Funded Projects

Although opioid-based analgesics have been proven effective in reducing the intensity of pain for many neuropathic pain conditions, their clinical utility is grossly limited due to the substantial risks involved in such therapy, including nausea, constipation, physical dependence, tolerance, and respiratory depression. Cumulative evidence suggests that human Mas-related G protein-coupled receptor X1 (MRGPRX1) is a promising target for pain with limited side effects due to its restricted expression in nociceptors within the peripheral nervous system; however, direct activation of MRGPRX1 at peripheral terminals is expected to induce itch side effects, limiting the therapeutic utility of orthosteric MRGPRX1 agonists. This finding led to the exploration of positive allosteric modulators (PAMs) of MRGPRX1 to potentiate the effects of the endogenous agonists at the central terminals of sensory neurons without activating peripheral MRGPRX1. An intrathecal injection of a prototype MRGPRX1 PAM, ML382, effectively attenuated evoked, persistent, and spontaneous pain without causing itch side effects. The goal of this study is to develop a CNS-penetrant small-molecule MRGPRX1 PAM that can be given orally to treat neuropathic pain conditions.

Pain signals originate predominantly in a subset of peripheral sensory neurons that harbor a distinct subset of voltage-gated sodium (NaV) channels; however, current NaV channel blockers, such as local anesthetics, are non-selective and also block NaV channels vital for function of the heart, muscle, and central nervous system. Genetic studies have identified human NaV1.7, NaV1.8, and NaV1.9 channel subtypes as key players in pain signaling and as major contributors to action potential generation in peripheral neurons. ProTx-II is a highly potent and moderately selective peptide toxin that inhibits human NaV1.7 activation. This study will optimize ProTx-II selectivity, potency, and stability by exploiting the new structures of ProTx-II—human NaV1.7 channel complexes, advances in rational peptide optimization, and rigorous potency and efficacy screens to generate high-affinity, selective inhibitors of human NaV1.7, NaV1.8, and NaV1.9 channels that can define a new class of biologics to treat pain.

Opioids are widely used pain treatments, despite their relative ineffectiveness for chronic pain and their high potential for misuse and addiction. There is thus an urgent need for alternative, non-addictive pain treatments. Genetic and functional studies of human pain disorders and animal models of pain have validated Nav1.7, a voltage-gated sodium channel as an attractive target for new pain treatments. Currently available blockers of these channels can sometimes provide symptomatic relief for patients but have worrisome side effects affecting the brain and heart. This study aims to develop and validate an innovative site-directed RNA editing strategy that will offer the ability to create new versions of molecules to block Nav1.7, toward establishing a novel, non-addictive approach to treat chronic pain.

Disruptions in make-up of the microbiome are associated with disorders characterized by chronic pain and inflammation, such as rheumatoid arthritis and fibromyalgia. The gut microbiome has immune and metabolic effects, and human gut-derived bacteria may be a source of novel, safe, and non-addictive pain treatments. However, connections between gut and pain signals, known as the “gut–pain axis,” are still poorly understood. This study aims to identify human-gut-native bacteria that i) interact with known pain targets in lab studies, ii) test their activity and analgesic/anti-inflammatory potential in an animal model, and iii) develop a computational approach to predict microbial-genetic effects on pain signals.

Pain caused by the degeneration of discs between vertebrae in the spine makes up a significant proportion of all chronic low back pain conditions. Although opioids are prescribed as treatments for this chronic condition, they often do not provide effective pain management, and currently there are no treatments that target the underlying disc disease. Notochordal cells mature into the cells that make up discs between vertebrae. Preliminary studies have shown that notochordal cells can be made from induced pluripotent stem cells, offering a potential replacement for diseased cells between discs. This study aims to develop a novel treatment for painful disc degeneration using a microgel/microtissue embedded with human notochordal cells made in the lab from induced pluripotent stem cells.

Current medications for chronic pain are largely ineffective and rely heavily on opioids, one contributor to the nation’s opioid crisis. The endocannabinoid system that consists of cannabinoid receptors (CB1R and CB2R) and their endogenous ligands is a natural pathway in the human body and has emerged as an alternative target for developing new pain medications with few side effects. Current molecules that bind to CB1R in the brain and spinal cord have psychoactive side effects, limiting their therapeutic use for treating chronic pain. This study aims to develop new molecules to bind to CB1R tightly and selectively, are metabolically stable, and are also unable to enter the brain.

Patients with severe, intractable chronic pain primarily receive treatment with opioids, and non-opioid treatment options are urgently needed. These patients may be candidates for treatment using other types of pain medications administered via intrathecal injection—that is, injection directly into the fluid-filled space between the membranes surrounding the brain and spinal cord. Intrathecal injection requires much lower medication doses than systemic administration. Centrexion Therapeutics Corporation seeks to develop CNTX-3100, a highly selective and highly potent novel small molecule that activates the nociception receptor (NOPr), for intrathecal administration using a pump approved by the U.S. Food and Drug Administration. In animal studies, such NOPr agonists had powerful analgesic effects when delivered directly to the spinal cord by intrathecal administration. CNTX-3100 has ideal properties for intrathecal delivery and in animal studies provided pain relief and a safety profile that was superior to intrathecally administered morphine. This project will scale up the drug, develop a formulation that ensures a stable product for intrathecal delivery, and conduct preclinical toxicity studies to prepare for a Phase 1 clinical trial.

Efforts to identify non-opioid analgesics for treatment of chronic pain have identified a protein, carbonic anhydrase-8 (CA8), in pain-sensing nerve cells in the spinal cord (dorsal root ganglion cells) whose expression regulates analgesic responses. Gene therapy delivering CA8 to dorsal root ganglion cells through clinically relevant routes of administration functions as a “local anesthetic” that induces long-lasting pain relief in animal models of chronic pain. This project will further develop CA8 gene therapy with the goal of treating chronic knee osteoarthritis pain. It will assess several gene therapy constructs to determine the doses needed, safety, efficacy, and specificity to nerve cells for each construct. It will then select the safest and most effective construct that can be administered via the least invasive route for further development. The project will include all steps necessary to identify one candidate gene therapy construct that will be suitable to begin clinical trials in patients with chronic knee osteoarthritis pain.

Cholecystokinin B receptor (CCKBR) is a molecule found in the brain that helps regulate anxiety and depression but also influences the development of tolerance to opioids. CCKBR levels are also increased in models of nerve injury-induced (neuropathic) pain. Therefore, targeting CCKBR may offer a new approach to treating neuropathic pain and the associated anxiety and depression. Researchers have developed mouse antibodies that can inactivate CCKBR. However, to be usable in humans without causing an immune response, these antibodies need to be modified to include more human sequences. This project will use a fragment of the CCKBR antibody, modify it with the addition of human antibody sequences, and then select the clones that bind most strongly and specifically to human CCKBR. These will then be tested in cell and animal models of neuropathic pain to identify the most promising candidates for further evaluation in humans.

Voltage-gated sodium channels such as Nav1.7, Nav1.8, and Nav1.9 transmit pain signals in nerve fibers and are molecular targets for pain therapy. While Nav channels have been validated as pharmacological targets for the treatment of pain, available therapies are limited due to incomplete efficacy and significant side effects. Taking advantage of recent advances in structural biology and computational-based protein design, this project aims to develop antibodies to attach to Nav channels and freeze them in an inactive state. These antibodies can then be further developed as novel treatments for chronic pain.

Chronic pain from tissue injury often stems from long-term changes in spinal cord circuits that change nerve sensation. Reversing these changes may provide better pain therapeutics. Previous work in animal models showed that activating G protein-coupled receptor 37 (GPR37) dampens nerve signal intensity after long-term stimulation and alleviates pain behavioral responses. This project aims to validate GPR37 in the spinal cord as a useful target for new treatments for neuropathic pain. The work will facilitate screening and identification of new molecules that activate GPR37, which can then be tested for efficacy and safety in further research in animal models of pain.

There is a continued need to discover and validate new targets for potential therapeutic strategies for effective and safe treatment of pain. This project focuses on the protein metadherin, also known as astrocyte elevated gene-1 protein (AEG-1), as a possible new target for pain treatment. Preliminary studies have shown that mice genetically engineered to lack metadherin had significantly lower inflammation and chronic pain-related behaviors. This project aims to further validate AEG-1 as a pain target and test whether reducing levels in white blood cells called macrophages might work as a therapeutic strategy to reduce chronic inflammatory and/or neuropathic pain using an innovative nanoparticle approach to target specific cells.

Neuropathic pain is characterized by neuronal hyperexcitability and spontaneous activity, properties associated with activity of hyperpolarization-activated, cyclic nucleotide-regulated (HCN1-4) channels, the source of the pacemaker current, Ih. Inhibition of HCN1-mediated Ih elicits marked antihyperalgesia in multiple animal models of neuropathic pain, including models for direct nerve injury and chemotherapy-induced peripheral neuropathy, and does so with little or no disruption to either normal pain processing or baseline behaviors and activities. The overall objective is to develop a peripherally restricted HCN1 inverse-agonist as a therapeutic for neuropathic pain. Researchers have generated a novel small molecule that combines an antihyperalgesic HCN1 inhibitor with a motif that controls distribution and membrane presentation and is a potential non-opioid antihyperalgesic treatment for peripheral neuropathic pain.