P-gp) modulator; inhibits P-gp-mediated multidrug-resistance (MDR). Reverses resistance to several cytotoxic drugs including mitoxantrone and doxorubicin (resistance factors are 2.0 and 6.5 respectively) in human MDR cancer cell lines. Non-immunosuppressive analog of cyclosporin A (Cat. No. 1101).