Ametantrone

The d(GGCGCC)₂ palindrome is encountered in several oncogenic and retroviral sequences. In order to target it, we previously designed several oligopeptide derivatives of the mitoxantrone and ametantrone anticancer intercalators. These have two arms with a cationic side-chain in the major groove, each destined to bind along each strand O₆/N₇ of the two successive guanine bases (G1-G2/G1'-G2') upstream from the central anthraquinone intercalation site. We retained from a previous study (El Hage et al., 2022) a tris-intercalating molecule with two outer 9-aminoacridine (9-AA) intercalators, denoted as III. We sought enhancements in both affinity and selectivity by simultaneously targeting the minor groove of the extracyclic -NH₂ groups of these bases and G4-G4' of the intercalation site. We considered derivatives of distamycin, having each pyrrole ring replaced by an imidazole to act as an in-register electron acceptor from the -NH₂ group of a target guanine. We substituted the C₆ and C₇ carbons of anthraquinone, or the C₈ and C₉ ones of anthracycline, by an (imidazole-amide)3 chain. Four different derivatives of III were designed with different connectors to the anthraquinone/anthracycline and 9-AA. Polarizable molecular dynamics simulations of their complexes with a double-stranded DNA 18-mer with a central d(C GGGC GCCC G)₂ palindrome sequence showed in-register minor groove binding to -NH₂ of G1-G₂/G1'-G2' to coexist with major groove recognition of O₆/N₇. Up to 12 H-bonds could be stabilized in the minor groove coexisting with four bidentate interactions of the alkyl diammonium moieties in the major groove. Since there is no mutual interference, the binding enthalpies, ΔH, contributed by each groove could add up and enable significant enhancements of the affinity constants. As was the case for their Lys precursor, these derivatives are amenable to chemical syntheses and in vitro and in vivo tests, for which the present results provide an incentive. The construction of derivatives III-A-III-D is modular. For in vitro experiments, this should enable unraveling the most important structural elements to further optimize both ΔH and TΔS and sequence selectivity and how this could translate to in vivo tests.

The resistance of cancer cells to chemotherapeutic agents, whether through intrinsic mechanisms or developed resistance, motivates the search for new chemotherapeutic strategies. In the present report, we demonstrate a facile synthetic strategy towards the discovery of new anti-cancer substances. This strategy is based on simple covalent coupling between known anti-cancer drugs, which results in novel 'chimeric' small molecules. One of these novel compounds, CM358, is the product of an amide bond formation between the known Topoisomerase II (Topo II) inhibitor amonafide (AM) and the known DNA mustard alkylator chlorambucil (CLB). It demonstrates significant enhanced cytotoxicity over an equimolar mixture of AM and CLB in various cancer cell lines and in a xenograft model of human metastatic melanoma. Topo II inhibition as well as in silico docking studies suggest that CM358 is a stronger Topo II binder than AM. This may be attributed, at least partially, to the placement of the CLB moiety in a favorable orientation with respect to DNA cross-linking with nearby guanines. In a human metastatic melanoma (WM 266-4) xenograft model, this compound was profoundly superior to a mixture of AM and CLB in reduction of tumor growth, maintenance of body weight and extension of overall survival.