Bioactive Indanes: Comparative in vitro Metabolism Study of PH46A, a New Potential Anti-inflammatory Agent and Biosynthesis of its Primary Metabolite PH132

Abstract

PH46A is the lead of a new class of bioactive indanes with potential for the treatment of inflammatory bowel disease. A qualitative in vitro metabolism profile of PH46A was investigated in preclinical studies, and the rate of its metabolism in cryopreserved hepatocytes prepared from male Sprague Dawley rat, Beagle dog, Cynomolgus monkey and pooled mixed gender human was compared by LC-MS. The clearance order of PH46A was determined to be rat>dog>monkey>human. The species tested which exhibited the closest clearance values to the human was monkey. Following incubation of PH46A with cryopreserved hepatocytes, 5 metabolites were identified, including M1 (keto-PH46), M2 (PH46-OH, PH132), M3 (PH46-diOH), M4 (keto-glucuronide-PH46) and M5 (glucuronide conjugate-PH46). It was found that the human metabolites M2 and M5 were also present in rat, dog and monkey, while M1 was present in all species except monkey. M2 was detected in dog and monkey by LC1 conditions, but only in dog by LC2. Therefore, the metabolism in rat was most similar to human, in terms of the metabolites observed, but all putative human metabolites were present in rat and dog. We further explored the characterization of key metabolite M2 (PH46-OH). Identical PH46-OH was obtained via a bio-catalytic oxidation method from PH46 using rat liver microsomes (RLM) and the human liver P450s (Cyp2D6, Cyp 2C19 and Cyp 4A11) following screening of selectAZyme panels of microbial P450s, recombinant human liver P450s and different microsomes. RLM was used in scale up production and PH132 was isolated and characterized as 4-(((1’S,2’S)-1’,6-dihydroxy-1’,3’-dihydro- 1H,2’H-[2,2’-biinden]-2’-yl)methyl) benzoic acid via LC-MS/MS, NMR and HRMS. The site of hydroxylation on the biindane scaffold was unexpected. The outcomes of these studies have provided valuable information for future pharmacokinetic and in vivo toxicological investigations.