Spirooxadiazoline-oxindoles derived from imatinib show antimyeloproliferative potential in K562 cells

Imatinib mesylate was the first representative BCR-ABL1 tyrosine kinase inhibitor (TKI) class for the treatment of chronic myeloid leukemia. Despite the revolution promoted by TKIs in the treatment of this pathology, a resistance mechanism occurs against all BCR-ABL1 inhibitors, necessitating a constant search for new therapeutic options. To develop new antimyeloproliferative substances, we applied a medicinal chemistry tool known as molecular hybridization to design 25 new substances. These compounds were synthesized and biologically evaluated against K562 cells, which express BCR-ABL1, a constitutively active tyrosine kinase enzyme, as well as in WSS-1 cells (healthy cells). The new compounds are conjugated hybrids that contain phenylamino-pyrimidine-pyridine (PAPP) and an isatin backbone, which are the main pharmacophoric fragments of imatinib and sunitinib, respectively. A spiro-oxindole nucleus was used as a linker because it occurs in many compounds with antimyeloproliferative activity. Compounds 2a, 2b, 3c, 4c, and 4e showed promise, as they inhibited cell viability by between 45% and 61% at a concentration of 10 µM. The CC50 of the most active substances was determined to be within 0.8-9.8 µM.

Synthesis, Molecular Docking, BSA, and in-vitro reactivation study of imidazopyridine oxime against paraoxon inhibited acetylcholinesterase

AIM

To synthesize and evaluate the fused heterocyclic imidazopyridine oxime as a reactivator against paraoxon inhibited acetylcholinesterase.

BACKGROUND

Organophosphorus compounds (OPs) include parathion, malathion, chlorpyrifos, monocrotophos, and diazinon which are commonly used in agriculture for enhancing agricultural productivity via killing crop-damaging pests. However, people may get exposed to OPs pesticides unintentionally/intentionally via ingestion, inhalation or dermal. The current treatment regimen includes reactivator such as mono or bis-pyridinium oximes along with anticholinergic and an anticonvulsant drugs are recommended for the treatment of OP poisoning. Unfortunately, the drawback of the existing reactivator is that owing to the permanent charge present on the pyridinium makes them inefficient to cross the blood-brain barrier (BBB) and reactivate OP-inhibited central nervous system (CNS) acetylcholinesterase. Therefore, there is a need of reactivator that could cross the BBB and reactivate the OP inhibited acetylcholinesterase.

OBJECTIVE

The objectives of the study were synthesis, molecular docking, BSA binding and in-vitro estimation of oximes of various substituted imidazo [1,2-a]pyridine against paraoxon inhibited acetylcholinesterase.

METHOD

The reactivators were synthesized in three steps and characterized using various spectroscopic techniques. Molecular docking study was performed on 2WHP and 3ZLV PDB using Autodock tool. The acid dissociation constant (pKa) of oximes was calculated experimentally and drug-likeness properties of the oximes were calculated In silico using mole inspiration and Swiss ADME software. The binding of oximes with bovine serum albumin (BSA) was also investigated by UV-Vis spectrophotometer. The reactivation potential of the oximes was determined by in vitro enzymatic assay.

RESULT

in-silico study inferred that synthesized molecules fulfilled the parameters that required for a successful CNS drug candidate. Further, in-vitro enzymatic assay indicated reasonable reactivation potential of the oximes against paraoxon-inhibited AChE. The binding of oximes with bovine serum albumin (BSA) revealed static quenching of intrinsic fluorescence of BSA by oxime. The binding constant value and number of binding sites were found 0.24 mol-1 and 1 respectively.

CONCLUSION

The results of study concluded that this scaffold could be used for further designing of more efficient uncharged reactivators.

Methyl Scanning and Revised Binding Mode of 2-Pralidoxime, an Antidote for Nerve Agent Poisoning

Organophosphorus nerve agents (OPNAs) inhibit acetylcholinesterase (AChE) and, despite the Chemical Weapons Convention arms control treaty, continue to represent a threat to both military personnel and civilians. 2-Pralidoxime (2-PAM) is currently the only therapeutic countermeasure approved by the United States Food and Drug Administration for treating OPNA poisoning. However, 2-PAM is not centrally active due to its hydrophilicity and resulting poor blood-brain barrier permeability; hence, these deficiencies warrant the development of more hydrophobic analogs. Specifically, gaps exist in previously published structure activity relationship (SAR) studies for 2-PAM, thereby making it difficult to rationally design novel analogs that are concomitantly more permeable and more efficacious. In this study, we methodically performed a methyl scan on the core pyridinium of 2-PAM to identify ring positions that could tolerate both additional steric bulk and hydrophobicity. Subsequently, SAR-guided molecular docking was used to rationalize hydropathically feasible binding modes for 2-PAM and the reported derivatives. Overall, the data presented herein provide new insights that may facilitate the rational design of more efficacious 2-PAM analogs.

Novel Insights into the Thioesterolytic Activity of N-Substituted Pyridinium-4-oximes

The pyridinium oximes are known esterolytic agents, usually classified in the literature as catalysts, which mimic the catalytic mode of hydrolases. Herein, we combined kinetic and computational studies of the pyridinium-4-oxime-mediated acetylthiocholine (AcSCh⁺) hydrolysis to provide novel insights into their potential catalytic activity. The N-methyl- and N-benzylpyridinium-4-oximes have been tested as oximolytic agents toward the AcSCh⁺, while the newly synthesized O-acetyl-N-methylpyridinium-4-oxime iodide was employed for studying the consecutive hydrolytic reaction. The relevance of the AcSCh⁺ hydrolysis as a competitive reaction to AcSCh⁺ oximolysis was also investigated. The reactions were independently studied spectrophotometrically and rate constants, k_oxime, k_w and k_OH, were evaluated over a convenient pH-range at I = 0.1 M and 25 °C. The catalytic action of pyridinium-4-oximes comprises two successive stages, acetylation (oximolysis) and deacetylation stage (pyridinium-4-oxime-ester hydrolysis), the latter being crucial for understanding the whole catalytic cycle. The complete mechanism is presented by the free energy reaction profiles obtained with (CPCM)/M06–2X/6–311++G(2df,2pd)//(CPCM)/M06–2X/6–31+G(d) computational model. The comparison of the observed rates of AcSCh⁺ oximolytic cleavage and both competitive AcSCh⁺ and consecutive pyridinium-4-oxime-ester hydrolytic cleavage revealed that the pyridinium-4-oximes cannot be classified as non-enzyme catalyst of the AcSCh⁺ hydrolysis but as the very effective esterolytic agents.