Discovery of potent, selective 4-fluoroproline-based thrombin inhibitors with improved metabolic stability.
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).
Staas
Donnette D
DD
Department of Medicinal Chemistry, Merck Research Laboratories, West Point, PA 19486, USA. donnette_staas@merck.com
Savage
Kelly L
KL
Sherman
Vanessa L
VL
Shimp
Heidi L
HL
Lyle
Terry A
TA
Tran
Lekhanh O
LO
Wiscount
Catherine M
CM
McMasters
Daniel R
DR
Sanderson
Philip E J
PE
Williams
Peter D
PD
Lucas
Bobby J
BJ
Krueger
Julie A
JA
Lewis
S Dale
SD
White
Rebecca B
RB
Yu
Sean
S
Wong
Bradley K
BK
Kochansky
Christopher J
CJ
Anari
M Reza
MR
Yan
Youwei
Y
Vacca
Joseph P
JP
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
D004791:Enzyme Inhibitors; C431803:fluoro-proline; D011392:Proline; D014357:Trypsin; D013917:Thrombin