Kinase domain inhibition of leucine rich repeat kinase 2 (LRRK2) using a [1,2,4]triazolo[4,3-b]pyridazine scaffold

Design, synthesis, biological evaluation, and docking studies of novel triazolo[4,3-b]pyridazine derivatives as dual c-Met/Pim-1 potential inhibitors with antitumor activity

Interest has been piqued in c-Met and Pim-1, potential new cancer treatment targets. A variety of triazolo[4,3-b]pyridazine derivatives were synthesized to create powerful dual c-Met/Pim-1 inhibitors having the pharmacophoric elements of both enzyme inhibitors. All derivatives were screened for their cytotoxic effects on 60 cancer cell lines. Compounds 4g and 4a, had strong antiproliferative cytotoxic impacts on tumor cells, with mean GI% values of 55.84 and 29.08%, respectively. Research revealed that 4g has more powerful inhibitory activity against c-Met and Pim-1, with IC50 of 0.163 ± 0.01 and 0.283 ± 0.01 μM, respectively than the reference and derivative 4a. Moreover, compound 4g was the subject of an additional investigation into biological processes. The findings showed that compound 4g caused MCF-7 cells to arrest in the S stage of the cell cycle. Also, it accelerated the progress of apoptosis 29.61-fold more than the control. Compound 4g demonstrated a significantly higher level of caspase-9 and a decreased level of p-PI3K, p-AKT, and p-mTOR compared to staurosporine. Later, analysis of 4g showed good drug-ability and pharmacokinetic properties. A similar mode of interaction at the ATP-binding site of c-Met and Pim-1 compared to the docked ligands was suggested by additional docking studies of compound 4g.

Cajanus cajan (L) Millsp seeds extract prevents rotenone-induced motor- and non-motor features of Parkinson disease in mice: Insight into mechanisms of neuroprotection

ETHNOPHARMACOLOGICAL RELEVANCE

Cajanus cajan (L) Millsp (Fabaceae) seed decoction is used by traditional healers in Nigeria as nerve tonic, hence, could be beneficial in the treatment of Parkinson's disease (PD), a progressive and debilitating neurodegenerative disease that imposes great burden on the healthcare system globally.

AIM OF THE STUDY

This study aimed at investigating the neuroprotective effect of ethanol seed extract of Cajanus cajan (CC) in the treatment of rotenone-induced motor symptoms and non-motor symptoms associated with PD.

MATERIALS AND METHODS

To assess the protective action of CC on rotenone-induced motor- and non-motor symptoms of PD, mice were first pretreated with CC (50, 100 or 200 mg/kg, p.o.) an hour before oral administration of rotenone (1 mg/kg, p.o, 0.5% in carboxyl-methylcellulose) for 28 consecutive days and weekly behavioural tests including motor assessment (open field test (OFT), rotarod, pole and cylinder tests) and non-motor assessment (novel object recognition (NOR), Y-maze test (YM), forced swim and tail suspension, gastric emptying and intestinal fluid accumulation tests) were carried out. The animals were euthanized on day 28 followed by the collection of brain for assessment of oxidative stress, inflammatory markers and immunohistochemical analysis of the striatum (STR) and substantia nigra (SN). Phytochemicals earlier isolated from CC were docked with protein targets linked with PD pathology such as; catechol-O-methyltransferase (COMT), tyrosine hydroxylase (TH) and Leucine rich receptor kinase (LRRK).

RESULTS

this study showed that CC significantly reduced rotenone-induced spontaneous motor impairment in OFT, pole, cylinder and rotarod tests in mice as well as significant improvement in non-motor features (significant reversal of rotenone-induced deficits discrimination index and spontaneous alternation behaviour in NORT and YM test, respectively, reduction in immobility time in forced swim/tail suspension test, gastrointestinal disturbance in intestinal transit time in mice. Moreso, rotenone-induced neurodegeneration, oxidative stress and neuroinflammation were significantly attenuated by CC administration. In addition, docking analysis showed significant binding affinity of CC phytochemicals with COMT, TH and LRRK2 receptors.

CONCLUSION

Cajanus cajan seeds extract prevented both motor and non-motor features of Parkinson disease in mice through its antioxidant and anti-inflammatory effects. Hence, could be a potential phytotherapeutic adjunct in the management of Parkinson disease.

Multi-method computational evaluation of the inhibitors against leucine-rich repeat kinase 2 G2019S mutant for Parkinson's disease

Leucine-rich repeat kinase 2 G2019S mutant (LRRK2 G2019S) is a potential target for Parkinson's disease therapy. In this work, the computational evaluation of the LRRK2 G2019S inhibitors was conducted via a combined approach which contains a preliminary screening of a large database of compounds via similarity and pharmacophore, a secondary selection via structure-based affinity prediction and molecular docking, and a rescoring treatment for the final selection. MD simulations and MM/GBSA calculations were performed to check the agreement between different prediction methods for these inhibitors. 331 experimental ligands were collected, and 170 were used to build the structure-activity relationship. Eight representative ligand structural models were employed in similarity searching and pharmacophore screening over 14 million compounds. The process for selecting proper molecular descriptors provides a successful sample which can be used as a general strategy in QSAR modelling. The rescoring used in this work presents an alternative useful treatment for ranking and selection.

Recent advances in targeting leucine-rich repeat kinase 2 as a potential strategy for the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. Several single gene mutations involved in PD have been identified such as leucine-rich repeat kinase 2 (LRRK2), the most common cause of sporadic and familial PD. Its mutations have attracted much attention to therapeutically targeting this kinase. To date, many compounds including small chemical molecules with diverse scaffolds and RNA agents have been developed with significant amelioration in preclinical PD models. Currently, five candidates, DNL201, DNL151, WXWH0226, NEU-723 and BIIB094, have advanced to clinical trials for PD treatment. In this review, we describe the structure, pathogenic mutations and the mechanism of LRRK2, and summarize the development of LRRK2 inhibitors in preclinical and clinical studies, trying to provide an insight into targeting LRRK2 for PD intervention in future.

Small-molecule LRRK2 inhibitors for PD therapy: Current achievements and future perspectives

Leucine-rich repeat kinase 2 (LRRK2) is a multifunctional protein that orchestrates a diverse array of cellular processes, including vesicle transport, autophagy, lysosome degradation, neurotransmission, and mitochondrial activity. Hyperactivation of LRRK2 triggers vesicle transport dysfunction, neuroinflammation, accumulation of α-synuclein, mitochondrial dysfunction, and the loss of cilia, ultimately leading to Parkinson's disease (PD). Therefore, targeting LRRK2 protein is a promising therapeutic strategy for PD. The clinical translation of LRRK2 inhibitors was historically impeded by issues surrounding tissue specificity. Recent studies have identified LRRK2 inhibitors that have no effect on peripheral tissues. Currently, there are four small-molecule LRRK2 inhibitors undergoing clinical trials. This review provides a summary of the structure and biological functions of LRRK2, along with an overview of the binding modes and structure-activity relationships (SARs) of small-molecule inhibitors targeting LRRK2. It offers valuable references for developing novel drugs targeting LRRK2.

Recent Update on the Development of Leucine- Rich Repeat Kinase 2 (LRRK2) Inhibitors: A Promising Target for the Treatment of Parkinson's Disease

Parkinson's disease is a relatively common neurological disorder with incidence increasing with age. Since current medications only relieve the symptoms and do not change the course of the disease, therefore, finding disease-modifying therapies is a critical unmet medical need. However, significant progress in understanding how genetics underpins Parkinson's disease (PD) has opened up new opportunities for understanding disease pathogenesis and identifying possible therapeutic targets. One such target is leucine-rich repeat kinase 2 (LRRK2), an elusive enzyme implicated in both familial and idiopathic PD risk. As a result, both academia and industry have promoted the development of potent and selective inhibitors of LRRK2. In this review, we have summarized recent progress on the discovery and development of LRKK2 inhibitors as well as the bioactivity of several small-molecule LRRK2 inhibitors that have been used to inhibit LRRK2 kinase activity in vitro or in vivo.

Exploring phenylcarbamoylazinane-1,2,4-triazole thioethers as lipoxygenase inhibitors supported with in vitro, in silico and cytotoxic studies

Searching small molecules as an auspicious approach to develop new anti-inflammatory drugs is a challenge for the researchers especially by modifying active pharmacophoric groups in the targeted molecules. In the current work, a series of new S-alkyl/aralky derivatives (8a-h; 9a-h) of 2-(4-ethyl/phenyl-5-(1-phenylcarbamoylpiperidine)-4H-1,2,4-triazol-3-ylthio)ether were synthesized and assessed for their inhibitory action against the 15-lipoxygenase from soybean (15-sLOX). The basic precursor ethyl piperidine-4-carboxylate (a) was consecutively changed into phenylcarbamoyl derivative (1), hydrazide (2), semicarbazides (3/4) and N-ethyl/phenyl-5-(1-phenylcarbamoylpiperidine)-1,2,4-triazoles (5/6), which further in association with electrophiles (7a-h) promoted to the final products (8a-h; 9a-h). The synthesized derivatives were characterized by FT-IR, ¹H-, ¹³C NMR spectroscopy, EI-MS, and HR-EI-MS spectrometry. Amongst these, 8a, 8c, and 9c, expressed potent inhibitory profiles against the 15-sLOX enzyme with IC₅₀ values of 12.52 ± 0.35 to 35.64 ± 0.29 µM, followed by the compounds 9b, 9g, 9d, 9a, 8b, 8e, 8d, 8g, 8h, 8f and 9h with IC₅₀ values in the range of 43.78 ± 0.43 to 108.65 ± 0.38 µM. All compounds exhibited variable cellular viability levels by MTT assay. Flow cytometric data demonstrated that 8f, 8g, 8h have maximal lymphocyte cellular viability and all compounds affected cells in the late apoptosis phase. In silico ADMET studies supported the drug-likeness of most of the molecules. These studies were supported by molecular docking against 15-sLOX, human 5-LOX (5-hLOX) and human 15-LOX (5-hLOX); that inhibitors of 15-sLOX docked-in the active pocket of either 5-hLOX or 15-hLOX and docking score remained constant for all three enzymes within a narrow range (-6.8 to -9.7) as did it for standard quercetin (-8.4 to -9.0). The most dominant bonding interactions were π-π, π-anion, and π-alkyl type along with the hydrogen bonding. The data collected altogether demonstrates the better possibility of some of these compounds as good LOX inhibitors in search for 'lead' as anti-inflammatory agents in the process of drug discovery and development.

Targeting leucine-rich repeat kinase 2 (LRRK2) for the treatment of Parkinson's disease

Leucine-rich repeat kinase 2 (LRRK2) is a serine-threonine kinase involved in multiple cellular processes and signaling pathways. LRRK2 mutations are associated with autosomal-inherited Parkinson's disease (PD), and evidence suggests that LRRK2 pathogenic variants generally increase kinase activity. Therefore, inhibition of LRRK2 kinase function is a promising therapeutic strategy for PD treatment. The search for drug-like molecules capable of reducing LRRK2 kinase activity in PD led to the design of selective LRRK2 inhibitors predicted to be within the CNS drug-like space. This review highlights the journey that translates chemical tools for interrogating the role of LRRK2 in PD into promising drug candidates, addressing the challenges in discovering selective and brain-penetrant LRRK2 modulators and exploring the structure–activity relationship of distinct LRRK2 inhibitors.

Discovery of potent azaindazole leucine-rich repeat kinase 2 (LRRK2) inhibitors possessing a key intramolecular hydrogen bond - Part 2

The discovery of disease-modifying therapies for Parkinson's Disease (PD) represents a critical need in neurodegenerative medicine. Genetic mutations in LRRK2 are risk factors for the development of PD, and some of these mutations have been linked to increased LRRK2 kinase activity and neuronal toxicity in cellular and animal models. As such, research towards brain-permeable kinase inhibitors of LRRK2 has received much attention. In the course of a program to identify structurally diverse inhibitors of LRRK2 kinase activity, a 5-azaindazole series was optimized for potency, metabolic stability and brain penetration. A key design element involved the incorporation of an intramolecular hydrogen bond to increase permeability and potency against LRRK2. This communication will outline the structure-activity relationships of this matched pair series including the challenge of obtaining a desirable balance between metabolic stability and brain penetration.

Brain penetrant kinase inhibitors: Learning from kinase neuroscience discovery

A recent review of kinase inhibitors in clinical trials for brain cancer noted differences in the properties of these compounds relative to the mean property parameters associated with drugs marketed for CNS-associated conditions. However, many of these kinase drugs arose from opportunistic observations of brain activity, rather than design or flow schemes focused on optimizing CNS penetration. Thus, this digest examines kinase inhibitors that have been developed specifically for neurodegenerative indications such as Alzheimer's or Parkinson's disease, and considers design, flow scheme, and the physicochemical properties associated with compounds that have demonstrated brain penetrance.

Computational assessment of thioether isosteres

Replacement of the sulfur atom in biologically active diaryl and heteroaryl thioethers (Ar-S-Ar', HAr-S-Ar, and HAr-S-HAr') with any of several one-atom or two-atom linkers can be expected to reduce the susceptibility of the analogue to metabolic oxidation, a well-documented problem for thioethers intended for medicinal chemistry applications. Ab initio calculations indicate how well various proposed thioether isosteric groups, including some new and unusual ones, may perform structurally and electronically in replacing the bridging sulfur atom. Four of these are calculationally evaluated as proposed substructures in Axitinib analogues. The predicted binding behavior of the latter within two different previously crystallographically characterized protein-Axitinib binding sites (VEGFR2 kinase and ABL1 T315I gatekeeper mutant kinase), and an assessment of their suitability and anticipated shortcomings, are presented.

Design of Leucine-Rich Repeat Kinase 2 (LRRK2) Inhibitors Using a Crystallographic Surrogate Derived from Checkpoint Kinase 1 (CHK1)

Mutations in leucine-rich repeat kinase 2 (LRRK2), such as G2019S, are associated with an increased risk of developing Parkinson's disease. Surrogates for the LRRK2 kinase domain based on checkpoint kinase 1 (CHK1) mutants were designed, expressed in insect cells infected with baculovirus, purified, and crystallized. X-ray structures of the surrogates complexed with known LRRK2 inhibitors rationalized compound potency and selectivity. The CHK1 10-point mutant was preferred, following assessment of surrogate binding affinity with LRRK2 inhibitors. Fragment hit-derived arylpyrrolo[2,3-b]pyridine LRRK2 inhibitors underwent structure-guided optimization using this crystallographic surrogate. LRRK2-pSer935 HEK293 IC₅₀ data for 22 were consistent with binding to Ala2016 in LRRK2 (equivalent to Ala147 in CHK1 10-point mutant structure). Compound 22 was shown to be potent, moderately selective, orally available, and brain-penetrant in wild-type mice, and confirmation of target engagement was demonstrated, with LRRK2-pSer935 IC₅₀ values for 22 in mouse brain and kidney being 1.3 and 5 nM, respectively.

Development of LRRK2 Inhibitors for the Treatment of Parkinson's Disease

Linkage and genome-wide association studies have identified a genetic risk locus for late-onset Parkinson's disease in chromosome 12, originally identified as PARK6. The causative gene was identified to code for a large multifunctional protein, LRRK2 (leucine-rich repeat kinase 2). The combined genetic and biochemical evidence supports a hypothesis in which the LRRK2 kinase function is causally involved in the pathogenesis of sporadic and familial forms of PD, and therefore that LRRK2 kinase inhibitors could be useful for treatment. Although LRRK2 has so far not been crystallised, the use of homology modelling and crystallographic surrogates has allowed the optimisation of chemical structures such that compounds of high selectivity with good brain penetration and appropriate pharmacokinetic properties are now available for understanding the biology of LRRK2 in vitro and in vivo. This chapter reviews LRRK2 biology, the structural biology of LRRK2 and gives an overview of inhibitors of LRRK2.

Small-Molecule Inhibitors of LRRK2

Mutations in the leucine-rich repeat kinase 2 (LRRK2) protein have been genetically and functionally linked to Parkinson's disease (PD). The kinase activity of LRRK2 is increased by pathogenic mutations; therefore, modulation of LRRK2 kinase activity by a selective small-molecule inhibitor has been proposed as a potentially viable treatment for Parkinson's disease. This chapter presents a historical overview of the development and bioactivity of several small-molecule LRRK2 inhibitors that have been used to inhibit LRRK2 kinase activity in vitro or in vivo. These compounds are important tools for understanding the cellular biology of LRRK2 and for evaluating the potential of LRRK2 inhibitors as disease-modifying PD therapies.

3D-QSAR and molecular docking study of LRRK2 kinase inhibitors by CoMFA and CoMSIA methods

Three-dimensional quantitative structure-activity relationship (3D-QSAR) modelling was conducted on a series of leucine-rich repeat kinase 2 (LRRK2) antagonists using CoMFA and CoMSIA methods. The data set, which consisted of 37 molecules, was divided into training and test subsets by using a hierarchical clustering method. Both CoMFA and CoMSIA models were derived using a training set on the basis of the common substructure-based alignment. The optimum PLS model built by CoMFA and CoMSIA provided satisfactory statistical results (q(2) = 0.589 and r(2) = 0.927 and q(2) = 0.473 and r(2) = 0.802, respectively). The external predictive ability of the models was evaluated by using seven compounds. Moreover, an external evaluation set with known experimental data was used to evaluate the external predictive ability of the porposed models. The statistical parameters indicated that CoMFA (after region focusing) has high predictive ability in comparison with standard CoMFA and CoMSIA models. Molecular docking was also performed on the most active compound to investigate the existence of interactions between the most active inhibitor and the LRRK2 receptor. Based on the obtained results and CoMFA contour maps, some features were introduced to provide useful insights for designing novel and potent LRRK2 inhibitors.

Chemical Biology of Leucine-Rich Repeat Kinase 2 (LRRK2) Inhibitors

There is an urgent need for the development of Parkinson's disease (PD) treatments that can slow disease progression. The leucine-rich repeat kinase 2 (LRRK2) protein has been genetically and functionally linked to PD, and modulation of LRRK2 enzymatic activity has been proposed as a novel therapeutic strategy. In this review, we describe the bioactivity of selected small molecules that have been used to inhibit LRRK2 kinase activity in vitro or in vivo. These compounds are important tools for understanding the cellular biology of LRRK2 and for evaluating the potential of LRRK2 inhibitors as disease-modifying PD therapies.

Discovery and preclinical profiling of 3-[4-(morpholin-4-yl)-7H-pyrrolo[2,3-d]pyrimidin-5-yl]benzonitrile (PF-06447475), a highly potent, selective, brain penetrant, and in vivo active LRRK2 kinase inhibitor

Leucine rich repeat kinase 2 (LRRK2) has been genetically linked to Parkinson's disease (PD) by genome-wide association studies (GWAS). The most common LRRK2 mutation, G2019S, which is relatively rare in the total population, gives rise to increased kinase activity. As such, LRRK2 kinase inhibitors are potentially useful in the treatment of PD. We herein disclose the discovery and optimization of a novel series of potent LRRK2 inhibitors, focusing on improving kinome selectivity using a surrogate crystallography approach. This resulted in the identification of 14 (PF-06447475), a highly potent, brain penetrant and selective LRRK2 inhibitor which has been further profiled in in vivo safety and pharmacodynamic studies.