title: Discovery of potent, selective 4-fluoroproline-based thrombin inhibitors with improved metabolic stability.
abstract: Previous reports from our laboratories described potent tripeptide thrombin inhibitors which incorporate heterocycle-substituted chlorophenyl groups in the P1 position. Using these as lead compounds for further optimization, we identified sites of metabolism and designed analogs with 4-fluoroproline in P2 and cyclopropane-containing side chains in P3 as an approach to reducing metabolism and improving their oral pharmacokinetic performance. The large (300-fold) difference in potency between analogs containing (4R)- and (4S)-4-fluoroproline was rationalized by analyzing inhibitor-enzyme interactions in crystal structures of related compounds and by molecular modeling which indicated that the more potent (4R)-4-fluoroproline isomer stabilizes a proline ring conformation that is preferred for binding to the enzyme. An optimal compound from this work, 41, exhibits high potency in a coagulation assay in human plasma (2xAPTT=190 nM), excellent selectivity versus the digestive enzyme trypsin (K(i)=3300 nM), and excellent oral bioavailability in dogs with moderate clearance (F=100%, CL=12 mL/min/kg).
authors.affiliation: Department of Medicinal Chemistry, Merck Research Laboratories, West Point, PA 19486, USA. donnette_staas@merck.com
authors.forename: Donnette D
authors.initials: DD
authors.lastname: Staas
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Savage
authors.forename: Vanessa L
authors.initials: VL
authors.lastname: Sherman
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Shimp
authors.forename: Terry A
authors.initials: TA
authors.lastname: Lyle
authors.forename: Lekhanh O
authors.initials: LO
authors.lastname: Tran
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Wiscount
authors.forename: Daniel R
authors.initials: DR
authors.lastname: McMasters
authors.forename: Philip E J
authors.initials: PE
authors.lastname: Sanderson
authors.forename: Peter D
authors.initials: PD
authors.lastname: Williams
authors.forename: Bobby J
authors.initials: BJ
authors.lastname: Lucas
authors.forename: Julie A
authors.initials: JA
authors.lastname: Krueger
authors.forename: S Dale
authors.initials: SD
authors.lastname: Lewis
authors.forename: Rebecca B
authors.initials: RB
authors.lastname: White
authors.forename: Sean
authors.initials: S
authors.lastname: Yu
authors.forename: Bradley K
authors.initials: BK
authors.lastname: Wong
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Kochansky
authors.forename: M Reza
authors.initials: MR
authors.lastname: Anari
authors.forename: Youwei
authors.initials: Y
authors.lastname: Yan
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Vacca
mesh_terms: D001665:Binding Sites; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008968:Molecular Conformation; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013917:Thrombin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014357:Trypsin / Q000187:drug effects / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; C431803:fluoro-proline; D011392:Proline; D014357:Trypsin; D013917:Thrombin