Synthesis and antitumor activity of water-soluble duocarmycin B1 prodrugs

A fundamental relationship between hydrophobic properties and biological activity for the duocarmycin class of DNA-alkylating antitumor drugs: hydrophobic-binding-driven bonding

Two systematic series of increasingly hydrophilic derivatives of duocarmycin SA that feature the incorporation of ethylene glycol units (n = 1-5) into the methoxy substituents of the trimethoxyindole subunit are described. These derivatives exhibit progressively increasing water solubility along with progressive decreases in cell growth inhibitory activity and DNA alkylation efficiency with the incremental ethylene glycol unit incorporations. Linear relationships of cLogP with -log IC50 for cell growth inhibition and -log AE (AE = cell-free DNA alkylation efficiency) were observed, with the cLogP values spanning the productive range of 2.5-0.49 and the -log IC50 values spanning the range of 11.2-6.4, representing IC50 values that vary by a factor of 10(5) (0.008 to 370 nM). The results quantify the fundamental role played by the hydrophobic character of the compound in the expression of the biological activity of members in this class (driving the intrinsically reversible DNA alkylation reaction) and define the stunning magnitude of its effect.

A Novel Class of in Vivo Active Anticancer Agents: Achiral seco-Amino- and seco-Hydroxycyclopropylbenz[e]indolone (seco-CBI) Analogues of the Duocarmycins and CC-1065

One achiral seco-hydroxycyclopropylbenz[e]indolone (seco-CBI) (12) and seven achiral seco-amino-CBI (11a-g) analogues of CC-1065 and the duocarmycins were designed, synthesized and evaluated for their DNA-binding and anticancer properties. These compounds contain a core 2-chloroethylnaphthalene structure and they do not have a stereocenter. From thermal cleavage gel analyses, compounds 11a-g and 12 demonstrated similar covalent sequence specificity to adozelesin 3 and the racemic seco-CBI-TMI 4 for binding to the 5'-AAAAA(865)-3' site. Continuous exposure of human (K562) and murine (B16, L1210 and P815) cancer cell lines to the compounds demonstrated their significant cytotoxicity, with IC50 values in the sub-micromolar range. Generally, a good leaving group on the ethyl moiety and a free amino or hydroxyl group on the naphthyl moiety are essential for activity. According to NCI's cytotoxicity screen, compounds 11a and 12 were active against human cancer cell lines derived from lung, colon, melanoma, renal system, and breast. At the respective doses of 15 and 20 mg/kg (administered via an ip route), compounds 11a and 12 inhibited the growth of murine B16-F0 melanoma in C57BL/6 mice, with minimal toxicity, and 11a gave a significant anticancer effect. The in vivo anticancer activity of compound 11a was confirmed in a human tumor xenograft study (advanced stage SC-OVCAR-3 ovarian cancer growing in scid mice). Finally, compound 11a was not toxic to murine bone marrow cell growth in culture at a dose that was toxic for the previously reported compound 4.

A novel class of achiral seco-analogs of CC-1065 and the duocarmycins: design, synthesis, DNA binding, and anticancer properties

The synthesis, DNA binding properties, and in vitro and in vivo anticancer activity of fifteen achiral seco-cyclopropylindoline (or achiral seco-CI) analogs (5a-o) of CC-1065 and the duocarmycins are described. The achiral seco-CI analogs contain a 4-hydroxyphenethyl halide moiety that is attached to a wide range of indole, benzimidazole, pyrrole, and pyridyl-containing noncovalent binding components. The 4-hydroxyphenethyl halide moiety represents the simplest mimic of the seco-cyclopropylpyrroloindoline (seco-CPI) pharmacophore found in the natural products, and it lacks a chiral center. The sequence and minor groove specificity of the achiral compounds was ascertained using a Taq DNA polymerase stop assay and a thermal induced DNA cleavage experiment using either a fragment of pBR322 or pUC18 plasmid DNA. For example, seco-CI-InBf (5a) and seco-CI-TMI (5c) demonstrated specificity for AT-rich sequences, particularly by reacting with the underlined adenine-N3 position of 5'-AAAAA(865)-3'. This is also the sequence that CC-1065 and adozelesin prefer to alkylate. The achiral seco-CI compounds were subjected to cytotoxicity studies against several human (K562, LS174T, PC3, and MCF-7) and murine cancer cell lines (L1210 and P815). Following continuous drug exposure, the achiral compounds were found to be cytotoxic, with IC(50) values in the muM range. Interestingly, the carbamate protected compound 5p was significantly less cytotoxic than agent 5c, supporting the hypothesis that loss of HCl and formation of a spiro[2,5]cyclopropylcyclohexadienone intermediate is necessary for biological activity. The achiral seco-CI compounds 5a and 5c were submitted to the National Cancer Institute for further cytotoxicity screening against a panel of 60 different human cancer cell lines. Both compounds showed significant activity, particularly against several solid tumor cell lines. Flow cytometry studies of P815 cells that were incubated with compound 5c at its IC(50) concentration for 24h showed induction of apoptosis in a large percentage of cells. Compounds 5a and 5c were selected by the NCI for an in vivo anticancer hollow-fiber test, and received composite scores of 18 and 22, respectively. These two compounds were subsequently evaluated for in vivo anticancer activity against the growth of a human advanced stage SC UACC-257 melanoma in skid mice. At a dose of 134 mg/kg administered IP, compound 5c gave a T/C value of 40% (for day 51), and the median number of days of doubling tumor growth was 27.7, versus 15.8 for untreated animals. For compound 5a, at 200mg/kg, the T/C was 58% and the median number of days of doubling tumor growth was 20.0 versus 8.7 for untreated animals. At these doses no toxicity or weight loss was observed for either compound. Furthermore, compound 5c was not toxic to murine bone marrow cell growth in culture, at a dose that was toxic for the previously reported seco-CBI (cyclopropylbenzoindoline)-TMI (4).

Phase II trial of KW2189 in patients with advanced malignant melanoma

KW-2189, a semisynthetic duocarmycine antibiotic has been shown to exert antiproliferative effects against human tumor cell lines in vitro and animal tumor models in vivo. Phase I studies identified myelosuppression as the most noteworthy adverse effect. Presented are two concurrent phase II studies assessing the antitumor and toxicity profile of KW-2189 in metastatic melanoma patients. One of the studies accrued patients with a history of prior melanoma therapy and the other accrued patients without a history of prior melanoma therapy. KW-2189 was administered at 0.4 mg/m2 to previously treated patients and 0.5 mg/m2 to the previously untreated. Treatment was administered intravenously on day 1 of a 6-week cycle. Thirty previously untreated and 15 previously treated patients were accrued. The toxicity profiles of the both groups of patients were similar. Of the 15 previously treated patients, 8 completed once cycle of treatment, 2 completed 2 cycles, and 5 completed 3 cycles. Dose modification for neutropenia/ thrombocytopenia was necessary in six patients. Among the previously untreated cohort (30 patients), 16 completed 1 cycle, 5 completed 2 cycles, 4 completed 3 cycles, 3 completed 4 cycles, and 2 completed 6 cycles. Doses were modified (neutropenia or thrombocytopenia) in 11 patients. None of the 15 previously treated patients responded to therapy. Four patients remained stable during two cycles. Five of the previously untreated patients achieved a partial remission/regression. Response duration ranged from 2.8 to 16.6 months. Overall objective response rate was 17%. Regarding survival, one previously treated patient is still alive 2.9 years after study entry, and three previously untreated patients are still alive 1.6, 2.3, and 2.9 years after study entry. The 1-year survival rate for previously treated patients is 27% and for the untreated patients is 23%. In summary, the lack of significant antitumor activity of KW-2189 and its associated toxicity suggest that further testing of this regimen in patients with stage IV melanoma is not warranted.