A compound having the formula: or a pharmaceutically acceptable salt thereof, wherein the groups Z connected to the C-2', C-7, and/or C-10 oxygen atoms are, independently, H, or a group of the formula IIA: wherein the wavy line represents the bond connecting formula IIA to the C-2', C-7, and/or C-10 oxygen atoms; is N-methyl-piperazino, provided that at least one Z is a group of the formula IIA; and is a Spacer selected from: (a) a chain of the type (CH 2) n, where n may range from 1 to 10, or (b) a derivative of the above (CH 2) n where one or more H atoms are replaced by: a linear, branched, or cyclic alkyl group containing from 1 to 10 C atoms, a heteroatom such as N, O, S, Si, which may be further connected to H atoms; or to heteroatoms such as N, O, S; or to linear, branched, or cyclic alkyl groups containing from 1 to 10 C atoms and facultatively incorporating one or more halogen atoms, a halogen atom; or (c) a derivative of the above (CH 2) n where one or more CH 2 's are replaced by: a heteroatom such as N, O, S, Si, which may be further connected to H atoms; or to heteroatoms such as N, O, S; or to linear, branched, or cyclic alkyl groups containing from 1 to 10 C atoms and facultatively incorporating one or more halogen atoms, a ring structure consisting of 3 to 10 carbon atoms and facultatively incorporating one of more heteroatoms such as N, O, S, Si, or halogen, as well as multiple bonds among pairs of atoms; or (d) a derivative of the above (CH 2) n where one or more pairs of adjacent C atoms share a double bond of E- or Z-geometry, or a triple bond. is N-methyl-piperazino, provided that at least one Z is a group of the formula IIA; and is a Spacer selected from: (a) a chain of the type (CH 2) n, where n may range from 1 to 10, or (b) a derivative of the above (CH 2) n where one or more H atoms are replaced by: a linear, branched, or cyclic alkyl group containing from 1 to 10 C atoms, a heteroatom such as N, O, S, Si, which may be further connected to H atoms; or to heteroatoms such as N, O, S; or to linear, branched, or cyclic alkyl groups containing from 1 to 10 C atoms and facultatively incorporating one or more halogen atoms, a halogen atom; or (c) a derivative of the above (CH 2) n where one or more CH 2 's are replaced by: a heteroatom such as N, O, S, Si, which may be further connected to H atoms; or to heteroatoms such as N, O, S; or to linear, branched, or cyclic alkyl groups containing from 1 to 10 C atoms and facultatively incorporating one or more halogen atoms, a ring structure consisting of 3 to 10 carbon atoms and facultatively incorporating one of more heteroatoms such as N, O, S, Si, or halogen, as well as multiple bonds among pairs of atoms; or (d) a derivative of the above (CH 2) n where one or more pairs of adjacent C atoms share a double bond of E- or Z-geometry, or a triple bond. (a) a chain of the type (CH 2) n, where n may range from 1 to 10, or (b) a derivative of the above (CH 2) n where one or more H atoms are replaced by: a linear, branched, or cyclic alkyl group containing from 1 to 10 C atoms, a heteroatom such as N, O, S, Si, which may be further connected to H atoms; or to heteroatoms such as N, O, S; or to linear, branched, or cyclic alkyl groups containing from 1 to 10 C atoms and facultatively incorporating one or more halogen atoms, a halogen atom; or (c) a derivative of the above (CH 2) n where one or more CH 2 's are replaced by: a heteroatom such as N, O, S, Si, which may be further connected to H atoms; or to heteroatoms such as N, O, S; or to linear, branched, or cyclic alkyl groups containing from 1 to 10 C atoms and facultatively incorporating one or more halogen atoms, a ring structure consisting of 3 to 10 carbon atoms and facultatively incorporating one of more heteroatoms such as N, O, S, Si, or halogen, as well as multiple bonds among pairs of atoms; or (d) a derivative of the above (CH 2) n where one or more pairs of adjacent C atoms share a double bond of E- or Z-geometry, or a triple bond.