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Deploying Automated Workstreams and Computational Approaches for Generation of Toxicity Data Used for Hazard Identification
Robert T. Dunn, II, Ph.D., DABT
SLAS Annual Meeting: ADMET Special Interest Group
January 27, 2016
Presentation Overview
• Toxicity testing: Brief Historical Perspective
• Predictive Safety
• Deploying automated workstreams for key assay platforms:
• Mitochondrial toxicity
• Hepatobiliary transport
• Computational approaches
• Future Directions
2
Classical Approaches to Toxicity Testing
• Labor intensive, costly, and time consuming
• Animal-centric
• 2 test species required for most regulatory submissions
• Rodent and non-rodent
• Uses fully integrated mammalian systems
• Not fully predictive of similar toxicities in human
• Species differences may lead to unexpected toxicities in early human trials
• Species may be more or less sensitive than humans
• Immune-mediated toxicities are poorly predicted using non-human systems
3
The Advent of Predictive Safety Goal: Reduce Late-Stage Safety Related Attrition
• In Vitro Safety assays
• Recent notable successes in earlier hazard identification
• BSEP profiling
• hERG (cardiac ion channel) testing
• Binding very high throughput/early triage
• Functional lower throughput but good correlation to in-vivo drug effects
• Following the Success noted with In vitro ADME assays
• In use for decades
• High throughput
• Simple in vitro systems
• Reduced the number of drug failures due to poor pharmacokinetic properties
4
Predictive Safety
• 3 Examples of assay platforms in use:
• Mitochondrial toxicity: “Mitomics”
• Hepatobiliary transport: BSEP
• Computational Screening: using structural information from the drug and target to predict toxicity
5
Automation Example: Isolated Mitochondrial Function Platform (IMF)
Automated assay initiation and data capture
• Platform is comprised of 21 assays
• 16 test articles/run
• 5 Automation protocols per run
1. Test article dilution (5X in buffer and 10X in water)
2. Automated assay preparation: rat heart mitochondria isolated and placed on robotics deck
3. Stamping diluted 5X TA into 384 well plates
4. Stamping diluted 10X TA into 384 well plates
5. Full 21 assay run
• Total automation run time = ~15hrs (overnight) • FTE Costs: 2 FTE, 2 business days (fully automated)
• FTE Costs: 4 FTE, 5 business days (partially automated)
6
Isolated Mitochondrial Function Profiling Assays Overview
Pathway Assay
TCA Glutamate oxidation
Pyruvate oxidation
Succinate oxidation
Citrate Synthase
Fatty Acid Oxidation Acetyl-CoA oxidation
Acetyl Carnitine oxidation
Butyryl-CoA oxidation
Octanoyl-CoA oxidation
Palmitoyl Carnitine oxidation
Palmitoyl-CoA oxidation
Electron Transport Chain
NADH oxidation
Complex I
Complex II
Complex III
Complex IV
Complex V
Uncoupling Oxidative Phosphorylation
Uncoupling via respiratory burst
Mitochondrial Membrane Potential (MMP)
Mitochondrial Swelling Mitochondrial Permeability Transition (MPT)
Calcium Homeostasis Calcium Loading Potential
Oxidative Stress Aconitase
Dykens and Will, 2007
Qu, Y., et al., 2013
Hamilton-Based Automation Systems
Shakers
Readers
Reader
eSwap
Washer
• Liquid Handler: Hamilton, MicroLab Star
• Robotic Arm: Hamilton, MicroLab eSwap
• Plate Reader Spectrophotometer: Molecular Devices, SpectraMax plus384
• Plate Reader Luminometer: Molecular Devices, LMax
• Plate Reader (2): Multi-Mode: Molecular Devices, M5
• Plate Reader Electrochemiluminescence: MesoScale Discovery (MSD), Sector Imager 6000™
• Robotic Incubator: Thermo Scientific, Cytomat
• Plate washer: Biotek, ELX405
• Plate Shakers (5): Thermo Scientiic, VARIOMAG® Teleshake
8
Front view Rear view
Automation System Control
9
GATE
CPU
Intra-network
MOTHER
CPU
Robotic Arm
Electrochemiluminescence
Shakers
Liquid Handler
Isolated Mitochondrial Function Profiling Dataset Examples
• By comparing potencies, a primary mitochondrial target can be identified
• Compounds can be compared via potencies at the same target or by their collection
of targets
• Results are reported to teams in a standard template that enables prioritization
decisions
Heat maps are generated for each
compound (or series of compounds)
Glutamate
Pyruvate
Succinate
Acetyl CoA
Acetyl Carnitine
Butyryl CoA
Octanoyl CoA
Palmitoyl CoA
Palmitoyl Carnitine
Citrate Synthase
NADH oxidation
Complex II
Complex III
Complex IV
Complex V
MMP
Uncoupling
MPT
Calcium Loading
Aconitase
concentration
Series A Series B
Concentration-response curves are
created for each assay and compared for
each compound Pyruvate Succinate Acetyl Carnitine
Palmitoyl Carnitine
NADH Complex I Complex II Complex III Complex IV
Complex V
Acetyl-CoA
Butyryl-CoA Octanoyl-CoA Palmitoyl-CoA Citrate Synthase
MMP Uncoupling MPT Calcium Loading
Aconitase
Glutamate
Bile Salt Export Pump (BSEP) • Other names include:
• ATP-binding cassette transporter ABCB11
• sister of p-glycoprotein (SPGP)
• Originally discovered in 1995 as SPGP in pig
• Discovered to play a major role in hepatobiliary excretion of conjugated bile salts
• Mutations of ABCB11 gene (in humans) are associated with familial intrahepatic cholestasis
11
Morgan, R. et al (2013) Tox Sci
Bile Acid Trafficking: High Level
OSTβ
OST
Conjugated BA
IBAT Conjugated BA
NTCP
Conjugated BA
Conjugated BA
Po
rta
l ve
in
Ileocyte
Hepatocyte
BSEP Conjugated BA
Cholesterol
Bile acids
Un-Conjugated +
Un-Conjugated +
Un-Conjugated +
MR
P3
MR
P4
MRP2
12
Membrane Vesicle Assay for Transporter Function
- Sf9 insect cells transfected with BSEP/Bsep - BSEP Assay is a highly stable platform - History:
- Manual assay that was run as needed - Transferred to Amgen HTS group to assess 1000’s of compounds/year in-house - Now outsourced to a 3rd party
Inverted membrane vesicle
3H-T
ATP
Test article BSEP
BSEP
3H-T
3H-T
13
Morgan et al, 2010, ToxSci
Comparison of the Css (total)/BSEP IC50 ratio with the BSEP IC50 value alone for 109 marketed or withdrawn drugs
25 µM IC50
10x safety margin
Morgan et al, 2013, ToxSci 14 Human BSEP IC50 (µM)
Off-Target Screening Moving toward computational screens
• Small molecule drugs are developed against specific targets to elicit a desired pharmacological effect
• Receptor proteins
• Enzymes
• Nuclear targets
• However small molecules often interact with other entities
• So called “off-target” effects*
• Off-target effects are identified using HT binding assays
15
*Fan, F., et al., Tox. Sci., 2015
Off-Target Screening
• A retrospective analysis of ~6,000 small molecules tested against 140 off-target entities
• For certain targets, high hit rates were observed
• >30% of compounds had binding activity
• Follow up functional assays were rarely positive
• Low sensitivity and specificity
• Creates additional work and resource drain to follow false hits
• Can we derive a computational approach to prioritize early off-target screening?
16
Off-Target Screening
• Computational platform: “Maestro” by Schrödinger
• The present analysis may be used to:
• Generate SAR for chemistry to “design out” off-target activities
• Build target structure-based predictions
• Build QSAR ligand-based predictions
17
Using assay data to identify “features” GPCR receptor example
18
EC50 data from 235 Amgen compounds
Scaffold summary based on
235 Amgen compounds
Importance analysis
of key functional
groups
R5: most
important for
activities
Off-Target Screening
• To avoid possible “hits” on the GPCR of interest we can virtually screen prior to ordering expensive assays
• Enables Medicinal Chemists to build safer molecules
• Prioritizes investment in cleaner molecular scaffolds
• Avoids unnecessary spend on riskier scaffolds or molecules
19
The Future…
• Using computational tools, build in early screening assays based solely on “in-silico” tools
• Can rule out “risky” chemical structures in virtual space
• Prevents unnecessary investment in assays for molecules that have a low likelihood of advancement
• Share the structural information on safety endpoints with medicinal chemists to feedback into the design of safer molecules
• Construct reference database of chemical structures that may pose a risk for various off-target entities (receptors, enzymes, etc)
20
Acknowledgements • Patrick Cosgrove
• Rocio Hernandez
• Ryan Morgan
• Yuan Chen
• Fan Fan
• Cindy Afshari
• Hisham Hamadeh
• Craig Spruiell
• Paul Santana
• Jeff Lawrence
• Paul Acton
• Nianyu Li
• Padma Narayanan
• Jesse Campbell (Telos Scientific) 21