Biricodar
Biricodar is a pipecolinate derivative.  Functioning as a modulator of P-glycoprotein (P-gp) and multidrug resistance protein (MRP-1), biricodar restores drug sensitivity to cells expressing P-glycoprotein and MRP1, the cellular efflux pumps that are the major causes in tumor cell resistance to chemotherapeutic agents.  This agent binds directly to Pgp and MRP-1 and inhibits efflux pump activity, resulting in increased intracellular accumulation and retention of cytotoxic agents.