At present several mechanisms responsible for the resistance of tumour cells to cytostatics are known. Most explored is the resistance conditioned by glycoprotein-P. Under laboratory conditions it proved possible to inhibit the resistance caused by glycoprotein-P by many substances which, however, on clinical administration have serious adverse side-effects. In practice verapamil was used, its effect was most marked in haematological malignant diseases. Side-effects of verapamil, however, do not permit to attain the necessary concentration. Obviously better results will be achieved by cyclosporin A which can attain a concentration in the organism which is necessary to inhibit glycoprotein-P without serious undesirable consequences. In the submitted paper the author reviews clinical studies concerned with possible inhibition of glycoprotein-P in patients with refractory myeloma.

Keywords: ATP Binding Cassette Transporter, Subfamily B, Member 1; Antineoplastic Agents /therapeutic use/; Carrier Proteins /physiology/; Cyclosporine /pharmacology/; Drug Resistance; Humans; Membrane Glycoproteins /physiology/; Multiple Myeloma /drug therapy/; Verapamil /pharmacology/