DM/PK-guided Lead Optimization A Historical Perspective of ......1/2 administered concomitantly to a...
Transcript of DM/PK-guided Lead Optimization A Historical Perspective of ......1/2 administered concomitantly to a...
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DM/PK-guided Lead OptimizationA Historical Perspective of a Paradigm Shift
Dhiren R. ThakkerSchool of Pharmacy
UNC-Chapel Hill
NEDMDGGerald Miwa Retirement Symposium
April 9, 2007
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Current ParadigmOptimizing Biology and ADME Synchronously
C. Breneman, Krisitn Bennett, J. Bi., M. Song, M. Embrechts– Rensselaer Polytechnic Institute www.drugmining.com
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DM/PK – Research Interface at Glaxo Late 1980’s – Early 1990’s
Preclinical DM/PK Research
Safety Assessment
Clinical DM/PK
Research DM/PK Group
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Ultra Short Acting OpioidRemifentanil -
Rapid Offset of Action Within 5 to 10 minutes after the discontinuation of ULTIVA, no residual analgesic activity is present.
Source: Ultiva® product labelChemical vs. Enzymatic Hydrolytic Rates
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Use of in vitro metabolism screen to identify
“Metabolic Hot Spot”
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Rationale for Incorporating Metabolic Studies Early in the Discovery Program
NH
N
O
HN
NH
O
O
Cl O OHNC
DihydropyridazinoneDHP-1
PhosphodiesteraseInhibition
β-Blockade
Potential metabolic hot spot
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PK of Parent and the Amine Metabolite Following Oral Administration of DHP-1 (5 mg/kg) to Male Beagle
Dog Suggests First Pass Metabolism
ParentAmine
10 20 30 40
Time (hrs)
0.1
1.0
Seru
m C
onc .
(μg/
ml)
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Major Metabolite of DHP-1
NH
N
O
HN
NH
O
O
Cl O OHNC
The Amine Metabolite
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Relative Rates of In Vitro Metabolism for Dihydropyridazinone Leads
10 20 30 40
Incubation Time (min)
50
100
Rem
aini
ng S
ubst
rate
(%)
DHP-1
DHP-2
DHP-3
Improvedmetabolicstability
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Functional Group Contributing to the Metabolic Hot Spot for Dihydropyridazinones
NH
N
O
HN
NH
O
O
Cl O OHNC
NH
N
O
HN
NH
O
O
Cl O OH
DHP-1-like compounds
DHP-2,3-like compounds
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Stabilizing a metabolic hot spot can uncover a secondary hot spot
NH
N
O
HN
NH
O
O
R3R3
R2 O OHNC
R1
(CH2)n
Metabolic Hot Spots
primarysecondary
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Rationally designed in vitro metabolism study, based on a good understanding of likely metabolic pathways, could lead to a
rapid solution
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Background• Phospholipase A-2 Inhibitors
for Inflammatory Diseases (Arthritis, Asthma)
• Glycerophospholipid derivatives
• Major problem – Poor bioavailability in rats
• First pass metabolism was implicated – absorption (permeability) was not a problem (Caco-2 studies, in vivo studies with radiolabeled compounds)
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Likely Metabolic Hot Spots
ROO
OPO
O-
Hydrolysis
Oxidation
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Evidence for Oxidative and Hydrolytic Metabolismof the Lead Compound
Oxidative metabolism
Incubation with liver homogenates + NADPH
Hydrolytic metabolism
Incubation with liver homogenates - NADPH
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In Vitro Metabolism of the Lead Compound by Rat Liver Enzymes and Caco-2 Cells
R O
O
PO O-
O2) fatty acid oxidation1) ω−hydroxylation
LIVER HOMOGENATE
ester + phosphonate cleavageLIVER HOMOGENATE & CACO-2 CELLS
ester cleavage
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Modification of Metabolic Hot Spots
RNO
OPO
O-
F F
FF
F
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In vitro studies do not provide guidance for improving in vivo metabolic clearance
A case for n-in-one in vivo PK studies
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Dutasteride® for BPH
The terminal elimination half-life of dutasteride® is 5 weeks at steady stateFrank Lee et al.
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Profile of the Lead Series
• Alpha-1 antagonistsfor BPH
• Once-a-day dosing• MW: 400-600, basic, clogP
5-7• Well-absorbed• Short half-life• Elimination predominantly by
metabolism• Highly protein bound
N
O
N
O
F FF
SO2NHR
R1
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Dog Microsomal Metabolism Screen
• Poor correlation between in vitro metabolism rate and in vivo T1/2 or CL
• Several possible reasons considered» Sequential metabolism» Phase II metabolism» Protein binding
• Follow-up studies showed that none of these reasons could explain the lack of correlation between in vitroand in vivo studies
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PK of Mixtures?????Origin of Cassette Dosing
The Challenge• Screen over 150 compounds to find a lead
appropriate for once-a-day dosing• The only predictive screen was in vivo PK in dogs• In vivo screen would be too slowThe Solution• In vivo PK studies of mixtures!!!
Judd Berman
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Cassette Dosing “Validation” (5-in-One)
• Five compounds of known CL, VSS, and T1/2administered concomitantly to a dog
• Dose=0.25 mg each compound/kg IV » 1/4th the dose of compounds administered individually
• Plasma samples assayed by LC/MS/MS» Assay for simultaneous analysis of 5 compounds
without interference from any of the metabolites
• Pharmacokinetic parameters compared to those previously obtained
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5-in-One Dog vs. Individual DosingHalf-life comparison
y = 0.8342x + 0.2875R2 = 0.9021
0
1
2
3
4
5
0 1 2 3 4 5Half-life (hr)--5-in-One Dosing
Hal
f-life
(hr)
--Ind
ivid
ual D
osin
g
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N-in-one in vivo screen worked
• Good correlation in PK parameters.• Useful for ranking compounds• 125 compounds screened in 10 dog studies
in 2 months.• Approximate structure-PK relationships developed• Compounds with a wide range of T1/2 could be
identified from which leads could be selected for further evaluation
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Half-lives of 125 Compounds in Dogs as Determined by Cassette Dosing
0
2
4
6
8
10
12
14
16
18H
alf-l
ife (h
)
N
O
N
O
F FF
SO2NHR
R1
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Acknowledgments• Kim Adkison• Charley Boehlert• Ken Brouwer• Lawrence Gan• Kathy Halm• Frank Lee• Diane Levesque• Doug Rickert• Archie Sinhababu• Bob St. Claire• Cosette Serabjit-Singh• Tim Tippin• Steve Unger• John Walsh• Souzan Yanni
• Judd Berman • Paul Feldman• Steve Frye• Jeff Leighton• Joel Shaffer• Elizabeth Sugg
• Peter Myers• Leslie Hudson
Gerald Miwa
DM/PK-guided Lead Optimization�A Historical Perspective of a Paradigm Shift��Current Paradigm�Optimizing Biology and ADME SynchronouslyDM/PK – Research Interface at Glaxo �Late 1980’s – Early 1990’sUltra Short Acting Opioid�Remifentanil - Rationale for Incorporating Metabolic Studies Early in the Discovery ProgramPK of Parent and the Amine Metabolite Following Oral Administration of DHP-1 (5 mg/kg) to Male Beagle Dog Suggests First Pass Major Metabolite of DHP-1Relative Rates of In Vitro Metabolism for Dihydropyridazinone LeadsFunctional Group Contributing to the Metabolic Hot Spot for DihydropyridazinonesStabilizing a metabolic hot spot can uncover a secondary hot spot BackgroundLikely Metabolic Hot Spots In Vitro Metabolism of the Lead Compound by Rat Liver Enzymes and Caco-2 CellsModification of Metabolic Hot Spots Dutasteride® for BPHProfile of the Lead SeriesDog Microsomal Metabolism ScreenPK of Mixtures?????�Origin of Cassette DosingCassette Dosing “Validation” (5-in-One)5-in-One Dog vs. Individual Dosing�Half-life comparisonN-in-one in vivo screen workedHalf-lives of 125 Compounds in Dogs as Determined by Cassette DosingAcknowledgments