Successes and Evolving Challenges Posed by the ... .pdf · Successes and Evolving Challenges Posed by the Comprehensive In Vitro Proarrhythmia (CiPA) ... CiPA 2015 Refinement

Successes and Evolving Challenges Posed by the Comprehensive In Vitro Proarrhythmia (CiPA) Initiative

Gary Gintant

Dept. Integrative Pharmacology

Integrated Sciences and Technology

AbbVie

For the CiPA Initiative

Outline

• Introduction and Rationale for CiPA Definition and Overarching Goals Scientific Underpinnings

• Components: Progress and Challenges Ionic Currents In Silico Reconstruction Stem-Cell Derived Cardiomyocytes Compound Selection/Regulatory

• Paths Forward and Conclusions

2 CiPA – SPS Webinar April 16, 2015 © 2015

CiPA: Comprehensive In Vitro Proarrhythmia Assay

Goal: Develop a new in vitro paradigm for cardiac safety evaluation of new drugs that provides a more accurate and comprehensive mechanistic-based assessment of proarrhythmic potential

- focus on proarrhythmia (not QT prolongation) to improve specificity compared to preclinical hERG and clinical TQT studies

How? - Define drug effects on multiple human cardiac currents, - Characterize integrated electrophysiologic response using in silico reconstructions of human ventricular electrophysiology, - Verify effects on human stem-cell derived ventricular myocytes


hERG Is Insufficient to Predict Delayed Repolarization

REPOLARIZATION: integrated response, multiple currents

DELAYED REPOLARIZATION: reduced NET outward current

- balance of outward repolarizing current (iKr/hERG) vs. inward depolarizing plateau current (Na or Ca)

Present (iKr, hERG) focus results in premature and unwarranted drug attrition, misclassification of risk


Drug Effects on Multiple Cardiac Currents Must Be Considered.

5

– Lack of selectivity of drugs on cardiac currents (ICaL vs. hERG)

– Effects on multiple channels (multi-channel block) define overall drug response (e.g., verapamil)

CiPA – SPS Webinar April 16, 2015 © 2015

Cellular Proarrhythmia: Abnormal Emergent Responses That Affect Repolarization (not simply hAPD or hQTc)

Focus on proarrhythmic vulnerability: impaired cellular repolarization, electrical instability and l

- In extreme form, instability manifest as early after-depolarizations (EAD’s) associated with initiation of proarrhythmia

- Proarrhythmic liability (an integrated, emergent effect) manifest on a cellular level with human responses

Impaired repolarization used to rank proarrhythmic risk based on comparisons with known clinical TdP drugs


Comprehensive In Vitro Proarrhythmia Assay: Four Overall Components

Evaluation of Clinical Drugs for

Proarrhythmic TdP Liability

7

Drug Effects on Multiple

Human Cardiac Currents

In Silico Reconstruction

Human Ventricular

Cellular Electrophysiology

In Vitro Effects Human Stem-Cell Derived Ventricular Myocytes

High Risk

Inter- mediate

Risk

Low Risk

Preclinical ECG & Phase 1 ECG Studies: Complementary Data CiPA – SPS Webinar April 16, 2015 © 2015

Core Component I. Human Ionic Currents, Voltage Clamp Studies, Heterologous Expression

- Ion Channel Working Group (SPS): develop protocols to assess drug effects on currents

- Standardized voltage clamp protocols to establish best practices, reduce bias and variability, allow comparisons of automated platforms across laboratories

- Information on kinetics-, voltage- and use-dependence to parameterize models for (essential for hERG)

Robust characterization of drug effects on human currents enables in silico reconstructions of integrated responses


- In Silico Group (FDA): Drug effect multiple human currents integrated to describe cellular electrophysiologic effects

- Define changes in repolarization instability, early afterdepolarizations, reduced upstroke velocity using select model (modified O’Hara-Rudy model considered)

- Ranking of integrated responses compared with clinical examples of different TdP liabilities

Core Component II: Computer Reconstructions of Drug Effects on Human Cellular Electrophysiology

9

+ =


Core Component II. Computer Reconstructions: Progress (FDA Lead)

Initial Test Case: d,l Sotalol (known torsadogen) - Recognized for QT prolongation and TdP

- O’Hara-Rudy model recapitulates delayed repolarization in human ventricular tissues based on IC50 values for hERG, Cav1.2 and Nav1.5 (Kramer et al. (2013)

- Not replicated by Grandi or ten Tusscher in silico models

- EAD’s with prominent iKr/hERG block not generated in either Ten Tusscher or Grandi in silico models


Core Component III: In vitro Effects, Human Stem Cell-Derived Ventricular Cardiomyocytes

- Myocyte Group (HESI): Verification of ion channel effects and in silico reconstructions with well characterized human stem-cell cardiomyocytes

- Inform on repolarization effects not anticipated from other approaches - channel modulation - emergent effects - physiologic conditions (37oC) - MEA & VSO approaches

11

Vo

ltag

e-S

en

siti

ve

Dye

(V

SO)

Mic

ro-E

lect

rod

e

Arr

ay (

MEA

)


Core Component III. Cardiomyocytes- Microelectrode Array (MEA) Pilot Study


12 site Pilot Study

Core Component III. Stem-cell Derived Cardiomyocytes: Progress

Test Protocol: - Confluent monolayers prepared according to manufacturer instructions - 10-30 minutes drug exposure - Individual or sequential (cumulative) exposure - 4 concentrations; 3 wells/conc. - Quality controls: stable baseline spontaneous rate, stable conduction across monolayers, post-dose signal quality

8 compound test set (blinded) - 4 “Calibration cmpds” to test assay sensitivity: IKr, IKs, INaF, ICaL - 4 “Test cmpds”: preliminary test set, high and low risk examples

Prelim. analysis; concordance across VSO & MEA; review ongoing

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"Test" Cmpds

Flecainide

Moxifloxacin

Quinidine

Ranolazine

= "High Risk" Category

= "Low Risk" Category

= Not Categorized, Channel Specific

Mexiletine (iNa)

Nifedipine* (iCaL)

E-4031 (iKr)

JNJ303 (iKs)

Pilot Studies - Stem Cell Derived Cardiomyocytes"Calibration" Cmpd & Current


Core Component III. Stem-cell Derived Cardiomyocytes: Progress

2 approaches - Multi-electrode arrays (MEA-8 sites) - Voltage-sensing optical (VSO-4 sites) - Dyes or integral sensing proteins

• 3 Myocyte Vendors - CDI, Axiogenesis, (Stanford University) - Myocytes prepared to vendor specifications; site familiarity

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MEA VSO


Pilot MEA Study: Trends Across 4 sites, 3 compounds, & 2 cells. Compounds 3, 1, 5

Sites A & B – Cells 1 & 2 – Plate 1

“3”

“1”

“5”

15

Cell A

Cell B

Core Component III. Stem-cell Derived Cardiomyocytes. Voltage sensitive optical probes (VSO) Study

Cell providers:

Assay companies/groups:

Voltage sensor

Detector

QuasAr1 (protein)

CMOS camera

FluoVolt (small molecule)

CMOS camera

Di-4-ANEPPS (small molecule)

CMOS camera

Di-4-ANEPPS (small molecule)

Photomultiplier

B I O S C I E N C E S

CiPA – SPS Webinar April 16, 2015 © 2015 16

VSO: Endpoints Minimum end-points include measures of repolarization timings and arrhythmia detection.

Primary end points:

• Spontaneous beat rate and regularity (adult human 1s)

• Action potential rise time (10-90%) (adult human 2-2.5ms)

• APD at 30%, 50% & 90% (adult human 200ms, 220, 270)

• AP triangulation index (APD90-APD30) (adult human 70ms)

• Incidence of early after depolarisation (EADs)

Rate sensitivity of the above parameters (paced only)

200ms

Baseline

Drug


C1_Baseline

200ms

C1_Drug

200ms

Baseline

Drug

200ms

Baseline

Drug

200ms

Baseline

Drug

100

200

300

400

500

600

700

AP

D3

0 (

% o

f b

as

eli

ne

)

Vehicle (DMSO)

Drug

[Drug]

C1 C2 C3 C4

100

200

300

400

500

600

700

*

*

AP

D5

0 (

% o

f b

as

eli

ne

)

Vehicle (DMSO)

Drug

[Drug] C1 C2 C3 C4

100

200

300

400

500

600

700

***

***

AP

D9

0 (

% o

f b

as

eli

ne

)

Vehicle (DMSO)

Drug

[Drug] C1 C2 C3 C4

Examples: Di-4-ANEPPS as Voltage Sensor


CiPA Pilot Myocyte Workstreams: Opportunities to Assess Experimental Variability

19

CiPA Stem Cell Cardiomyocyte Pilot Studies MicroElectrode Array (MEA) Voltage-Sensing Optical (VSO)

CiPA Myocyte Workstream Multiple Multiple MEA Multiple

Volunteer List Replicates, Stem Cells Platforms Type Stem Cells

1 Myocyte Type Across 1 Platform 1 Myocyte Type Indicator Across 1 Platform

MES Site 1

MEA Site 2

MEA Site 3

MEA Site 4

MEA Site 5

MEA Site 6

MEA Site 7

MEA Site 8

MEA Site 9

MEA Site 10

VSO Site 1

Di-4-ANEPPS

VSO Site 2

Di-4-ANEPPS

VSO Site 3

QuasAr1

VSO Site 4

FluoVolt


Clinical Foundations: Compound Selection & Clinical Regulatory Group

• Compound Selection/Regulatory (CSRC): Categorization available drugs for proarrhythmic risk: - High, Intermediate, Low risk categories - Evaluate clinical data for proarrhythmia - Overall experience, history, patient population, pharmacokinetics - 29 drugs nominated for model development and verification

• Input from clinical developers/regulators - Validation & acceptance of CiPA paradigm

• Define Phase 1 ECG Verification Efforts

20

TdP Risk


Provides “Gold Standard” for Calibrating CiPA Studies

Criteria for Compound Selection

- No prominent proarrhythmic / active metabolites

- Good solubility

- Defined cellular electrophysiology

- Ranking compounds based on clinically demonstrated torsadogenic risk and proarrhythmic incidence - published reports, FDA AERS database, additional data sources, expert opinion

- Compounds grouped into ‘high’, ‘intermediate’ and ‘very low’ (i.e., none) risk categories - Intermediate risk compounds grouped into one category - ‘Very low’ risk no discernable risk

- Culled from much larger list of candidates 21 CiPA – SPS Webinar April 16, 2015 © 2015

Compounds List:

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CiPA Redfern CiPA Redfern CiPA Redfern

HIGH RISK Category INTERMEDIATE RISK Category LOW RISK Category

Azimilide 1 Astemizole 2 Diltiazem 5

Bepridil 3 Chlorpromazine - Loratadine 5

Dofetilide 1 Cisapride 2 Metoprolol -

Ibutilide 1 Clarithromycin 4 Mexiletine -

Quinidine 1 Clozapine - Nifedipine 4

Vandetanib - Domperidone 4 Nitrendipine 5

Methadone - Droperidol - Ranolazine -

D,l Sotalol 1 Terfenadine 2 Tamoxifen 5

Pimozide 3 Verapamil 5

Risperidone 5

Ondansetron -


Group Efforts Against Timelines

Parties Involved:

Cardiac Safety Research Consortium: Cmpd Selection Team FDA: In Silico Working Group ILSI-HESI: Myocyte Stem Cell Working Group Safety Pharm. Society: Ion Channel Working Group

J-iCSA – 2015(?)

Regulators: FDA, Health Canada, EMEA, Japan Japanese Safety Pharmacology Society Academic Contributors Vendors and Suppliers

Timelines: Progress Review: 1Q 2016


Future Activities: CiPA 2015

Refinement-Evaluations of Voltage Clamp Protocols

Preliminary test of In Silico Reconstructions Based on Ionic Current Studies

Assessment of CiPA Stem Cell Cardiomyocyte Pilot Study Results - Planning / Initiation of Validation Studies - Define set of validation compounds - Consult/collaborate/compare with J-iCSA

Further discussion with Regulators - Expectations of CiPA Package of regulators, industry - Relation to eQT Clinical Efforts - How to integrate in vitro/in silico preclinical results with emerging clinical eQT approaches


CiPA: proarrhythmic risk assessment based on mechanistic understanding of integrated, cellular emergent drug effects on multiple human cardiac currents

Expectations: - reduce unwarranted attrition early candidates - enable rapid progression of low risk TdP drugs to phase 1 studies (and confirmatory clinical ECG findings)


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Successes and Evolving Challenges Posed by the ... .pdf · Successes and Evolving Challenges Posed by the Comprehensive In Vitro Proarrhythmia (CiPA) ... CiPA 2015 Refinement