Fine-tuned PEGylation of chitosan to maintain optimal siRNA-nanoplex bioactivity.

Polyethylene glycol (PEG) is a widely used modification for drug delivery systems. It reduces undesired interaction with biological components, aggregation of complexes and serves as a hydrophilic linker of ligands for targeted drug delivery. However, PEGylation can also lead to undesired changes in physicochemical characteristics of chitosan/siRNA nanoplexes and hamper gene silencing. To address this conflicting issue, PEG-chitosan copolymers were synthesized with stepwise increasing degrees of PEG substitution (1.5% to 8.0%). Subsequently formed PEG-chitosan/siRNA nanoplexes were characterized physicochemically and biologically. The results showed that small ratios of chitosan PEGylation did not affect nanoplex stability and density. However, higher PEGylation ratios reduced nanoplex size and charge, as well as cell uptake and final siRNA knockdown efficiency. Therefore, we recommend fine-tuning of PEGylation ratios to generate PEG-chitosan/siRNA delivery systems with maximum bioactivity. The degree of PEGylation for chitosan/siRNA nanoplexes should be kept low in order to maintain optimal nanoplex efficiency.

Isoxazolone based inhibitors of p38 MAP kinases.

SAR of N-alkylated isoxazolones as p38 MAP kinase inhibitors was realized. The data herein show the possibility of transferring the SAR study and evaluation from N-1-substituted imidazole to isoxazolones. Optimization of substituent was realized.

4-(4-Fluoro-phen-yl)-2-methyl-3-(1-oxy-4-pyridyl)isoxazol-5(2H)-one.

The crystal structure of the title compound, C(15)H(11)FN(2)O(3), was determined as part of a study on the biological activity of isoxazolone derivatives as p38 mitogen-activated protein kinase (MAPK) inhibitors. The dihedral angles between rings are isoxazole/benzene = 55.0 (3)°, isoxazole/pyridine = 33.8 (2)° and benzene/pyridine = 58.1 (2)°.

Are MAP kinases drug targets? Yes, but difficult ones.

Pharmaceutical companies are facing an increasing interest in new target identification and validation. In particular, extensive efforts are being made in the field of protein kinase inhibitors research and development, and the past ten years of effort in this field have altered our perception of the potential of kinases as drug targets. Therefore, in the drug discovery process, the selection of relevant, susceptible protein kinase targets combined with searches for leads and candidates have become a crucial approach. The success of recent launches of protein kinase inhibitors (Gleevec, Imatinib, Sutent, Iressa, Nexavar, Sprycel) gave another push to this field. Numerous other kinase inhibitors are currently undergoing clinical trials or clinical development. Some questions are nevertheless unanswered, mostly related to the great number of known kinases in the human genome, to their similarity with each other, to the existence of functionally redundant kinases for specific pathways, and also because the connection between particular pathways and diseases is not always clear. The review is leading the reader through a panoramic view of protein kinase inhibition with a major focus on MAPK, successful examples and clinical candidates.

4-[4-(4-Fluoro-phen-yl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-3-yl]-1-methyl-pyridinium iodide-4-[3-(4-fluoro-phen-yl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-4-yl]-1-methyl-pyridinium iodide (0.6/0.4).

The crystal structure of the title compound, C(16)H(16)FN(2)O(2) (+)·I(-), was determined as part of a study of the biological activity of isoxazolone derivatives as p38 mitogen-activated protein kinase (MAPK) inhibitors. The X-ray crystal structure of 4-[4-(4-fluoro-phenyl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-3-yl]-1-methyl-pyridinium iodide showed the presence of the regioisomer 4-[3-(4-fluoro-phenyl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-4-yl]-1-methyl-pyridinium iodide. The synthesis of the former compound was achieved by reacting 4-(4-fluoro-phenyl)-3-(4-pyridyl)isoxazol-5(2H)-one after treatment with Et(3)N in dimethyl-formamide, with iodo-methane. The unexpected formation of the regioisomer could be explained by a rearrangement occurring via aziridine of the isoxazolone compound. The regioisomers have site occupancies of 0.632 (4)/0.368 (4). The two six members rings make a dihedral angle of 66.8 (2)°.

Substituted isoxazoles as potent inhibitors of p38 MAP kinase.

In a continuous effort to develop improved p38 MAP (mitogen-activated protein) kinase inhibitors, we focused our attention on the suitability of the isoxazole ring as a bioisosteric replacement for the imidazole ring of SB-203580. 3,4- and 4,5-disubstituted as well as 3,4,5-trisubstituted isoxazole derivatives were synthesized. These compounds were tested in an in vitro enzyme-linked immunosorbent assay of isolated p38 MAP kinase and for inhibitory potency against cytochrome P450. Compound 4 a displays a highly promising profile for development as an anti-inflammatory agent owing to its enhanced suppression of cytokine release, decreased affinity for cytochrome P450 and a twofold decrease in IC50 toward isolated p38 MAP kinase.