Principal Investigator/Program Director (Last, First, Middle: Ridong Chen Project Summary More than 25 million Americans suffer from chronic pain. In recent decades, due to the lack of other effective treatments, there has been an overreliance on opioids despite their poor ability to improve function. This has been contributing to a significant and alarming epidemic of opioid overdose deaths and addictions. Osteoarthritis (OA) is the most common degenerative joint disease, affecting 34% of people over 65 years of age and nearly 27 million people in the United States. The main symptom of OA patients is pain following a significant loss of the articular cartilage. As there are currently no disease modifying agents, analgesics are the mainstay of treatment but often deliver limited efficacy and can induce serious injury and death. We have designed and optimized a protein-based and long-acting analgesic. The therapy will deliver robust efficacy without causing significant side effects as it preferably targets to inflamed tissues and only activates peripheral and -opioid receptors on sensory neurons or immune cells. In the proposed studies, we will evaluate the dose-response of the proprietary drug candidate in a well-established rat model of OA pain. We also will determine the potential side effects in the Functional Observational Battery assays in healthy rats, along with a general toxicological screen of major organ systems. The long-term goal is to develop the drug candidate as a safe and effective analgesic therapy. Weekly or bi-weekly dosing will provide sustained pain relief for OA pain patients without addiction and other adverse side effects.