Lead hopping and focused library design applied to the synthesis of activators of the nitric oxide s

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Lead hopping and focused library design applied
to the synthesis of activators of the nitric
oxide sensor- soluble guanylate cyclase

• David Selwood
• The Wolfson Institute for Biomedical Research
• University College London

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The Cruciform Building
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The Wolfson Institute for Biomedical Research
Multidisciplinary research environment including
biological/medicinal chemistry Academic and
collaborative research- Tripos Spin-out
companies- NCE discovery (medicinal chemistry
provider)
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Haem site model
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Soluble Guanylate Cyclase

• Activation of sGC by nitric oxide results in
  conversion of GTP to cGMP
• cGMP is a second messenger with many downstream
  physiological effects
• Effects include smooth muscle relaxation,
  neurotransmission and platelet reactivity

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Soluble Guanylate Cyclase
4 known human isoforms ?1 ?2 ?1 ?2 The ?1?1
dimer forms an active enzyme with high affinity
for NO Other proteins control tissue specificity
No crystal structure
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Chemical Starting Point
Low potency activator Not an NO donor Activity
in tissues gtgt enzyme activity Broad spectrum
PDE and ion channel blocker
YC-1
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New lead
sss
100 molecules
YC-1
benzydamine, CFM1113 Enzyme EC50 1 mM Platelet
10 mM
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SAR exercise
J. Med Chem 2001, 44, 681-693
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  a Relative Enzyme Activity, enzyme activity
relative to compd 3. b Concentration required to
inhibit collagen induced platelet aggregation by
50.
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CoMFA (molecular fields are compared) analysis
of molecules 96 molecules in SAR. R20.79,
Q20.55
H-bond Acceptor favored here
Steric wall here
-Predict activities of novel analogs
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Summary of CoMFA results

• Alignment based on heteroatoms in ring system
• Shows important roles of amine and acceptor in
  ring
• Qualitative only, not really predictive

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EC50 0.18 mM
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SAR study

• Critical importance of NMe2 and HBA
• Improved enzyme potency- Benzydamine 1.02,
• CFM1510 EC50 0.18 mM
• No activity against PDEs
• Platelet activity CFM1571 5-10 mM

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Library designPhysicochemical constraints
clogP gt 3.0 is required for inhibition of
platelet aggregation
Plot of -logIC50 from the platelet assay versus
CMR and clogP
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Constraints for library design

• basic pharmacophore already established
• reactive/ toxic groups eliminated
• Mwt lt 500, LogP gt 2.0 lt 4.0
• 147 amines from ACD
• 50 reagents selected

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Solution Libraries and Scavenger Resins
PS-DIPA HATU, ACN

PS-carbonate
filter
Parlow JJ, Tet. Lett 1997, 38, 7959
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Crude compound
TMU
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purity and yield of amide libraries
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Mitsunobu N alkylations
Tsunoda
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Ion exchange catch and release
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Boronic acid Copper mediated N-arylations
1) PS carbonate 2) silica plug
N2 selective
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Focussed libraries of pyrazoles, indazoles

• No further gains in potency versus enzyme
• Tissue activity 2-10 mM
• Better pharmacokinetics

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Pharmacokinetic parameters (rats) all dosed at
2mg except 1571 dosed at 5mg/kg CFM1949 8hr time
point underestimates F value
Platelet 2.76
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H-bond Acceptor favored here
Steric wall here
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Improve potency?
Search for new leads- selection criteria

• Dimethyl amine
• HBA near an aromatic ring system
• Possible bioisosteric replacements for pyrazole

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Search methods

• 2D searching of LeadQuest
• Similarity searches
• Substructure searches
• 3D pharmacophore searches
• 200-300 molecules in total

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Hit structures
REA 1.63 No platelet activity
0099-57
REA 1.89 No platelet activity
0099-08
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Library synthesis

• amides and ureas
• 1 x 96 library
• Constraints as before
• Mwt lt500
• clogP gt2 lt4

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Selected compounds
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Pharmacokinetics
 
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Overlay of CFM2531 and benzydamine
GASP
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Amides

• Better enzyme potency and platelet activity
• Best activity in compounds of the CFM2351 type
• Improved PK
• Active against collagen and ADP stimulated
  platelet aggregation
• Chemically simpler than pyrazole series
• Molecules in preclinical evaluation as
  anti-thrombotics

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Molecular constraints

• 5HT1B/1D agonists

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Size and lipophilicity
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5HT1B/1D agonists

• Selectivity constraints (5HT2A)
• Size and lipophilicity constraints
• CNS side effects
• Toxic sub-series

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4991
Went through phase 2 development J. Med. Chem.
2001
5HT1B 5HT1D Agonism (5HT is 1.0) 6.95 7.80 0.0
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QSAR?
that drug development by chemical modification
of a seed or lead compound with quantitative
structure activity relationship analysis would be
associated with lower bioavailability, higher
bound fraction and lower urinary excretion.
From an analysis of 222 drugs by Sakaeda Biol.
Pharm. Bull. 24(8) 935940 (2001)
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Drugs should be made as hydrophilic as possible
without loss of efficacy Hansch et al.
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Synthesis with frontiers

• 1 Dont apply strict Lipinski rules for screening
  libraries do allow gt 350
• 2 Define physicochemical constraints for a given
  target/series/indication
• 3 Selectivity constraints
• 4 Avoid obvious toxicity / metabolism problems

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Project Team guanylate cyclase

• Project coordinators Prof Ken Powell, Prof.
  Robert Glen
• Chemistry Dr David Selwood
• Karen Reynolds, Marcel Kling, Maria Goggins, Chi
  Kit Woo, Surinda Chana, David Madge
• Pharmacology Dr. Jeremy Stables
• Jo Budworth, Dick Campbell, Adrian Hobbs, Mark
  Tatlock, David Brummell, Kerry Wheeler, Graham
  Spacey, Sylvie Meillerais.
• Molecular Modeling
• Qian Liu, Grant Wishart
• FUNDING FROM BBSRC AND TRIPOS

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References
YC-1 analogues. . Heterocycles in
press.   Pyrazole amide libraries. Bioorg. Med.
Chem. Lett. 2001, 11, 1089-1092.   5HT1D/1B
agonist 4991W. J. Med Chem 2001, 44,
681-693.   Indazole and pyrazole guanylate
cyclase activators. J. Med Chem. 2001, 44,
78-93.