Synthesis, receptor binding and functional studies of mesoridazine stereoisomers

Spiro Scaffold Chiral Organocatalyst of 3,2'-Pyrrolidinyl Spiro-oxindole Amine and Its Catalytic Evaluation in the Enantioselective Aldol Condensation between 3-(3-Hydroxy-1H-pyrazol-1-yl)-Oxindole and Paraformaldehyde

The spiro scaffold chiral organocatalyst of 3,2'-pyrrolidinyl spiro-oxindole amine was successfully prepared from racemic spiro-oxindole amine using l-menthol as a chiral pool in 4 steps in 28%-40% overall yields with at least 99% ee in scale-up preparation, and its catalytic activity was evaluated in the enantioselective aldol condensation between 3-(3-hydroxy-1H-pyrazol-1-yl)-oxindole and paraformaldehyde. The spiro organocatalyst showed superior catalytic activity and selectivity compared with its counterparts, and most substrates offered good to excellent results with up to 96% yield in 96% ee.

A Novel Derivative of Thioridazine Shows Low Toxicity and Efficient Activity against Gram-Positive Pathogens

Thioridazine hydrochloride (HCl) has been suggested as a promising antimicrobial helper compound for the treatment of infections with antimicrobial-resistant bacteria. Unfortunately, the therapeutic concentration of thioridazine HCl is generally higher than what can be tolerated clinically, in part due to its toxic side effects on the central nervous system. Therefore, we aimed to synthesize a less toxic thioridazine derivative that would still retain its properties as a helper compound. This resulted in a compound designated 1-methyl-2-(2-(2-(methylthio)-10H-phenothiazin-10-yl)ethyl)-1-pentylpiperidin-1-ium bromide (abbreviated T5), which exhibited low blood–brain barrier permeability. The lowest minimal inhibitory concentration (MIC) against Staphylococcus aureus exposed to the novel compound was reduced 32-fold compared to thioridazine HCl (from 32 µg/mL to 1 µg/mL). The MIC values for T5 against five Gram-positive pathogens ranged from 1 µg/mL to 8 µg/mL. In contrast to thioridazine HCl, T5 does not act synergistically with oxacillin. In silico predictive structure analysis of T5 suggests that an acceptably low toxicity and lack of induced cytotoxicity was demonstrated by a lactate dehydrogenase assay. Conclusively, T5 is suggested as a novel antimicrobial agent against Gram-positive bacteria. However, future pharmacokinetic and pharmacodynamic studies are needed to clarify the clinical potential of this novel discovery.

Crystal structure of dopamine receptor D4 bound to the subtype selective ligand, L745870

Multiple subtypes of dopamine receptors within the GPCR superfamily regulate neurological processes through various downstream signaling pathways. A crucial question about the dopamine receptor family is what structural features determine the subtype-selectivity of potential drugs. Here, we report the 3.5-angstrom crystal structure of mouse dopamine receptor D4 (DRD4) complexed with a subtype-selective antagonist, L745870. Our structure reveals a secondary binding pocket extended from the orthosteric ligand-binding pocket to a DRD4-specific crevice located between transmembrane helices 2 and 3. Additional mutagenesis studies suggest that the antagonist L745870 prevents DRD4 activation by blocking the relative movement between transmembrane helices 2 and 3. These results expand our knowledge of the molecular basis for the physiological functions of DRD4 and assist new drug design.

Combination of experimental and in silico methods for the assessment of the phototransformation products of the antipsychotic drug/metabolite Mesoridazine

The lack of studies on the fate and effects of drug metabolites in the environment is of concern. As their parent compounds, metabolites enter the aquatic environment and are subject to biotic and abiotic process. In this regard, photolysis plays an important role. This study combined experimental and in silico quantitative structure-activity relationship (QSAR) methods to assess the fate and effects of Mesoridazine (MESO), a pharmacologically active human drug and metabolite of the antipsychotic agent Thioridazine, and its transformation products (TPs) formed through a Xenon lamp irradiation. After 256min, the photodegradation of MESO⋅besylate (50mgL^-1) achieved 90.4% and 6.9% of primary elimination and mineralization, respectively. The photon flux emitted by the lamp (200-600nm) was 169.55Jcm^-2. Sixteen TPs were detected by means of liquid chromatography-high resolution mass spectrometry (LC-HRMS), and the structures were proposed based on MSⁿ fragmentation patterns. The main transformation reactions were sulfoxidation, hydroxylation, dehydrogenation, and sulfoxide elimination. A back-transformation of MESO to Thioridazine was evidenced. Aerobic biodegradation tests (OECD 301 D and 301F) were applied to MESO and the mixture of TPs present after 256min of photolysis. Most of TPs were not biodegraded, demonstrating their tendency to persist in aquatic environments. The ecotoxicity towards Vibrio fischeri showed a decrease in toxicity during the photolysis process. The in silico QSAR tools QSARINS and US-EPA PBT profiler were applied for the screening of TPs with character of persistence, bioaccumulation, and toxicity (PBT). They have revealed the carbazole derivatives TP 355 and TP 337 as PBT/vPvB (very persistent and very bioaccumulative) compounds. In silico QSAR predictions for mutagenicity and genotoxicity provided by CASE Ultra and Leadscope® indicated positive alerts for mutagenicity on TP 355 and TP 337. Further studies regarding the carbazole derivative TPs should be considered to confirm their hazardous character.

A small molecule screening to detect potential therapeutic targets in human podocytes

WIDMEIER E, TAN W, AIRIK M, HILDEBRANDT F

A small molecule screening to detect potential therapeutic targets in human podocytes. Am J Physiol Renal Physiol 312: F157-F171, 2017. First published October 19, 2016; doi:10.1152/ajprenal.00386.2016. Steroid-resistant nephrotic syndrome (SRNS) inevitably progresses to end-stage kidney disease, requiring dialysis or transplantation for survival. However, treatment modalities and drug discovery remain limited. Mutations in over 30 genes have been discovered as monogenic causes of SRNS. Most of these genes are predominantly expressed in the glomerular epithelial cell, the podocyte, placing it at the center of the pathogenesis of SRNS. Podocyte migration rate (PMR) represents a relevant intermediate phenotype of disease in monogenic causes of SRNS. We therefore adapted PMR in a high-throughput manner to screen small molecules as potential therapeutic targets for SRNS. We performed a high-throughput drug screening of a National Institutes of Health Clinical Collection (NCC) library (n = 725 compounds) measuring PMR by videomicroscopy. We used the Woundmaker to perform individual 96-well scratch wounds and screened compounds using a quantitative kinetic live cell imaging migration assay using IncuCyte ZOOM technology. Using a normal distribution for the average PMR in wild-type podocytes with a vehicle control (DMSO), we applied a 90% confidence interval to define "distinct" compounds (5% faster/slower PMR) and found that 12 of 725 compounds (at 10 μM) reduced PMR. Clusters of drugs that alter PMR included actin/tubulin modulators such as the azole class of antifungals and antineoplastic vinca-alkaloids. We hereby identify compounds that alter PMR. The PMR assay provides a new avenue to test therapeutics for nephrotic syndrome. Positive results may reveal novel pathways in the study of glomerular diseases such as SRNS.

Mechanisms of action of antipsychotic drugs of different classes, refractoriness to therapeutic effects of classical neuroleptics, and individual variation in sensitivity to their actions: Part I

Many issues remain unresolved about antipsychotic drugs. Their therapeutic potency scales with affinity for dopamine D2 receptors, but there are indications that they act indirectly, with dopamine D1 receptors (and others) as possible ultimate targets. Classical neuroleptic drugs disinhibit striatal cholinergic interneurones and increase acetyl choline release. Their effects may then depend on stimulation of muscarinic receptors on principle striatal neurones (M4 receptors, with reduction of cAMP formation, for therapeutic effects; M1 receptors for motor side effects). Many psychotic patients do not benefit from neuroleptic drugs, or develop resistance to them during prolonged treatment, but respond well to clozapine. For patients who do respond, there is a wide (>ten-fold) range in optimal doses. Refractoriness or low sensitivity to antipsychotic effects (and other pathologies) could then arise from low density of cholinergic interneurones. Clozapine probably owes its special actions to direct stimulation of M4 receptors, a mechanism available when indirect action is lost.

Endophytic fungi as models for the stereoselective biotransformation of thioridazine

The stereoselective kinetic biotransformation of thioridazine, a phenothiazine neuroleptic drug, by endophytic fungi was investigated. In general, the sulfur of lateral chain (position 2) or the sulfur of phenothiazinic ring (position 5) were oxidated yielding the major human metabolites thioridazine-2-sulfoxide and thioridazine-5-sulfoxide. The quantity of metabolites biosynthesized varied among the 12 endophytic fungi evaluated. However, mono-2-sulfoxidation occurred in higher ratio and frequency. Among the 12 fungi evaluated, 4 of them deserve prominence for presenting an evidenced stereoselective biotransformation: Phomopsis sp. (TD2), Glomerella cingulata (VA1), Diaporthe phaseolorum (VR4), and Aspergillus fumigatus (VR12). Both enantiomers of thioridazine were consumed by the fungi; however, the 2-sulfoxidation yielded preferentially the R configuration at the sulfur atom.

Comparison of the Effects of Thioridazine and Mesoridazine on the QT Interval in Healthy Adults After Single Oral Doses

We compared the effects of single doses of thioridazine and mesoridazine on the heart rate-corrected QT (QTc) interval in healthy adult volunteers. QTc intervals and plasma concentrations of thioridazine, mesoridazine, and metabolites were measured after single oral doses of thioridazine hydrochloride 50 mg, mesoridazine besylate 50 mg, or placebo in a double-blind, crossover study. Mean maximum increases in the QTc interval following thioridazine (37.3+/-4.1 ms, P=0.023) and mesoridazine (46.6+/-7.4 ms, P=0.021) were similar and significantly greater than following placebo (12.9+/-8.1 ms). The area under the effect-time curve over 8 h following drug administration was similar between the two drugs (129.3+/-22.1 vs 148.3+/-43.0 ms h). In conclusion, thioridazine and mesoridazine are associated with similar effects on the QTc interval.