Patent ID: 7183319

Claim:
A compound having the formula (Ia), (Ib) or (Ic), or a pharmaceutically acceptable salt thereof: wherein R a is hydrogen or —COOR b , R b is hydrogen or C 1-6 alkyl; R d and R e independently represent hydrogen and hydroxy, R f is hydrogen, C 1-4 alkyl or halogen, X is —CHOH—, —CH 2 —oxygen or sulphur, m is zero or 1, W is oxygen or sulphur, and —ODrug is selected from: a residue of taxol or gemcitabine; —NHDrug is selected from: or a residue of daunomycin; and —N(Drug) 2 is: and with the provisos (1) that where said compound has general formula (Ia) wherein m is zero, W represents oxygen, R d is hydrogen and R e is hydroxyl in the para position, and R a represents —COOMe, —ODrug does not represent a residue of digoxin, and (2) that where said compound has general formula (Ib) wherein m is zero, W represents oxygen and R d is hydrogen, R e is hydroxyl in the para position.