cc-1065 and Leukemia-P388

A series of nitrogen mustard analogues of the DNA minor groove binding fluorophore pibenzimol (Hoechst 33258) have been synthesized and evaluated for antitumor activity. Conventional construction of the bisbenzimidazole ring system from the piperazinyl terminus, via two consecutive Pinner-type reactions, gave low yields of products contaminated with the 2-methyl analogue which proved difficult to separate. An alternative synthesis was developed, involving construction of the bisbenzimidazole from the mustard terminus, via Cu(2+)-promoted oxidative coupling of the mustard aldehydes with 3,4-diaminobenzonitrile to form the monobenzimidazoles, followed by a Pinner-type reaction and condensation with 4-(1-methyl-4-piperazinyl)-o-phenylenediamine. This process gives higher yields and pure products. The mustard analogues showed high hypersensitivity factors (IC50AA8/IC50 UV4), typical of DNA alkylating agents. There was a large increase in cytotoxicity (85-fold) across the homologous series which cannot be explained entirely by changes in mustard reactivity and may be related to altering orientation of the mustard with respect to the DNA resulting in different patterns of alkylation. Pibenzimol itself (which has been evaluated clinically as an anticancer drug) was inactive against P388 in vivo using a single-dose protocol, but the short-chain mustard homologues were highly effective, eliciting a proportion of long-term survivors.

Topics: Alkylating Agents; Animals; Antineoplastic Agents; Binding Sites; Bisbenzimidazole; Cell Survival; Cricetinae; DNA; Leukemia L1210; Leukemia P388; Molecular Structure; Nitrogen Mustard Compounds; Structure-Activity Relationship; Tumor Cells, Cultured

The synthesis, physicochemical properties, and biological activities of a series of novel spiro cyclopropyl compounds, modeled on the potent antitumor antibiotic CC-1065 (1), are described. Many of these synthetic analogues are significantly more effective than 1 against murine tumors. In particular, compound 27 exhibits high activity and potency. Structure-activity analysis supports a molecular mechanism for biological action involving hydrophobic interaction of the drug with DNA and acid-catalyzed alkylation of DNA.

Topics: Animals; Antibiotics, Antineoplastic; Chemical Phenomena; Chemistry, Physical; Circular Dichroism; DNA; Duocarmycins; Female; Indoles; Leucomycins; Leukemia L1210; Leukemia P388; Mice; Mice, Inbred DBA; Solubility

CC-1065 is a potent antitumor antibiotic that binds covalently to N3 of adenine in the minor groove of DNA. The CC-1065 molecule is made up of three repeating pyrroloindole subunits, one of which (the left-hand one or A subunit) contains a reactive cyclopropyl function. The drug reacts with adenines in DNA in a highly sequence-specific manner, overlapping four base pairs to the 5'-side of the covalently modified base. Concomitant with CC-1065 covalent binding to DNA is an asymmetric effect on local DNA structure which extends more than one helix turn to the 5'-side of the covalent binding site. The DNA alkylation, sequence specificity, and biological potency of CC-1065 and a select group of trimeric synthetic analogues were evaluated. The results suggest that (a) noncovalent interactions between this series of compounds and DNA do not lead to the formation of complexes stable enough to be detected by footprinting methods, (b) sequence specificity and alkylation intensity can be modulated by the substituents on the nonreactive middle and right-hand segments, and (c) biological potency correlates well with ability to alkylate DNA. In addition, the extent and the sequence specificity of covalent adduct formation between linear DNA fragments and three analogues comprised of the CC-1065 alkylating subunit linked to zero (analogue A), one (analogue AB), or two (analogue ABC) nonreactive indole subunits were compared.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Alkylation; Animals; Antibiotics, Antineoplastic; Base Sequence; Chemical Phenomena; Chemistry; Deoxyribonuclease I; DNA; Duocarmycins; Indoles; Leucomycins; Leukemia L1210; Leukemia P388; Mice; Structure-Activity Relationship

CC-1065 was found to cause delayed toxicity at therapeutic doses, therefore, a large number of analogs have since been synthesized. A series of analogs with simplified but closely related structures were chosen for this investigation because some were found to be superior to CC-1065 in the treatment of several experimental tumors. The inhibition of L1210 cell growth by U-68,415 was comparable to that by CC-1065. A similar situation was true in terms of their in vivo potency; however, U-68,415 was superior to CC-1065 in terms of anti-P388 leukemia activity. At the optimal dosage, U-68,415 produced 4 out of 6 long-term (greater than 30 day) survivors; whereas CC-1065 produced a mere 62% increase of life span (ILS) and no long-term survivors. The order of antitumor potency and effectiveness of the CC-1065 analogs was U-68,415 greater than U-66,694 greater than U-68,819 greater than U-66,664, which was parallel to the inhibition of L1210 cell growth. CC-1065 and all the analogs tested here inhibited DNA synthesis approximately 10 times more than RNA synthesis. Protein synthesis was the least inhibited. On a molar basis, U-68,415 was about 6-9 times more inhibitory toward cellular DNA synthesis than CC-1065, yet the interaction and/or binding of CC-1065 to DNA determined by circular dichroism, DNA melting or differential cytotoxicity assay was much stronger than that of U-68,415.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antibiotics, Antineoplastic; Cell Survival; DNA-Directed DNA Polymerase; DNA, Neoplasm; Duocarmycins; Indoles; Leucomycins; Leukemia L1210; Leukemia P388; Mice; RNA, Neoplasm; Structure-Activity Relationship; Tumor Cells, Cultured