Brain-Penetrant scFv Antibody Block of P2X4 Receptor for the Treatment of Chronic Pain
Abstract
Headaches and chronic pain are chief complaints of approximately 772,000 military Service and Veteran personnel in the VA health care system since 2001 of those deployed in Operation Iraqi Freedom or Operation Enduring Freedom (OIF/OEF). Management of recurrent neuropathic face, neck, head, and limb pain remains unsatisfactory since it is not responsive to migraine or common analgesic (NSAIDs, opiate) therapy. Between 2000 and 2015, the number of prescriptions for opiates dramatically increased by 270%, even though the risk of side effects such as addiction, fatal overdose, drowsiness, fatigue, constipation, nausea, stomach, and liver damage is high. There is clearly a great need for development of non-opiate chronic pain therapies for treatment of military Service and Veteran personnel as well as for the general public. The overall study goal of the current proposal is to alleviate untreatable chronic pain induced by nerve damage. Damaged peripheral nerves cause an immune cell invasion and persisting nerve overactivation referred to as “neuropathic pain.” Neuropathic pain is the result of changes in the signaling molecules in the peripheral nerve cells and increases release of inflammatory mediators that can cause acute pain to persist as chronic pain. This proposal outlines studies using models of both a head/facial/orofacial and a lower limb pain model induced by injury to the trigeminal and sciatic nerves, respectively. Both models transition from acute to chronic pain persisting for months. These nerves commonly injured in military action provide the brain with sensory information from regions above the neck and the lower limb. The studies use a small antibody technology to devise a non-opioid therapy with dual use effectiveness for both chronic pain and anxiety behaviors in the study mice. We will use the small, brain penetrant therapeutic single chain variable fragment (scFv) antibodies produced through the technology that will allow us to inhibit pain- and anxiety-related behaviors in the nerve injury models. The P2X4 receptor targeted by the therapy is a molecule sparse in control conditions but increased after nerve injury to signal nerve overactivity, increased inflammatory response, and increased pain. Hypothesis: High affinity, humanized scFv antibody generated to block P2X4R restores baseline pain- and anxiety-related behavior and neuronal firing while reducing inflammatory mediators in chronic pain mouse models. Aim 1: Generate and characterize humanized, high affinity, matured scFvs from selected parent murine scFv antibodies. ScFv antibodies have promising biotherapeutic applications for both nervous and immune systems recognized as interactive in chronic pain. Their solubility and small size allows them to cross the blood-brain barrier. ScFvs are being investigated as successful cancer therapies and our scFv targeting P2X4 may provide chronic pain relief in the future. Humanization will move the scFv forward for human trials in the future. Aim 2: Determine the analgesic efficacy and stability of selective humanized scFv biotherapeutics confirmed by repeat dose-response testing, with more than one batch of compound in acute and chronic pain models activating the trigeminal nerve with eventual effects on anxiety- and depression-like behaviors. The proposed studies address the therapeutic value of the P2X4R scFv antibody in vivo with sciatic and trigeminal nerve injury models that mimic human chronic neuropathic pain conditions. Both the Spared Nerve Injury (SNI) and Foramen Rotundum Inflammatory Constriction Trigeminal Infraorbital Nerve injury (FRICT-ION) models persist through long timeframes suitable for testing therapeutics for chronic pain (>6 weeks–6 months). A single dose of the P2X4R scFv antibody given in week 3 or 6 after nerve injury successfully reverses chronic pain and anxiety behaviors to baseline in the study mice. Aim 3: Evaluation of potency, mechanism
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 10, 2021
- Source ID
- W81XWH2010930
Entities
People
- Karin N Westlund
Organizations
- Health Sciences Center, University of New Mexico
- United States Army