Cirrhosis characterized by progressive liver disease is a leading cause of morbidity from chronic abuse of ethanol worldwide. In addition, hepatic fibrosis is also associated with increased rates of hepatocellular carcinoma, which is usually fatal. There is currently no approved drug to treat alcoholic liver fibrosis. The endocannabinoid receptors (CBRs), particularly CB1R, have recently emerged as pre-clinically validated targets to treat liver fibrosis and other related disorders. Both CB1R and CB2R are expressed in the central nervous system (CNS). They also exist peripherally in a variety of tissues including the liver. CB1R and CB2R play reciprocal roles in progression of liver disease. While CB1R and CB2R are marginally expressed in normal liver, they undergo marked upregulation upon liver injury or onset of alcoholic liver disease in hepatocytes and hepatic stellate cells (HSC). Past studies also indicate that antagonists of CB1R are promising candidates for further development and testing to treat alcoholic liver disease. Currently available CB1R antagonists are unsuitable for use in liver fibrosis due to their deleterious effects on the CNS. For example, the selective CB1R antagonist SR141716 (Rimonabant(c)), which was developed by Sanofi-Aventis for obesity, produced undesirable CNS-related side effects in patients including depression and suicidal ideation. This is a particular concern in a large population of alcoholics who suffer from depression. These side effects led the FDA to reject this compound for use in the US and it was withdrawn from Europe post-approval. In spite of these limitations, data from the Rimonabant for Obesity (RIO) trial and follow-up studies indicate that CNS related effects aside, SR141716 is well tolerated in general and has several positive non-CNS related properties, such as improved blood lipid profile, and insulin sensitivity in users. These results also indicate that an effective strategy to target CB1R in alcoholic liver disease and other related etiologies that would by-pass the CNS-related concerns of chronically antagonizing this receptor is to develop peripherally restricted CB1R antagonists that cannot permeate the blood-brain barrier (BBB), which is the overall goal of this research project. Through our ongoing NIAAA-funded small research grant (R03AA017514), we have identified CB1R antagonists based upon the core SR141716 structure that have reduced permeability across the BBB. Using these early compounds with pharmacologically relevant activity at CB1R as templates for further refinement through rational drug design, we expect to develop and test the next generation of compounds to serve as leads for medications development to treat alcoholic liver fibrosis through the following specific aims: Through aim 1 we propose to synthesize additional analogs of SR141716 with structural properties designed to limit their transport across the BBB. Through aim 2, we propose to characterize these synthesized compounds using functional in vitro assays. Further, we will also study pharmacokinetic properties of a select number of active compounds in rodents including BBB permeability and half-life. Additionally, we propose to conduct gene expression profiling experiments to compare and contrast the genome-wide effects of our best lead to SR141716 in a hepatic stellate cell-line stably expressing CB1R. Through aim 3, we propose to conduct efficacy testing of our best compound in an in vivo Lieber-DeCarli rodent model of alcoholic steatosis. We will evaluate several biomarkers of ALD to monitor efficacy of the test compound in this well-established model of alcoholic liver disease.
Project Narrative Alcoholic liver disease has a high mortality rate and increases the chance of developing liver cancer. There are no FDA-approved drugs available currently to treat this disease. Our goal is to develop drugs to treat alcoholic liver disease by targeting a particular type of protein called the type 1 cannabinoid receptor that has been implicated as a target for this disorder. Using medicinal chemistry and pharmacology, we propose to synthesize and test compounds that inhibit the function of type 1 cannabinoid receptors.
