A series of case studies: practical methodology for identifying antinociceptive multi-target drugs

Novel Phenylene Lipids That Are Positive Allosteric Modulators of Glycine Receptors and Inhibitors of Glycine Transporter 2

Chronic pain is a complex condition that remains resistant to current therapeutics. We previously synthesized a series of N-acyl amino acids (NAAAs) that inhibit the glycine transporter, GlyT2, some of which are also positive allosteric modulators of glycine receptors (GlyRs). In this study, we have synthesized a library of NAAAs that contain a phenylene ring within the acyl tail with the objective of improving efficacy at both GlyT2 and GlyRs and also identifying compounds that are efficacious as dual-acting modulators to enhance glycine neurotransmission. The most efficacious positive allosteric modulator of GlyRs was 2-[8-(2-octylphenyl)octanoylamino]acetic acid (8-8 OPGly) which potentiates the EC5 for glycine activation of GlyRα1 by 1500% with an EC50 of 664 nM. Phenylene-containing NAAAs with a lysine headgroup were the most potent inhibitors of GlyT2 with (2S)-6-amino-2-[8-(3-octylphenyl)octanoylamino]hexanoic acid (8-8 MPLys) inhibiting GlyT2 with an IC50 of 32 nM. The optimal modulator across both proteins was (2S)-6-amino-2-[8-(2-octylphenyl)octanoylamino]hexanoic acid (8-8 OPLys), which inhibits GlyT2 with an IC50 of 192 nM and potentiates GlyRs by up to 335% at 1 μM. When tested in a dual GlyT2/GlyRα1 expression system, 8-8 OPLys caused the greatest reductions in the EC50 for glycine. This suggests that the synergistic effects of a dual-acting modulator cause greater enhancements in glycinergic activity compared to single-target modulators and may provide an alternate approach to the development of new non-opioid analgesics for the treatment of chronic pain.

Anti-nociceptive potential of an isatin-derived dual fatty acid amide hydrolase-monoacylglycerol lipase inhibitor

BACKGROUND

Recently, we have reported an isatin-derived carbohydrazone, 5-chloro-N'-(6-chloro-2-oxoindolin-3-ylidene)-2-hydroxybenzohydrazide (SIH 3) as dual nanomolar FAAH (fatty acid amide hydrolase)-MAGL (monoacylglycerol lipase) inhibitor with good CNS penetration and neuroprotective activity profile. In this study, we further investigated the pharmacological profile of compound SIH 3 in the neuropathic pain model along with acute toxicity and ex vivo studies.

METHODS

Chronic constrictive injury (CCI) was used to induce neuropathic pain in male Sprague-Dawley rats and the anti-nociceptive activity of the compound SIH 3 was investigated at 25, 50, and 100 mg/kg ip. Subsequently, locomotor activity was measured by rotarod and actophotometer experiments. The acute oral toxicity of the compound was assessed as per the OECD guidelines 423.

RESULTS

Compound SIH 3 showed significant anti-nociceptive activity in the CCI-induced neuropathic pain model without altering the locomotor activity. Furthermore, compound SIH 3 showed an excellent safety profile (up to 2000 mg/kg, po) in the acute oral toxicity study and was also non-hepatotoxic. Further, ex vivo studies revealed that the compound SIH 3 produces a significant antioxidant effect in oxidative stress induced by CCI.

CONCLUSION

Our findings suggest that the investigated compound SIH 3 has the potential to be developed as an anti-nociceptive agent.

Positive Allosteric Modulators of Glycine Receptors and Their Potential Use in Pain Therapies

Glycine receptors are ligand-gated ion channels that mediate synaptic inhibition throughout the mammalian spinal cord, brainstem, and higher brain regions. They have recently emerged as promising targets for novel pain therapies due to their ability to produce antinociception by inhibiting nociceptive signals within the dorsal horn of the spinal cord. This has greatly enhanced the interest in developing positive allosteric modulators of glycine receptors. Several pharmaceutical companies and research facilities have attempted to identify new therapeutic leads by conducting large-scale screens of compound libraries, screening new derivatives from natural sources, or synthesizing novel compounds that mimic endogenous compounds with antinociceptive activity. Advances in structural techniques have also led to the publication of multiple high-resolution structures of the receptor, highlighting novel allosteric binding sites and providing additional information for previously identified binding sites. This has greatly enhanced our understanding of the functional properties of glycine receptors and expanded the structure activity relationships of novel pharmacophores. Despite this, glycine receptors are yet to be used as drug targets due to the difficulties in obtaining potent, selective modulators with favorable pharmacokinetic profiles that are devoid of side effects. This review presents a summary of the structural basis for how current compounds cause positive allosteric modulation of glycine receptors and discusses their therapeutic potential as analgesics. SIGNIFICANCE STATEMENT: Chronic pain is a major cause of disability, and in Western societies, this will only increase as the population ages. Despite the high level of prevalence and enormous socioeconomic burden incurred, treatment of chronic pain remains limited as it is often refractory to current analgesics, such as opioids. The National Institute for Drug Abuse has set finding effective, safe, nonaddictive strategies to manage chronic pain as their top priority. Positive allosteric modulators of glycine receptors may provide a therapeutic option.

Analgesic Alkaloids Derived From Traditional Chinese Medicine in Pain Management

Chronic pain is one of the most prevalent health problems. The establishment of chronic pain is complex. Current medication for chronic pain mainly dependent on anticonvulsants, tricyclic antidepressants and opioidergic drugs. However, they have limited therapeutic efficacy, and some even with severe side effects. We turned our interest into alkaloids separated from traditional Chinese medicine (TCM), that usually act on multiple drug targets. In this article, we introduced the best-studied analgesic alkaloids derived from TCM, including tetrahydropalmatine, aloperine, oxysophocarpine, matrine, sinomenine, ligustrazine, evodiamine, brucine, tetrandrine, Stopholidine, and lappaconitine, focusing on their mechanisms and potential clinical applications. To better describe the mechanism of these alkaloids, we adopted the concept of drug-cloud (dCloud) theory. dCloud illustrated the full therapeutic spectrum of multitarget analgesics with two dimensions, which are “direct efficacy”, including inhibition of ion channels, activating γ-Aminobutyric Acid/opioid receptors, to suppress pain signal directly; and “background efficacy”, including reducing neuronal inflammation/oxidative stress, inhibition of glial cell activation, restoring the balance between excitatory and inhibitory neurotransmission, to cure the root causes of chronic pain. Empirical evidence showed drug combination is beneficial to 30–50% chronic pain patients. To promote the discovery of effective analgesic combinations, we introduced an ancient Chinese therapeutic regimen that combines herbal drugs with “Jun”, “Chen”, “Zuo”, and “Shi” properties. In dCloud, “Jun” drug acts directly on the major symptom of the disease; “Chen” drug generates major background effects; “Zuo” drug has salutary and supportive functions; and “Shi” drug facilitates drug delivery to the targeted tissue. Subsequently, using this concept, we interpreted the therapeutic effect of established analgesic compositions containing TCM derived analgesic alkaloids, which may contribute to the establishment of an alternative drug discovery model.

Glycinergic Modulation of Pain in Behavioral Animal Models

Animal models of human pain conditions allow for detailed interrogation of known and hypothesized mechanisms of pain physiology in awake, behaving organisms. The importance of the glycinergic system for pain modulation is well known; however, manipulation of this system to treat and alleviate pain has not yet reached the sophistication required for the clinic. Here, we review the current literature on what animal behavioral studies have allowed us to elucidate about glycinergic pain modulation, and the progress toward clinical treatments so far. First, we outline the animal pain models that have been used, such as nerve injury models for neuropathic pain, chemogenic pain models for acute and inflammatory pain, and other models that mimic painful human pathologies such as diabetic neuropathy. We then discuss the genetic approaches to animal models that have identified the crucial glycinergic machinery involved in neuropathic and inflammatory pain. Specifically, two glycine receptor (GlyR) subtypes, GlyRα1(β) and GlyRα3(β), and the two glycine transporters (GlyT), GlyT1 and GlyT2. Finally, we review the different pharmacological approaches to manipulating the glycinergic system for pain management in animal models, such as partial vs. full agonism, reversibility, and multi-target approaches. We discuss the benefits and pitfalls of using animal models in drug development broadly, as well as the progress of glycinergic treatments from preclinical to clinical trials.

An Optimized Terpene Profile for a New Medical Cannabis Oil

The purpose of this analytical study was to develop an advanced formulation of medical Cannabis oil (MCO) comparing the chemical profile of different extracts obtained with two existing methods (SIFAP and CALVI) and one original upgraded (CERFIT) method. Preparation methods were applied with varying solvent, temperature, and duration of the decarboxylation and extraction steps. HPLC-MS/MS TSQ and GC/FID-HS analyses were performed to investigate cannabinoid and terpene contents in the three oil extracts. Cannabinoids profile remained comparable between the formulations. CERFIT extracts exhibited a superior quantity of total terpene hydrocarbon forms (e.g., limonene and α-pinene) with no degradation occurrence (i.e., oxidized terpenes not quantifiable). Thus, this new method optimized the phytochemical profile of the MCO presenting a value opportunity to obtain a standardized high-level therapeutic product.

Emerging drugs for the treatment of postsurgical pain

INTRODUCTION

Postoperative pain is a distressful experience and remains to be a significant concern after surgery. Current agents either fail to prevent or minimize postoperative pain or cause a series of adverse effects, addiction, or abuse. Opioids have been the gold standard in the treatment of postoperative pain despite their well-described adverse effects. Many new agents with different mechanisms of action have been recently introduced to address this issue.

AREAS COVERED

This current review summarizes the list of new and emerging drugs investigated for their efficacy in controlling the postoperative pain and decreasing the need for rescue opioid use, adverse effect profile, abuse, and addiction potential.

EXPERT OPINION

Opioids have unrivaled analgesic efficacy. However adverse effects of opioids led to the search for better options. In mild pain most of the emerging drugs have been shown to control postoperative pain and decrease the use of rescue opioid, however fail to control pain after major surgeries causing severe pain. Specific agents such as Oliceridine, new local anesthetics, etc., are effective in controlling severe pain and hold a promise to replace opioids in the near future.

Exploratory study of VVZ-149, a novel analgesic molecule, in the affective component of acute postoperative pain after laparoscopic colorectal surgery

STUDY OBJECTIVE

VVZ-149 is a small molecule that inhibits the glycine transporter type 2 and the serotonin receptor 5-hydroxytryptamine 2A. In the present study, we investigated the efficacy and safety of VVZ-149 as a single-use injectable analgesic for treating moderate to severe postoperative pain after colorectal surgery.

DESIGN

Randomized, parallel group, double-blind Phase 2 clinical trial (NCT02489526).

SETTING

3 academic institutions in the United States.

PATIENTS

60 patients undergoing laparoscopic colorectal surgery.

INTERVENTIONS

A continuous 8-h intravenous infusion of VVZ-149 Injections (n = 40) or placebo (n = 20) administered after emergence from anesthesia.

MEASUREMENTS

The outcome measures included pain intensity (PI), opioid consumption via patient-controlled analgesia (PCA), and rescue dosing provided "as needed". Early rescue dosing with opioids postoperatively was associated with preoperative negative affect (anxiety, depression, and pain catastrophizing), enabling it to be used as an indirect measure of the affective component of pain. Efficacy outcomes were compared between treatment groups based on preoperative negative affect and early rescue dosing of opioids.

MAIN RESULTS

Postoperative PI was non-significantly lower in patients receiving VVZ-149 compared to those receiving placebo. The VVZ-149 group had a 34.2% reduction in opioid consumption for 24 h post-dose, along with fewer PCA demands. Somnolence and headache was higher in the intervention group. For patients characterized by high levels of preoperative negative affect, the VVZ-149 group experienced a significant pain reduction and 40% less opioid use compared to the placebo group.

CONCLUSIONS

VVZ-149 resulted in a non-significant reduction of postoperative pain during the first 8 h after surgery. Post hoc analysis indicates that VVZ-149 may benefit patients with negative affect who otherwise have higher postoperative opioid use. REGISTRATION NUMBER: www.clinicaltrials.gov, ID: NCT02489526.

Analgesic Potential of Terpenes Derived from Cannabis sativa

Pain prevalence among adults in the United States has increased 25% over the past two decades, resulting in high health-care costs and impacts to patient quality of life. In the last 30 years, our understanding of pain circuits and (intra)cellular mechanisms has grown exponentially, but this understanding has not yet resulted in improved therapies. Options for pain management are limited. Many analgesics have poor efficacy and are accompanied by severe side effects such as addiction, resulting in a devastating opioid abuse and overdose epidemic. These problems have encouraged scientists to identify novel molecular targets and develop alternative pain therapeutics. Increasing preclinical and clinical evidence suggests that cannabis has several beneficial pharmacological activities, including pain relief. Cannabis sativa contains more than 500 chemical compounds, with two principle phytocannabinoids, Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD). Beyond phytocannabinoids, more than 150 terpenes have been identified in different cannabis chemovars. Although the predominant cannabinoids, Δ9-THC and CBD, are thought to be the primary medicinal compounds, terpenes including the monoterpenes β-myrcene, α-pinene, limonene, and linalool, as well as the sesquiterpenes β-caryophyllene and α-humulene may contribute to many pharmacological properties of cannabis, including anti-inflammatory and antinociceptive effects. The aim of this review is to summarize our current knowledge about terpene compounds in cannabis and to analyze the available scientific evidence for a role of cannabis-derived terpenes in modern pain management. SIGNIFICANCE STATEMENT: Decades of research have improved our knowledge of cannabis polypharmacy and contributing phytochemicals, including terpenes. Reform of the legal status for cannabis possession and increased availability (medicinal and recreational) have resulted in cannabis use to combat the increasing prevalence of pain and may help to address the opioid crisis. Better understanding of the pharmacological effects of cannabis and its active components, including terpenes, may assist in identifying new therapeutic approaches and optimizing the use of cannabis and/or terpenes as analgesic agents.

Propionamide Derivatives as Dual μ-Opioid Receptor Agonists and σ1 Receptor Antagonists for the Treatment of Pain

A new series of propionamide derivatives was developed as dual μ-opioid receptor agonists and σ1 receptor antagonists. Modification of a high-throughput screening hit originated a series of piperazinylcycloalkylmethyl propionamides, which were explored to overcome the challenge of achieving balanced dual activity and convenient drug-like properties. The lead compound identified, 18g, showed good analgesic effects in several animal models of both acute (paw pressure) and chronic (partial sciatic nerve ligation) pain, with reduced gastrointestinal effects in comparison with oxycodone.

Co-Immobilized Capillary Enzyme Reactor Based on Beta-Secretase1 and Acetylcholinesterase: A Model for Dual-Ligand Screening

We have developed a dual enzymatic system assay involving liquid chromatography-mass spectrometry (LC–MS) to screen AChE and BACE1 ligands. A fused silica capillary (30 cm × 0.1 mm i.d. × 0.362 mm e.d.) was used as solid support. The co-immobilization procedure encompassed two steps and random immobilization. The resulting huAChE+BACE1-ICER/MS was characterized by using acetylcholine (ACh) and JMV2236 as substrates. The best conditions for the dual enzymatic system assay were evaluated and compared to the conditions of the individual enzymatic system assays. Analysis was performed in series for each enzyme. The kinetic parameters (K_Mapp) and inhibition assays were evaluated. To validate the system, galantamine and a β-secretase inhibitor were employed as standard inhibitors, which confirmed that the developed screening assay was able to identify reference ligands and to provide quantitative parameters. The combination of these two enzymes in a single on-line system allowed possible multi-target inhibitors to be screened and identified. The innovative huAChE+BACE1-ICER/MS dual enzymatic system reported herein proved to be a reliable tool to identify and to characterize hit ligands for AChE and BACE1 in an enzymatic competitive environment. This innovative system assay involved lower costs; measured the product from enzymatic hydrolysis directly by MS; enabled immediate recovery of the enzymatic activity; showed specificity, selectivity, and sensitivity; and mimicked the cellular process.

Inhibition of Glycine Re-Uptake: A Potential Approach for Treating Pain by Augmenting Glycine-Mediated Spinal Neurotransmission and Blunting Central Nociceptive Signaling

Among the myriad of cellular and molecular processes identified as contributing to pathological pain, disinhibition of spinal cord nociceptive signaling to higher cortical centers plays a critical role. Importantly, evidence suggests that impaired glycinergic neurotransmission develops in the dorsal horn of the spinal cord in inflammatory and neuropathic pain models and is a key maladaptive mechanism causing mechanical hyperalgesia and allodynia. Thus, it has been hypothesized that pharmacological agents capable of augmenting glycinergic tone within the dorsal horn may be able to blunt or block aberrant nociceptor signaling to the brain and serve as a novel class of analgesics for various pathological pain states. Indeed, drugs that enhance dysfunctional glycinergic transmission, and in particular inhibitors of the glycine transporters (GlyT1 and GlyT2), are generating widespread interest as a potential class of novel analgesics. The GlyTs are Na⁺/Cl⁻-dependent transporters of the solute carrier 6 (SLC6) family and it has been proposed that the inhibition of them presents a possible mechanism by which to increase spinal extracellular glycine concentrations and enhance GlyR-mediated inhibitory neurotransmission in the dorsal horn. Various inhibitors of both GlyT1 and GlyT2 have demonstrated broad analgesic efficacy in several preclinical models of acute and chronic pain, providing promise for the approach to deliver a first-in-class non-opioid analgesic with a mechanism of action differentiated from current standard of care. This review will highlight the therapeutic potential of GlyT inhibitors as a novel class of analgesics, present recent advances reported for the field, and discuss the key challenges associated with the development of a GlyT inhibitor into a safe and effective agent to treat pain.

Cannabis sativa terpenes are cannabimimetic and selectively enhance cannabinoid activity

Limited evidence has suggested that terpenes found in Cannabis sativa are analgesic, and could produce an "entourage effect" whereby they modulate cannabinoids to result in improved outcomes. However this hypothesis is controversial, with limited evidence. We thus investigated Cannabis sativa terpenes alone and with the cannabinoid agonist WIN55,212 using in vitro and in vivo approaches. We found that the terpenes α-humulene, geraniol, linalool, and β-pinene produced cannabinoid tetrad behaviors in mice, suggesting cannabimimetic activity. Some behaviors could be blocked by cannabinoid or adenosine receptor antagonists, suggesting a mixed mechanism of action. These behavioral effects were selectively additive with WIN55,212, suggesting terpenes can boost cannabinoid activity. In vitro experiments showed that all terpenes activated the CB1R, while some activated other targets. Our findings suggest that these Cannabis terpenes are multifunctional cannabimimetic ligands that provide conceptual support for the entourage effect hypothesis and could be used to enhance the therapeutic properties of cannabinoids.

Virus-CKB: an integrated bioinformatics platform and analysis resource for COVID-19 research

Given the scale and rapid spread of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), there is an urgent need for medicines that can help before vaccines are available. In this study, we present a viral-associated disease-specific chemogenomics knowledgebase (Virus-CKB) and apply our computational systems pharmacology-target mapping to rapidly predict the FDA-approved drugs which can quickly progress into clinical trials to meet the urgent demand of the COVID-19 outbreak. Virus-CKB reuses the underlying platform of our DAKB-GPCRs but adds new features like multiple-compound support, multi-cavity protein support and customizable symbol display. Our one-stop computing platform describes the chemical molecules, genes and proteins involved in viral-associated diseases regulation. To date, Virus-CKB archived 65 antiviral drugs in the market, 107 viral-related targets with 189 available 3D crystal or cryo-EM structures and 2698 chemical agents reported for these target proteins. Moreover, Virus-CKB is implemented with web applications for the prediction of the relevant protein targets and analysis and visualization of the outputs, including HTDocking, TargetHunter, BBB predictor, NGL Viewer, Spider Plot, etc. The Virus-CKB server is accessible at https://www.cbligand.org/g/virus-ckb.

Role of VVZ-149, a Novel Analgesic Molecule, in the Affective Component of Pain: Results from an Exploratory Proof-of-Concept Study of Postoperative Pain following Laparoscopic and Robotic-Laparoscopic Gastrectomy

OBJECTIVE

VVZ-149 is a small molecule that both inhibits the glycine transporter type 2 and the serotonin receptor 5 hydroxytryptamine 2 A. In a randomized, parallel-group, and double-blind trial (NCT02844725), we investigated the analgesic efficacy and safety of VVZ-149 Injections, which is under clinical development as a single-use injectable product for treating moderate to severe postoperative pain.

METHODS

Sixty patients undergoing laparoscopic and robotic-laparoscopic gastrectomy were randomly assigned to receive a 10-hour intravenous infusion of VVZ-149 Injections or placebo, initiated approximately 1 hour before completion of surgical suturing. Major outcomes included pain intensity and opioid consumption via patient-controlled analgesia and rescue analgesia provided "as needed." The treatment efficacy of VVZ-149 was further examined in a subpopulation requiring early rescue medication, previously associated with the presence of high levels of preoperative negative affect in a prior Phase 2 study (NCT02489526).

RESULTS

Pain intensity was lower in the VVZ-149 (n = 30) than the placebo group (n = 29), reaching statistical significance at 4 hours post-emergence (P < .05), with a 29.5% reduction in opioid consumption for 24 hours and fewer demands for patient-controlled analgesia. In the rescued subgroup, VVZ-149 further reduced pain intensity (P < .05) with 32.6% less opioid consumption for 24 hours compared to placebo patients.

CONCLUSIONS

VVZ-149 demonstrated effective analgesia with reduced postoperative pain and opioid requirements. Consistent with the results from the previous Phase 2 study, patients with early rescue requirement had greater benefit from VVZ-149, supporting the hypothesis that VVZ-149 may alleviate the affective component of pain and mitigate excessive use of opioids postoperatively.

Pain-CKB, A Pain-Domain-Specific Chemogenomics Knowledgebase for Target Identification and Systems Pharmacology Research

A traditional single-target analgesic, though it may be highly selective and potent, may not be sufficient to mitigate pain. An alternative strategy for alleviation of pain is to seek simultaneous modulation at multiple nodes in the network of pain-signaling pathways through a multitarget analgesic or drug combinations. Here we present a comprehensive pain-domain-specific chemogenomics knowledgebase (Pain-CKB) with integrated computing tools for target identification and systems pharmacology research. Pain-CKB is constructed on the basis of our established chemogenomics technology with new features, including multiple compound support, multicavity protein support, and customizable symbol display. The determination of bioactivity is also revised to avoid the use of complex machine learning models. Our one-stop computing platform describes the chemical molecules, genes, and proteins involved in pain regulation. To date, Pain-CKB has archived 272 analgesics in the market, 84 pain-related targets with 207 available 3D crystal or cryo-EM structures, and 234 662 chemical agents reported for these target proteins. Moreover, Pain-CKB implements user-friendly web-interfaced computing tools and applications for the prediction and analysis of the relevant protein targets and visualization of the outputs, including HTDocking, TargetHunter, BBB permeation predictor, NGL viewer, Spider Plot, etc. The Pain-CKB server is accessible at https://www.cbligand.org/g/pain-ckb.

Neurobiology of glycine transporters: From molecules to behavior

Glycine transporters (GlyTs) are Na⁺/Cl^--dependent neurotransmitter transporters, responsible for l-glycine uptake into the central nervous system. GlyTs are members of the solute carrier family 6 (SLC6) and comprise glycine transporter type 1 (SLC6A9; GlyT1) and glycine transporter type 2 (SLC6A5; Glyt2). GlyT1 and GlyT2 are expressed on both astrocytes and neurons, but their expression pattern in brain tissue is foremost related to neurotransmission. GlyT2 is markedly expressed in brainstem, spinal cord and cerebellum, where it is responsible for glycine uptake into glycinergic and GABAergic terminals. GlyT1 is abundant in neocortex, thalamus and hippocampus, where it is expressed in astrocytes, and involved in glutamatergic neurotransmission. Consequently, inhibition of GlyT1 transporters can modulate glutamatergic neurotransmission through NMDA receptors, suggesting an alternative therapeutic strategy. In this review, we focus on recent progress in the understanding of GlyTs role in brain function and in various diseases, such as epilepsy, hyperekplexia, neuropathic pain, drug addiction, schizophrenia and stroke, as well as in neurodegenerative disorders.

Identification of N-acyl amino acids that are positive allosteric modulators of glycine receptors

Glycine receptors (GlyRs) mediate inhibitory neurotransmission within the spinal cord and play a crucial role in nociceptive signalling. This makes them primary targets for the development of novel chronic pain therapies. Endogenous lipids have previously been shown to modulate glycine receptors and produce analgesia in pain models, however little is known about what chemical features mediate these effects. In this study, we characterised lipid modulation of GlyRs by screening a library of N-acyl amino acids across all receptor subtypes and determined chemical features crucial for their activity. Acyl-glycine's with a C18 carbon tail were found to produce the greatest potentiation, and require a cis double bond within the central region of the carbon tail (ω6 - ω9) to be active. At 1 µM, C18 ω6,9 glycine potentiated glycine induced currents in α₃ and α₃β receptors by over 50%, and α₁, α₂, α₁β and α₂β receptors by over 100%. C18 ω9 glycine (N-oleoyl glycine) significantly enhance glycine induced peak currents and cause a dose-dependent shift in the glycine concentration response. In the presence of 3 µM C18 ω9 glycine, the EC_5o of glycine at the α₁ receptor was reduced from 17 µM to 10 µM. This study has identified several acyl-amino acids which are positive allosteric modulators of GlyRs and make promising lead compounds for the development of novel chronic pain therapies.

Solid-Supported Proteins in the Liquid Chromatography Domain to Probe Ligand-Target Interactions

Ligand-target interactions play a central role in drug discovery processes because these interactions are crucial in biological systems. Small molecules-proteins interactions can regulate and modulate protein function and activity through conformational changes. Therefore, bioanalytical tools to screen new ligands have focused mainly on probing ligand-target interactions. These interactions have been evaluated by using solid-supported proteins, which provide advantages like increased protein stability and easier protein extraction from the reaction medium, which enables protein reuse. In some specific approaches, precisely in the ligand fishing assay, the bioanalytical method allows the ligands to be directly isolated from complex mixtures, including combinatorial libraries and natural products extracts without prior purification or fractionation steps. Most of these screening assays are based on liquid chromatography separation, and the binding events can be monitored through on-line or off-line methods. In the on-line approaches, solid supports containing the immobilized biological target are used as chromatographic columns most of the time. Several terms have been used to refer to such approaches, such as weak affinity chromatography, high-performance affinity chromatography, on-flow activity assays, and high-performance liquid affinity chromatography. On the other hand, in the off-line approaches, the binding event occurs outside the liquid chromatography system and may encompass affinity and activity-based assays in which the biological target is immobilized on magnetic particles or monolithic silica, among others. After the incubation step, the supernatant or the eluate from the binding assay is analyzed by liquid chromatography coupled to various detectors. Regardless of the selected bioanalytical approach, the use of solid supported proteins has significantly contributed to the development of automated and reliable screening methods that enable ligands to be isolated and characterized in complex matrixes without purification, thereby reducing costs and avoiding time-laborious steps. This review provides a critical overview of recently developed assays.

Discovery of dual-acting opioid ligand and TRPV1 antagonists as novel therapeutic agents for pain

In order to discover a novel type of analgesic, we investigated dual activity ligands with TRPV1 antagonism and mu-opioid receptor affinity with the goal of eliciting synergistic analgesia while avoiding the side effects associated with single targeting. Based on a combination approach, a series of 4-benzyl-4-(dimethylamino)piperidinyl analogues were designed, synthesized and evaluated for their receptor activities. Among them, compound 49 exhibited the most promising dual-acting activity toward TRPV1 and the mu-opioid receptor in vitro. In vivo,49 displayed potent, dose-dependent antinociceptive activity in both the 1st and 2nd phases in the formalin assay. Consistent with its postulated mechanism, we confirmed that in vivo, as in vitro, compound 49 both antagonized TRPV1 and functioned as a mu-opioid agonist. This result indicates that dual-acting TRPV1 antagonist/mu-opioid ligands can be made and represent a new and promising class of analgesic.

Development of Fangjiomics for Systems Elucidation of Synergistic Mechanism Underlying Combination Therapy

The rapid development of omics technology provides an opportunity for fulfilling the understanding of the synergistic mechanism of combination therapy. However, a systems theory to analyze synergy remains an ongoing challenge. Fangjiomics is a novel systems science based on a holistic theory integrated with reductionism which has been utilized to systematically elucidate the synergistic mechanisms underlying combination therapy using multi-target-, pathway- or network-based quantitative methods. Besides, our ability to understand the polyhierarchical structure in synergy is driven based on multi-level omics data fusion in Fangjiomics. According to the basic principle of “Jun-Chen-Zuo-Shi”, further global integration across various omics platforms and phenotype-driven quantitative multi-scale modeling would accelerate development in Fangjiomics-based dissection of synergy in multi-drug combination therapies.

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Fangjiomics is a novel systems science based on a holistic theory integrated with reductionism.

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We developed the pathway-based analysis of synergistic mechanisms in Fangjiomics.

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The theory of network-based synergistic targets is proposed in Fangjiomics.

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The hierarchical relationship of synergy in multilevel omics is dissected in Fangjiomics.

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The principle of “Jun-Chen-Zuo-Shi” is proposed to accelerate the development in Fangjiomics-based dissection of synergy.

Modulation of Glycine-Mediated Spinal Neurotransmission for the Treatment of Chronic Pain

Chronic pain constitutes a significant and expanding worldwide health crisis. Currently available analgesics poorly serve individuals suffering from chronic pain, and new therapeutic agents that are more effective, safer, and devoid of abuse liabilities are desperately needed. Among the myriad of cellular and molecular processes contributing to chronic pain, spinal disinhibition of pain signaling to higher cortical centers plays a critical role. Accumulating evidence shows that glycinergic inhibitory neurotransmission in the spinal cord dorsal horn gates nociceptive signaling, is essential in maintaining physiological pain sensitivity, and is diminished in pathological pain states. Thus, it is hypothesized that agents capable of enhancing glycinergic tone within the dorsal horn could obtund nociceptor signaling to the brain and serve as analgesics for persistent pain. This Perspective highlights the potential that pharmacotherapies capable of increasing inhibitory spinal glycinergic neurotransmission hold in providing new and transformative analgesic therapies for the treatment of chronic pain.

Safety, Tolerability, and Pharmacokinetic Characteristics of a Novel Nonopioid Analgesic, VVZ-149 Injections in Healthy Volunteers: A First-in-Class, First-in-Human Study

VVZ-149, a dual antagonist of GlyT2 and 5HT₂ A receptors, is an investigational analgesic with a novel mechanism of action that is currently under early-stage clinical development as an injectable agent for the treatment of postoperative pain. Here, the safety, tolerability, and pharmacokinetics of VVZ-149 injections in healthy male volunteers were explored in a randomized, double-blind, single- and multiple-ascending-dose (SAD and MAD, respectively), placebo-controlled clinical study. Subjects randomly received a 4-hour intravenous infusion of 0.25-8 mg/kg VVZ-149 or placebo in the SAD study (n = 46) or a 4-hour intravenous infusion of 4-7 mg/kg VVZ-149 or placebo twice daily for 3 days in the MAD study (n = 20). Serial blood and urine samples were collected for the pharmacokinetic analysis of VVZ-149 and its active metabolite (VVZ-368). Noncompartmental and compartmental pharmacokinetic analyses were performed. Various dosing scenarios were simulated to identify the adequate dosing regimen for the subsequent trials. Plasma exposure to VVZ-149 and VVZ-368 showed a dose-proportional increase. VVZ-149 did not accumulate in the plasma, whereas the plasma concentration of VVZ-368 increased by 1.23- to 2.49-fold after the fifth and sixth doses, respectively, in the MAD trial. Among the simulated dosing regimens, a loading dose followed by a maintenance dose was found to be an optimal dosing regimen, yielding the effective concentration estimated from animal studies in rat models of neuropathic or inflammatory pain. Single- or multiple-dose administration of VVZ-149 was generally well tolerated. These results showed that 0.5-8 mg/kg VVZ-149 exhibited linear pharmacokinetic characteristics and can be safely administered in further clinical studies.

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology

Apart from having been used and misused for at least four millennia for, among others, recreational and medicinal purposes, the cannabis plant and its most peculiar chemical components, the plant cannabinoids (phytocannabinoids), have the merit to have led humanity to discover one of the most intriguing and pleiotropic endogenous signaling systems, the endocannabinoid system (ECS). This review article aims to describe and critically discuss, in the most comprehensive possible manner, the multifaceted aspects of 1) the pharmacology and potential impact on mammalian physiology of all major phytocannabinoids, and not only of the most famous one Δ9-tetrahydrocannabinol, and 2) the adaptive pro-homeostatic physiological, or maladaptive pathological, roles of the ECS in mammalian cells, tissues, and organs. In doing so, we have respected the chronological order of the milestones of the millennial route from medicinal/recreational cannabis to the ECS and beyond, as it is now clear that some of the early steps in this long path, which were originally neglected, are becoming important again. The emerging picture is rather complex, but still supports the belief that more important discoveries on human physiology, and new therapies, might come in the future from new knowledge in this field.

Combination therapeutics in complex diseases

The biological redundancies in molecular networks of complex diseases limit the efficacy of many single drug therapies. Combination therapeutics, as a common therapeutic method, involve pharmacological intervention using several drugs that interact with multiple targets in the molecular networks of diseases and may achieve better efficacy and/or less toxicity than monotherapy in practice. The development of combination therapeutics is complicated by several critical issues, including identifying multiple targets, targeting strategies and the drug combination. This review summarizes the current achievements in combination therapeutics, with a particular emphasis on the efforts to develop combination therapeutics for complex diseases.

A novel substituted aminoquinoline selectively targets voltage-sensitive sodium channel isoforms and NMDA receptor subtypes and alleviates chronic inflammatory and neuropathic pain

Recent understanding of the systems that mediate complex disease states, has generated a search for molecules that simultaneously modulate more than one component of a pathologic pathway. Chronic pain syndromes are etiologically connected to functional changes (sensitization) in both peripheral sensory neurons and in the central nervous system (CNS). These functional changes involve modifications of a significant number of components of signal generating, signal transducing and signal propagating pathways. Our analysis of disease-related changes which take place in sensory neurons during sensitization led to the design of a molecule that would simultaneously inhibit peripheral NMDA receptors and voltage sensitive sodium channels. In the current report, we detail the selectivity of N,N-(diphenyl)-4-ureido-5,7-dichloro-2-carboxy-quinoline (DCUKA) for action at NMDA receptors composed of different subunit combinations and voltage sensitive sodium channels having different α subunits. We show that DCUKA is restricted to the periphery after oral administration, and that circulating blood levels are compatible with its necessary concentrations for effects at the peripheral cognate receptors/channels that were assayed in vitro. Our results demonstrate that DCUKA, at concentrations circulating in the blood after oral administration, can modulate systems which are upregulated during peripheral sensitization, and are important for generating and conducting pain information to the CNS. Furthermore, we demonstrate that DCUKA ameliorates the hyperalgesia of chronic pain without affecting normal pain responses in neuropathic and inflammation-induced chronic pain models.

Glycine transporter2 inhibitors: Getting the balance right

Neurotransmitter transporters are targets for a wide range of therapeutically useful drugs. This is because they have the capacity to selectively manipulate the dynamics of neurotransmitter concentrations and thereby enhance or diminish signalling through particular brain pathways. High affinity glycine transporters (GlyTs) regulate extracellular concentrations of glycine and provide novel therapeutic targets for neurological disorders.

Discovery of novel 2,5-dioxoimidazolidine-based P2X(7) receptor antagonists as constrained analogues of KN62

Novel 2,5-dioxoimidazolidine-based conformationally constrained analogues of KN62 (1) were developed as P2X7 receptor (P2X7R) antagonists using a rigidification strategy of the tyrosine backbone of 1. SAR analysis of the 2,5-dioxoimidazolidine scaffold indicated that piperidine substitution at the N3 position and no substitution at N1 position were preferable. Further optimization of the substituents at the piperidine nitrogen and the spacer around the skeleton resulted in several superior antagonists to 1, including 1-adamantanecarbonyl analogue 21i (IC50 = 23 nM in ethidium uptake assay; IC50 = 14 nM in IL-1β ELISA assay) and (3-CF3-4-Cl)benzoyl analogue (-)-21w (54 nM in ethidium uptake assay; 9 nM in IL-1β ELISA assay), which was more potent than the corresponding (+) isomer. Compound 21w displayed potent inhibitory activity in an ex vivo model of LTP-induced pain signaling in the spinal cord and significant anti-inflammatory activity in in vivo models of carrageenan-induced paw edema and type II collagen-induced joint arthritis.

Prospects for multitarget lipid-raft-coated silica beads: a remarkable online biomaterial for discovering multitarget antitumor lead compounds

Application of lipid raft biomaterial with multiple cancer-related receptors for screening novel multitarget antitumour lead compounds.

Design and synthesis of potent and selective P2X₃ receptor antagonists derived from PPADS as potential pain modulators

Pyridoxalphosphate-6-azophenyl-2',4'-disulfonate (7a, PPADS), a nonselective P2X receptor antagonist, was extensively modified to develop more stable, potent, and selective P2X₃ receptor antagonists as potential antinociceptive agents. Based on the results of our previous report, all strong anionic groups in PPADS including phosphate and sulfonate groups were changed to carboxylic acids or deleted. The unstable azo (-NN-) linkage of 7a was transformed to more stable carbon-carbon, ether or amide linkages through the synthesis of the 5-hydroxyl-pyridine moieties with substituents at 2 position via a Diels-Alder reaction. This resulted in the retention of antagonistic activity (IC50 = 400 ∼ 700 nM) at the hP2X₃ receptor in the two-electrode voltage clamp (TEVC) assay system on the Xenopus oocytes. Introduction of bulky aromatic groups at the carbon linker, as in compounds 13 h-n, dramatically improved the selectivity profiles of hP2X₃ when compared with mP2X₁ and hP2X₇ receptors. Among the substituents tested at the 2-position, the m-phenoxybenzyl group showed optimum selectivity and potency at the hP2X₃ receptor. In searching for effective substituents at the 4- and 3-positions, we found that compound 36j, with 4-carboxaldehyde, 3-propenoic acid and 2-(m-phenoxy)benzyl groups, was the most potent and selective hP2X₃ receptor antagonist with an IC50 of 60 nM at hP2X₃ and marginal antagonistic activities of 10 μM at mP2X₁ and hP2X₇. Furthermore, using an ex-vivo assay system, we found that compound 36j potently inhibited pain signaling in the rat dorsal horn with 20 μM 36j displaying 65% inhibition while 20 μM pregabalin, a clinically available drug, showed only 31% inhibition.

Immobilized magnetic beads based multi-target affinity selection coupled with high performance liquid chromatography-mass spectrometry for screening anti-diabetic compounds from a Chinese medicine "Tang-Zhi-Qing"

We developed an approach for screening bioactive compounds from botanical drug using multiple target-immobilized magnetic beads coupled with high performance liquid chromatography-mass spectrometry. This novel approach was called magnetic beads based multi-target affinity selection-mass spectrometry (MT-ASMS). It can enrich and identify different types of ligands from mixture extracts. Multiple targets (maltase, invertase, lipase) were immobilized on the magnetic beads by covalent linkage using 1-(3-dimethyl-aminopropyl)-3-ethyl-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as reaction reagents, respectively. The properties of enzyme conjugated magnetic beads were characterized using transmission electron microscopy, X-ray diffractometer and vibration sample magnetometer. Several factors including pH, ion strength, incubation time and temperature were optimized using three known ligands (caffeic acid, ferulic acid, and hesperidin). The established MT-ASMS approach was applied to screening for ligands from a Chinese medicine "Tang-Zhi-Qing", which was used to treat type II diabetes in China. Seven bound compounds were identified via liquid chromatography-mass spectrometry (LC/MS). Five active compounds including 2,3,4,6-tetra-O-galloyl-D-glucose, 1,2,3,4-tetra-O-galloyl-D-glucose, 1,2,3,4,6-penta-O-galloyl-d-glucose, quercetin-3-O-β-D-glucuronide and quercetin-3-O-β-D-glucoside were identified and their activities were validated by conventional inhibitory assay. Our findings suggested that the proposed approach is efficient in screening compounds with multiple activities from extracts of botanical drugs.

Troubleshooting and deconvoluting label-free cell phenotypic assays in drug discovery

INTRODUCTION

Central to drug discovery and development is to comprehend the target(s), potency, efficacy and safety of drug molecules using pharmacological assays. Owing to their ability to provide a holistic view of drug actions in native cells, label-free biosensor-enabled cell phenotypic assays have been emerging as new generation phenotypic assays for drug discovery. Despite the benefits associated with wide pathway coverage, high sensitivity, high information content, non-invasiveness and real-time kinetics, label-free cell phenotypic assays are often viewed to be a blackbox in the era of target-centric drug discovery.

METHODS

This article first reviews the biochemical and biological complexity of drug-target interactions, and then discusses the key characteristics of label-free cell phenotypic assays and presents a five-step strategy to troubleshooting and deconvoluting the label-free cell phenotypic profiles of drugs.

RESULTS

Drug-target interactions are intrinsically complicated. Label-free cell phenotypic signatures of drugs mirror the innate complexity of drug-target interactions, and can be effectively deconvoluted using the five-step strategy.

DISCUSSION

The past decades have witnessed dramatic expansion of pharmacological assays ranging from molecular to phenotypic assays, which is coincident with the realization of the innate complexity of drug-target interactions. The clinical features of a drug are defined by how it operates at the system level and by its distinct polypharmacology, ontarget, phenotypic and network pharmacology. Approaches to examine the biochemical, cellular and molecular mechanisms of action of drugs are essential to increase the efficiency of drug discovery and development. Label-free cell phenotypic assays and the troubleshooting and deconvoluting approach presented here may hold great promise in drug discovery and development.

Application of ED-optimality to screening experiments for analgesic compounds in an experimental model of neuropathic pain

In spite of the evidence regarding high variability in the response to evoked pain, little attention has been paid to its impact on the screening of drugs for inflammatory and neuropathic pain. In this study, we explore the feasibility of introducing optimality concepts to experimental protocols, enabling estimation of parameter and model uncertainty. Pharmacokinetic (PK) and pharmacodynamic data from different experiments in rats were pooled and modelled using nonlinear mixed effects modelling. Pain data on gabapentin and placebo-treated animals were generated in the complete Freund's adjuvant model of neuropathic pain. A logistic regression model was applied to optimise sampling times and dose levels to be used in an experimental protocol. Drug potency (EC(50)) and interindividual variability (IIV) were considered the parameters of interest. Different experimental designs were tested and validated by SSE (stochastic simulation and estimation) taking into account relevant exposure ranges. The pharmacokinetics of gabapentin was described by a two-compartment PK model with first order absorption (CL = 0.159 l h(-1), V(2) = 0.118 l, V(3) = 0.253 l, Ka = 0.26 h(-1), Q = 1.22 l h(-1)). Drug potency (EC(50)) for the anti-allodynic effects was estimated to be 1400 ng ml(-1). Protocol optimisation improved bias and precision of the EC50 by 6 and 11.9. %, respectively, whilst IIV estimates showed improvement of 31.89 and 14.91 %, respectively. Our results show that variability in behavioural models of evoked pain response leads to uncertainty in drug potency estimates, with potential impact on the ranking of compounds during screening. As illustrated for gabapentin, ED-optimality concepts enable analysis of discrete data taking into account experimental constraints.

P2Y purinergic receptors: new targets for analgesic and antimigraine drugs

Millions of individuals worldwide suffer from acute and, more severely, chronic pain conditions (e.g., neuropathic pain, and migraine). The latter bear tremendous personal, familial, and social costs, since sufferers and their relatives undergo a complete turnaround of their lives with the search of relief from pain becoming their pivotal thought. Sadly, to date no effective pharmacological approaches are available which can alleviate chronic pain significantly or in the long run in all patients. The current central strategy for the development of new and effective painkillers lies in the hypothesis that cellular and/or molecular players in nociception must exists that are not targeted by "classical" analgesics, and therefore researchers have put tremendous efforts into the in-depth analysis of the pathways leading to pain development and maintenance over time. In this complex scenario, two outsiders are now taking the center stage: glial cells in sensory ganglia and in the central nervous system, thanks to their ability to communicate with neurons and to modulate their firing, and the purinergic system. Extracellular purine and pyrimidine nucleotides are involved in the physiology of virtually every body district, and their extracellular concentrations massively increase under pathological situations, suggesting that they might represent potential targets for the modulation of disease-associated symptoms, like pain. Here, we provide an overview of the present knowledge of the role of nucleotides in nociception, with a particular emphasis on G protein-coupled P2Y receptors and their involvement in the communication between first- and second-order neurons in sensory nerve pathways and surrounding glial cells.

Is poor research the cause of the declining productivity of the pharmaceutical industry? An industry in need of a paradigm shift

For the past 20 years target-based drug discovery has been the main research paradigm used by the pharmaceutical industry and billions of dollars have been invested into this approach. However, recent industry data strongly indicate that the target-based approach is not an effective drug discovery paradigm and is likely to be the cause of the productivity crisis the industry is experiencing. However, from a theoretical and scientific perspective the target-based approach appears sound, so why is it not more successful? The purpose of this paper is first to analyse the real-life implementation of the target-based approach to identify possible reasons for the high failure rate and second to suggest changes to the drug discovery approach, which can improve productivity.