Award

Abstract Acute and chronic pain affect more than 50 million Americans and there is an enormous unmet need for safer pain relief. Although acetaminophen (ApAP) is among the medicines most commonly used for pain relief, hepatotoxicity is a risk and overdose is the most common cause of acute fulminant hepatic failure. Oxidation of ApAP to N-acetyl-p-benzoquinone imine (NAPQI) leads to hepatotoxicity. We synthesized ApAP analogues bearing a heterocyclic moiety linked to the p-acylaminophenol fragment, and analogs to its metabolite were then created to further enhance the safety profile (eliminating liver and kidney toxicity) while retaining analgesia and antipyresis. Liquid chromatography tandem mass spectrometry demonstrated no NAPQI formation in mice after intraperitoneal or oral administration of toxic doses of these new chemical entities while NAPQI was formed in the liver of ApAP-treated mice. Immunostaining for nitrotyrosine, a mitochondrial free radical marker, was observed in liver from ApAP-treated mice but not in mice treated with the new chemical entities. Moreover, the integrity of hepatic tight junctions, another hallmark of ApAP-hepatotoxicity, was lost in mice after high doses of ApAP, but not in mice treated with these new chemical entities. Next, extensive proof of concept studies using different in vivo analgesia assays (von Frey, cold tail flick and abdominal writhing) and in vivo anti-pyretic models (LPS- and Baker’s yeast) led us to a lead compound for pre-clinical development, SRP-3D (diethylamide [DA]). To date, we have completed the following IND-enabling studies for SRP-3D (DA): 1) scale synthesis of 1kg cGMP, 2) establishment of bioanalytical methods, 3) characterization of the cytochrome P450 isoenzyme profile, 4) demonstration of the lead compound’s stability and metabolites in human hepatocytes, and 5) confirmation that it is not mutagenic (Ames test). Taken together the results of these IND-enabling studies support the following Specific Aims for this STTR-HEAL Fast-Track project. Specific Aim 1: Demonstrate the feasibility for drug development of SRP-3D (DA); Specific Aim 2: Determine the most effective oral and intravenous formulations of SRPs-3D (DA) for both chronic and acute pain indications; and Specific Aim 3: Further de-risk development toward an IND submission by completing GLP-toxicology. Our proposed studies also include defining analgesia profile in gender and during aging. These Aims will be a decisive step in commercialization of SRP-3D (DA) to treat acute and chronic pain safely. Given the widespread use of ApAP, the risk of hepatotoxicity with overuse and the ongoing opioid epidemic, this new chemical entity represents a novel non-narcotic analgesic without hepatotoxicity.Project Narrative Acute and chronic pain management is one of the most prevalent and costly public health issues worldwide. Current medications are either highly addictive or cause harm to the liver and kidney with overuse or abuse. In this HEAL STTR Fast-Track project application, we describe a new class of non-opioid small molecules devoid of the potential for abuse. In pre-clinical studies, our lead molecule reduced pain without the liver and kidney toxicity associated with current common over-the-counter analgesics.