Response to Referee Suggestions! ! Referee 2! ! 1. "Tariquidar is reported in literature as a dual ligand (P-gp/BCRP) and likely this is the cause of its failure both when with antineplastic agents co-administrated and in PET studies.! In fact seems that it is a P-gp inhibitor(?) and BCRP substrate.! Considering that all molecules reported in the present paper bear the tariquidar scaffold I think that BCRP activity of compound 4 should be reported."! ! To address this comment, we performed an in vitro ATPase experiment to study the modulatory activity of compound 4 against purified BCRP membranes. We found that at a relatively high concentration (1 μM), of compound 4 did not show any significant modulatory activity against BCRP. The procedure and results are summarized on page 16 of the Supplementary Information file.! !!2. "I suppose that the authors have been already demonstrated the P-gp level be Western blot in the employed cells. They should report this reference or alternatively, demonstrated by WB the abundance of P-gp with respect to other efflux pumps into the cells."! !! A Western blot showing the abundance of MDR1 in the HT1080-MDR1++ cells was added to the Supplementary Information (Figure S10).