Mechanism of DNA strand breaks by mitonafide, an imide derivative of 3-nitro-1,8-naphthalic acid

A series of DNA targeted Cu (II) complexes containing 1,8-naphthalimide ligands: Synthesis, characterization and in vitro anticancer activity

Copper(II) complexes are very promising candidates for platinum-based anticancer agents. Herein, three Cu (II) complexes (1-3) containing 1,8-naphthalimide ligands were synthesized and characterized by FT-IR, elemental analysis, ESI-MS and single crystal X-ray diffraction (complex 3). In addition, a control compound (complex 4) without 1,8-naphthalimide ligand was synthesized and characterized. The in vitro anticancer activity of the synthesized complexes against five cancer cell lines and one normal cell line was evaluated by MTS assay. The results displayed the antitumor activity of complexes 1-3 was controlled by the aliphatic chain length of ligands, their cytotoxicity was in the order 3 > 2 > 1, giving the IC50 values ranging from 2.874 ± 0.155 μM to 31.47 ± 0.29 μM against five cancer cell lines. Complex 4 showed less activity in comparison with complex 1-3. Notably, complexes 1-3 displayed much higher selectivity (SI = 2.65 to 10.16) compared to complex 4 (SI = 1.0), indicated that the introduction of 1,8-naphthalimide group not only increased the activity of this series of compounds but also enhanced their specific selectivity to cancer cells. Compound 3 induced apoptosis in cancer cells and blocked the S-phase and G2/M of cancer cells. The interaction with DNA of complexes 3 and 4 was studied by UV/Vis spectroscopic titrations, competitive DNA-binding experiment, viscometry and CD spectra. The results showed that complex 3 interacted with DNA in an intercalating mode, but the interaction mode of compound 4 with DNA was electrostatic interaction.

Unique Photophysical Properties of 1,8-Naphthalimide Derivatives: Generation of Semi-stable Radical Anion Species by Photo-Induced Electron Transfer from a Carboxy Group

The development of anion sensors for selective detection of a specific anion is a crucial research topic. We previously reported a selective photo-induced colorimetric reaction of 1-methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium (MNEI) having a cationic receptor in the presence of molecules having multiple carboxy groups, such as succinate, citrate, and polyacrylate. However, the mechanism underlying this reaction was not clarified. Here, we investigate the photo-induced colorimetric reaction of N-[2-(trimethylammonium)ethyl]-1,8-naphthalimide (TENI), which has a different cationic receptor from MNEI and undergoes the photo-induced colorimetric reaction, and its analogues to clarify the reaction mechanism. The TENI analogues having substituents on the naphthalene ring provide important evidence, suggesting that the colorimetric chemical species were radical anions generated via photo-induced electron transfer from carboxylate to the naphthalimide derivative. The generation of the naphthalimide-based radical anion is verified by ¹H NMR and cyclic voltammetry analyses, and photo-reduction of methylene blue is mediated by TENI. In addition, the role of the cationic receptor for the photo-induced colorimetric reaction is investigated with TENI analogues having different hydrophilic groups instead of the trimethylammonium group. Interestingly, the photo-induced colorimetric reaction is observed in a nonionic analogue having a polyethylene glycol group, indicating that the colorimetric reaction does not require a cationic receptor. On the other hand, we reveal that the trimethylammonium group stabilizes the radical anion species. These generation and stabilization phenomena of naphthalimide-based radical anion species will contribute to the development of sophisticated detection systems specific for carboxylate.

The Synthesis and Antitumor Activity of 1,8-Naphthalimide Derivatives Linked 1,2,3-Triazole

In this study, acenaphthylene was used as the raw material, and a series of novel 1,8-naphthalimide-1,2,3-triazole derivatives was obtained through oxidation, acylation, alkylation, and click reactions, and subsequently, their anti-tumor activities were tested. After screening, we found that Compound 5e showed good activity against H1975 lung cancer cells, with the half maximal inhibitory concentration (IC₅₀) reaching 16.56 μM.

Design, synthesis and antitumor evaluation of new 1,8-naphthalimide derivatives targeting nuclear DNA

Four series of new 3-nitro naphthalimides derivatives, 4(4a‒4f), 5(5a‒5i), 6(6a‒6e) and 7 (7a‒7j), were designed and synthesized as antitumor agents. Methyl thiazolyl tetrazolium (MTT) screening assay results revealed that some compounds displayed effective in vitro antiproliferative activity on SMMC-7721, T24, SKOV-3, A549 and MGC-803 cancer cell lines in comparison with 5-fluorouracil (5-FU), mitonafide and amonafide. Nude mouse xenotransplantation model assay results indicated that compounds 6b and 7b exhibited good in vivo antiproliferative activity in MGC-803 xenografts in comparison with amonafide and cisplatin, suggesting that compounds 6b and 7b could be good candidates for antitumor agents. Gel electrophoresis assay indicated that DNA and Topo I were the potential targets of compounds 6b and 7b, and comet assay confirmed that compounds 6b and 7b could induce DNA damage, while the further study showed that the 6b- and 7b-induced DNA damage was accompanied by the upregulation of p-ATM, P-Chk2, Cdc25A and p-H2AX. Cell cycle arrest studies demonstrated that compounds 6b and 7b arrested the cell cycle at the S phase, accompanied by the upregulation of the expression levels of the antioncogene p21 and the down-regulation of the expression levels of cyclin E. Apoptosis assays indicated that compounds 6b and 7b caused the apoptosis of tumor cells along with the upregulation of the expression of Bax, caspase-3, caspase-9 and PARP and the downregulation of Bcl-2. These mechanistic studies suggested that compounds 6b and 7b exerted their antitumor activity by targeting to DNA, thereby inducing DNA damage and Topo I inhibition, and consequently causing S stage arrest and the induction of apoptosis.

Naphthalimides Selectively Inhibit the Activity of Bacterial, Replicative DNA Ligases and Display Bactericidal Effects against Tubercle Bacilli

The DNA ligases, enzymes that seal breaks in the backbones of DNA, are essential for all organisms, however bacterial ligases essential for DNA replication use β-nicotinamide adenine dinucleotide as their co-factor, whereas those that are essential in eukaryotes and viruses use adenosine-5'-triphosphate. This fact leads to the conclusion that NAD⁺-dependent DNA ligases in bacteria could be targeted by their co-factor specific inhibitors. The development of novel alternative medical strategies, including new drugs, are a top priority focus areas for tuberculosis research due to an increase in the number of multi-drug resistant as well as totally drug resistant tubercle bacilli strains. Here, through the use of a virtual high-throughput screen and manual inspection of the top 200 records, 23 compounds were selected for in vitro studies. The selected compounds were evaluated in respect to their Mycobacterium tuberculosis NAD⁺ DNA ligase inhibitory effect by a newly developed assay based on Genetic Analyzer 3500 Sequencer. The most effective agents (e.g., pinafide, mitonafide) inhibited the activity of M. tuberculosis NAD⁺-dependent DNA ligase A at concentrations of 50 µM. At the same time, the ATP-dependent (phage) DNA LigT₄ was unaffected by the agents at concentrations up to 2 mM. The selected compounds appeared to also be active against actively growing tubercle bacilli in concentrations as low as 15 µM.

Phase I study of mitonafide with a 3-day administration schedule: early interruption due to severe central nervous system toxicity

Eleven patients with solid tumors for whom effective therapy was not available entered a phase I study of mitonafide given as a short intravenous (i.v.) infusion daily for 3 consecutive days. The initial dose level was selected according to the experience from another phase I study using a 5-day administration schedule. Six patients entered the first dose level (180 mg/m2/day x 3 days) and 4 of them had grade 3-4 leukopenia. This level was considered to be the maximum tolerated dose (MTD) and no further dose escalations were attempted. The following 5 patients received a dose approximately 10% inferior to the previous one (160 mg/m2/day x 3 days). Three of them had grade 3-4 neutropenia. Three partial responses were observed in total. After inclusion of 11 patients, an unexpected toxicity, central nervous system (CNS) toxicity, consisting of severe loss of memory, temporospatial disorientation and high integrative function impairment was observed in 5 patients (46%). A median patients' follow-up of 3 months after treatment discontinuation showed that these alterations were progressive and not reversible. This disabling toxicity prompted us to an early study interruption. In conclusion, mitonafide, when administered as a short 3-day i.v. infusion, can induce severe and irreversible CNS toxicity. Nevertheless, since antitumor activity has been observed, further development of the drug is recommended with different schedules of administration that have shown not to produce neurotoxicity, i.e., 5-day continuous infusion.

Phase I study of mitonafide in solid tumors

Mitonafide was the first synthetized compound of a new series of 3-nitronaphthalimides with intercalative properties. A phase I study with a conventional escalation scheme was developed. The schedule of drug administration was a daily x 5 days by short (1 h) intravenous (i.v.) infusion, every 21 days. Thirty evaluable patients were treated at doses from 15.4 mg/m2/d x 5 days to 138.6 mg/m2/d x 5 days. The study was interrupted due to appearance of central nervous system toxicity in 5 patients treated at doses above 118 mg/m2 x 5 days. This toxicity consisted firstly of loss of memory in all patients. It was irreversible and progressed in 3 patients to disorientation and confusion, leading to dementia in one of them. This was considered to be dose-limiting toxicity, and since it appeared to be related to the administration schedule, no further studies with short i.v. infusions of mitonafide are recommended. A phase I study utilizing a more desirable administration schedule over longer periods of time is ongoing in other centers.

Phase I study of mitonafide in 120 hour continuous infusion in non-small cell lung cancer

Mitonafide is the lead compound of a new series of antitumor drugs, the 3-Nitronaphthalimides, which have shown antineoplastic activity in vitro as well as in vivo. This phase I Mitonafide study in non-small cell lung cancer using a 120-hour continuous infusion (120 h. C.I.) schedule of administration was designed to deliver the maximum amount of drug while avoiding the risk of central nervous system (CNS) toxicity, previously observed in studies with daily short (1 hour) administration schedules. Twenty patients were treated at doses ranging from 107-200 mg/m2 x 120 h. C.I. Dose-limiting toxicity with this schedule of administration was leukopenia. Other toxicities were mild or not relevant. No CNS toxicity was observed. The recommended dose for phase II C.I. Mitonafide studies is 170 mg/m2 x 120 h. C.I. in previously untreated patients. Plasma level monitoring is recommended.

Toxicity of 3-nitronaphthalimides to V79 379A Chinese hamster cells

The cellular uptake and toxicity of a number of substituted 3-nitronaphthalimides was investigated. Uptake of these compounds into cells was initially rapid and reached a plateau after several hours, where in some cases intracellular concentrations were much greater than the corresponding extracellular concentrations. Little uptake was obtained, however, with a compound carrying an acidic substituent. Toxicity studies divided the compounds into two main groups; those where survival curves were convex and those where survival curves were concave. The shapes of survival curves of the latter group did not appear to reflect depletion of extracellular drug. Uptake and toxicity of different drugs were not well correlated and bioreductive metabolism of the nitro-substituent did not appear to be a major contributor to toxicity. There was no consistent differential toxicity of these drugs in aerobic and hypoxic conditions. It was concluded that the nature of the ring substituent had more effect on toxicity than the absolute concentration of the naphthalimide ring or bioreductive metabolism of the nitro-group.