Therapeutic compounds

A compound of formula I:

• wherein:
• each A, B, D, and E is independently —C(═O)NH—CH(Ra)—, —C(═O)—NH—C(═O)—, or a group of the formula:
• each R1, R2, R3, R4, and R5 is independently H, (C1-C6)alkyl, or (C1-C6)alkoxy, wherein each (C1-C6)alkyl and (C1-C6)alkoxy is optionally substituted with OH, (C1-C6)alkoxy, (C1-C6)alkylthio, aryl, NRcRd, or —C(═O)NRcRd;
• each R6, R7, and R8 is independently H;
• or each R6 and R7 together with the atoms to which they are attached form a benzo ring and R8 is H;
• or R6 is H and R7 and R8 together with the atoms to which they are attached form a benzo ring;
• each X is independently NH, S, or O;
• each Z is independently N or CH;
• the bond represented by ----- is a single or a double bond;
• each Ra is independently H, aryl, or (C1-C6)alkyl that is optionally substituted with OH, (C1-C6)alkoxy, (C1-C6)alkylthio, aryl, NReRf, or —C(═O)NReRf;
• each Rc and Rd is independently H or (C1-C6)alkyl;
• or Rc and Rd together with the nitrogen to which they are attached form a pyrrolidino, piperidino, piperazino, morpholino, thiomorpholino, or azepino ring;
• and
• each Re and Rf is independently H or (C1-C6)alkyl;
• or Re and Rf together with the nitrogen to which they are attached form a pyrrolidino, piperidino, piperazino, morpholino, thiomorpholino, or azepino ring;
• or a salt thereof;
• provided the compound of formula I is not telomestatin or dehydrotelomestatin.