Helping to End Addiction Long-term (HEAL): Probe/Drug Lead Production

National Center For Advancing Translational Sciences

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Abstract

HEAL Compound Library ETB created a comprehensive annotated HEAL library of compounds for addiction and pain relevant targets. A screening-ready copy, available through collaborative efforts, allows rapid strategic screening for drug repurposing, innovative profiling, and hypothesis testing of novel targets and tool compounds, thus fast-tracking efforts to develop novel pharmacotherapies for pain, addiction, and overdose. Development of Gpr151 Modulators for the Treatment of Opioid Dependence This collaboration is developing novel Gpr151 modulators to facilitate long-term abstinence in opioid-dependent individuals. Gpr151 is an orphan G-protein coupled receptor expressed in the central nervous system (CNS), medial habenula, and immune system. The team confirmed assay robustness and reliability to execute HTS against Gpr151. They validated and optimized two assays. Two stages of HTS are complete. Over 52,150 compounds were screened. The team cherry-picked promising, efficacious hits for follow-up and cross-validation. Medicinal chemists will begin structure-activity-relationship (SAR) studies on top analogs. The GPR151 team is also set to collaborate with NCI to screen the Natural Products Library, a copy of which is housed at NCATS. Optimization of Allosteric Regulators of the NaV1.7 Sodium Channel for Chemotherapy-induced Peripheral Neuropathy (CIPN) Long-term use of opioids to treat chronic pain caused by CIPN can result in tolerance and addiction. There is a need for safe, non-addictive drugs for those that suffer from neuropathic pain. The project team is optimizing a novel lead series of NaV1.7 sodium channel allosteric regulators, such that one lead reaches the stage of a clinical candidate. The team developed and optimized high-throughput assays to assess NaV1.7 function. Virtual screening hits were also identified. Medicinal chemists synthesized hundreds of analogs, several of which will be optimized. SAR studies are ongoing. Select compounds are undergoing additional analysis and validation. High Throughput Screen to Identify Glutamate Carboxypeptidase II (GCPII) Brain-Penetrable-Inhibitors for the Treatment of Pain GCPII is a membrane-bound, zinc metalloenzyme that catalyzes the hydrolysis of neuropeptide N-acetyl-aspartate-glutamate (NAAG) to N-acetyl-aspartate (NAA) and glutamate. Inhibition of GCPII in the brain results in increased extracellular NAAG and decreased extracellular glutamate. These effects diminish glutamate transmission, which is associated with pain sensation and transmission. Consequently, no inhibitors have moved into the clinic because of poor brain penetration, low oral bioavailability, and low membrane permeability. These limitations are being addressed by the team as they focus on the identification of brain penetrable, small molecule inhibitors of GCPII. The team developed and optimized an LC-MS assay. They completed a pilot screen and identified 113 compounds with >50% inhibition. Forty-eight compounds were selected for testing in 7-point dose response. Confirmed hits will be validated. The HEAL Library was also screened, and the team will conduct follow-up testing on active hits. Next steps include expanded HTS and analog testing. Adenylyl Cyclase 1 (AC1) Inhibitors as Opioid Alternatives for Chronic and Inflammatory Pain Neuronal adenylyl cyclase type I (AC1) is a highly expressed enzyme in neuronal tissues associated with pain processing and neuronal plasticity. Preclinical studies showed that AC1 could be a promising target to treat chronic and inflammatory pain. This project will focus on the development and mechanistic characterization of AC1selective, CNS penetrant small molecule inhibitors as a nonopioid treatment for chronic pain. This project was delayed because of the COVID-19 pandemic. Pilot screening will begin in late August 2021. 5-HT7 Receptor Agonists as Novel Treatments for Pain, Opioid-Induced Hyperalgesia, and Opioid Use Disorder G-coupled 5-HT7 serotonin receptor (5-HT7R) is a novel molecular target for pain. Several agonists have been identified, but they are largely understudied, and it is unclear why they havent been developed further. This project evaluated known agonists and furthered their preclinical development through pharmacokinetic (PK) studies. E-55888, MSD-5a, and AS-19 are commercially available and reported to have anti-nociceptive effects. NCATS synthesized these compounds and completed ADME/PK studies. In vitro, all three have low to moderate solubility, high PAMPA permeability (except for AS-19), and poor metabolic stability. In vivo PK studies showed that all three compounds got into the brain and had a short plasma half-life (less than one hour). Identification of Brain-Permeant Small Molecule Modulators of GAL1R Receptor Mu-opioid receptors (MOR) mediate the analgesic and addictive effects of opioids. Galanin, a neuropeptide, exerts analgesic effects by acting on galanin 1 receptor (Gal1R) localized in the spinal cord. Galanin counteracts the addictive effects of opioids by acting on Gal1R that forms complexes with MOR localized in the mesencephalon; additionally, Gal1R mediates the dopaminergic effects of opioids. This project is looking for potent and selective Gal1R ligands with the ability to cross the blood-brain barrier (BBB) and provide strong analgesia with low abuse liability when combined with opioids. The team developed a suite of primary, counter, orthogonal, and supplemental assays for this project. Over 183,800 compounds were screened. Sixty-two hits were validated, and 13 of them were further confirmed and validated by the team. Compounds are being tested in a radioligand binding assay, and SAR studies were initiated as well. The joint team will also collaborate with NCI to screen the Natural Products Library. Chemical Modulators of the PIEZO2 Mechanoreceptor for the Study and Treatment of Pain The stretch-gated ion channel PIEZO2 was identified as a novel pain target. Human subjects with inherited loss-of-function mutations in this gene fail to develop mechanical allodynia, a common type of chronic pain whereby normally innocuous touch becomes painful. Its suggested that topical PlEZO2 antagonists may be effective for treating this type of pain. PIEZO2 loss-of-function has been linked to chronic itch as well, implying that a topical PIEZO2 agonist may be an effective itch treatment. The goal of this collaboration is to characterize small molecule probes for PIEZO2. The team is engineering excitable HEK cells that stably express different genes for HTS. Once HTS is complete, hits will be validated and optimized. Leads will be tested in animal models to demonstrate target engagement and efficacy. Additionally, a proof-of-concept study is underway to see if antibodies have the ability to restrict Piezo2 function when targeting two separate regions. Substance P Antibody Development Blocking the interaction between inflammatory neuropeptides and their receptors is an approach for treating chronic pain and migraine. Small molecule antagonists have failed due to multiple receptors per peptide; however, theres been success using antibodies to block the function of CGRP, an inflammatory neuropeptide. Unfortunately, these antibodies do not cross the BBB. Other neuropeptides (such as substance P) are known to contribute to chronic pain. This project aims to develop cell-based assays and identify BBB-penetrant, functional antibodies to neuropeptides with roles in chronic pain and migraine; it could make an impact by identifying new, non-addictive treatments. The team screened anti-substance P antibodies, and they are also developing in vivo assays to measure antibody efficacy.