title: A proposed screening paradigm for discovery of covalent inhibitor drugs.
abstract: The in vitro and in vivo preclinical ADME properties of 10 clinically late stage or marketed covalent inhibitors were evaluated in order to define advancement criteria for discovery of future drugs in this arena. Our studies revealed the following: After incubating with S9 fractions for 30 minutes, the rat and human in vitro stability for these compounds ranged from 1% to 100%. The blood stability ranged from 30% to 100%. There was a broad range of CYP inhibition with prevalence for time-dependent inhibition of at least one enzyme. The Caco-2 permeability (A→B) ranged from negligible (0.6 x 10(-6) cm/s) to highly permeable (31 x 10(-6) cm/s) and the efflux ratio also varied widely (0.2-30). Most of the compounds were highly protein bound in both rat and human with binding ≥ 90%. Rat plasma clearance for the 10 compounds ranged from slow (11 mL/min/kg) to very rapid (350 mL/min/kg). The Vss ranged from low (0.67 L/kg) to very high (115 L/kg). MRT's also ranged from short (0.5 hr) to long (7.4 hr). The oral exposures also showed a very broad range with CMax's ranging from 0.01-77 μM and exposure levels ranging from 0.03-106 μM.hr. In conclusion, the wide range in in vitro and in vivo ADME data makes these particular ADME assays non-discriminatory in the selection of promising compounds. In our opinion, non-traditional assays such as target mass modification, target confirmation by amino acid sequencing, cellular target occupancy, and target turnover rate data in combination with the pharmacokinetic profiles are the critical considerations for progression of irreversible compounds in early discovery.
authors.forename: Mehran F
authors.initials: MF
authors.lastname: Moghaddam
authors.forename: Yang
authors.initials: Y
authors.lastname: Tang
authors.forename: Zhihong
authors.initials: Z
authors.lastname: O'Brien
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Richardson
authors.forename: Maria
authors.initials: M
authors.lastname: Bacolod
authors.forename: Prasoon
authors.initials: P
authors.lastname: Chaturedi
authors.forename: Julius
authors.initials: J
authors.lastname: Apuy
authors.affiliation: Department of Drug Metabolism and Pharmacokinetics, Celgene Corporation, 10300 Campus Point Dr, Suite 100, San Diego, CA 92121, USA. mmoghadd@celgene.com.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Kulkarni
mesh_terms: D061605:Administration, Intravenous; D000284:Administration, Oral; D000818:Animals; D018938:Caco-2 Cells; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D055808:Drug Discovery / Q000379:methods*; D004355:Drug Stability; D057166:High-Throughput Screening Assays; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007527:Isoenzymes; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D008954:Models, Biological; D010539:Permeability; D011485:Protein Binding; D051381:Rats; D013379:Substrate Specificity; D057188:Workflow
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System