Purpose: The pipecolinate derivative VX-710 (biricodar; Incel) is a clinically applicable modulator of P-glycoprotein (Pgp) and multidrug resistance protein (MRP-1); we studied its activity against the third multidrug resistance (MDR)-associated drug efflux protein, breast cancer resistance protein (BCRP).
Experimental design: VX-710 modulation of uptake, retention, and cytotoxicity of mitoxantrone, daunorubicin, doxorubicin, topotecan, and SN38 was studied in cell lines overexpressing Pgp, MRP-1 and wild-type (BCRP(R482)) and mutant (BCRP(R482T)) BCRP.
Results: In 8226/Dox6 cells (Pgp), VX-710 increased mitoxantrone and daunorubicin uptake by 55 and 100%, respectively, increased their retention by 100 and 60%, respectively, and increased their cytotoxicity 3.1- and 6.9-fold, respectively. In HL60/Adr cells (MRP-1), VX-710 increased mitoxantrone and daunorubicin uptake by 43 and 130%, increased their retention by 90 and 60%, and increased their cytotoxicity 2.4- and 3.3-fold. In 8226/MR20 cells (BCRP(R482)), VX-710 increased mitoxantrone uptake and retention by 60 and 40%, respectively, and increased cytotoxicity 2.4-fold. VX-710 increased daunorubicin uptake and retention by only 10% in 8226/MR20 cells, consistent with the fact that daunorubicin is not a substrate for BCRP(R482), but, nevertheless, it increased daunorubicin cytotoxicity 3.6-fold, and this increase was not associated with intracellular drug redistribution. VX-710 had little effect on uptake, retention, or cytotoxicity of mitoxantrone, daunorubicin, doxorubicin, topotecan, or SN38 in MCF7 AdVP3000 cells (BCRP(R482T)).
Conclusions: VX-710 modulates Pgp, MRP-1, and BCRP(R482), and has potential as a clinical broad-spectrum MDR modulator in malignancies such as the acute leukemias in which these proteins are expressed.