Millions of Americans suffer from sleep disturbances among which insomnia is the most common. Insomnia is often poorly treated with current pharmacotherapies and we propose to develop a new sleep-promoting therapeutic based on selective and direct activation of the G protein-gated inward rectifier K+ channels (GIRK). GIRK channels in the brain (predominantly GIRK1/2) play a key role in controlling neuronal excitability. Activation of the GIRK channels by neurotransmitters and neuropeptides, such as GABA and galanin, promote sleep. The link between GIRK function and animal NREM sleep was based on both preclinical and clinical evidence that shows GIRK activation by GABAB agonists, e.g., baclofen and ?-hydroxybutyric acid (GHB), preferentially promote non-rapid eye movement (NREM) sleep, leading to enhanced maintenance of sleep. In our collaborative project led by Dr. Weaver, we discovered the GIRK channel biologic probe ML297, which selectively activates recombinant human GIRK channels with a half-maximal effective concentration (EC50) of ~160 nM for neuronal GIRK1/2 with a ~4-fold selectivity over cardiac GIRK1/4 channels. Recently, we eliminated the concern of ML297 on cardiac safety using the cardiac ion channels panel consisting of hERG, hCav1.2 and hNav1.5 channels (IC50 =52, 22 and >30?M, respectively). ML297 had little effects on spontaneous action potential firing in hiPSCderived cardiomyocytes upto 10µM. Pharmacokinetic (PK) studies indicated that ML297 had acceptable brain penetration. Pharmacodynamic (PD) studies confirmed that ML297 can activate native neuronal GIRK channels in hypocretin/orexin neurons and hippocampal neurons. Furthermore ML297 (3060 mg/kg, i.p.) inhibited spontaneous activity and prolonged inactive/sleep state in mice using our validated noninvasive wake/sleep monitoring system SmartCageTM. A study employing electroencephalogram and electromyogram (EEG/EMG) recordings revealed that ML297 significantly enhanced NREM sleep in mice in a dose-dependent manner. We now propose to use ML297 as a starting point to develop a new therapeutic for insomnia because it is amenable to chemical modification to generate druggable analogs and it has no intellectual property roadblocks. We will achieve our goal through the accomplishment of two Specific Aims. Aim 1 Lead modification. Explore the structure-activity relationship (SAR) of ~200 new synthetic analogs derived from ML297 and identify the top 10 modified leads with increased potency and selectivity. Aim 2. Therapeutic lead discovery through in vitro and in vivo PK studies. We will determine the in vivo PK profiles of the top 3 new leads and test the best lead in a pilot sleep study in rats using EEG/EMG. Success in the Phase I project will demonstrate feasibility of discovering a druggable GIRK1/2 channel direct activator. In a Phase II project, we will focus on lead optimization to discover a safe therapeutic candidate with desirable PK/PD profile for the IND-enabling studies, and ultimately for the treatment of chronic insomnia.
Public Health Relevance Statement: 8. PROJECT NARRATIVE Millions of Americans suffer from sleep disorders, especially insomnia, which is often poorly treated. Chronic insomnia can lead to reduced quality of life and increased risks for cardiovascular diseases and metal disorders. We propose to develop a novel drug that can promote sleep and improve the maintenance of sleep in order to enhance sleep quality.
NIH Spending Category: Behavioral and Social Science; Brain Disorders; Cardiovascular; Heart Disease; Mental Health; Neurosciences; Sleep Research
Project Terms: Acids; Action Potentials; Adenosine; Adult; Agonist; American; Amnesia; analog; Animals; Anxiety; Area Under Curve; Arousal; Baclofen; base; Benzodiazepines; Binding Proteins; Biological; Biological Availability; Brain; Cardiac; Cardiac Myocytes; cardiovascular disorder risk; Cell Line; chemical synthesis; Chemicals; Chemosensitization; Chronic; Chronic Insomnia; chronic pain; Clinical; clinical development; Cognitive; comorbidity; Contracts; Dependence; design; Disease; Dose; drug candidate; Drug Kinetics; efficacy testing; Electroconvulsive Shock; Electroencephalogram; Electroencephalography; Emotional; excitatory neuron; falls; Family; Galanin; gamma-Aminobutyric Acid; GIRK1 subunit, G protein-coupled inwardly-rectifying potassium channel; Goals; GTP-Binding Proteins; Half-Life; Heart Atrium; Heart Rate; Hippocampus (Brain); Histamine Receptor; Human; hypocretin; improved; In Vitro; in vivo; innovation; Intellectual Property; Investigational Drugs; Investments; inward rectifier potassium channel; Ion Channel; Lead; lead optimization; Link; Liver Microsomes; Maintenance; Melatonin Receptors; Mental Depression; Metals; Modification; Mus; Muscle Cells; neuronal excitability; Neurons; Neuropeptides; Neurotransmitters; non rapid eye movement; non-invasive monitor; novel; novel therapeutics; Oral; patch clamp; Penetration; Pentylenetetrazole; Pharmaceutical Preparations; Pharmacodynamics; Pharmacologic Substance; Pharmacotherapy; Phase; Physiological; Plasma; Play; Polysomnography; Population; pre-clinical; Quality of life; Rattus; receptor; Recombinants; Regulation; Research Contracts; response; Risk; Role; Safety; Seizures; Sleep; Sleep Architecture; Sleep Disorders; Sleep disturbances; sleep onset insomnia; sleep quality; Sleeplessness; Stress; Structure-Activity Relationship; success; System; Testing; Therapeutic; therapeutic candidate; Toxicology; Ventricular Function; voltage
