Discovery of Potent and Selective Urea-Based ROCK Inhibitors and Their Effects on Intraocular Pressure in Rats

Application and Study of ROCK Inhibitors in Pulmonary Fibrosis: Recent Developments and Future Perspectives

Rho-associated coiled-coil-containing kinases (ROCKs), serine/threonine protein kinases, were initially identified as downstream targets of the small GTP-binding protein Rho. Pulmonary fibrosis (PF) is a lethal disease with limited therapeutic options and a particularly poor prognosis. Interestingly, ROCK activation has been demonstrated in PF patients and in animal PF models, making it a promising target for PF treatment. Many ROCK inhibitors have been discovered, and four of these have been approved for clinical use; however, no ROCK inhibitors are approved for the treatment of PF patients. In this article, we describe ROCK signaling pathways and the structure-activity relationship, potency, selectivity, binding modes, pharmacokinetics (PKs), biological functions, and recently reported inhibitors of ROCKs in the context of PF. We will also focus our attention on the challenges to be addressed when targeting ROCKs and discuss the strategy of ROCK inhibitor use in the treatment of PF.

Cobalt(III)-catalyzed weakly coordinating arylurea-directed regioselective mono-olefination

Here, we developed an air-stable, earth-abundant cobalt(III)-catalyzed regioselective mono-olefination of arenes directed by urea under mild conditions through a cross-dehydrogenative coupling (CDC) process. Under the optimized conditions, a high regioselectivity of mono-olefination was achieved with various electron-rich and electron-deficient arenes, which afforded E-alkenylated products (with yields of up to 90%). In contrast to the conditions used for noble-metal-catalyzed olefination directed by weakly coordinating groups, our reaction was operated under mild conditions, including mild temperature (40 °C) and non-metallic oxidant.

LIM Kinases, Promising but Reluctant Therapeutic Targets: Chemistry and Preclinical Validation In Vivo

LIM Kinases are important actors in the regulation of cytoskeleton dynamics by controlling microtubule and actin filament turnover. The signaling pathways involving LIM kinases for actin filament remodeling are well established. They are downstream effectors of small G proteins of the Rho-GTPases family and have become promising targets for the treatment of several major diseases because of their position at the lower end of these signaling cascades. Cofilin, which depolymerizes actin filaments, is the best-known substrate of these enzymes. The phosphorylation of cofilin to its inactive form by LIM kinases avoids actin filament depolymerization. The balance between phosphorylated and non-phosphorylated cofilin is thought to play an important role in tumor cell invasion and metastasis. Since 2006, many small molecules have been developed for LIMK inhibition, and in this review article, we will discuss the structure–activity relationships of the few inhibitor families that have been tested in vivo on different pathological models.

Design, synthesis, and biological evaluation of urea-based ROCK2 inhibitors

A series of urea-based ROCK2 inhibitors were design and synthesized. The inhibitory activity on ROCK2 was screened by enzyme-linked immunosorbent assay (ELISA). The study results showed that the urea derivatives exhibited certain ROCK2 inhibitory activity. The most potent compound 10p showed ROCK2 inhibitory activity with the IC₅₀  value of 0.03 μM. A preliminary structure-activity relationship was then summarized. The molecular docking studies showed that further optimization needs to conduct to obtain more potent ROCK inhibitors.

Synthesis, X-ray Structure Determination, and Comprehensive Photochemical Characterization of (Trifluoromethyl)diazirine-Containing TRPML1 Ligands

Potential (trifluoromethyl)diazirine-based TRPML1 ion channel ligands were designed and synthesized, and their structures were determined by single-crystal X-ray diffraction analysis. Photoactivation studies via ¹⁹F NMR spectroscopy and HPLC-MS analysis revealed distinct kinetical characteristics in selected solvents and favorable photochemical properties in an aqueous buffer. These photoactivatable TRPML activators represent useful and valuable tools for TRPML photoaffinity labeling combined with mass spectrometry.

Rho-kinase (ROCK) Inhibitors - A Neuroprotective Therapeutic Paradigm with a Focus on Ocular Utility

BACKGROUND

Glaucoma is a progressive optic neuropathy causing visual impairment and Retinal Ganglionic Cells (RGCs) death gradually posing a need for neuroprotective strategies to minimize the loss of RGCs and visual field. It is recognized as a multifactorial disease, Intraocular Pressure (IOP) being the foremost risk factor. ROCK inhibitors have been probed for various possible indications, such as myocardial ischemia, hypertension, kidney diseases. Their role in neuroprotection and neuronal regeneration has been suggested to be of value in the treatment of neurological diseases, like spinal-cord injury, Alzheimer's disease and multiple sclerosis but recently Rho-associated Kinase inhibitors have been recognized as potential antiglaucoma agents.

EVIDENCE SYNTHESIS

Rho-Kinase is a serine/threonine kinase with a kinase domain which is constitutively active and is involved in the regulation of smooth muscle contraction and stress fibre formation. Two isoforms of Rho-Kinase, ROCK-I (ROCK β) and ROCK-II (ROCK α) have been identified. ROCK II plays a pathophysiological role in glaucoma and hence the inhibitors of ROCK may be beneficial to ameliorate the vision loss. These inhibitors decrease the intraocular pressure in the glaucomatous eye by increasing the aqueous humour outflow through the trabecular meshwork pathway. They also act as anti-scarring agents and hence prevent post-operative scarring after the glaucoma filtration surgery. Their major role involves axon regeneration by increasing the optic nerve blood flow which may be useful in treating the damaged optic neurons. These drugs act directly on the neurons in the central visual pathway, interrupting the RGC apoptosis and therefore serve as a novel pharmacological approach for glaucoma neuroprotection.

CONCLUSION

Based on the results of high-throughput screening, several Rho kinase inhibitors have been designed and developed comprising of diverse scaffolds exhibiting Rho kinase inhibitory activity from micromolar to subnanomolar ranges. This diversity in the scaffolds with inhibitory potential against the kinase and their SAR development will be intricated in the present review. Ripasudil is the only Rho kinase inhibitor marketed to date for the treatment of glaucoma. Another ROCK inhibitor AR-13324 has recently passed the clinical trials whereas AMA0076, K115, PG324, Y39983 and RKI-983 are still under trials. In view of this, a detailed and updated account of ROCK II inhibitors as the next generation therapeutic agents for glaucoma will be discussed in this review.

Understanding metabolism related differences in ocular efficacy of MGV354

MGV354 was being developed as a novel ocular therapy for lowering of intraocular pressure, a key modifiable risk factor for glaucoma. MGV354 is an activator of soluble guanylate cyclase, an enzyme known to be involved in the regulation of IOP. MGV354 has been shown to robustly lower IOP over 24 h after a single topical ocular drop in rabbit and monkey pharmacology models. However, MGV354 failed to produce similar results in patients with ocular hypertension or open-angle glaucoma. With an objective of explaining the lack of efficacy in the clinic, we attempted to study whether human metabolism was significantly different from animal metabolism. The present study documents the investigation of metabolism of MGV354 in an effort to understand potential differences in biotransformation pathways of MGV354 in rabbits, monkeys, and humans. Overall twenty-six metabolites, formed via oxidative and conjugative pathways, were identified in vitro and in vivo. In vitro hepatic metabolism was qualitatively similar across species, with minor but distinct differences. There were no observable interspecies differences in the hepatic and ocular metabolism of MGV354. Although ocular metabolism was not as extensive as hepatic, the results do not explain the lack of efficacy of MGV354 in clinical studies.

Targeting Schlemm's Canal in the Medical Therapy of Glaucoma: Current and Future Considerations

Schlemm’s canal (SC) is a unique, complex vascular structure responsible for maintaining fluid homeostasis within the anterior segment of the eye by draining the excess of aqueous humour. In glaucoma, a heterogeneous group of eye disorders afflicting approximately 60 million individuals worldwide, the normal outflow of aqueous humour into SC is progressively hindered, leading to a gradual increase in outflow resistance, which gradually results in elevated intraocular pressure (IOP). By and large available antiglaucoma therapies do not target the site of the pathology (SC), but rather aim to decrease IOP by other mechanisms, either reducing aqueous production or by diverting aqueous flow through the unconventional outflow system. The present review first outlines our current understanding on the functional anatomy of SC. It then summarizes existing research on SC cell properties; first in the context of their role in glaucoma development/progression and then as a target of novel and emerging antiglaucoma therapies. Evidence from ongoing research efforts to develop effective antiglaucoma therapies targeting SC suggests that this could become a promising site of future therapeutic interventions.

A review on ROCK-II inhibitors: From molecular modelling to synthesis

Rho kinase enzyme expressed in different disease conditions and involved in mediating vasoconstriction and vascular remodeling in the pathogenesis. There are two isoforms of Rho kinases, namely ROCK I and ROCK II, responsible for different physiological function due to difference in distribution, but almost similar in structure. The Rho kinase 2 belongs to AGC family and is widely distributed in brain, heart and muscles. It is responsible for contraction of vascular smooth muscles by calcium sensitization. Its defective and unwanted expression can lead to many medical conditions like multiple sclerosis, myocardial ischemia, inflammatory responses, etc. Many Rho kinase 1 and 2 inhibitors have been designed for Rho/Rho kinase pathway by use of molecular modeling studies. Most of the designed compounds have been modeled based on ROCK 1 enzyme. This article is focused on Rho kinase 2 inhibitors as there are many ways to improvise by use of Computer aided drug designing as very less quantum of research work carried out. Herein, the article highlights different stages of designing like docking, SAR and synthesis of ROCK inhibitors and recent advances. It also highlights future prospective to improve the activity.

Discovery of Molecular Therapeutics for Glaucoma: Challenges, Successes, and Promising Directions

Glaucoma, a heterogeneous ocular disorder affecting ∼60 million people worldwide, is characterized by painless neurodegeneration of retinal ganglion cells (RGCs), resulting in irreversible vision loss. Available therapies, which decrease the common causal risk factor of elevated intraocular pressure, delay, but cannot prevent, RGC death and blindness. Notably, it is changes in the anterior segment of the eye, particularly in the drainage of aqueous humor fluid, which are believed to bring about changes in pressure. Thus, it is primarily this region whose properties are manipulated in current and emerging therapies for glaucoma. Here, we focus on the challenges associated with developing treatments, review the available experimental methods to evaluate the therapeutic potential of new drugs, describe the development and evaluation of emerging Rho-kinase inhibitors and adenosine receptor ligands that offer the potential to improve aqueous humor outflow and protect RGCs simultaneously, and present new targets and approaches on the horizon.

Discovery of lipoic acid-4-phenyl-1H-pyrazole hybrids as novel bifunctional ROCK inhibitors with antioxidant activity

A potently selective ROCK2 inhibitor with antioxidative properties.

Rho Kinase (ROCK) Inhibitors and Their Therapeutic Potential

Rho kinases (ROCKs) belong to the serine-threonine family, the inhibition of which affects the function of many downstream substrates. As such, ROCK inhibitors have potential therapeutic applicability in a wide variety of pathological conditions including asthma, cancer, erectile dysfunction, glaucoma, insulin resistance, kidney failure, neuronal degeneration, and osteoporosis. To date, two ROCK inhibitors have been approved for clinical use in Japan (fasudil and ripasudil) and one in China (fasudil). In 1995 fasudil was approved for the treatment of cerebral vasospasm, and more recently, ripasudil was approved for the treatment of glaucoma in 2014. In this Perspective, we present a comprehensive review of the physiological and biological functions for ROCK, the properties and development of over 170 ROCK inhibitors as well as their therapeutic potential, the current status, and future considerations.

Bis-aryl urea derivatives as potent and selective LIM kinase (Limk) inhibitors

The discovery/optimization of bis-aryl ureas as Limk inhibitors to obtain high potency and selectivity and appropriate pharmacokinetic properties through systematic SAR studies is reported. Docking studies supported the observed SAR. Optimized Limk inhibitors had high biochemical potency (IC50 < 25 nM), excellent selectivity against ROCK and JNK kinases (>400-fold), potent inhibition of cofilin phosphorylation in A7r5, PC-3, and CEM-SS T cells (IC50 < 1 μM), and good in vitro and in vivo pharmacokinetic properties. In the profiling against a panel of 61 kinases, compound 18b at 1 μM inhibited only Limk1 and STK16 with ≥80% inhibition. Compounds 18b and 18f were highly efficient in inhibiting cell-invasion/migration in PC-3 cells. In addition, compound 18w was demonstrated to be effective on reducing intraocular pressure (IOP) on rat eyes. Taken together, these data demonstrated that we had developed a novel class of bis-aryl urea derived potent and selective Limk inhibitors.

Discovery of novel inhibitors for the treatment of glaucoma

INTRODUCTION

Glaucoma is a neurodegenerative disease with heterogeneous causes that result in retinal ganglionic cell (RGC) death. The discovery of ocular antihypertensives has shifted glaucoma therapy, largely, from surgery to medical intervention. Indeed, several intraocular pressure (IOP)-lowering drugs, with different mechanisms of action and RGC protective property, have been developed.

AREAS COVERED

In this review, the authors discuss the main new class of kinase inhibitors used as glaucoma treatments, which lower IOP by enhancing drainage and/or lowering production of aqueous humor. The authors include novel inhibitors under preclinical evaluation and investigation for their anti-glaucoma treatment. Additionally, the authors look at treatments that are in clinics now and which may be available in the near future.

EXPERT OPINION

Treatment of glaucoma remains challenging because the exact cause is yet to be delineated. Neuroprotection to the optic nerve head is undisputable. The novel Rho-associated kinase inhibitors have the capacity to lower IOP and provide optic nerve and RGC protection. In particular, the S-isomer of roscovitine has the capacity to lower IOP and provide neuroprotection. Combinations of selected drugs, which can provide maximal and sustained IOP-lowering effects as well as neuroprotection, are paramount to the prevention of glaucoma progression. In the near future, microRNA intervention may be considered as a potential therapeutic target.

Copper-catalyzed O-arylation of N-protected 1,2-aminoalcohols using functionalized trivalent organobismuth reagents

The O-arylation of 1,2-aminoalcohols using functionalized triarylbismuth reagents is reported.

Rho kinase inhibitors: a patent review (2012 - 2013)

INTRODUCTION

The Rho kinase/ROCK is critical in vital signal transduction pathways central to many essential cellular activities. Since ROCK possess multiple substrates, modulation of ROCK activity is useful for treatment of many diseases.

AREAS COVERED

Significant progress has been made in the development of ROCK inhibitors over the past two years (Jan 2012 to Aug 2013). Patent search in this review was based on FPO IP Research and Communities and Espacenet Patent Search. In this review, patent applications will be classified into four groups for discussions. The grouping is mainly based on structures or scaffolds (groups 1 and 2) and biological functions of ROCK inhibitors (groups 3 and 4). These four groups are i) ROCK inhibitors based on classical structural elements for ROCK inhibition; ii) ROCK inhibitors based on new scaffolds; iii) bis-functional ROCK inhibitors; and iv) novel applications of ROCK inhibitors.

EXPERT OPINION

Although currently only one ROCK inhibitor (fasudil) is used as a drug, more drugs based on ROCK inhibition are expected to be advanced into market in the near future. Several directions should be considered for future development of ROCK inhibitors, such as soft ROCK inhibitors, bis-functional ROCK inhibitors, ROCK2 isoform-selective inhibitors, and ROCK inhibitors as antiproliferation agents.

Advances in the studies of roles of Rho/Rho-kinase in diseases and the development of its inhibitors

RhoA/Rho-kinase pathway plays a pivotal role in numerous fundamental cellular functions including contraction, motility, proliferation, differentiation and apoptosis. The pathway is also involved in the development of many diseases such as vasospasm, pulmonary hypertension, cancer and central nervous systems (CNS) disorders. The inhibitors of Rho kinase have been extensively studied since the Rho/Rho-kinase pathway was verified as a target for a number of diseases. Herein, we reviewed the advances in the studies of the roles of Rho/Rho-kinase in diseases and the development of Rho-kinase inhibitors in recent five years.

Synthesis and biological evaluation of urea derivatives as highly potent and selective rho kinase inhibitors

RhoA and its downstream effector ROCK mediate stress fiber formation and cell contraction through their effects on the phosphorylation of myosin light chain (MLC). Inhibition of the RhoA/ROCK pathway has proven to be a promising strategy for several indications such as cardiovascular disease, glaucoma, and inflammatory disease. In 2010, our group reported urea-based ROCK inhibitors as potential antiglaucoma agents. These compounds showed potent IC50 values in enzymatic and cell-based assays and significant intraocular pressure (IOP)-lowering effects in rats (∼7 mmHg). (22) To develop more advanced ROCK inhibitors targeting various potential applications (such as myocardial infarction, erectile dysfunction, multiple sclerosis, etc.) in addition to glaucoma, a thorough SAR for this urea-based scaffold was studied. The detailed optimization process, counter-screening, and in vitro and in vivo DMPK studies are discussed. Potent and selective ROCK inhibitors with various in vivo pharmacokinetic properties were discovered.

Ca2+ sensitization pathways accessed by cholinergic neurotransmission in the murine gastric fundus

Ca(2+) sensitization of contraction has typically been investigated by bathing muscles in solutions containing agonists. However, it is unknown whether bath-applied agonists and enteric neurotransmission activate similar Ca(2+) sensitization mechanisms. We investigated protein kinase C (PKC)-potentiated phosphatase inhibitor protein of 17 kDa (CPI-17) and myosin phosphatase targeting subunit 1 (MYPT1) phosphorylation in murine gastric fundus muscles stimulated by bath-applied carbachol (CCh) or cholinergic motor neurotransmission. CCh increased MYPT1 phosphorylation at Thr696 (pT696) and Thr853 (pT853), CPI-17 at Thr38 (pT38), and myosin light chain at Ser19 (pS19). Electrical field stimulation (EFS) only increased pT38. In the presence of neostigmine, EFS increased pT38, pT853 and pS19. In fundus muscles of W/W(v) mice, EFS alone increased pT38 and pT853. Atropine blocked all contractions and all increases in pT696, pT853, pT38 and pS19. The Rho kinase (ROCK) inhibitor SAR1x blocked increases in pT853 and pT696. The PKC inhibitors Go6976 and Gf109203x or nicardipine blocked increases in pT38 and pT696. These findings suggest that cholinergic motor neurotransmission activates PKC-dependent CPI-17 phosphorylation. Bath-applied CCh recruits additional ROCK-dependent MYPT1 phosphorylation due to exposure of the agonist to a wider population of muscarinic receptors. Intramuscular interstitial cells of Cajal (ICC-IMs) and cholinesterases restrict ACh accessibility to a select population of muscarinic receptors, possibly only those expressed by ICC-IMs. These results provide the first biochemical evidence for focalized (or synaptic-like) neurotransmission, rather than diffuse 'volume' neurotransmission in a smooth muscle tissue. Furthermore, these findings demonstrate that bath application of contractile agonists to gastrointestinal smooth muscles does not mimic physiological responses to cholinergic neurotransmission.

Amino acid derived quinazolines as Rock/PKA inhibitors

SAR and lead optimization studies for Rock inhibitors based on amino acid-derived quinazolines are described. Studies demonstrated that these amino acid derived quinazolinones were mainly pan-Rock (I & II) inhibitors. While selectivity against other kinases could be achieved, selectivity for most of these compounds against PKA was not achieved. This is distinct from Rock inhibitors based on non-amino acid derived quinazolinones, where high selectivity against PKA could be obtained.(22) The inhibitors presented here in some cases possessed sub-nanomolar inhibition of Rock, nanomolar potency in ppMLC cell based assays, low to fair cytochrome P-450 inhibition, and good human microsomal stability.

Pyridylthiazole-based ureas as inhibitors of Rho associated protein kinases (ROCK1 and 2)

Potent ROCK inhibitors of a new class of 1-benzyl-3-(4-pyridylthiazol-2-yl)ureas have been identified. Remarkable differences in activity were observed for ureas bearing a benzylic stereogenic center. Derivatives with hydroxy, methoxy and amino groups at the meta position of the phenyl ring give rise to the most potent inhibitors (low nM). Substitutions at the para position result in substantial loss of potency. Changes at the benzylic position are tolerated resulting in significant potency in the case of methyl and methylenehydroxy groups. X-Ray crystallography was used to establish the binding mode of this class of inhibitors and provides an explanation for the observed differences of the enantiomer series. Potent inhibition of ROCK in human lung cancer cells was shown by suppression of the levels of phosphorylation of the ROCK substrate MYPT-1.