Chronic pain is a long-term, debilitating condition that is typically treated with prescription opioid drugs over lengthy periods of time with repeated drug administration. The problem with long-term opioid drug use is the development of addiction that results in detrimental drug tolerance and dependence, drug abuse, and overdose death. Non-addictive drugs to treat chronic pain are an unmet need in therapeutics, so that patients will not be subjected to the detrimental consequences of long- term opioid use for chronic pain conditions of nerve injury, stroke, cancer, arthritis, and many related conditions. Development of effective, non-addicting pain medications is a public health priority, indicated by NIH. This project addresses the critical need to develop non-addictive drugs for the treatment of chronic pain. The strategy to find a non-addictive therapeutic agent for chronic pain will be to target antisense oligonucleotide (ASO) drug molecules to reduce spinal dynorphin A and alleviate chronic pain. The ASO approach to alleviate chronic pain obliterates the need for long-term opioid drug use that causes addiction. Dynorphin A has been validated as a key factor in the development and maintenance of chronic pain, since knockout of the dynorphin gene blocks chronic pain in mouse models of chronic pain, and IT (intrathecal) administration of antibodies to dynorphin A attenuates the chronic pain state. Participation of dynorphin A in chronic pain is indicated by elevation of spinal dynorphin during chronic pain, and IT administration of dynorphin enhances chronic pain. ASO targeting of spinal dynorphin is a logical and innovative approach for development of non- addictive drugs to treat chronic pain. The research plan will be achieved in two specific aims. Aim 1 will design and screen ASO molecules for reduction of dynorphin A in cultured neurons using quantitative mass spectrometry analyses of peptides. Aim 2 will assess IT ASOs for their abilities to reduce the elevation in spinal dynorphin A during chronic pain modeled by SNL (spinal nerve injury) in mice, and to alleviate the chronic pain state as assessed by behavioral assays for pain. Pilot data shows that an anti-dynorphin ASO reduces spinal dynorphin A in mice in vivo, supporting the feasibility of this project. Effective candidate ASOs will be evaluated for initial ASO pharmacokinetics, efficacy to reduce chronic pain, and dynorphin A pharmacodynamics. This project will make important contributions to the field to develop non-addictive drugs for the treatment of chronic pain.