Abstract: The invention relates to a simple quantitative fluorescent assay method for determining the activity of transport proteins, more specifically multi-drug resistance associated proteins (MRPs). The method of the invention is performed on a well sealed culture of polarized cells expressing a transport protein of interest grown to confluency on a permeable support, said confluent cell culture forming well separated apical and basolateral compartments. The cells are contacted with a cell permeable non-fluorescent derivative of a fluorescent compound (e.g. calcein AM) in one compartment and, after a certain period of incubation, the fluorescence intensity detected in a sample taken from the opposite compartment is indicative of the activity of the transport protein of interest expressed in the cells.

Abstract: Disclosed herein are methods and reagent kits for the quantitative in vitro determination of the functional determination of multi-drug resistance in cells, as well as for the clinical screening of potential modulators of multi-drug resistant transport activity in cells. The method of the invention is based on the measurement of the accumulation rate of free calcein within the cells of the specimen (advantageously by fluorescence measurement), after exposing the cells in vitro to a cell permeable form of calcein that is a good substrate for MDR proteins present in the sample. The cell permeable form of calcein is converted within the cell by intracellular enzymes to free calcein. Comparison of free calcein accumulation in the presence and absence of a potential inhibitor of transport activity permits the rapid screening of such inhibitors.

Abstract: The invention features novel peptide derivatives called Reversins, and provides for their use in a method of reducing the activity of the multi-drug transporter protein MDR1 in order to overcome multidrug resistance in a mammal. The peptide derivatives are of the formula (I) X1n-X2-X3(X4)n-X5, wherein n is 0 or 1, and each n is the same or different; X1 is BOC, BOC-Asu, Z-Asu, benzyloxycarbonyl, Glu(OBzl)-OBzl, Trp-OMe, Trp-Phe-OMe, Phe-Trp-OMe, Phe-Phe-OtBu, Trp-Trp-OtBu, indoloacetyl, benzoyl, an alkylanine of 1-4 carbons, dibenzylamide, tryptamide, 1-amino-adamantine, aminomethylcyclohexane, indoline, phenylethylamide or dicyclohexylamide; X2 is Glu(OBzl), Asp(OBzl), succinyl, O,O-dibenzoyltartaroyl, diphenoyl, muconyl, Thx, Cpa, Asu, Nal, Pen, Phg, Dbt, Lys(BOC), Lys(Z), Cys(Bzl), Thr(Bzl), Glu(OtBu), tert.-Leu, Leu, Nle, Pro, Phe, Tyr(Bzl), or Ser(Bal); X3 is Asp, Asu, Lys, Glu, Trp, Thx, Cpa, Nal, Pen, Phg, Dbt, Glu(OtBu), tert.

Abstract: Disclosed herein are methods and reagent kits for the quantitative in vitro determination of the functional determination of multi-drug resistance in cells, as well as for the clinical screening of potential modulators of multi-drug resistant transport activity in cells

Abstract: Disclosed herein are methods and reagents kits forth quantitative in vitro determination of the functional determination of multi-drug resistance in cells, as well as for the clinical screening of potential modulators of multi-drug resistant transport activity in cells. The method of the invention is based on the measurement of the accumulation rate of free calcein within the cells of the specimen (advantageously by flourescence measurement), after exposing the cells in vitro to a cell permeable form of calcein that is a good substrate for MDR proteins present in the sample. The cell permeable form of calcein is converted within the cell by intracellular enzymes to free calcein. Comparison of free calcein accumulation in the presence and absence of a potential inhibitor of transport activity permits the rapid screening of such inhibitors.