Isolation and structure elucidation of the main UV-A photoproducts of vandetanib.

Exposure of aqueous solutions of the antitumor drug vandetanib to UV-A light results in the photochemical degradation. Two main photodegradation products were identified by HPLC-MS analysis and their structures were elucidated, after their isolation by HPLC, on the basis of LC-MS and NMR spectra. The photoproducts derived from a simple debromination (N-(2-fluorophenyl)-6-methoxy-7-((1-methylpiperidin-4 yl)methoxy)quinazolin-4-amine, FP3) or from the loss of the bromide atom followed by the solvent addition (N-(4-hydroxy-2-fluorophenyl)-6-methoxy-7-((1-methylpiperidin-4 yl)methoxy)quinazolin-4-amine, FP2). At our knowledge this is the first report about the photodegradation of vandetanib.

Interaction of ionizing radiation and ZRBA1, a mixed EGFR/DNA-targeting molecule.

ZRBA1 is a molecule termed 'combi-molecule' designed to induce DNA-alkylating lesions and to block epidermal growth factor receptor (EGFR) tyrosine kinase. Owing to its ability to downregulate the EGFR tyrosine kinase-mediated antiapoptotic signaling and DNA repair proteins, we inferred that it could significantly sensitize cells to ionizing radiation. Using the MDA-MB-468 human breast cancer cell line in which ZRBA1 has already been reported to induce significant EGFR/DNA-targeting potency, the results showed that: (i) concurrent administration of ZRBA1 and 4 Gy radiation led to a significant decrease in cell viability, (ii) the greater efficacy of the combination was sequential, being limited to conditions wherein the drug was administered concurrently with radiation or before radiation, and (iii) the efficacy enhancement of the combination was further confirmed by clonogenic assays from which a dose enhancement factor of 1.34 could be observed at survival fraction of 0.01. Flow cytometric analysis showed significant enhancement of cell cycle arrest in G2/M (P<0.046, irradiated cells vs. cells treated with ZRBA1 and radiation) and increased apoptosis when ZRBA1 was combined with radiation. Likewise, significant levels of double-strand breaks were observed for the combination, as determined by neutral comet assay (P<0.045, irradiated cells vs. cells treated with ZRBA1 and radiation). These results in toto suggest that the superior efficacy of the ZRBA1 plus radiation combination may be secondary to the ability of ZRBA1 to arrest the cells in G2/M, a cell cycle phase in which tumor cells are sensitive to radiation. Furthermore, the increased levels of DNA damage, combined with the concomitant downregulation of EGFR-mediated signaling by ZRBA1, may account for the significant levels of cell killing induced by the combination.

Microwave-assisted efficient and convenient synthesis of 2,4(1H,3H)-quinazolinediones and 2-thioxoquinazolines.

An efficient and convenient method was developed for the preparation of 2,4(1H,3H)-quinazolinediones and 2-thioxoquinazolinones. Substituted methyl anthranilate reacted with various iso(thio)cyanates in DMSO/H2O without any catalyst or base by using microwave irradiation to generate diversity on the 2,4(1H,3H)-quinazolinediones or 2-thioxoquinazolinones. A variety of substrates can participate in the process with good yields and high purities, making this methodology suitable for library synthesis in drug discovery efforts.

Thiazolo[5,4-f]quinazolin-9-ones, inhibitors of glycogen synthase kinase-3.

In an effort to identify new protein kinase inhibitors with increased potency and selectivity, we have developed the microwave-assisted synthesis of thiazolo[5,4-f]quinazolin-9-ones. The effects of eighteen derivatives on CDK1/cyclin B, CDK5/p25, and GSK-3 were investigated. Several turned out to inhibit GSK-3 in the micromolar range. Molecular modeling studies suggest that the most selective GSK-3 inhibitors 7a-d bind into the ATP-binding site through a key hydrogen bond interaction with Val135 and target the specific hydrophobic backpocket of the enzyme.

Synthesis and evaluation of the antiproliferative activity of novel thiazoloquinazolinone kinases inhibitors.

The microwave-assisted synthesis of a family of 2,8-substituted thiazoloquinazolinones is described. The preliminary evaluation of the antiproliferative activity and the capacity of these molecules to inhibit CDKs and GSK-3 are reported. A lead compound was identified, constituting a scaffold from which more potent inhibitors could be designed.

Analysis of violet-excited fluorochromes by flow cytometry using a violet laser diode.

BACKGROUND: Low power violet laser diodes (VLDs) have been evaluated as potential replacements for water-cooled argon-ion and krypton-ion ultraviolet and violet lasers for DNA content analysis using the Hoechst dyes and 4,6-diamidino-2-phenylindole (Shapiro HMN, Perlmutter NG: Cytometry 44:133-136, 2001). In this study, we used a VLD to excite a variety of violet-excited fluorescent molecules important in biomedical analysis, including the fluorochromes Cascade Blue and Pacific Blue, the expressible fluorescent protein cyan fluorescent protein (CFP), and the fluorogenic alkaline phosphatase (AP) substrate 2-(5'-chloro-2'-phosphoryloxyphenyl)-6-chloro-4-(3H)-quinazoline (ELF-97; for endogenous AP detection and cell surface labeling with AP-conjugated antibodies). METHODS: Comparisons were made between VLD excitation and a krypton-ion laser emitting at 407 nm (both at higher power levels and with the beam attenuated at levels approximating the VLD) on the same FACSVantage SE stream-in-air flow cytometer. We evaluated a Power Technology 408-nm VLD (30 mW) equipped with circularization optics (18 mW maximum output, set to 15 mW) and a Coherent I-302C krypton-ion laser emitting at power levels ranging from 15 to 75 mW. RESULTS: Cascade Blue, Pacific Blue, and CFP showed comparable signal-to-noise ratios and levels of sensitivity with VLD excitation versus the krypton-ion laser at high and VLD-matched power outputs. Multicolor fluorescent protein analysis with 488-nm excitation of green fluorescent protein and DsRed and VLD excitation of CFP was therefore feasible and was demonstrated. Similar levels of excitation efficiency between krypton-ion and VLD sources also were observed for ELF-97 detection. CONCLUSIONS: These evaluations confirmed that VLDs may be cost- and maintenance-effective replacements for water-cooled gas lasers for applications requiring violet excitation in addition to DNA binding dyes.

Afloqualone phototoxicity--photosensitized lipid peroxidative potency and its biological significance.

Photosensitivity due to afloqualone (AQ), a muscle relaxant acting on the central nervous system, has tended to increase with increasing clinical use of this drug by orthopedists. The initial step leading to drug photosensitivity is a photochemical reaction between photo excited phototoxic compounds (drugs) or their metabolites and target molecules in skin. The present study was an attempt to determine whether unsaturated lipids are one of the target molecules of AQ-photosensitivity. Squalene, an unsatulated model lipid, was subjected to UVA irradiation in the presence of AQ and production of squalene hydroperoxides was confirmed. AQ-photosensitized peroxidation of squalene was repressed in the presence of 2.5-dimethylfuran, a singlet oxygen acceptor. Production of singlet oxygen by UVA irradiation of AQ was also observed in aqueous solution. These findings suggested participation of singlet oxygen in the AQ photosensitized peroxidation of squalene. Although photohemolysis was not observed by UVA irradiation in the presence of AQ, We propose that lipids can be a target molecule of AQ-phototoxicity, and lipid peroxidation might be one of the important factors responsible for induction of the AQ phototoxic reaction.