The overall goal of this project is to develop peripherally restricted partial agonists of the cannabinoid receptors (CB1 and CB2) for the treatment of non-alcoholic steatohepatitis (NASH). These compounds are expected to mimic the peripheral effects of THC ((?)-trans-??-tetrahydrocannabinol), the only known orthosteric ligand of the CB receptors in marijuana while avoiding adverse CNS related side-effects. There are two known cannabinoid receptors ? CB1 and CB2. The CB1 receptor is highly expressed on neurons of the CNS along with certain peripheral organs like the liver, pancreas, skeletal muscle and adipose tissue. The CB2 receptor is mostly expressed on immune cells Epidemiological studies indicate that marijuana users have reduced rates of NASH, type 2 diabetes and obesity. These contrarian effects are in sharp contrast to known orexigenic effects of marijuana via the CNS. These observations can be explained by disparate pharmacological effects of THC ? a partial agonist. A partial agonist can act like a traditional agonist when excess receptors are present. However, a partial agonist can also act as a functional antagonist when number of receptors is limited by competing with a full agonist and by reducing downstream signaling. In the injured liver, the expression of CB1 is low to moderate but there is a large influx of CB2 expressing immune cells. Further, expression of the full agonist endocannabinoid 2-AG is ~1000-fold higher than that of the partial agonist AEA. We hypothesized that in NASH a partial agonist might be able to reduce fatty liver via functional antagonism of CB1 while producing anti- inflammatory effects by targeting CB2. We successfully tested this hypothesis using a well characterized partial agonist of CB receptors and an early lead compound in a model of NASH. Continuation of our preliminary studies is proposed through 3 integrated specific aims: (1) Synthesize partial CB receptor agonists that are peripherally restricted. We have started to explore a primary indazole scaffold and a secondary pyrazole scaffold to produce partial agonists of CB receptors that have limited CNS penetration. Continued refinement of early leads will lead to compounds with optimized drug-like properties. (2) Perform pharmacological characterization using various functional and binding assays and ADMET profiling of synthesized compounds to identify promising leads. Select compounds will undergo pharmacokinetic evaluation and behavioral profiling to rule out CNS-effects. (3) Perform efficacy testing in NASH models. We propose to evaluate our most promising leads in models of NASH for efficacy. In tandem, we will assess various biomarkers of efficacy and perform receptor occupancy studies to identify an optimized mature lead and two backups for further development.
Our goal is to treat a type of liver disease called nonalcoholic steatohepatitis (NASH). We will make compounds that target the cannabinoid receptors to treat NASH but these compounds will not get into the brain and produce adverse effects like what is seen with marijuana.
