Chapter 2 Drug screening

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Chapter 2 Drug screening discovery (design)

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6. ??Serendipity
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1.?????????????
1???????????????,????(??????)
Reserpine??????????? ?????,???????????
2???????????,?????????,???
Paclitaxel ????????,???????????,?????????????????
docetaxel?????,??gt???,?????
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3???????
Km10mM
LDL-C ?????????????? ???Penicillium
citrinum????Lovastatin
Ki 1nM
Lovastatin
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statins
Fluvastatin
Pitavastatin(Nisvastatin)
Atorvastatin (Lipitor, best sale)
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???DNA topoisomerase I (????) ??SCLC,???,???
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???? Procaine (1905)
Lidocaine (1943 Synthesis 1949 on market)
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• ??Batroxobin,????????
• ??Tetrodotoxin,????????????
• ??Apamin,???????????????????

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2??????(HTS)
Cons Low hit rate 0.001 Low druggability High
false positive rate
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????Combinatorial chemistry

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??????Combinatorial biosynthesis

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??????Combinatorial biocatalysis

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5-hydroxytryptamine (5-HT)????,???--gt??? 5-HT
receptor isomers 5-HT1, 5-HT2, 5-HT3
Activity(5-HT1) 2 (vs. 5-HT)
Activity(5-HT2) 1/25
Sumatriptan (GSK,2009 expired)Activity(5-HT1)
¼ ?5-HT2, 5-HT3,?????????????
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5-HT3?????
Clebopride Dopamine blocker ?????

• 5-HT3 blocker
• gt clebopride 300 folds
• ?dopamine ??

Metoclopramide Block dopamine 5-HT3 ??,????
granisetron
palonosetron
Ondansetron
Setrons ?????????????
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????????(angiotensin-converting enzyme, ACE)???
Angiotensin I
Bradykinin ?????
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu
Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg
ACE
ACE
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe
Arg-Pro-Pro-Gly-Phe-Ser-Pro
(angiotensin II ??????)
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Hypothetical active site of carboxypeptidase A
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Hypothetical binding of inhibitors to ACE
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ACE????????
captopril
enalapril
Enalaprilat (enalapril???????)
ACE???
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H2??????????

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IIb/IIIa????????

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• ?IIb/IIIa?????????????????????????Arg-Gly-Asp(RGD)
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• ?????????RGD???????,???IIb/IIIa??????????????????
• ?????RGD???????????????????,???????????????

RGD
Sibrofiban
Roxifiban
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4?SOSA
?????????,??????.
Acetazolamide ????
hydrochlorthiazide
Dichlorphenamide
chlorthiazide
bendroflumethiazide ?????
cyclothiazide ?????
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Sulfasomizole?????,????????????????
sulfasomizole
Carbutamide, ???????,?????
Iproniazid?????,????? ????????MAO?????????
phenelzine
Isoniazid ????
iproniazid
????
tranylcypromine
selegiline
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Zaprinast
sildenafil
cGMP????,?????
cGMP?NO????? ??????(ED)
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6???
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More good luck
Penicillin
Chlordiazepoxide (Roche)
cisplatin
carboplatin
oxaliplatin
lobaplatin
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7?Fragment based lead discovery
Fragments
Fragment-based Screening
102 104 RO3 compounds
Fragment grow, link and merge
Target
Full screening Lipinski's RO5
Library Synthesis
High Throughput Screening
(106 compounds, 2M/Screening)
Small is better (sample bigger chemical space,
higher hit rate, higher Ligand Efficiency, less
false positive results, more intuitive to
medicinal chemists)
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Fragment Based Lead Discovery
Target
X-ray / NMR Structures
Fragment Library
Hubbard et al (2007), Curr Topics Med Chem, 7,
1568
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Clinical candidates of fragment-derived compounds
Compound Company Status Target Therapy areas
Vemurafenib Plexxikon/Roche Phase IV B-RAF Melonoma (first FBDD drug on market, FDA approved in 2011)
ABT-263 Abbott Genentech Phase II Bcl-xL Small-cell lung cancer, CML, Lymphoma, Hematological neoplasm Cancer
ABT-869 Abbott Phase II VEGF and PDGF receptor tyrosine kinase family members Non-small-cell lung cancer, etc.
AT-7519 Astex Phase II CDK family members Multiple myeloma cancer
AT-9283 Astex Phase II Aurora kinase family members Flt3 tyrosine kinase, Jak2 tyrosine kinase Abl tyrosine kinase Hematological neoplasm Solid tumor
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Compound Company Status Target Therapy areas
DG-051 deCODE Phase II Leukotriene A4 hydrolase Myocardial infarction
PLX-204 Plexxikon Phase II PPAR alpha, delta, gamma Inflammatory disease Cardiovascular disease Non-insulin dependent diabetes
LY-517717 Lilly Tularik Phase II Factor Xa Thrombosis
NVP-AUY-922 Vernalis Novartis Phase II ATPase Hsp 90 Cancer Solid tumor
ABT-518 Abbott Phase I Gelatinase Metalloprotease-2 Metalloprotease-9 Solid tumor
IC-776 Lilly ICOS Phase I CD11a, ICAM Inflammatory disease, Psoriasis, Autoimmune disease
AT-13387 Astex Phase I Hsp 90 Cancer
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Compound Company Status Target Therapy areas
PLX-4032 Plexxikon Roche Phase I Raf B protein kinase Melanoma Cancer
PLX-5568 Plexxikon Roche Phase I Raf protein kinase Pain, Polycystic kidney disease
SNS-314 Sunesis Phase I Aurora protein kinase Cancer solid tumor
AT-13148 Astex, ICR CRT AstraZeneca Phase I AKT protein kinase Cancer
SGX-393 Lilly (SGX) IND for Phase I Abl tyrosine kinase Cancer
Weak binding between the target and a small
molecule fragment is detected by biophysical
methods, e.g., NMR, SPR or cross-validated by
these two techniques.
Ref Expert Opin. Drug Discov. (2009) 41125
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Fragment Selection
RO3 110 lt MW lt250 300 cLogP lt 2 3 (or
cLogD lt 2 3) 2 lt NO lt 6 logS gt -4.5
TPSA lt 110 Maximize the shape and electrical
diversities (Openbabel Pipeline Pilot) to cover
the chemical space for prototypical
compounds High ligand efficiency LE
RTln(KD)/HAC LE improves from 0.3 to 0.5
during hits to leads (H2L) Final 1K2K
fragment library (Commercial library Maybridge
or Chembridge)
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Most used Fragments Screening methods
Screening method Library size Primary screening Protein amount Pros Cons
Crystallography 1K N gt10mg Low hit rate, low throughput Heavily involved in H2L, LO.
NMR 1K Y gt10mg High hit rate (28, indicate druggability). Ligand based (STD WaterLOGSY) observation in cocktail Less false positive results
ITC 1 2K N g
SPR 2 5K Y mg 3 weeks screening Cross validation with NMR
HCS 5 30K Y require bioassay development for different targets (difficulty in outsourcing) High false positive rate
gt10 fragment derived compounds in clinical phase
II from pharmaceutical companies, e.g., Novartis,
Lily, Abbott, Genentech, Astex, Vernalis, deCODE,
Plexxikon. gt20 fragment derived compounds in
clinical phase I since 2005.
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Hits to leads
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Evolving Fragments - In Practice
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