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The West coast regional safety pharmacology society meeting update: Filling translational gaps in safety assessment
Journal of Pharmacological and Toxicological Methods 98 (2019) 106582
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Review
The West coast regional safety pharmacology society meeting update: Filling translational gaps in safety assessment
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Najah Abi-Gergesa, , Carrie McMahonb, Hugo Vargasc, Philip Sagerd, Ray Chuic, Dale Stevense, Jonathan Davilaf, Johanna R. Schaubg, Joseph C. Wuh, Carlos del Rioi, Chris Mathesa, Paul E. Millera, Leigh Ann Burns-Naasb, Andre Ghettia a
AnaBios Corporation, San Diego, CA 92109, USA Gilead Sciences, Inc., Foster City, CA 94404, USA c Amgen Inc., Thousand Oaks, CA 92320, USA d Stanford University, School of Medicine, Stanford, CA 94305, USA e Genentech Inc., South San Francisco, CA 94080, USA f NeuCyte Labs, Sunnyvale, CA 94089, USA g Pliant Therapeutics, Inc., South San Francisco, CA 94080, USA h Stanford University School of Medicine, Stanford Cardiovascular Institute, Stanford, CA 94305, USA i MyoKardia, Inc., South San Francisco, CA 94080, USA b
A R T I C LE I N FO
A B S T R A C T
Keywords: Drug discovery Predictivity Safety pharmacology Translational science
The Safety Pharmacology Society (SPS) held a West Coast Regional Meeting in Foster City, CA on November 14, 2018 at the Gilead Sciences Inc. site. The meeting was attended by scientists from the pharmaceutical and biotechnology industry, contract research organizations (CROs) and academia. A variety of scientific topics were presented by speakers, covering a broad variety of topics in the fields of safety risk assessment; from proarrhythmia and contractility risk evaluation, to models of heart failure and seizure in-a-dish; and discovery sciences; from stem cells and precision medicine, to models of inherited cardiomyopathy and precision cut tissue slices. The present review summarizes the highlights of the presentations and provides an overview of the high level of innovation currently underlying many frontiers in safety pharmacology.
1. An introduction to the meeting content Drug developers rely on safety pharmacology to identify and predict, prior to clinical trials, adverse effects of novel drugs on major organ systems, including cardiovascular, central nervous, respiratory, renal and gastrointestinal (Bass, Hombo, Kasai, Kinter, & Valentin, 2015; Hamdam et al., 2013; Pugsley, Authier, & Curtis, 2008). The implementation of ICH S7A/S7B guidance (Anon 2000; 2005a) originally drafted by the International Conference on Harmonization made safety pharmacology an integral part of preclinical drug discovery and established rigorous safety standards for drug candidates entering clinical studies (Cavero, 2009). Next, the introduction of exploratory safety pharmacology has resulted in early hazard detection and mitigation (Cavero, 2009; Stark & Steger-Hartmann, 2016; Valentin et al., 2018). For example, the models currently used to evaluate the potential of drug-induced delay of ventricular repolarization are effective in reducing the number of clinical candidates associated with QT
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prolongation (Ewart et al., 2014; Park et al., 2018; Pollard et al., 2017; Valentin et al., 2009; Vargas et al., 2015; Wallis, 2010). However, the concordance between preclinical and clinical cardiovascular assessment for changes in heart rate and blood pressure, pro-arrhythmia risk, is still poor (Ewart et al., 2014; Gintant, Sager, & Stockbridge, 2016; Sager, Gintant, Turner, Pettit, & Stockbridge, 2014). Similarly, the prediction of drug-related risks on central nervous and respiratory systems remains a significant challenge (Mead et al., 2016; unpublished data, IQ Consortium nonclinical to clinical translational database). Therefore, translational gaps exist and new validated collaborative approaches, preferably human-based and applicable to early stages of preclinical development, are needed to ensure a high level of confidence in their predictive value. Partnerships across pharmaceutical companies and between pharmaceutical companies and regulators could greatly benefit the validation of these new approaches. The Safety Pharmacology Society (SPS), which holds an annual global meeting, also supports regional SPS meetings (Pannirselvam
Corresponding author at: 3030 Bunker Hill St., Suite 312, San Diego, CA 92109, USA. E-mail address: [email protected] (N. Abi-Gerges).
https://doi.org/10.1016/j.vascn.2019.106582 Received 6 May 2019; Accepted 7 May 2019 Available online 09 May 2019 1056-8719/ © 2019 Elsevier Inc. All rights reserved.
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liability of test articles” (ICH S7B and E14 Q&A Endorsed by the ICH Assembly on 15 November 2018; Anon, 2018). Being able to directly assess the effects of drugs in adult human primary cardiomyocytes with high sensitivity and specificity may simplify the pro-arrhythmic assessment and require less ion channel testing and in silico modelling (Nguyen et al., 2017). The lack of ideal operator characteristics in the iPSC-CMs may be due to the fact that these cardiomyocytes are not fully mature with the full range of adult ion channel expression (van Meer, Tertoolen, & Mummery, 2016; Robertson, Tran, & George, 2013). This is supported by the observations that adult human primary cardiomyocytes culled from ethically consented human donor hearts (Nguyen et al., 2017) have been shown to be highly predictive in assessing the known pro-arrhythmic risk of individual drugs, and consequently they are now a core element of the ICH S7B Implementation Working Concept paper that aims to revise the S7B guidance (Anon, 2018). CiPA is currently being assessed by the ICH S7B and E14 Implementation Working Group for possible inclusion in S7B to inform regulatory decision making (Anon, 2018). Finally, Dr. Sager concluded that he expects CiPA to undergo further development and modifications over time as science and exciting advances in other approaches evolve.
et al., 2017). The 2018 West Coast SPS Regional Meeting, which was organized at Gilead Sciences Incorporated in the San Francisco Bay Area, was aimed at discussing strategies to address translational gaps in the fields of drug safety assessment and discovery sciences. The meeting covered several efforts in translational science being conducted across the West Coast pharmaceutical/biotechnology industry as well as in academic institutions. It highlighted translational scientific advances in different areas, i.e., cardiac safety & pharmacology, cardiovascular toxicology, translational science, genomics and precision medicine, seizure, liver fibrosis, heart failure and cardiomyopathy, human primary cells and tissues, and human stem cells. This meeting report outlines the content presented and debated at the meeting. 2. Safety risk assessment 2.1. Mechanistic approaches to assessing the pro-arrhythmic potential of drugs (Philip Sager, Stanford University) Dr. Sager launched the discussion of cardiac safety risk assessment by presenting an overview on mechanistic approaches to assess the proarrhythmic potential of novel drugs. He first introduced the core elements of the ICH S7B guideline, which focuses on the preclinical measurement of the hERG-related cardiac ion channel current and the animal and human assessment of QTc prolongation (Anon, 2005a), to assess a drug's proclivity to cause torsade de pointes (TdP). While this strategy has been effective in that drugs are not being approved with unanticipated pro-arrhythmic liability, it has become clear that there are serious shortcomings of this approach (Sager et al., 2014). These include a relatively low positive predictive value of hERG block or QTc prolongation to identify a drug as actually being pro-arrhythmic. This has resulted in the premature termination of drugs that reduce hERG and prolong the QTc interval, but have a low arrhythmic risk and would have had favorable benefit to risk ratios. This negative impact on the drug development pipeline has potential downstream unfavorable implications for public health. Dr. Sager stressed that over the last 19 years since ICH E14 (Anon, 2005b) and ICH S7B were finalized in 2005, there has been considerable insight into the mechanism of TdP and the primary role that early afterdepolarizations play in the genesis of TdP. This understanding calls for a mechanistic approach to assessing a drug's proclivity to cause TdP, independent of effects on hERG and the QTc. There are important outcomes of being able to characterize a drugs pro-arrhythmic potential, instead of relying on surrogates without high positive predictive values. These include reducing the premature termination of drugs with favorable benefit to risk profiles, making development more straightforward with benign labelling of drugs with a low pro-arrhythmic risk (despite modest QTc prolongation), using preclinical assays to improve candidate selection, move the bulk of pro-arrhythmic assessment to the discovery phase, and permit earlier removal of regulatory uncertainty. Additionally, such an approach should permit the revision of current labels for some drugs, removing QT risk language. Next, Dr. Sager reviewed the Comprehensive In Vitro Pro-arrhythmia Assay (CiPA) as one such approach. It relies on testing the effects of a drug on hERG, and the L-type Ca and late inward sodium currents (with additional testing of the slowly activating delayed rectifier current and the peak inward sodium current in selected situations) and determining a pro-arrhythmic score using in silico cardiomyocyte action potential modelling (Gintant et al., 2016; Sager et al., 2014). Unanticipated effects in humans, for example due to human specific metabolites or pharmacokinetic differences, can be assessed by evaluating ECG's in Phase 1 clinical study. Human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) experiments were performed as part of CiPA, and their ability to correctly predict the pro-arrhythmic likelihood of low-risk drugs did not show high specificity (Blinova et al., 2018), but still may “provide insights into the relative pro-arrhythmic
2.2. Pro-Arrhythmia evaluation in a dog model of heart failure: Augmenting the nonclinical tool box (Ray Chui, Amgen, Inc.) In his opening slides, Dr. Chui reiterated the fact that drug-induced ventricular arrhythmias can be induced by various pharmacological agents, leading to an arrhythmic emergency that can culminate in sudden cardiac death. Regulatory guidance on QT prolongation (ICH S7B/E14; Anon, 2005a,b) has sought to address these concerns, however a considerable volume of data has demonstrated that QT liability is not synonymous with pro-arrhythmic risk. In light of the complexity of this issue, numerous models have been proposed. Then, Dr. Chui emphasized the importance to evaluate the proarrhythmic potential of the well-characterized canine right ventricular tachypacing (VTP) induced heart failure model. This highly reproducible model has demonstrated mechanical, structural and neurohormonal alterations comparable to human dilated cardiomyopathy, manifesting as reduced cardiac reserve and function, as well as a prolonged QT phenotype (Moe & Armstrong, 1999; Yarbrough & Spinale, 2003). For example, QT interval data were found to be 321 ± 46 ms (n = 47) and 280 ± 24 ms (n = 240) in VTP and normal dogs anesthetized with chloralose anesthesia, respectively (values are mean ± SD). As such, this model satisfies several physiological criteria for enhanced sensitivity to arrhythmia induction. Data with dofetilide, a well-known torsadogenic drug, shows exaggerated impacts on QT, JTpeak and Tpeak-Tend intervals (Boulay et al., 2019; Johannesen et al., 2014, 2016; Vicente et al., 2015). Dr. Chui proposed that follow-up studies may include autonomic modulation and electrophysiological stress testing as part of a more extensive characterization. In conclusion, Dr. Chui suggested that continuing investigation into this model, along with other cardiovascular disease models, is urgently warranted, as a means to augment pro-arrhythmic risk assessment in preclinical safety. 2.3. Preclinical human contractility safety testing (Najah Abi-Gerges, AnaBios Corporation) Dr. Abi-Gerges presented an overview on myocardial contractility and its modulation by drugs. Drug-induced changes in contractility can lead to serious adverse events including heart failure; Dr. Abi-Gerges reviewed the current translational challenges in predicting the inotropic potential of drugs and stressed the urgent need for a predictive human cardiomyocyte-based model for reliable detection of inotropic toxicity early in the discovery process. In this context, significant excitement has been generated by the recent development of methods that 2
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parameters. Echocardiography (Day 5) showed preservation of systolic function, and increased plasma biomarkers correlated with previously confirmed histopathological findings. To determine a potential screening assay for the drug-related adverse cardiovascular effects in vivo, an ex vivo human primary cardiomyocyte assay (Nguyen et al., 2017) was performed. Results of the assay predicted that the compound had the potential to induce negative inotropy, negative lusitropy, and an absence of structural cardiotoxicity with a potential for aftercontraction, a pro-arrhythmia marker. Taken together, the compound was characterized in vivo with a steep dose response curve with a unique cardiotoxicity profile leading to its discontinuation from development. Additional follow-up ex vivo human primary cardiomyocyte and tissue assays are ongoing to elucidate potential mechanisms responsible for driving the tachycardia and/ or contractility effects.
enable the procurement and experimental interrogation of donor heart preparations, like adult human primary cardiomyocytes (Nguyen et al., 2017; Page et al., 2016; Qu et al., 2018). These cells exhibit the expected physiological and pharmacological properties (Nguyen et al., 2017). To establish the clinical relevance of a contractility model based on the use of isolated adult human cardiomyocytes, a panel of 50 reference drugs with known clinical outcomes was tested. This reference set included both positive as well as negative inotropes, spanning diverse mechanisms of action. Cardiomyocyte contractility was measured using non-invasive bright-field imaging, in conjunction with electrical field stimulation. The data demonstrated a high degree of correlation between the cellular in vitro model and the clinical data. In addition, this experimental model provides valuable insights into the specific mechanism of action for compounds that exhibit inotropic effects. Dr. Abi-Gerges also discussed data related to the cardiotoxicity of specific Tyrosine Kinase Inhibitors (TKI). While TKIs can provide effective treatment to cancer patients, they have been associated with cardiotoxicity that manifests as reduced ejection fraction (Mellor, Bell, Valentin, & Roberts, 2011). In this study, the effects of 8 TKIs (4 known to induce reduction in cardiac contractility in patients and 4 without contractility risk) were evaluated using human cardiomyocyte contractility-based model. Cardiomyocyte contractility was significantly reduced by all known toxic TKIs, while the TKIs with no known clinical contractility risk did not affect cardiomyocyte function. Given the potential of adult human primary cardiomyocytes for (i) allowing an integrated evaluation of all human cardiac targets, (ii) predicting clinical outcomes and (iii) their compatibility with screening platforms, Dr. Abi-Gerges advocated for the use of adult human primary cardiomyocytes in early contractility and safety screening. In this strategy, drugs not associated with a contractility risk could progress to next discovery stage, while drugs associated with risk would require medicinal chemistry-based improvements. The adult human primary cardiomyocyte-based screening, once implemented, could be expected to accelerate preclinical drug development, by providing highly relevant and predictive data to enable focusing of resources on the most promising leads.
2.5. Nonclinical cardiovascular assessment of small molecule DNA-1 (Dale Stevens, Genentech, Inc.) Mr. Stevens started his presentation by confirming Genentech's commitment is to be an industry leader in the advancement of methods to reduce, replace, and refine (3Rs) the use of animals in research (Tornqvist et al., 2014). As such, Genentech department of Safety Assessment continues to find opportunities to refine nonclinical study designs and testing strategies to collect the most meaningful nonclinical data. Then, Mr. Stevens presented DNA-1, which is a small molecule currently being developed for an oncology indication. As part of the Investigational New Drug (IND) enabling toxicology studies, refinements to the cynomolgus monkey 28-day repeat-dose pivotal toxicology study were made to collect additional cardiovascular data by instrumenting recovery animals (vehicle control & middle dose groups only, N of 4 per group) with DSI Physiotel™ telemetry implants (Data Sciences International) to measure electrocardiographic and hemodynamic endpoints after repeated dosing. This was performed in addition to the conduct of a standard double Latin square cynomolgus monkey cardiovascular telemetry study. Although a double Latin square cardiovascular telemetry study provides greater statistical power to assess potential test article related effects, inclusion of telemetry cardiovascular assessment in a repeat-dose study offers the opportunity to assess for potential cumulative effects. Whilst no cardiovascular changes were noted in the double Latin square cardiovascular telemetry study after a single dose, statistically significant (p value of 0.01) dose-related increases in RR interval and decreases in heart rate were observed in DNA-1 treated cynomolgus monkeys as compared to vehicle control treated animals after 4-weeks of dosing in the 28-day repeat-dose pivotal toxicology study. Changes were considered within the normal physiological range for cynomolgus monkeys and not adverse. Translation of these cardiovascular effects were seen with the Phase 1 trial with Grade 1 bradycardia observed in 5 of 28 patients. Patients were asymptomatic. The inclusion of telemetry implanted recovery animals is not standard for small molecule IND enabling pivotal toxicology studies at Genentech, but this practice may provide meaningful data to help inform the clinical development plan of early development stage molecules and should be considered as a 3Rs refinement.
2.4. Cardiovascular risk assessment in radio telemetry-instrumented male cynomolgus monkeys following oral administration of a multi-kinase inhibitor (Carrie McMahon, Gilead Sciences, Inc.) Dr. McMahon introduced the beneficial anti-tumor effect of small molecule kinase inhibitors, often associated with a variety of cardiotoxicities (Zamorano et al., 2016), which appear to be mediated through a range of mechanisms (Doherty et al., 2013; Sharma et al., 2017) driven in some cases by the primary pharmacology while in others, off-target effects have been implicated (Force & Kolaja, 2011). She presented a case study with data describing a multi-kinase inhibitor intended for solid tumor oncology indications, that was initially characterized with overt cardiotoxicity in a 28-day repeat dose cynomolgous monkey study. Studies were subsequently conducted to determine if (1) a prodromal biomarker of cardiovascular toxicity could be identified to support monitoring in the clinic, and (2) a mechanism of the cardiotoxicity could be determined, either driven by the primary pharmacology or off-target effects to screen against for future compounds. Dr. McMahon described further investigation of the cardiotoxicity in a 5-day repeat dose study in telemetered monkeys. Heart rate, body temperature, left ventricular pressure, arterial blood pressure and ECGs were recorded continuously. Following the first dose at the highest dose level, previously shown to be associated with overt histopathological cardiotoxicity, an acute-onset decrease in body temperature preceded a prolonged tachycardia and ST segment elevation. On subsequent dosing days there was a drug-related attenuation of the response to the dosing procedure, decreases in arterial blood pressure, negative ionotropic and lusitropic effects and the absence of the normal nocturnal dip in these
2.6. Predicting seizure liabilities in a dish using human iPSC-based neural cells (Jonathan Davila, NeuCyte Labs) Dr. Davila's presentation underlined the fact that the high attrition rate of novel central nervous system (CNS) drugs during clinical development has been a major challenge to the pharmaceutical industry (Harrison, 2016). This is largely attributed to the lack of biologically relevant models to study functional links between target and phenotype. NeuCyte's mission is to accelerate and optimize CNS drug discovery by developing more predictive assays and platforms for phenotypic screening. Based on the SynFire® technology for generating 3
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3.2. Stem cells and genomics for precision medicine (Joseph C Wu, Stanford University, School of Medicine)
human induced pluripotent stem cell (iPSC)-derived induced neurons (iNs) through direct reprogramming, Dr. Davila highlighted the fact that NeuCyte has developed a proprietary in vitro human neural platform for complex electrophysiological and morphological readouts. These neuronal co-cultures expressed pan-neuronal and subtype-specific markers and exhibited proper morphology and mature complex network activities, making them suitable for target identification and validation, efficacy testing and neurotoxicity assessment. Upon exposure to the Health and Environmental Sciences Institute (HESI) Neutox Microelectrode Array (MEA) group test compounds (Roberts et al., 2015), NeuCyte's neural co-culture system showed reproducible and robust dose dependent changes in spike rates, bursting and network firing parameters. These changes were not seen in the negative control compounds, acetaminophen and amoxicillin. This indicates that this system has the potential to predict seizure liabilities. Moreover, by focusing on a select set of network firing MEA parameters NeuCyte has begun to identify firing patterns resembling ictal discharges as they occur during status epilepticus. Through clustering analysis, compounds can be clustered by firing patterns into mode of action (MOA) groups, such as dopamine receptor blockers, K+ channel blockers, GABAA receptor blockers and more. Moving forward, Dr. Davila stressed that more seizurogenic and non-seizurogenic compounds with well-defined modes of action need to be tested to further optimize the seizure prediction capacity of iNs.
Dr. Wu started his presentation by accentuating the fact that heart disease continues to kill more Americans than any other cause, accounting for over 20% of total deaths each year. Many drugs designed to treat or prevent heart disease and stroke have been developed, but many of these drugs are imprecise – they do not benefit large portions of the population with the condition that they target. Such issues with efficacy are thought to arise from variations in individuals' genetics, environment, and lifestyle. Precision medicine is an emerging approach for disease prevention and treatment that aims to increase treatment efficacy by considering such variations. The ability to cheaply, quickly, and reliably sequence an individual human genome was an essential step in making precision medicine a reality, allowing rapid identification of genetic variants. However, the significance of these many variants remains unknown, as methods to unambiguously determine whether or not a particular genetic variant is pathogenic are lacking. Dr. Wu stated that this problem is the “Achilles heel” of precision medicine, as it makes clinical interpretation and risk assessment difficult, which causes incredible stress for patients and their families. iPSCs show great promise for precision medicine and in addressing this “Achilles heel.” iPSCs can be generated from different tissues, including a patient's blood, skin, hair, or fat, which are then reprogrammed into a wide variety of cell types, including iPSC-derived cardiomyocytes (iPSC-CMs), that can be used for research or clinical applications. iPSCs derived from disease patients are now used for understanding basic disease mechanisms, drug discovery, and drug efficacy testing at the individual level. Biobanks of such cells facilitate this “clinical-trial-in-a-dish” approach to drug testing. iPSCs can even be used as a source for cell transplantation. iPSC-CMs can now be generated with incredibly high efficiency to help our understanding of the molecular mechanisms underlying varying forms of heart diseases and develop and test drugs to treat them. For example, a patient carrying a particular MYL3 genetic variant (c.170C > A) was referred to Stanford laboratory (Ma et al., 2018). Many variants of the MYL3 gene have been linked to familial hypertrophic cardiomyopathy, and this particular variant carried by the patient had been classified as “likely pathogenic,” although the supporting data were not conclusive. The Stanford investigators generated iPSC-CMs from this patient and compared their behavior to cells derived from a family member without the variant. Further, CRISPR was used to introduce the c.170C > A MYL3 genetic variant into a control cell line (Ma et al., 2018). In all cases, the cells lacked a pathogenic phenotype, suggesting that what was initially annotated as a “likely pathogenic” variant is actually a “benign” variant in this patient. In terms of predicting drug efficacy, iPSC technology is uniquely able to link genotype with drug response phenotype, a key precision medicine goal. At the Stanford Cardiovascular Institute, we have established the Cardiac iPSC Biobank, a biorepository of 1000 iPSC lines from patients with different cardiovascular histories, ethnicities, and genders, complemented by isogenic control lines created using CRISPR genome editing. All of the iPSC lines (including both iPSC-CMs and iPSC-derived endothelial cells) are sequenced (Matsa et al., 2016). Our goal is to create a diverse and representative database on how human genetic variation influences drug response phenotypes in the general population, which is then linked to patients' medical information using a clinical database. The end aim is to bring cardiovascular precision medicine fully into the clinic at Stanford.
3. Discovery sciences 3.1. Utilization of precision cut tissue slices to evaluate integrin inhibition for the treatment of fibrosis (Johanna R Schaub, Pliant Therapeutics, Inc.) Dr. Schaub presented Pliant Therapeutics' mission to develop bestin-class small molecule inhibitors for fibrotic diseases. As a part of a drug development toolkit, Pliant utilizes precision cut tissue slices (PCTS; de Graaf et al., 2010). PCTS are thin (~150–400 μm) sections of living tissue than are cultured ex vivo and utilized for assessing target expression and therapeutic efficacy. PCTS can be generated from healthy or diseased, rodent or human tissue from lung, liver, kidney, and intestines. Dr. Schaub added that PCTS bridge traditional cell-based assays, preclinical in vivo studies, and clinical studies. The advantages for PCTS come from the presence of multiple cell types and the native architecture and extracellular matrix (ECM) of the tissue of origin, variables that can be missing from cell-based assays. Slices generated from preclinical models are higher throughput than in vivo studies, allowing more conditions to be tested with fewer animals. Slices generated from human tissue provide the opportunity to evaluate efficacy in tissue from the desired patient population. Then, Dr. Schaub presented how Plaint has been utilizing both lung and liver tissues for assessing target expression and anti-fibrotic activity of its integrin inhibitors. Human precision cut lung slices are viable in culture for at least 7 days allowing a window of opportunity to both induce fibrosis in normal tissue with a cocktail of profibrogenic factors and to inhibit fibrosis in tissue from idiopathic pulmonary fibrosis patients with integrin inhibitors. Additionally, human precision cut liver slices are viable in culture for only 2 days, but still provide a platform for determining efficacy of antifibrotics at the gene expression level. PCTS have also been used in the development of imaging tools, testing fluorescent probes to monitor target distribution and target engagement of inhibitors. In summary, precision cut tissue slices are an ex vivo system that bridges traditional cell-based and in vivo assays, providing the native cell types and architecture found in vivo while allowing for higher throughput analysis. Further, human tissue can be used to bridge preclinical models and clinical studies, allowing efficacy testing in patient tissue. Dr. Schaub concluded that Pliant has successfully used this platform in the development of integrin inhibitors as antifibrotics.
3.3. Leveraging large animal models of inherited cardiomyopathy in preclinical pharmacology: the missing piece (Carlos del Rio, MyoKardia, Inc.) Dr. del Rio focused in his on hypertrophic cardiomyopathy (HCM), a heritable cardiac disease that is characterized by hyper-contractility, 4
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impaired filling, and exertional intolerance (Marian & Braunwald, 2017). Given, in part, to the well-established structural and biochemical differences between humans and existing preclinical rodent models, the molecular basis for this pathophysiology remain poorly understood, hindering the development of targeted and more effective therapies. Therefore, a large-animal model of HCM was developed by introducing a heterozygous knock-in R403Q MYH7 (beta myosin) mutation in Yucatan mini-pigs (del Rio et al., 2017). In the setting of this novel model, in vivo and ex vivo studies were performed in to determine both its translational value and the association between induced myofilament abnormalities and the in vivo clinical phenotype. Moreover, the in vivo systolic/diastolic effects of direct myosin-attenuation with a smallmolecule allosteric modulator (MYK-581, a mavacamten analog), were evaluated in both mutant animals and age-matched wildtype (WT) herd-mates (del Rio et al., 2018). Muscle fibers from mutant pigs showed increased Ca2+ sensitivity with decreased cooperativity, favoring enhanced inotropy. Concordant with these observations, mutant pigs showed hyper-contractility in vivo as indicated by both imaging-based (cMR, echocardiography) and invasive load-dependent/-independent inotropic indices. R403Q MYH7 pigs also exhibited diastolic impairments as well as blunted β-adrenergic (β-AR) functional recruitment (a potential mechanism for exertional intolerance in patients), presenting markedly elevated left ventricular (LV) end-diastolic filling pressures (EDPs) and stiffer ventricles. MYK-581 behaved like a negative inotrope in WT animals; however, in mutant animals, it normalized ejection fraction and improved LV compliance, increasing end-diastolic dimensions while lowering EDP. MYK-581 also improved β-AR reserve in the HCM pigs. Notably, direct myosin-modulation with Mavacamten can normalize contractility and improve exercise capacity in patients with HCM. Taken together, this translational dataset highlights the value of novel large-animal models on inherited cardiomyopathy to investigate the mechanistic link between in vivo phenotypes, biophysical twitch mechanics, and sarcomere-mutations while supporting the hypothesis that myofilament-targeted therapies could provide benefit to HCM patients.
by AstraZeneca (Pollard et al., 2017) and the FDA-HESI consortium (Park et al., 2018) also demonstrated the predictive value of the hERG assay and dog or primate QTc studies for predicting FIH or TQT outcomes. A key common message from all these diverse studies is that agents with wide margins (10–30 fold) between therapeutic exposures and drug (unbound) levels associated with QTc prolongation or hERGblockade, have low risk for drug-induced pro-arrhythmia. Given the value of the current ICH S7B models for pro-arrhythmia risk assessment, Dr. Vargas concluded that the new models proposed by the CiPA initiative may be most useful as early stage or follow-up assays, depending on risk evaluation need. These additional tools may assist de-risk drugs with complex off-target profiles (e.g., multi-ion channel inhibition) during candidate selection, or improve clinical risk translation through the use of human cardiomyocyte assays (adult primary (Nguyen et al., 2017) or iPSC-derived (Ando et al., 2017; Blinova et al., 2018)) for assessing altered repolarization, for agents entering Phase 1 clinical trial. 5. Meeting summary, conclusions and future opportunities The West Coast SPS Regional Meeting in Foster City covered a wide range of topics, such as assessment of drug-induced cardiotoxicity (proarrhythmia and contractility risk) and seizure liability, translation of SP data, precision cut tissue slice assay for evaluation of anti-fibrotic potential of drugs, large animal model of inherited cardiomyopathy, engineering of human stem cell-derived tissue constructs, stem cells and genomics for precision medicine, and two case studies on the cardiovascular risk assessment of two small molecules for oncology indications. The presentations generated many questions and provoked exciting discussions. The discussions helped crystalize several key messages and future opportunities: (1) The urgent need for reliable human-relevant in vitro/ex vivo models, with high sensitivity and specificity to predict clinical outcomes, and enable mechanistic investigations, was underlined by several presentations. The potential of new strategies addressing this need was discussed by Drs. Sager, Abi-Gerges, McMahon, Davila, Schaub and Vargas and ability of some of the new models to provide mechanistic insights into cardiotoxicity and neurotoxicity was underlined by Drs Abi-Gerges and Davila. The importance of mechanistic studies, was recently discussed at a Food and Drug Administration White Oak Campus workshop entitled “Cardiomyocytes for mechanistic cardiovascular safety liabilities” (Anon, 2019), and presentations and discussions at the West Coast SPS Regional Meeting also stressed the importance of assays that, by having mechanistic relevance, can generate data useful not only to predict the clinical outcome, but also deconvolute toxicity signals and potentially help with the development of risk mitigation strategies. In this context, several of the participants expressed the belief that powerful new insights could be generated in the coming years from the combination of mechanistic data with analysis tools derived from machine learning and artificial intelligence. Collaborations between pharmaceutical industry experts, regulators and key opinion leaders would be needed to refine this new mechanistic drug discovery paradigm. (2) Large animal models, with either normal or diseased hearts continue to be vital for assessing in vivo cardiovascular effects of drugs and enabling development of safe and effective drugs. The suitability of these large animal models was underscored by Drs Chui, McMahon, del Rio, Vargas and Mr. Stevens, and continuing evaluation of models with diseased hearts is necessary to increase cardiotoxicity assessment of drugs in preclinical safety pharmacology studies. (3) There is a growing demand for models that can simultaneously predict multiple liabilities. An example was provided with the use of adult human primary cardiomyocytes to simultaneously predict
4. Translation of safety pharmacology testing to human trials: what do we know? (Hugo Vargas, Amgen, Inc.) Since the implementation of guidelines ICH S7A (Anon, 2000) and ICH S7B (Anon, 2005a), the community of SP scientists have gained valuable knowledge about the clinical relevance and translational value of the nonclinical models, e.g., in vivo core battery and hERG functional assay. These insights have been gained primarily through data-sharing efforts from individual companies, or pharma industry consortia. The compiling and sharing of real-world nonclinical and clinical SP data from diverse sources has been critical to driving “what we know” about translational value. Dr. Vargas focused in his presentation on recent efforts that underscore the value of nonclinical models and their ability to predict clinical findings, with a focus on QTc prolongation risk evaluation. To date, five publications have examined the real-world nonclinical QTc internal and hERG potency and their relationship to clinical QTc findings, e.g., first-in-human (FIH), TQT, etc. (Ewart et al., 2014; Park et al., 2018; Pollard et al., 2017; Vargas et al., 2015; Wallis, 2010). All of these evaluations focused on small molecules drugs (proprietary molecules; agents in the public domain) and examined the predictive ability of the hERG potency assay and/or the in vivo QTc study (in conscious or anesthetized non-rodent models). A common finding from these investigations is that nonclinical approaches described by ICH S7B are very effective at assessing the clinical risk associated with hERG-mediated QTc risk prolongation. For example, in a data set of 113 small molecules with a range of hERG potencies, the in vivo QT assay conducted in telemetered dogs showed high specificity for predicting FIH-QT findings (Ewart et al., 2014). Similar investigations conducted 5
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drug-induced inotropic and pro-arrhythmia risk (Nguyen et al., 2017) or inotropic risk and structural toxicity with tyrosine kinase inhibitors (Dr Abi-Gerges). (4) iPSC lines can help the understanding of drug efficacy while linking genotype with drug response phenotype of a patient population. A future goal of data obtained from patient-derived stem cells, will be the development of databases that will document how genetic variants affect drug response phenotypes. (5) In his closing remarks, Dr. Vargas recommended a collaborative effort to ensure that new models are adequately validated so as to provide a high level of confidence in their predictive value. Partnerships across pharmaceutical companies and between pharmaceutical companies and regulators could greatly benefit the model validation efforts.
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Clinical Pharmacology & Therapeutics, 96(5), 549–558. https://doi.org/10.1038/clpt. 2014.155 (Epub 2014 Jul 23). Johannesen, L., Vicente, J., Mason, J. W., Erato, C., Sanabria, C., Waite-Labott, K., ... Strauss, D. G. (2016). Late sodium current block for drug-induced long QT syndrome: Results from a prospective clinical study. Clinical Pharmacology & Therapeutics, 99(2), 214–223. https://doi.org/10.1002/cpt.205 (Epub 2015 Nov 28). Ma, N., Zhang, J., Itzhaki, I., Zhang, S. L., Chen, H., Haddad, F., ... Wu, J. C. (2018). Determining the pathogenicity of a genomic variant of uncertain significance using CRISPR/Cas9 and human-induced pluripotent stem cells. Circulation, 138(23), 2666–2681. https://doi.org/10.1161/CIRCULATIONAHA.117.032273. Marian, A. J., & Braunwald, E. (2017). Hypertrophic cardiomyopathy: Genetics, pathogenesis, clinical manifestation, diagnosis and therapy. Circulation Research, 121, 749–770. https://doi.org/10.1161/CIRCRESAHA.117.311059.). Matsa, E., Burridge, P. W., Yu, K. H., Ahrens, J. H., Termglinchan, V., Wu, H., ... Wu, J. C. (2016). Transcriptome profiling of patient-specific human iPSC-cardiomyocytes predicts individual drug safety and efficacy responses in vitro. Cell Stem Cell, 19(3), 311–325. https://doi.org/10.1016/j.stem.2016.07.006 (Epub 2016 Aug 18). Mead, A. N., Amouzadeh, H. R., Chapman, K., Ewart, L., Giarola, A., Jackson, S. J., ... Vargas, H. M. (2016). Assessing the predictive value of the rodent neurofunctional assessment for commonly reported adverse events in phase I clinical trials. Regulatory Toxicology and Pharmacology, 80, 348–357. https://doi.org/10.1016/j.yrtph.2016.05. 002. Mellor, H. R., Bell, A. R., Valentin, J. P., & Roberts, R. R. A. (2011). Cardiotoxicity associated with targeting kinase pathways in cancer. Toxicological Sciences, 120(1), 14–32. https://doi.org/10.1093/toxsci/kfq378. Moe, G. W., & Armstrong, P. (1999). Pacing-induced heart failure: A model to study the mechanism of disease progression and novel therapy in heart failure. Cardiovascular Research, 42(3), 591–599. Nguyen, N., Nguyen, W., Nguyenton, B., Ratchada, P., Page, G., Miller, P.E., … AbiGerges, N. (2017). Adult human primary cardiomyocyte-based model for the simultaneous prediction of drug-induced inotropic and pro-arrhythmia risk. Frontiers in Physiology, 8:1073. doi: https://www.frontiersin.org/articles/10.3389/fphys. 2017.01073/full 2017. Page, G., Ratchada, P., Miron, Y., Steiner, G., Ghetti, A., Miller, P. E., ... Abi-Gerges, N. (2016). Human ex-vivo action potential model for pro-arrhythmia risk assessment. Journal of Pharmacological and Toxicological Methods, 81, 183–195. https://doi.org/ 10.1016/j.vascn.2016.05.016. Pannirselvam, M., Brabham, T., Botchway, A. W., Hodges, D. B., Traebert, M., & Pugsley, M. K. (2017). The northeast regional SPS meeting update: Safety pharmacology innovations and applications. Journal of Pharmacological and Toxicological Methods, 85, 82–86. https://doi.org/10.1016/j.vascn.2016.11.005. Park, E., Gintant, G. A., Bi, D., Kozeli, D., Pettit, S. D., Pierson, J. B., ... Valentin, J. P. (2018). Can non-clinical repolarization assays predict the results of clinical thorough QT studies? Results from a research consortium. British Journal of Pharmacology, 175, 606–617. Pollard, C. E., Skinner, M., Lazic, S. E., Prior, H. M., Conlon, K. M., Valentin, J. P., & Dota, C. (2017). An analysis of the relationship between preclinical and clinical QT interval-related data. Toxicological Sciences, 159, 94–101. Pugsley, M. K., Authier, S., & Curtis, M. J. (2008). Principles of safety pharmacology. British Journal of Pharmacology, 154, 1382–1399. Qu, Y., Page, G., Abi-Gerges, N., Miller, P. E., Ghetti, A., & Vargas, H. M. (2018). Action potential recordings and pro-arrhythmia risk analysis in human ventricular trabeculae. Frontiers in Physiology, 8, 1109. https://doi.org/10.3389/fphys.2017.01109 (eCollection 2017). Roberts, R. A., Aschner, M., Calligaro, D., Guilarte, T. R., Hanig, J. P., Herr, D. W., ... Lynch, J. J. (2015). Translational biomarkers of neurotoxicity: A heath and environmental sciences institute perspective on the way forward. Toxicological Sciences, 148(2), 332–340. https://doi.org/10.1093/toxsci/kfv188. Robertson, C., Tran, D. D., & George, S. C. (2013). Maturation phases of human
Disclaimer The opinions presented here are those of the author's interpretation and summary of the West Coast Regional SPS Meeting and not necessarily those of author's associated companies and universities. Acknowledgements The authors are grateful for the contribution of all participants to the meeting, the organizational support of Ellen Leonard, Krystle Correll and Gary Watkins, and for Gilead Sciences, Inc. for hosting the meeting. References Ando, H., Yoshinaga, T., Yamamoto, W., Asakura, K., Uda, T., Taniguchi, T., ... Sekino, Y. (2017). A new paradigm for drug-induced torsadogenic risk assessment using human iPS cell-derived cardiomyocytes. Journal of Pharmacological and Toxicological Methods, 84, 111–127. https://doi.org/10.1016/j.vascn.2016.12.003. Anon (2000). Committee for Proprietary Medicinal Products (CPMP). Safety pharmacology studies for human pharmaceuticals. London: The European Agency for the evaluation of medicinal products November 16, Reference CPMP/ICH/539/00. Anon. (2005a). ICH S7B note for guidance on the nonclinical evaluation of the potential for delayed ventricular repolarization (QT interval prolongation) by human pharmaceuticals. (London, 25 May). Reference CHMP/ICH/423/02. Anon. (2005b). ICH E14 note for guidance on the clinical evaluation of QT/QTc interval prolongation and proarrhythmic potential for non-antiarrhythmic drugs. (London, 25 May). Reference CHMP/ICH/2/04 Anon (2018). E14/S7B questions & answers: Clinical and non-clinical evaluation of QT/ QTc interval prolongation and pro-arrhythmic potential. https://www.ich.org/ products/guidelines/efficacy/article/efficacy-guidelines.html#13-3. Anon (2019). Food and Drug Administration workshop “Cardiomyocytes for mechanistic cardiovascular safety liabilities”. https://www.fda.gov/Drugs/NewsEvents/ ucm631998.htm. Bass, A. S., Hombo, T., Kasai, C., Kinter, L. B., & Valentin, J. P. (2015). A historical view and vision into the future of the field of safety pharmacology. Handbook of Experimental Pharmacology, 229, 3–45. https://doi.org/10.1007/978-3-662-469439_1. Blinova, K., Dang, Q., Millard, D., Smith, G., Pierson, J., Guo, L., ... Gintant, G. (2018). International multisite study of human-induced pluripotent stem cell-derived cardiomyocytes for drug proarrhythmic potential assessment. Cell Reports, 24(13), 3582–3592. https://doi.org/10.1016/j.celrep.2018.08.079. Boulay, E., Abernathy, M. M., Chui, R., Friedrichs, G. S., Gendron-Parra, N., GreiterWilke, A., ... Authier, S. (2019). A proof-of-concept evaluation of JTPc and Tp-Tec as proarrhythmia biomarkers in preclinical species: A retrospective analysis by an HESIsponsored consortium. International Journal of Toxicology, 38(1), 23–32. https://doi. org/10.1177/1091581818813601 (Epub 2018 Dec 19). Cavero, I. (2009). Exploratory safety pharmacology: a new safety paradigm to de-risk drug candidates prior to selection for regulatory science investigations. Expert Opinion on Drug Safety, 8(6), 627–648. de Graaf, I. A. M., Olinga, P., de Jager, M. H., Merema, M. T., de Kanter, R., van de Kerkhof, E. G., & Groothuis, G. M. M. (2010). Preparation and incubation of precision-cut liver and intestinal slices for application in drug metabolism and toxicological studies. Nature Methods, 5, 1540–1551. https://doi.org/10.1038/nprot. 2010.111. del Rio, C. L., Henze, M. P., Wong, F. L., Evanchik, M. J., Divekar, A., Gifford, L. M., ... Green, E. M. (2017). A novel mini-pig genetic model of hypertrophic cardiomyopathy: Altered myofilament dynamics, hyper-contractility, and impaired systolic/ diastolic functional reserve in vivo. Circulation, 136(suppl_1), A20770. del Rio, C.L., Yadav, A., Huang, N., Geist, G.E., Ueyama, Y., Youngblood, B.L., … F. (2018). Acute effects of a small-molecule direct myosin-attenuator (MYK-581) in a
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van Meer, B. J., Tertoolen, L. G. J., & Mummery, C. L. (2016). Measuring physiological responses of human pluripotent stem cell derived cardiomyocytes to drugs and disease. Stem Cells, 34(8), 2008–2015. https://doi.org/10.1002/stem.2403 (Epub 2016 Jun 30). Vargas, H. M., Bass, A. S., Koerner, J., Matis-Mitchell, S., Pugsley, M. K., Skinner, M., ... Valentin, J. P. (2015). Evaluation of drug-induced QT interval prolongation in animal and human studies: A literature review of concordance. British Journal of Pharmacology, 172, 4002–4011. Vicente, J., Johannesen, L., Mason, J. W., Crumb, J. W., Pueyo, E., Stockbridge, N., & Strauss, D. G. (2015). Comprehensive T wave morphology assessment in a randomized clinical study of dofetilide, quinidine, ranolazine, and verapamil. Journal of the American Heart Association, 4(4), https://doi.org/10.1161/JAHA.114.001615 (pii: e001615). Wallis, R. M. (2010). Integrated risk assessment and predictive value to humans of nonclinical repolarization assays. British Journal of Pharmacology, 159, 115–121. Yarbrough, W. M., & Spinale, F. G. (2003). Large animal models of congestive heart failure: A critical step in translating basic observations into clinical applications. Journal of Nuclear Cardiology, 10(1), 77–86. Zamorano, J. L., Lancellotti, P., Rodriguez Munoz, D., Aboyans, V., Asteggiano, R., Galderisi, M., ... Suter, T. M. (2016). ESC position paper on cancer treatments and cardiovascular toxicity developed under the auspices of the ESC Committee for practice guidelines: The task Force for cancer treatments and cardiovascular toxicity of the European Society of Cardiology (ESC). European Heart Journal, 37(36), 2768–2801. https://doi.org/10.1093/eurheartj/ehw211 (Epub 2016 Aug 26).
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Contents lists available at ScienceDirect
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Review
The West coast regional safety pharmacology society meeting update: Filling translational gaps in safety assessment
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Najah Abi-Gergesa, , Carrie McMahonb, Hugo Vargasc, Philip Sagerd, Ray Chuic, Dale Stevense, Jonathan Davilaf, Johanna R. Schaubg, Joseph C. Wuh, Carlos del Rioi, Chris Mathesa, Paul E. Millera, Leigh Ann Burns-Naasb, Andre Ghettia a
AnaBios Corporation, San Diego, CA 92109, USA Gilead Sciences, Inc., Foster City, CA 94404, USA c Amgen Inc., Thousand Oaks, CA 92320, USA d Stanford University, School of Medicine, Stanford, CA 94305, USA e Genentech Inc., South San Francisco, CA 94080, USA f NeuCyte Labs, Sunnyvale, CA 94089, USA g Pliant Therapeutics, Inc., South San Francisco, CA 94080, USA h Stanford University School of Medicine, Stanford Cardiovascular Institute, Stanford, CA 94305, USA i MyoKardia, Inc., South San Francisco, CA 94080, USA b
A R T I C LE I N FO
A B S T R A C T
Keywords: Drug discovery Predictivity Safety pharmacology Translational science
The Safety Pharmacology Society (SPS) held a West Coast Regional Meeting in Foster City, CA on November 14, 2018 at the Gilead Sciences Inc. site. The meeting was attended by scientists from the pharmaceutical and biotechnology industry, contract research organizations (CROs) and academia. A variety of scientific topics were presented by speakers, covering a broad variety of topics in the fields of safety risk assessment; from proarrhythmia and contractility risk evaluation, to models of heart failure and seizure in-a-dish; and discovery sciences; from stem cells and precision medicine, to models of inherited cardiomyopathy and precision cut tissue slices. The present review summarizes the highlights of the presentations and provides an overview of the high level of innovation currently underlying many frontiers in safety pharmacology.
1. An introduction to the meeting content Drug developers rely on safety pharmacology to identify and predict, prior to clinical trials, adverse effects of novel drugs on major organ systems, including cardiovascular, central nervous, respiratory, renal and gastrointestinal (Bass, Hombo, Kasai, Kinter, & Valentin, 2015; Hamdam et al., 2013; Pugsley, Authier, & Curtis, 2008). The implementation of ICH S7A/S7B guidance (Anon 2000; 2005a) originally drafted by the International Conference on Harmonization made safety pharmacology an integral part of preclinical drug discovery and established rigorous safety standards for drug candidates entering clinical studies (Cavero, 2009). Next, the introduction of exploratory safety pharmacology has resulted in early hazard detection and mitigation (Cavero, 2009; Stark & Steger-Hartmann, 2016; Valentin et al., 2018). For example, the models currently used to evaluate the potential of drug-induced delay of ventricular repolarization are effective in reducing the number of clinical candidates associated with QT
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prolongation (Ewart et al., 2014; Park et al., 2018; Pollard et al., 2017; Valentin et al., 2009; Vargas et al., 2015; Wallis, 2010). However, the concordance between preclinical and clinical cardiovascular assessment for changes in heart rate and blood pressure, pro-arrhythmia risk, is still poor (Ewart et al., 2014; Gintant, Sager, & Stockbridge, 2016; Sager, Gintant, Turner, Pettit, & Stockbridge, 2014). Similarly, the prediction of drug-related risks on central nervous and respiratory systems remains a significant challenge (Mead et al., 2016; unpublished data, IQ Consortium nonclinical to clinical translational database). Therefore, translational gaps exist and new validated collaborative approaches, preferably human-based and applicable to early stages of preclinical development, are needed to ensure a high level of confidence in their predictive value. Partnerships across pharmaceutical companies and between pharmaceutical companies and regulators could greatly benefit the validation of these new approaches. The Safety Pharmacology Society (SPS), which holds an annual global meeting, also supports regional SPS meetings (Pannirselvam
Corresponding author at: 3030 Bunker Hill St., Suite 312, San Diego, CA 92109, USA. E-mail address: [email protected] (N. Abi-Gerges).
https://doi.org/10.1016/j.vascn.2019.106582 Received 6 May 2019; Accepted 7 May 2019 Available online 09 May 2019 1056-8719/ © 2019 Elsevier Inc. All rights reserved.
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liability of test articles” (ICH S7B and E14 Q&A Endorsed by the ICH Assembly on 15 November 2018; Anon, 2018). Being able to directly assess the effects of drugs in adult human primary cardiomyocytes with high sensitivity and specificity may simplify the pro-arrhythmic assessment and require less ion channel testing and in silico modelling (Nguyen et al., 2017). The lack of ideal operator characteristics in the iPSC-CMs may be due to the fact that these cardiomyocytes are not fully mature with the full range of adult ion channel expression (van Meer, Tertoolen, & Mummery, 2016; Robertson, Tran, & George, 2013). This is supported by the observations that adult human primary cardiomyocytes culled from ethically consented human donor hearts (Nguyen et al., 2017) have been shown to be highly predictive in assessing the known pro-arrhythmic risk of individual drugs, and consequently they are now a core element of the ICH S7B Implementation Working Concept paper that aims to revise the S7B guidance (Anon, 2018). CiPA is currently being assessed by the ICH S7B and E14 Implementation Working Group for possible inclusion in S7B to inform regulatory decision making (Anon, 2018). Finally, Dr. Sager concluded that he expects CiPA to undergo further development and modifications over time as science and exciting advances in other approaches evolve.
et al., 2017). The 2018 West Coast SPS Regional Meeting, which was organized at Gilead Sciences Incorporated in the San Francisco Bay Area, was aimed at discussing strategies to address translational gaps in the fields of drug safety assessment and discovery sciences. The meeting covered several efforts in translational science being conducted across the West Coast pharmaceutical/biotechnology industry as well as in academic institutions. It highlighted translational scientific advances in different areas, i.e., cardiac safety & pharmacology, cardiovascular toxicology, translational science, genomics and precision medicine, seizure, liver fibrosis, heart failure and cardiomyopathy, human primary cells and tissues, and human stem cells. This meeting report outlines the content presented and debated at the meeting. 2. Safety risk assessment 2.1. Mechanistic approaches to assessing the pro-arrhythmic potential of drugs (Philip Sager, Stanford University) Dr. Sager launched the discussion of cardiac safety risk assessment by presenting an overview on mechanistic approaches to assess the proarrhythmic potential of novel drugs. He first introduced the core elements of the ICH S7B guideline, which focuses on the preclinical measurement of the hERG-related cardiac ion channel current and the animal and human assessment of QTc prolongation (Anon, 2005a), to assess a drug's proclivity to cause torsade de pointes (TdP). While this strategy has been effective in that drugs are not being approved with unanticipated pro-arrhythmic liability, it has become clear that there are serious shortcomings of this approach (Sager et al., 2014). These include a relatively low positive predictive value of hERG block or QTc prolongation to identify a drug as actually being pro-arrhythmic. This has resulted in the premature termination of drugs that reduce hERG and prolong the QTc interval, but have a low arrhythmic risk and would have had favorable benefit to risk ratios. This negative impact on the drug development pipeline has potential downstream unfavorable implications for public health. Dr. Sager stressed that over the last 19 years since ICH E14 (Anon, 2005b) and ICH S7B were finalized in 2005, there has been considerable insight into the mechanism of TdP and the primary role that early afterdepolarizations play in the genesis of TdP. This understanding calls for a mechanistic approach to assessing a drug's proclivity to cause TdP, independent of effects on hERG and the QTc. There are important outcomes of being able to characterize a drugs pro-arrhythmic potential, instead of relying on surrogates without high positive predictive values. These include reducing the premature termination of drugs with favorable benefit to risk profiles, making development more straightforward with benign labelling of drugs with a low pro-arrhythmic risk (despite modest QTc prolongation), using preclinical assays to improve candidate selection, move the bulk of pro-arrhythmic assessment to the discovery phase, and permit earlier removal of regulatory uncertainty. Additionally, such an approach should permit the revision of current labels for some drugs, removing QT risk language. Next, Dr. Sager reviewed the Comprehensive In Vitro Pro-arrhythmia Assay (CiPA) as one such approach. It relies on testing the effects of a drug on hERG, and the L-type Ca and late inward sodium currents (with additional testing of the slowly activating delayed rectifier current and the peak inward sodium current in selected situations) and determining a pro-arrhythmic score using in silico cardiomyocyte action potential modelling (Gintant et al., 2016; Sager et al., 2014). Unanticipated effects in humans, for example due to human specific metabolites or pharmacokinetic differences, can be assessed by evaluating ECG's in Phase 1 clinical study. Human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) experiments were performed as part of CiPA, and their ability to correctly predict the pro-arrhythmic likelihood of low-risk drugs did not show high specificity (Blinova et al., 2018), but still may “provide insights into the relative pro-arrhythmic
2.2. Pro-Arrhythmia evaluation in a dog model of heart failure: Augmenting the nonclinical tool box (Ray Chui, Amgen, Inc.) In his opening slides, Dr. Chui reiterated the fact that drug-induced ventricular arrhythmias can be induced by various pharmacological agents, leading to an arrhythmic emergency that can culminate in sudden cardiac death. Regulatory guidance on QT prolongation (ICH S7B/E14; Anon, 2005a,b) has sought to address these concerns, however a considerable volume of data has demonstrated that QT liability is not synonymous with pro-arrhythmic risk. In light of the complexity of this issue, numerous models have been proposed. Then, Dr. Chui emphasized the importance to evaluate the proarrhythmic potential of the well-characterized canine right ventricular tachypacing (VTP) induced heart failure model. This highly reproducible model has demonstrated mechanical, structural and neurohormonal alterations comparable to human dilated cardiomyopathy, manifesting as reduced cardiac reserve and function, as well as a prolonged QT phenotype (Moe & Armstrong, 1999; Yarbrough & Spinale, 2003). For example, QT interval data were found to be 321 ± 46 ms (n = 47) and 280 ± 24 ms (n = 240) in VTP and normal dogs anesthetized with chloralose anesthesia, respectively (values are mean ± SD). As such, this model satisfies several physiological criteria for enhanced sensitivity to arrhythmia induction. Data with dofetilide, a well-known torsadogenic drug, shows exaggerated impacts on QT, JTpeak and Tpeak-Tend intervals (Boulay et al., 2019; Johannesen et al., 2014, 2016; Vicente et al., 2015). Dr. Chui proposed that follow-up studies may include autonomic modulation and electrophysiological stress testing as part of a more extensive characterization. In conclusion, Dr. Chui suggested that continuing investigation into this model, along with other cardiovascular disease models, is urgently warranted, as a means to augment pro-arrhythmic risk assessment in preclinical safety. 2.3. Preclinical human contractility safety testing (Najah Abi-Gerges, AnaBios Corporation) Dr. Abi-Gerges presented an overview on myocardial contractility and its modulation by drugs. Drug-induced changes in contractility can lead to serious adverse events including heart failure; Dr. Abi-Gerges reviewed the current translational challenges in predicting the inotropic potential of drugs and stressed the urgent need for a predictive human cardiomyocyte-based model for reliable detection of inotropic toxicity early in the discovery process. In this context, significant excitement has been generated by the recent development of methods that 2
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parameters. Echocardiography (Day 5) showed preservation of systolic function, and increased plasma biomarkers correlated with previously confirmed histopathological findings. To determine a potential screening assay for the drug-related adverse cardiovascular effects in vivo, an ex vivo human primary cardiomyocyte assay (Nguyen et al., 2017) was performed. Results of the assay predicted that the compound had the potential to induce negative inotropy, negative lusitropy, and an absence of structural cardiotoxicity with a potential for aftercontraction, a pro-arrhythmia marker. Taken together, the compound was characterized in vivo with a steep dose response curve with a unique cardiotoxicity profile leading to its discontinuation from development. Additional follow-up ex vivo human primary cardiomyocyte and tissue assays are ongoing to elucidate potential mechanisms responsible for driving the tachycardia and/ or contractility effects.
enable the procurement and experimental interrogation of donor heart preparations, like adult human primary cardiomyocytes (Nguyen et al., 2017; Page et al., 2016; Qu et al., 2018). These cells exhibit the expected physiological and pharmacological properties (Nguyen et al., 2017). To establish the clinical relevance of a contractility model based on the use of isolated adult human cardiomyocytes, a panel of 50 reference drugs with known clinical outcomes was tested. This reference set included both positive as well as negative inotropes, spanning diverse mechanisms of action. Cardiomyocyte contractility was measured using non-invasive bright-field imaging, in conjunction with electrical field stimulation. The data demonstrated a high degree of correlation between the cellular in vitro model and the clinical data. In addition, this experimental model provides valuable insights into the specific mechanism of action for compounds that exhibit inotropic effects. Dr. Abi-Gerges also discussed data related to the cardiotoxicity of specific Tyrosine Kinase Inhibitors (TKI). While TKIs can provide effective treatment to cancer patients, they have been associated with cardiotoxicity that manifests as reduced ejection fraction (Mellor, Bell, Valentin, & Roberts, 2011). In this study, the effects of 8 TKIs (4 known to induce reduction in cardiac contractility in patients and 4 without contractility risk) were evaluated using human cardiomyocyte contractility-based model. Cardiomyocyte contractility was significantly reduced by all known toxic TKIs, while the TKIs with no known clinical contractility risk did not affect cardiomyocyte function. Given the potential of adult human primary cardiomyocytes for (i) allowing an integrated evaluation of all human cardiac targets, (ii) predicting clinical outcomes and (iii) their compatibility with screening platforms, Dr. Abi-Gerges advocated for the use of adult human primary cardiomyocytes in early contractility and safety screening. In this strategy, drugs not associated with a contractility risk could progress to next discovery stage, while drugs associated with risk would require medicinal chemistry-based improvements. The adult human primary cardiomyocyte-based screening, once implemented, could be expected to accelerate preclinical drug development, by providing highly relevant and predictive data to enable focusing of resources on the most promising leads.
2.5. Nonclinical cardiovascular assessment of small molecule DNA-1 (Dale Stevens, Genentech, Inc.) Mr. Stevens started his presentation by confirming Genentech's commitment is to be an industry leader in the advancement of methods to reduce, replace, and refine (3Rs) the use of animals in research (Tornqvist et al., 2014). As such, Genentech department of Safety Assessment continues to find opportunities to refine nonclinical study designs and testing strategies to collect the most meaningful nonclinical data. Then, Mr. Stevens presented DNA-1, which is a small molecule currently being developed for an oncology indication. As part of the Investigational New Drug (IND) enabling toxicology studies, refinements to the cynomolgus monkey 28-day repeat-dose pivotal toxicology study were made to collect additional cardiovascular data by instrumenting recovery animals (vehicle control & middle dose groups only, N of 4 per group) with DSI Physiotel™ telemetry implants (Data Sciences International) to measure electrocardiographic and hemodynamic endpoints after repeated dosing. This was performed in addition to the conduct of a standard double Latin square cynomolgus monkey cardiovascular telemetry study. Although a double Latin square cardiovascular telemetry study provides greater statistical power to assess potential test article related effects, inclusion of telemetry cardiovascular assessment in a repeat-dose study offers the opportunity to assess for potential cumulative effects. Whilst no cardiovascular changes were noted in the double Latin square cardiovascular telemetry study after a single dose, statistically significant (p value of 0.01) dose-related increases in RR interval and decreases in heart rate were observed in DNA-1 treated cynomolgus monkeys as compared to vehicle control treated animals after 4-weeks of dosing in the 28-day repeat-dose pivotal toxicology study. Changes were considered within the normal physiological range for cynomolgus monkeys and not adverse. Translation of these cardiovascular effects were seen with the Phase 1 trial with Grade 1 bradycardia observed in 5 of 28 patients. Patients were asymptomatic. The inclusion of telemetry implanted recovery animals is not standard for small molecule IND enabling pivotal toxicology studies at Genentech, but this practice may provide meaningful data to help inform the clinical development plan of early development stage molecules and should be considered as a 3Rs refinement.
2.4. Cardiovascular risk assessment in radio telemetry-instrumented male cynomolgus monkeys following oral administration of a multi-kinase inhibitor (Carrie McMahon, Gilead Sciences, Inc.) Dr. McMahon introduced the beneficial anti-tumor effect of small molecule kinase inhibitors, often associated with a variety of cardiotoxicities (Zamorano et al., 2016), which appear to be mediated through a range of mechanisms (Doherty et al., 2013; Sharma et al., 2017) driven in some cases by the primary pharmacology while in others, off-target effects have been implicated (Force & Kolaja, 2011). She presented a case study with data describing a multi-kinase inhibitor intended for solid tumor oncology indications, that was initially characterized with overt cardiotoxicity in a 28-day repeat dose cynomolgous monkey study. Studies were subsequently conducted to determine if (1) a prodromal biomarker of cardiovascular toxicity could be identified to support monitoring in the clinic, and (2) a mechanism of the cardiotoxicity could be determined, either driven by the primary pharmacology or off-target effects to screen against for future compounds. Dr. McMahon described further investigation of the cardiotoxicity in a 5-day repeat dose study in telemetered monkeys. Heart rate, body temperature, left ventricular pressure, arterial blood pressure and ECGs were recorded continuously. Following the first dose at the highest dose level, previously shown to be associated with overt histopathological cardiotoxicity, an acute-onset decrease in body temperature preceded a prolonged tachycardia and ST segment elevation. On subsequent dosing days there was a drug-related attenuation of the response to the dosing procedure, decreases in arterial blood pressure, negative ionotropic and lusitropic effects and the absence of the normal nocturnal dip in these
2.6. Predicting seizure liabilities in a dish using human iPSC-based neural cells (Jonathan Davila, NeuCyte Labs) Dr. Davila's presentation underlined the fact that the high attrition rate of novel central nervous system (CNS) drugs during clinical development has been a major challenge to the pharmaceutical industry (Harrison, 2016). This is largely attributed to the lack of biologically relevant models to study functional links between target and phenotype. NeuCyte's mission is to accelerate and optimize CNS drug discovery by developing more predictive assays and platforms for phenotypic screening. Based on the SynFire® technology for generating 3
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3.2. Stem cells and genomics for precision medicine (Joseph C Wu, Stanford University, School of Medicine)
human induced pluripotent stem cell (iPSC)-derived induced neurons (iNs) through direct reprogramming, Dr. Davila highlighted the fact that NeuCyte has developed a proprietary in vitro human neural platform for complex electrophysiological and morphological readouts. These neuronal co-cultures expressed pan-neuronal and subtype-specific markers and exhibited proper morphology and mature complex network activities, making them suitable for target identification and validation, efficacy testing and neurotoxicity assessment. Upon exposure to the Health and Environmental Sciences Institute (HESI) Neutox Microelectrode Array (MEA) group test compounds (Roberts et al., 2015), NeuCyte's neural co-culture system showed reproducible and robust dose dependent changes in spike rates, bursting and network firing parameters. These changes were not seen in the negative control compounds, acetaminophen and amoxicillin. This indicates that this system has the potential to predict seizure liabilities. Moreover, by focusing on a select set of network firing MEA parameters NeuCyte has begun to identify firing patterns resembling ictal discharges as they occur during status epilepticus. Through clustering analysis, compounds can be clustered by firing patterns into mode of action (MOA) groups, such as dopamine receptor blockers, K+ channel blockers, GABAA receptor blockers and more. Moving forward, Dr. Davila stressed that more seizurogenic and non-seizurogenic compounds with well-defined modes of action need to be tested to further optimize the seizure prediction capacity of iNs.
Dr. Wu started his presentation by accentuating the fact that heart disease continues to kill more Americans than any other cause, accounting for over 20% of total deaths each year. Many drugs designed to treat or prevent heart disease and stroke have been developed, but many of these drugs are imprecise – they do not benefit large portions of the population with the condition that they target. Such issues with efficacy are thought to arise from variations in individuals' genetics, environment, and lifestyle. Precision medicine is an emerging approach for disease prevention and treatment that aims to increase treatment efficacy by considering such variations. The ability to cheaply, quickly, and reliably sequence an individual human genome was an essential step in making precision medicine a reality, allowing rapid identification of genetic variants. However, the significance of these many variants remains unknown, as methods to unambiguously determine whether or not a particular genetic variant is pathogenic are lacking. Dr. Wu stated that this problem is the “Achilles heel” of precision medicine, as it makes clinical interpretation and risk assessment difficult, which causes incredible stress for patients and their families. iPSCs show great promise for precision medicine and in addressing this “Achilles heel.” iPSCs can be generated from different tissues, including a patient's blood, skin, hair, or fat, which are then reprogrammed into a wide variety of cell types, including iPSC-derived cardiomyocytes (iPSC-CMs), that can be used for research or clinical applications. iPSCs derived from disease patients are now used for understanding basic disease mechanisms, drug discovery, and drug efficacy testing at the individual level. Biobanks of such cells facilitate this “clinical-trial-in-a-dish” approach to drug testing. iPSCs can even be used as a source for cell transplantation. iPSC-CMs can now be generated with incredibly high efficiency to help our understanding of the molecular mechanisms underlying varying forms of heart diseases and develop and test drugs to treat them. For example, a patient carrying a particular MYL3 genetic variant (c.170C > A) was referred to Stanford laboratory (Ma et al., 2018). Many variants of the MYL3 gene have been linked to familial hypertrophic cardiomyopathy, and this particular variant carried by the patient had been classified as “likely pathogenic,” although the supporting data were not conclusive. The Stanford investigators generated iPSC-CMs from this patient and compared their behavior to cells derived from a family member without the variant. Further, CRISPR was used to introduce the c.170C > A MYL3 genetic variant into a control cell line (Ma et al., 2018). In all cases, the cells lacked a pathogenic phenotype, suggesting that what was initially annotated as a “likely pathogenic” variant is actually a “benign” variant in this patient. In terms of predicting drug efficacy, iPSC technology is uniquely able to link genotype with drug response phenotype, a key precision medicine goal. At the Stanford Cardiovascular Institute, we have established the Cardiac iPSC Biobank, a biorepository of 1000 iPSC lines from patients with different cardiovascular histories, ethnicities, and genders, complemented by isogenic control lines created using CRISPR genome editing. All of the iPSC lines (including both iPSC-CMs and iPSC-derived endothelial cells) are sequenced (Matsa et al., 2016). Our goal is to create a diverse and representative database on how human genetic variation influences drug response phenotypes in the general population, which is then linked to patients' medical information using a clinical database. The end aim is to bring cardiovascular precision medicine fully into the clinic at Stanford.
3. Discovery sciences 3.1. Utilization of precision cut tissue slices to evaluate integrin inhibition for the treatment of fibrosis (Johanna R Schaub, Pliant Therapeutics, Inc.) Dr. Schaub presented Pliant Therapeutics' mission to develop bestin-class small molecule inhibitors for fibrotic diseases. As a part of a drug development toolkit, Pliant utilizes precision cut tissue slices (PCTS; de Graaf et al., 2010). PCTS are thin (~150–400 μm) sections of living tissue than are cultured ex vivo and utilized for assessing target expression and therapeutic efficacy. PCTS can be generated from healthy or diseased, rodent or human tissue from lung, liver, kidney, and intestines. Dr. Schaub added that PCTS bridge traditional cell-based assays, preclinical in vivo studies, and clinical studies. The advantages for PCTS come from the presence of multiple cell types and the native architecture and extracellular matrix (ECM) of the tissue of origin, variables that can be missing from cell-based assays. Slices generated from preclinical models are higher throughput than in vivo studies, allowing more conditions to be tested with fewer animals. Slices generated from human tissue provide the opportunity to evaluate efficacy in tissue from the desired patient population. Then, Dr. Schaub presented how Plaint has been utilizing both lung and liver tissues for assessing target expression and anti-fibrotic activity of its integrin inhibitors. Human precision cut lung slices are viable in culture for at least 7 days allowing a window of opportunity to both induce fibrosis in normal tissue with a cocktail of profibrogenic factors and to inhibit fibrosis in tissue from idiopathic pulmonary fibrosis patients with integrin inhibitors. Additionally, human precision cut liver slices are viable in culture for only 2 days, but still provide a platform for determining efficacy of antifibrotics at the gene expression level. PCTS have also been used in the development of imaging tools, testing fluorescent probes to monitor target distribution and target engagement of inhibitors. In summary, precision cut tissue slices are an ex vivo system that bridges traditional cell-based and in vivo assays, providing the native cell types and architecture found in vivo while allowing for higher throughput analysis. Further, human tissue can be used to bridge preclinical models and clinical studies, allowing efficacy testing in patient tissue. Dr. Schaub concluded that Pliant has successfully used this platform in the development of integrin inhibitors as antifibrotics.
3.3. Leveraging large animal models of inherited cardiomyopathy in preclinical pharmacology: the missing piece (Carlos del Rio, MyoKardia, Inc.) Dr. del Rio focused in his on hypertrophic cardiomyopathy (HCM), a heritable cardiac disease that is characterized by hyper-contractility, 4
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impaired filling, and exertional intolerance (Marian & Braunwald, 2017). Given, in part, to the well-established structural and biochemical differences between humans and existing preclinical rodent models, the molecular basis for this pathophysiology remain poorly understood, hindering the development of targeted and more effective therapies. Therefore, a large-animal model of HCM was developed by introducing a heterozygous knock-in R403Q MYH7 (beta myosin) mutation in Yucatan mini-pigs (del Rio et al., 2017). In the setting of this novel model, in vivo and ex vivo studies were performed in to determine both its translational value and the association between induced myofilament abnormalities and the in vivo clinical phenotype. Moreover, the in vivo systolic/diastolic effects of direct myosin-attenuation with a smallmolecule allosteric modulator (MYK-581, a mavacamten analog), were evaluated in both mutant animals and age-matched wildtype (WT) herd-mates (del Rio et al., 2018). Muscle fibers from mutant pigs showed increased Ca2+ sensitivity with decreased cooperativity, favoring enhanced inotropy. Concordant with these observations, mutant pigs showed hyper-contractility in vivo as indicated by both imaging-based (cMR, echocardiography) and invasive load-dependent/-independent inotropic indices. R403Q MYH7 pigs also exhibited diastolic impairments as well as blunted β-adrenergic (β-AR) functional recruitment (a potential mechanism for exertional intolerance in patients), presenting markedly elevated left ventricular (LV) end-diastolic filling pressures (EDPs) and stiffer ventricles. MYK-581 behaved like a negative inotrope in WT animals; however, in mutant animals, it normalized ejection fraction and improved LV compliance, increasing end-diastolic dimensions while lowering EDP. MYK-581 also improved β-AR reserve in the HCM pigs. Notably, direct myosin-modulation with Mavacamten can normalize contractility and improve exercise capacity in patients with HCM. Taken together, this translational dataset highlights the value of novel large-animal models on inherited cardiomyopathy to investigate the mechanistic link between in vivo phenotypes, biophysical twitch mechanics, and sarcomere-mutations while supporting the hypothesis that myofilament-targeted therapies could provide benefit to HCM patients.
by AstraZeneca (Pollard et al., 2017) and the FDA-HESI consortium (Park et al., 2018) also demonstrated the predictive value of the hERG assay and dog or primate QTc studies for predicting FIH or TQT outcomes. A key common message from all these diverse studies is that agents with wide margins (10–30 fold) between therapeutic exposures and drug (unbound) levels associated with QTc prolongation or hERGblockade, have low risk for drug-induced pro-arrhythmia. Given the value of the current ICH S7B models for pro-arrhythmia risk assessment, Dr. Vargas concluded that the new models proposed by the CiPA initiative may be most useful as early stage or follow-up assays, depending on risk evaluation need. These additional tools may assist de-risk drugs with complex off-target profiles (e.g., multi-ion channel inhibition) during candidate selection, or improve clinical risk translation through the use of human cardiomyocyte assays (adult primary (Nguyen et al., 2017) or iPSC-derived (Ando et al., 2017; Blinova et al., 2018)) for assessing altered repolarization, for agents entering Phase 1 clinical trial. 5. Meeting summary, conclusions and future opportunities The West Coast SPS Regional Meeting in Foster City covered a wide range of topics, such as assessment of drug-induced cardiotoxicity (proarrhythmia and contractility risk) and seizure liability, translation of SP data, precision cut tissue slice assay for evaluation of anti-fibrotic potential of drugs, large animal model of inherited cardiomyopathy, engineering of human stem cell-derived tissue constructs, stem cells and genomics for precision medicine, and two case studies on the cardiovascular risk assessment of two small molecules for oncology indications. The presentations generated many questions and provoked exciting discussions. The discussions helped crystalize several key messages and future opportunities: (1) The urgent need for reliable human-relevant in vitro/ex vivo models, with high sensitivity and specificity to predict clinical outcomes, and enable mechanistic investigations, was underlined by several presentations. The potential of new strategies addressing this need was discussed by Drs. Sager, Abi-Gerges, McMahon, Davila, Schaub and Vargas and ability of some of the new models to provide mechanistic insights into cardiotoxicity and neurotoxicity was underlined by Drs Abi-Gerges and Davila. The importance of mechanistic studies, was recently discussed at a Food and Drug Administration White Oak Campus workshop entitled “Cardiomyocytes for mechanistic cardiovascular safety liabilities” (Anon, 2019), and presentations and discussions at the West Coast SPS Regional Meeting also stressed the importance of assays that, by having mechanistic relevance, can generate data useful not only to predict the clinical outcome, but also deconvolute toxicity signals and potentially help with the development of risk mitigation strategies. In this context, several of the participants expressed the belief that powerful new insights could be generated in the coming years from the combination of mechanistic data with analysis tools derived from machine learning and artificial intelligence. Collaborations between pharmaceutical industry experts, regulators and key opinion leaders would be needed to refine this new mechanistic drug discovery paradigm. (2) Large animal models, with either normal or diseased hearts continue to be vital for assessing in vivo cardiovascular effects of drugs and enabling development of safe and effective drugs. The suitability of these large animal models was underscored by Drs Chui, McMahon, del Rio, Vargas and Mr. Stevens, and continuing evaluation of models with diseased hearts is necessary to increase cardiotoxicity assessment of drugs in preclinical safety pharmacology studies. (3) There is a growing demand for models that can simultaneously predict multiple liabilities. An example was provided with the use of adult human primary cardiomyocytes to simultaneously predict
4. Translation of safety pharmacology testing to human trials: what do we know? (Hugo Vargas, Amgen, Inc.) Since the implementation of guidelines ICH S7A (Anon, 2000) and ICH S7B (Anon, 2005a), the community of SP scientists have gained valuable knowledge about the clinical relevance and translational value of the nonclinical models, e.g., in vivo core battery and hERG functional assay. These insights have been gained primarily through data-sharing efforts from individual companies, or pharma industry consortia. The compiling and sharing of real-world nonclinical and clinical SP data from diverse sources has been critical to driving “what we know” about translational value. Dr. Vargas focused in his presentation on recent efforts that underscore the value of nonclinical models and their ability to predict clinical findings, with a focus on QTc prolongation risk evaluation. To date, five publications have examined the real-world nonclinical QTc internal and hERG potency and their relationship to clinical QTc findings, e.g., first-in-human (FIH), TQT, etc. (Ewart et al., 2014; Park et al., 2018; Pollard et al., 2017; Vargas et al., 2015; Wallis, 2010). All of these evaluations focused on small molecules drugs (proprietary molecules; agents in the public domain) and examined the predictive ability of the hERG potency assay and/or the in vivo QTc study (in conscious or anesthetized non-rodent models). A common finding from these investigations is that nonclinical approaches described by ICH S7B are very effective at assessing the clinical risk associated with hERG-mediated QTc risk prolongation. For example, in a data set of 113 small molecules with a range of hERG potencies, the in vivo QT assay conducted in telemetered dogs showed high specificity for predicting FIH-QT findings (Ewart et al., 2014). Similar investigations conducted 5
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drug-induced inotropic and pro-arrhythmia risk (Nguyen et al., 2017) or inotropic risk and structural toxicity with tyrosine kinase inhibitors (Dr Abi-Gerges). (4) iPSC lines can help the understanding of drug efficacy while linking genotype with drug response phenotype of a patient population. A future goal of data obtained from patient-derived stem cells, will be the development of databases that will document how genetic variants affect drug response phenotypes. (5) In his closing remarks, Dr. Vargas recommended a collaborative effort to ensure that new models are adequately validated so as to provide a high level of confidence in their predictive value. Partnerships across pharmaceutical companies and between pharmaceutical companies and regulators could greatly benefit the model validation efforts.
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