PROJECT SUMMARY The U.S. is reeling from a public health crisis driven by the misuse of prescription opioids (e.g., oxycodone), heroin and fentanyl derivatives. Medication-assisted treatment (MAT) aids in reducing mortality, opioid withdrawal, intake and opioid-seeking behaviors, thus substantially improving the odds of successful recovery from OUD, particularly when coupled with psychosocial interventions. This crisis has crystalized the need to establish new pathways to develop additional and/or adjunctive therapeutics to extend recovery and improve outcomes in this chronic medical disorder. However, the surprising lack of knowledge of the molecular, genetic, and epigenetic neuropathophysiology of OUD has restricted our understanding and treatment of this disorder. One such cellular adaptation involves altered gene expression in the absence of changes in gene encoding through epigenetics. In this light, the intended biological target of the present U18 is a member of the bromodomain and extra-terminal domain-containing (BET) family of chromatin “reader” proteins. The BET family is comprised of bromodomain testis-specific protein (BRDT) and bromodomain (BRD)-containing protein 2 (BRD2), BRD3 and BRD4. Our preliminary data indicate that increased expression of BRD4 in the nucleus accumbens (NAc) may be a driver of withdrawal-related sequela associated with continued oxycodone-taking. We also found that the patent-protected, highly selective BDR4 inhibitor ZL0987 exerted a sustained suppression of oxycodone self-administration. Based upon these findings, we will test the hypotheses that the highly selective BRD4 inhibitor ZL0987 will suppress oxycodone, but not food, self-administration upon chronic administration (Aim 1) and that pretreatment with ZL0987, which reduces oxycodone SA, will negate or normalize transcriptomic profiles and BDR4 protein interactions relative to food self-administration. Target engagement will be investigated through transcriptional and chromatin-related consequences of oxycodone vs. food self- administration using genome-wide and candidate (i.e., BRD4)-based approaches [e.g., RNA-Seq and chromatin immunoprecipitation with DNA sequencing (ChIP-Seq) analysis of BRD4 binding sites] in NAc harvested from rats at early and late withdrawal from oxycodone or food self-administration under controlled conditions. The results from the present studies will lay the foundation for a completely novel and highly relevant research track that will foster in-depth investigation of differential BRD4 involvement in neurobiological circuitry involved in OUD. This is a highly innovative and speculative direction and the outcomes will position our team to move forward into initiatives that enable development of novel ligands that inhibit the BRD4 protein complex, identification of potential off-target interactions for lead drug candidates, and in vivo studies to restore BRD4 protein function to ameliorate OUD. These innovative aims are consistent with the goals of the U18 program to support creative, cutting edge research that promises to result in better treatments, and potential cures, for the acquired neural disorder OUD.

PROJECT NARRATIVE The incidence of opioid use disorder is dramatically increasing with the continuing opioid misuse and overdose crisis in the United States. The present project will explore a patent-protected, novel small molecule inhibitor of epigenetic processing as a novel target for an OUD medication through understanding the pathophysiological changes in a key brain area which sustains opioid intake.