Development of selective calpain-1 inhibitors for chronic pain

PROJECT SUMMARY Never in the history of the United States has the unmet medical need to develop novel, non-opioid therapeutics for chronic pain been more urgent than it is today. More than 65 million US adults suffer from chronic pain, resulting in almost $635 billion in annual healthcare costs. Despite their limited efficacy, and potential for addiction, tolerance, and impaired motor performance, opioids have become a mainstay for chronic pain management, resulting in an opioid epidemic that is ravaging communities throughout the US. Thus, there is an urgent need to develop novel, non-opioid therapies for chronic pain management. This application addresses this unmet medical need by leveraging our novel artificial intelligence (AI)-driven drug discovery platform to develop selective inhibitors of calpain-1 as novel non-opioid therapeutics for chronic pain. Studies in chronic neuropathic pain animal models have shown that nerve injury overactivates calpain-1, which downregulates K+ Cl- cotransporter activity, resulting in diminished synaptic inhibition and neuropathic pain. Prior work by our group has also shown that both pharmacological inhibition and whole body genetic knockout of calpain-1 attenuates chronic pain behaviors in mouse models of sickle cell disease (SCD). Importantly, the analgesic effect of calpain-1 inhibition did not induce tolerance side effects, suggesting the potential for calpain-1 inhibitors to be non-addictive. By applying our innovative artificial intelligence (AI)-driven drug discovery platform to screen a virtual chemical library, we identified four (4) novel calpain-1 inhibitors, and validated them for efficacy in biochemical assays. Here, we propose to progress our most potent hit compound to a lead compound that is calpain-1 selective, cysteine protease family selective, non-opioid, and CNS penetrant with efficacy demonstrated in at least 1 of 3 chronic pain animal models tested, including chronic sickle cell disease pain, chronic inflammatory pain, and chronic neuropathic pain. Three aims are proposed, including Aim 1: Synthesize ~100 analogs of our most potent hit compound, and characterize in vitro activity and selectivity. Success criteria: Top 20 cell-permeable, calpain-1 inhibitors, moderately selective against calpain-2, and highly selective against cathepsins and caspase-1, Aim 2: Evaluate ADME-Tox and PK profile of our top 20 calpain-1 inhibitors from Aim 1. Success criteria: Top 2 CNS-penetrant selective calpain-1 inhibitors with favorable in vivo PK profile, and Aim 3: Determine the efficacy and PK/PD relationship of our top calpain-1 inhibitor in 3 chronic pain animal models. Success: at least 40% reduction in mechanical hyperalgesia in at least 1 of the 3 chronic pain animal models tested. Successful completion of this Phase I will yield a novel CNS-penetrant, selective calpain-1inhibitor with efficacy demonstrated in at least 1 chronic pain animal model. Our overall product would be the first, oral, CNS acting, selective calpain-1 inhibitor for chronic pain. Importantly, our product would reduce opioid usage in chronic pain patients, and help to stem the US opioid epidemic.PROJECT NARRATIVE Never in the history of the United States has the unmet medical need to develop novel, non-opioid therapeutics for chronic pain been more urgent than it is today. Calpains are enzymes that have been shown to cause pain in many animal models of chronic pain. We propose to leverage our proprietary artificial intelligence (AI)-driven drug discovery platform to develop a selective calpain-1 inhibitor as a novel, non-opioid therapeutic for chronic pain.