Synthesis of PF-6870961, a major hydroxy metabolite of the novel ghrelin receptor inverse agonist PF-5190457

Preclinical and human studies have indicated involvement of the ghrelin system in alcohol-related behaviors illuminating the possibility of using ghrelin receptor blockers as a pharmacological intervention for alcohol use disorder (AUD). Preliminary data from a recently conducted phase 1b human study with a ghrelin receptor inverse agonist, PF-5190457 (2-(2-methylimidazo[2,1-b][1,3thiazol-6-yl)-1-{2-(1R)-5-(6-methylpyrimidin-4-yl)-2,3-dihydro-1H-inden-1-yl]-2,7-diazaspiro[3.5]non-7-ylethanone), provided evidence on the safety and tolerability of this compound when co-administered with alcohol. Furthermore, the study revealed important information on the biotransformation pathways for this compound and prompted the discovery and then synthesis of a newly identified major metabolite, PF-6870961 ((R)-1-(2-(5-(2-hydroxy-6-methylpyrimidin-4-yl)-2,3-dihydro-1H-inden-1-yl)-2,7-diazaspiro[3.5]nonan-7-yl)-2-(2-methylimidazo[2,1-b]thiazol-6-yl)ethan-1-one). The metabolite was synthesized and fully characterized through a design that enabled it to be prepared in useful quantities. The synthesis provided direct access to the recently discovered PF-6870961 and is allowing researchers to conduct additional and deeper evaluation of its in vitro and in vivo properties.

Endocrine effects of the novel ghrelin receptor inverse agonist PF-5190457: Results from a placebo-controlled human laboratory alcohol co-administration study in heavy drinkers

Both animal and human work suggests that the ghrelin system may be involved in the mechanisms that regulate the development and maintenance of alcohol use disorder. Previously, in a Phase 1b study, we tested pharmacological blockade of the growth hormone secretagogue receptor 1a (GHS-R1a, also known as the ghrelin receptor), in heavy drinking individuals with PF-5190457, an orally bioavailable, potent and selective GHS-R1a inverse agonist. We report here the effects of PF-5190457 on endocrine blood concentrations of amylin, gastric inhibitory polypeptide, glucagon-like peptide 1, insulin, leptin, pancreatic polypeptide, peptide YY, thyroid stimulating hormone, free triiodothyronine (T3), thyroxine (T4), cortisol, prolactin, and glucose during PF-5190457 dosing, as compared to placebo, in absence of alcohol as well as during an alcohol challenge when PF-5190457 was on steady-state. Blood hormone levels were largely unaffected by PF-5190457, both during dosing and in the context of alcohol challenge. The safety-related relevance of these findings to further develop PF-5190547 in alcohol use disorder is discussed. CLINICALTRIALS.GOV: NCT02039349. This article is part of the special issue on 'Neuropeptides'.

Discovery of PF-5190457, a Potent, Selective, and Orally Bioavailable Ghrelin Receptor Inverse Agonist Clinical Candidate

The identification of potent, highly selective orally bioavailable ghrelin receptor inverse agonists from a spiro-azetidino-piperidine series is described. Examples from this series have promising in vivo pharmacokinetics and increase glucose-stimulated insulin secretion in human whole and dispersed islets. A physicochemistry-based strategy to increase lipophilic efficiency for ghrelin receptor potency and retain low clearance and satisfactory permeability while reducing off-target pharmacology led to the discovery of 16h. Compound 16h has a superior balance of ghrelin receptor pharmacology and off-target selectivity. On the basis of its promising pharmacological and safety profile, 16h was advanced to human clinical trials.