New water-soluble duocarmycin derivatives: synthesis and antitumor activity of A-ring pyrrole compounds bearing beta-heteroarylacryloyl groups

Synthesis and reactions of 2-cyano-2-(5-oxo-3-phenyl-thiazolidin-2-ylidene)-acetamides

The base promoted nucleophilic addition of cyanoacetamide derivatives 2a,b to equimolar amount of phenyl isothiocyanate in DMF containing potassium hydroxide afforded the corresponding potassium sulfide salts 3a,b which were not isolated but which underwent heterocyclisation upon treatment with chloroacetyl chloride to give the corresponding 2-cyano-2-(5-oxo-3-phenylthiazolidin-2-ylidene)-acetamide derivatives 4a,b. The reactions of 4a,b with aryl diazonium salts, bromine and aromatic aldehydes were studied in order to obtain compounds 5–11.

A Revised Synthesis of the Antitumour Antibiotic L-azatyrosine via 2-iodo-5-methoxypyridine

A revised synthesis of the antitumour antibiotic L-azatyrosine is reported, the main features of which are the unam-biguous synthesis of the previously misinterpreted 2-iodo-5-methoxypyridine and subsequent palladium-catalysed coupling with an iodoalanine-derived zinc reagent.

The Difference a Single Atom Can Make: Synthesis and Design at the Chemistry-Biology Interface

A Perspective of work in our laboratory on the examination of biologically active compounds, especially natural products, is presented. In the context of individual programs and along with a summary of our work, selected cases are presented that illustrate the impact single atom changes can have on the biological properties of the compounds. The examples were chosen to highlight single heavy atom changes that improve activity, rather than those that involve informative alterations that reduce or abolish activity. The examples were also chosen to illustrate that the impact of such single-atom changes can originate from steric, electronic, conformational, or H-bonding effects, from changes in functional reactivity, from fundamental intermolecular interactions with a biological target, from introduction of a new or altered functionalization site, or from features as simple as improvements in stability or physical properties. Nearly all the examples highlighted represent not only unusual instances of productive deep-seated natural product modifications and were introduced through total synthesis but are also remarkable in that they are derived from only a single heavy atom change in the structure.

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 unique class of duocarmycin and CC-1065 analogues subject to reductive activation

N-Acyl O-amino phenol derivatives of CBI-TMI and CBI-indole2 are reported as prototypical members of a new class of reductively activated prodrugs of the duocarmycin and CC-1065 class of antitumor agents. The expectation being that hypoxic tumor environments, with their higher reducing capacity, carry an intrinsic higher concentration of "reducing" nucleophiles (e.g., thiols) capable of activating such derivatives (tunable N-O bond cleavage) and increasing their sensitivity to the prodrug treatment. Preliminary studies indicate the prodrugs effectively release the free drug in functional cellular assays for cytotoxic activity approaching or matching the activity of the free drug, yet remain essentially stable and unreactive to in vitro DNA alkylation conditions (<0.1-0.01% free drug release) and pH 7.0 phosphate buffer, and exhibit a robust half-life in human plasma (t1/2 = 3 h). Characterization of a representative O-(acylamino) prodrug in vivo indicates that they approach the potency and exceed the efficacy of the free drug itself (CBI-indole2), indicating that not only is the free drug effectively released from the inactive prodrug but also that they offer additional advantages related to a controlled or targeted release in vivo.

Synthesis and antitumor activity of CBI-bearing ester and carbamate prodrugs of CC-1065 analogue

Prodrugs of a CBI-bearing CC-1065 analogue were synthesized. Antitumor activity of the compounds was evaluated against tumor cells in vitro and in mouse tumor models. Compounds 1 and 7, bearing methylpiperazine and DHA moieties, respectively, showed significant antitumor activity in both the L1210 leukemia and Lewis lung carcinoma mouse tumor models. For the carbamate prodrugs 1-4 and 6, there is a good correlation between the drug's potency both in vitro and in animal tumor models; however, there is no correlation between the prodrug's antitumor activity and the type of bonds linking the free drug. There are no significant differences between the antitumor activities of those that can or cannot be protonated at physiological pH. Compounds 6 and 7, each bearing a DHA moiety, did not show significantly improved antitumor activity compared to other prodrugs bearing DHA moieties, suggesting that DHA may not be used universally to significantly improve a drug's antitumor efficacy.

Preliminary structure-antiangiogenic activity relationships of 4-senecioyloxymethyl-6,7-dimethoxycoumarin

Through a systematic modification of the novel angiogenesis inhibitor 4-senecioyloxymethyl-6,7-dimethoxycoumarin (1) we found that a 6,7-dimethoxy moiety is important for bioactivity of 1. Replacement of the lactone functionality in coumarin 1 by an amide decreased its activity. By substitution of the senecioyl chain with various cinnamoyl groups we discovered 6d, bearing a 4-methoxycinnamoyl instead of senecioyl side chain, with inhibitory activity in HUVEC tube formation assay enhanced by one order of magnitude compared to 1. We have also synthesized compound 12, an analogue of 6d, with equipotency and improved water solubility.

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.

Synthesis and antitumor activity of duocarmycin derivatives: A-ring pyrrole compounds bearing beta-(5',6',7'-trimethoxy-2'-indolyl)acryloyl group

A series of A-ring pyrrole derivatives of duocarmycin bearing beta-(5',6',7'-trimethoxy-2'-indolyl)acryloyl group were synthesized, and evaluated for in vitro anticellular activity against HeLa S3 cells and in vivo antitumor activity against murine sarcoma 180 in mice. New Seg-B analogues bearing beta-(5',6',7'-trimethoxy-2'-indolyl)acryloyl group containing double bond as spacer had lower peripheral blood toxicity than the derivatives bearing 5',6',7'-trimethoxyindole-2'-carboxyl group in Seg-B of the natural type. Moreover, most of them exhibited potent antitumor activity against in vivo murine tumor models.

Synthesis and antitumor activity of duocarmycin derivatives: modification at the C-7 position of segment-A of A-ring pyrrole compounds

A series of the C7-substituted A-ring pyrrole derivatives of duocarmycin were synthesized, and evaluated for in vitro anticellular activity against HeLa S3 cells and in vivo antitumor activity against murine sarcoma 180 in mice. All of the C7-substituted A-ring pyrrole compounds decreased potency in vitro and in vivo. However, some showed strong antitumor activity with T/C values less than 0.3. Among them, the 7-formyl compound 5d showed remarkable potent in vivo antitumor activity and low peripheral blood toxicity, which were equal to 2c.

Synthesis and antitumor activity of duocarmycin derivatives: modification at C-8 position of A-ring pyrrole compounds bearing the simplified DNA-binding groups

A series of the 8-O-substituted A-ring pyrrole derivatives of duocarmycin bearing the simplified DNA-binding moieties such as cinnamoyl or heteroarylacryloyl groups were synthesized, and evaluated for in vitro anticellular activity against HeLa S3 cells and in vivo antitumor activity against murine sarcoma 180 in mice. In addition, the stability of the 8-O-substituted analogues in aqueous solution and the conversion to their active form (cyclopropane compound) from the 8-O-substituted analogues in mice or human serum were examined. The 8-O-substituted A-ring pyrrole derivatives bearing the simplified DNA-binding moieties showed remarkably potent in vivo antitumor activity and low peripheral blood toxicity compared with the 8-O-substituted A-ring pyrrole derivatives having the trimethoxyindole skeleton in segment-B (Seg-B), which were equal to 8-O-[(N-methylpiperazinyl)carbonyl] derivatives of 4'-methoxycinnamates and 4'-methoxy-beta-heteroarylacrylates. Moreover, among 8-O-substituted analogues, several compounds can be chemically or enzymatically converted to their active form in human serum. This result indicated that new 8-O-substituted derivatives were different prodrugs from KW-2189 and 8-O-substituted analogues being the same type of prodrug as KW-2189.