JPM-06280; No of Pages 5 Journal of Pharmacological and Toxicological Methods xxx (2015) xxx–xxx
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Original article
The shifting landscape of safety pharmacology in 2015 Michael K. Pugsley a,⁎, Simon Authier a, Michael Stonerook b, Michael J. Curtis c a b c
CiToxLAB Research Inc., 445 Armand Frappier, Laval, QC H7V 4B3, Canada Columbia, MO, United States Cardiovascular Division, Rayne Institute, St Thomas' Hospital, London SE17EH, UK
a r t i c l e
i n f o
Article history: Received 27 May 2015 Received in revised form 28 May 2015 Accepted 29 May 2015 Available online xxxx
a b s t r a c t The relative importance of the discipline of safety pharmacology (which integrates physiology, pharmacologyand toxicology) has evolved since the incorporation of the Safety Pharmacology Society (SPS) as an entity on August 10, 2000. Safety pharmacology (SP), as a synthesis of these other fields of knowledge, is concerned with characterizing the safety profile (or potential undesirable pharmacodynamic effects) of new chemical entities (NCEs) and biologicals. Initially focused on the issue of drug-induced QT prolongation it has developed into an important discipline over the past 15 years with expertise beyond its initial focus on torsades de pointes (TdP). It has become a repository for interrogation of models for drug safety studies and innovative non-clinical model development, validation and implementation. Thus, while safety pharmacology consists of the triumvirate obligatory cardiovascular, central nervous system (CNS) and respiratory system core battery studies it also involves assessing drug effects on numerous other physiological systems (e.g., ocular, auditory, renal, gastrointestinal, blood, immune) leveraging emerging new technologies in a wide range of non-clinical drug safety testing models. As with previous editorials that preface the themed issue on safety pharmacology methods published in the Journal of Pharmacological and Toxicological Methods (JPTM), we highlight here the content derived from the most recent (2014) SPS meeting held in Washington, DC. The dynamics of the discipline remain fervent and method development, extension and refinement are reflected in the content. This issue of the JPTM continues the tradition of providing a publication summary of articles (reviews, commentaries and methods) with impact on the discipline of safety pharmacology. © 2015 Elsevier Inc. All rights reserved.
1. Current status of manuscript submissions to SP issue of JPTM During the last SPS meeting, diverse scientific topics were discussed in a series of symposia composed of internationally-recognized scientists. The sessions encompassed core-battery related topics such as models for the assessment of cardiac function and dysfunction and provided an overview of the central nervous system. However, interesting new topics were introduced such as non-cardiac ion channels and models used in the assessment of peripheral neuropathy and altered autonomic function. While the zebrafish (Sushi or Science?) continues to be a model advocated for use in early safety studies, other thoughtprovoking topics included ‘Nausea and Vomiting: Not a Gagging Matter’ and ‘Should the Sleep State be a Target for Safety Pharmacology?’ The meeting concluded with an important session that provided an update as well as pharmaceutical and regulatory perspectives on the Comprehensive In Vitro Proarrhythmia Assay (CIPA) currently in development. As in previous years, manuscript submissions as content for the focused issue of JPTM are almost as diverse as the nature of the discipline itself but have generally been comprised of topics consistent with those ⁎ Corresponding author. E-mail address: [email protected] (M.K. Pugsley).
safety issues concerning both the pharmaceutical industry as well as regulatory authorities. An overview of the topics that have been published in JPTM can be seen in Fig. 1. When we compared the other vital core battery components (i.e., the CNS and respiratory organ systems) to the cardiovascular system they were a small component of the overall meeting content, unless perhaps some impending regulatory document was to be issued, otherwise they lagged behind in terms of prevalence. Surprisingly there is a marked increase in the number of articles in this issue that examine and investigates CNS drug safety methods and include topics that range from abuse liability and auditory function to methods applied to the assessment of seizure risk. 2. The Diplomate In Safety Pharmacology certification Authier et al. (2015) provide a comprehensive overview of the development and implementation of the Diplomate in Safety Pharmacology (DSP) certification program. The article describes the process by which candidates can obtain certification in understanding of the principles and practice of SP, as has been done by other professional scientific disciplines such as the American Board of Toxicology (ABT) or Society for Toxicologic Pathology (STP). The article outlines advantages to certification including authentication of the discipline within the overall
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Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
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M.K. Pugsley et al. / Journal of Pharmacological and Toxicological Methods xxx (2015) xxx–xxx
Fig. 1. Publication trends for manuscripts that have been published in the annual focused issue of the Journal of Pharmacological & Toxicological Methods. Included are the total number of articles published each year and the nature of the content. Trends for paper were segregated based upon content and whether it involved core battery studies, i.e., the CNS, cardiovascular or respiratory system. Trends are also shown for content related to Supplemental Safety Pharmacology studies (i.e., renal or GI), whether surveys were published as well as recent manuscripts involved in characterizing pluripotent cardiac (iPSC-CM) stem cells and animal welfare.
pharmaceutical community and with regulatory authorities; it encourages participation in SPS activities by other professionals (toxicologists, clinicians, academics) who wish to broaden their professional expertise and it provides an opportunity for candidates to strengthen their fundamental scientific knowledge, consolidate their understanding of regulatory guidelines and stimulate the sharing of methods and model development in the form of publications and presentations on relevant topics in SP. In order to become a DSP the candidates must successfully complete a certification exam conducted at the annual SPS meeting. The DSP exam material consists primarily of information pertinent to the conduct of vital function core battery studies (CNS, cardiovascular, respiratory), supplemental SP studies (renal/urinary, gastrointestinal, autonomics, blood), understanding Regulatory Guidelines (ICHS7A, ICHS7B) as well as relevant cross-functional knowledge (e.g., physiology, pharmacology, biochemistry, pathology, and statistics). 3. Methods used to evaluate CNS function in SP Gauvin, Dalton, and Baird (in press) explored the application (for future studies) of the standard infrared photobeam locomotor activity system. This method is a quantification system used to assess behavior over long time intervals and there is much interest to apply such a system during the investigation of drug withdrawal in rodents. Since locomotor activity in the rat is considered a highly sensitive measure of behavior and a highly reliable index of withdrawal intensity, it is thought that such a system can be used by safety pharmacologists to assist in the determination of the potential abuse liability of a new chemical entity (NCE). The authors showed that minimal differences occur in general animal activity between experimentally-naïve rats and animals that have had surgery and are jacketed in order to implant femoral catheters. They also assessed arterial blood gas monitoring in order to compare whether there were differences in pulmonary function and metabolism between these groups. All the parameters that were assessed appeared stable for the 12 hour monitoring period. A current topic of interest to the CNS community involves the assessment of the seizure risk of an NCE. Metea, Litwak, and Arrezzo (2015) provide a comprehensive review of the non-clinical methods that can be used in the assessment of seizure risk. Discussion regarding in vitro pharmacological profiling, in silico modeling as well as pro-convulsant models (i.e., chemical convulsants, chronic kindling, electroshock) are included in the review and it highlights the strengths and limitations of the use of the electroencephalogram (EEG) patterns that can be
obtained in non-clinical studies. Importantly, the authors highlight appropriate species selection for seizure liability studies and methods of EEG collection methods and data analysis reporting from non-clinical animal models, both of which are essential components of the conduct of proper SP studies. In a second paper, Gauvin, McComb, Code, Dalton, and Baird (2015) characterize the abuse liability of the narcotic analgesic hydrocodone (4,5α-epoxy-3-methoxy-17-methylmorphinan-6-one). Hydrocodone is one of the first FDA approved opioids (in 1943 as Hycodon) and remains one of the most frequently prescribed opioids within the US (as Vicodin or hydrocodone/acetaminophen). In 2007 it was reported that the US consumed 99% of the worldwide supply of the narcotic (Ocampo, 2009; US DEA, 2014a). A review of the US DEA apparent aggregate production quota showed that 99,625 kg of hydrocodone was produced for use in the US in 2014 (US DEA Diversion Control, 2014). Hydrocodone, regardless of the amount or other constituents contained within the formulation, remains a Schedule II compound (US DEA, 2014b). The authors compared the effects of hydrocodone to morphine and oxycodone in a series of self-administration, drug discrimination, and repeat-dose two week dependence liability studies with interesting results. Gilbert, Sgro, Modlin, Wheat, and Kallman (in press) provide a brief communication that effectively describes the patency and longevity of an i.v. self-administration model using rats. The authors explain the improvements in methods they made regarding femoral catheter implantation and examine, chronologically, the number of skin button repairs and catheter replacement surgeries that were needed in animals trained to respond to injections of a reinforcement drug under a fixed ratio schedule. The authors tested 4 different skin button types in the study and conclude with outlining the usefulness of one particular type of skin button for use in long duration (N6 months) safety studies. This is a very informative paper that reduces study duration and increases efficiency by improving upon non-clinical surgical methods. Abernathy, Gauvin, Tapp, Yoder, and Baird (2015) provide a very interesting review article that highlights the auditory system and the possible impact a drug can have on function. It should be known, and may be surprising, that over 700 drugs (or their combinations) have a potential risk for effects on the human auditory system (Cary, Clarke, & Delic, 1997). In the ICH S7A guideline (US FDA, 2001) under section 2.8.1 entitled ‘Follow-up Studies For Safety Pharmacology Core Battery’ it describes (in subsection 2.8.1.1) some additional central nervous system studies including “Behavioral pharmacology, learning and memory, ligand-specific binding, neurochemistry, visual, auditory and/or electrophysiology examinations”. The nature of these types of studies provides a greater depth of understanding than can be provided by the core battery studies on vital functions. Thus, otic drugs either administered within the ear itself or are systemically bioavailable and distribute to the auditory system must be assessed with regard to their safety profile using special study methods. The effects of novel drugs that may impact auditory function need to be evaluated for effects on components of the external ear (i.e., auditory canal and tympanic membrane), middle ear (i.e., the malleus, incus and stapes) as well as the inner ear (i.e., cochlea, organ of Corti, or hair cells) and the vestibulocochlear nerve. The US FDA requires that such drugs be evaluated with the Auditory Brainstem Response (ABR) (US FDA, 2008). As Abernathy et al. (2015) outline, the ABR is an auditory evoked potential that assesses function and drug effects on function by establishing minimum intensity thresholds. These thresholds can then be monitored and changes reflect the impact of dysfunction that develops with drug administration. Drug effects can be either conductive, i.e., changes that occlude the sound conduction pathways in the external or middle ear, or sensorineural, i.e., central hearing impairment occurs due to changes or damage to the inner ear components. The authors discuss the components of the test and outline suggestions regarding conduct of auditory function studies in non-clinical species and conclude that ABR is suitable for use in drug safety evaluations.
Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
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4. Cardiovascular methods in safety pharmacology assessment The article by Morrissette et al. (in press) describes a number of standard correction methods, routinely used in safety pharmacology studies, to determine what best corrects drug-induced QT changes for heart rate in an anesthetized guinea pig model. This is a very well assembled series of studies. While the content is quite familiar to most safety pharmacologists, the nature of the compounds that were tested in the system to ‘stress’ the QT-HR relationship includes ivabradine and ephedrine infusions along with atrial pacing and dofetilide, D,L-sotalol and verapamil administration. The correction formulas used included Bazett (QT / (RR)1/2), Fridericia (QT / (RR)1/3) and Van de Water (QT − 0.0871{60 / (HR) − 1}) in order to determine the best fit formula for the conditions assessed. The authors found that the best fit correction formula was dependent upon the HR range to which it was applied, as one might anticipate, but the authors also remind us that researchers need to identify and understand the study/ model conditions under which the test article is being assessed as these can dramatically affect heart rate. Ideally these details should be known prior to the conduct of the study. Kremer et al. (in press) evaluate the Jacketed External Telemetry (JET™) system in male and female dogs in combination with an implanted miniature blood pressure transmitter (the JET-BP Add-on). They examined the tolerability, functionality, and sensitivity of this combined study design by testing low and high doses of etilefrine (a sympathomimetic amine used in the treatment of orthostatic hypotension), sotalol and hydralazine. The authors found that the pharmacological responses of all the positive controls were dose related as desired. Interestingly they conducted a retrospective power analysis (of a noncentral t-distribution at a power of 0.8 and a significance level of 0.05) which confirmed that the study design (6 dogs/sex/group) permitted detection and statistical differentiation of minor (5–15%) changes in the ECG and blood pressure measurements. Importantly, an anatomical and clinical pathology assessment did not provide any untoward findings that would prevent the use of this system in toxicology studies. Kaiser, Tichenor, Regalia, York, and Holzgrefe (2015) provide a timely paper that outlines the effects of different types of social environments on heart rate and ECG variables in primates using the Jacketed External Telemetry (JET™) system. The authors used several different social housing paradigms and evaluated the influence of each social situation on heart rate. There are few published accounts describing either animal or scientific compromise in cardiovascular safety studies resulting from efforts to socially house the animals. Previously, Klumpp, Trautmann, Markert, and Guth (2006) published on optimizing the experimental environment for the conduct of dog telemetry studies. These authors showed differences in HR and BP with dogs depending upon the cage configuration and group composition during the study. Readers are referred to the US Dept. of Agriculture website (http://awic.nal.usda.gov/research-animals/laboratory-animal-species/ nonhuman-primates) where there are a number of documents that describe “The Welfare of Nonhuman Primates Used in Research” as outlined in the European Commission, Scientific Committee on Animal Health and Animal Welfare. The 2002 report at the site includes information about various enrichment aspects such as social housing, animal training, and provision of visual barriers. This is a timely paper that outlines the effects of different types of social environments on heart rate in jacketed primates and places this issue into the safety pharmacology realm. The authors use several different social housing paradigms and evaluate the influence of that social situation on heart rate and the EKG. Xing et al. (2015) provide a very informative paper that is similarly well timed regarding optimizing animal housing conditions during the conduct of safety pharmacology studies. The paper nicely reviews EKG data obtained from jacketed male and female primates and the effects of moxifloxacin, the clinically used positive thorough QT study (TQT) control drug. The authors examined whether group housing of primates, rather than single housing, was feasible and whether this change
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in housing conditions from a standard, accepted study design would impact the data collected. An assessment of statistical power was also conducted. The authors found that group housing was associated with significantly lower heart rates and the PR and QT intervals on the corresponding EKGs were significantly higher (at the multiple time points assessed) compared to when animals were singly housed. Moxifloxacin increased QT and QTc intervals, as anticipated, but did not differentially affect HR or the PR interval under either housing condition. Conduct of the statistical power analysis suggested that group housing did not negatively impact the magnitude of detectable changes in EKG measures and rather, better power was achieved under group housing conditions. The study concludes that group housing conditions for primates should be considered when conducting EKG assessments in safety pharmacology (or toxicology) studies. Wallis, Gharanei, and Maddock (in press) provide a very interesting and timely literature review article on cardiac contractility. Currently work is ongoing by those in the pharmaceutical industry and contract research organizations through consortia such as the Health and Environmental Sciences Institute (HESI) to evaluate measures of cardiac inotropy (i.e., + dP/dtmax or the QA interval) and lusitropy (− dP/ dtmax or tau) as additional functional physiological endpoints to examine drug safety within the conduct of the safety pharmacology evaluation of a NCE (Sarazan, Kroehle, & Main, 2012; Pierson et al., 2013; Guth et al., 2015). The paper outlines the concordance between ex vivo assays ranging from perfused Langendorff whole hearts or tissues (ventricles, atria or papillary muscle) isolated from hearts from many different species. The authors conclude with appraisal of the usefulness of using in vitro assays as a sensitive hazard identification assay for assessing drug effects on cardiac contractility. 5. In silico safety pharmacology methods In their paper, Williams and Mirams (2015) provide an overview of their available open source software and web portal that permits safety pharmacologists (and others) to input data that they have for blockade of the proposed CIPA in channels (IKr, ICaL, INa, IKs, IK1 and Ito) to conduct simulations using different mathematical models. The models available include the Ten Tusscher and Panfilov (2006), Grandi, Pasqualini, and Bers (2010), O'Hara, Virág, Varró, and Rudy (2011) and human stemcell derived myocyte (Paci, Hyttinen, Aalto-Setala, & Severi, 2013). The web portal can be found at https://chaste.cs.ox.ac.uk/ActionPotential. Users can input their own data as suggested by the authors using human IC50 values for channel block derived from full, or extrapolated, concentration–response curves. The program will then determine effects on the cardiac AP and whether there is a potential for development of aberrant rhythms. The software program provides a simple means for examination of drug effects on the CIPA ion channels in response to the CIPA initiative and allows the user access to emerging technology with applicability to cardiac electrophysiology simulations. 6. Stem cells and safety pharmacology Current alternative screening models and methods under consideration by the safety pharmacology and regulatory communities for the CIPA initiative include human stem cells in which hERG (IKr) as well as other cardiac ion currents such as the fast inward sodium (INa), calcium (ICaL) and additional potassium currents (IK1 and IKs) can be assessed in totality (Pugsley, Authier, & Curtis, 2008; Pugsley, Dalton, Authier, & Curtis, 2014). Thus, rather than examining drug effects on heterogeneously expressed human ion channel isoforms in HEK or CHO cell lines (as is current practice) to characterize drug safety, the safety pharmacology and scientific community is investigating applicability of human induced pluripotent stem cells (Peng, Lacerda, Kirsch, Brown, & Bruening-Wright, 2010). Induced pluripotent stem cell cardiac myocytes (iPSC-CMs) of somatic origin continue to be evaluated for all aspects of their electrophysiological potential (Tanaka et al., 2009;
Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
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Gibson, Yue, Bronson, Palmer, & Numann, 2014). In this issue of the Journal, Asakura et al. (2015) conduct a very comprehensive assessment in the characterization of the electrophysiological effects of drugs (E4031, moxifloxacin, terfenadine, and aspirin) on cardiac stem cells using multi-electrode array (MEA) systems. As the authors note, the MEA system is frequently used in such assessments but the optimal experimental conditions (i.e., filter frequency, cell plating density etc.) have not been completely defined. Extracellular field potentials (FPs) were recorded from iPS cell-derived cardiomyocyte (iCell® hiPSC-CM) sheets at 0.1 or 1 Hz in the absence and presence of drugs. Studies also examined the relationship between FPs and cardiac action potentials (APs) by simultaneous recording both parameters using the FluoVolt™ membrane potential dye. The authors conclude that FP waveform amplitudes increase with increasing plate density of cells and that FP can be used to assess the QT effects of novel drugs but electrophysiological study conditions should be defined in order to produce consistent, reliable data. Rast et al. (2015) describe the use of an integrated platform that incorporates multi-well field potential (FP) recording methods with the use of Fura-2-based calcium transient ratiometry. The cells used are human induced pluripotent stem cell derived cardiomyocytes (hi-PSC-CM). The authors tested a number of calcium channel blockers (verapamil, diltiazem and nifedipine) and the calcium-SR storage blocker ryanodine as well as calcium channel agonists (FPL 64176 and BAY K 8644). A physiological assessment was also made using (±)isoprenaline and the M2 agonist, arecaidine propargyl ester. This study is a definite first for safety pharmacology since it combines complementary in vitro methods with a potential for use in development of the CIPA initiative currently ongoing between the pharmaceutical industry, contract research organizations and regulatory authorities (FDA) (Sager, Gintant, Turner, Pettit, & Stockbridge, 2014). The authors describe the technical difficulties associated with resolution and matching of calcium transients with the FP but show that the combined technology platforms provides for advanced interpretation of the FPs recorded in terms of drug effects on cellular calcium modulation. 7. A best practices survey on renal safety pharmacology Benjamin et al. (2015) conducted a survey designed to investigate current best practices with regard to assessment of drug-induced renal toxicity. The survey was designed to determine the strategies that are taken by industry scientists to investigate observed renal toxicity in either single safety pharmacology or repeat dose toxicology studies. It also attempted to ascertain the nature of any mechanistic studies that might be conducted and whether the validation of drug-induced kidney injury (DIKI) biomarkers was impactful for drug safety assessments. The survey showed that renal safety pharmacology studies are not frequently conducted but that urinary measurements are most commonly conducted with repeat-dose toxicity studies. Not surprisingly, there was an indication of a lack of consistent use of DIKI biomarkers in urinary safety studies. 8. Summary As in the past, safety pharmacology continues to seek to provide validation and refine methods for use in preclinical hazard identification of NCE adverse effect liability. It does so in accordance with the scientific methods that rapidly progress with technological advances for functional measures. Additionally safety pharmacology seeks to organize and strategize the implementation of methods according to the guidance issued by the ICH while aiming to maximize translational value of the data acquired in hope of better predictivity in drug discovery and development. At the same time, through publication of its works, it seeks to globally inform safety pharmacologists and those involved in drug safety assessment.
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US DEA (2014b). Drugs of abuse (2011 edition). A DEA resource guide. US Department of Justice (http://www.dea.gov/pr/multimedia-library/publications/drug_of_abuse.pdf). US DEA Diversion Control (2014). Aggregate production quota history for selected substances. http://www.deadiversion.usdoj.gov/quotas/quota_history.pdf US FDA (2001). ICHS7A: Safety pharmacology studies for human pharmaceuticals. Federal Register, 66, 36791–36792. US FDA (2008). Guidance for industry and review staff nonclinical safety evaluation of reformulated drug products and products intended for administration by an alternate route. Available at: http://www.fda.gov/cder/guidance/index.html Wallis, R., Gharanei, M., & Maddock, H.L. (2015). Predictivity of in vitro non-clinical cardiac contractility assays for effects in humans — A literature search. Journal of Pharmacological and Toxicological Methods http://dx.doi.org/10.1016/j.vascn.2015.05. 009 (pii: S1056-8719(15)00065-9, in press). Williams, G., & Mirams, G.R. (2015). A web portal for in-silico action potential predictions. Journal of Pharmacological and Toxicological Methods http://dx.doi.org/10.1016/j. vascn.2015.05.002 (pii: S1056-8719(15)00049-0). Xing, G., Lu, J., Hu, M., Wang, S., Zhao, L., Zheng, W., Schofield, J., Oldman, K., Adkins, D., Yu, H., Platz, S., Ren, J., & Skinner, M. (2015). Effects of group housing on ECG assessment in conscious cynomolgus monkeys. Journal of Pharmacological and Toxicological Methods http://dx.doi.org/10.1016/j.vascn.2015.05.004 (pii: S1056-8719(15)00051-9).
Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
Contents lists available at ScienceDirect
Journal of Pharmacological and Toxicological Methods journal homepage: www.elsevier.com/locate/jpharmtox
Original article
The shifting landscape of safety pharmacology in 2015 Michael K. Pugsley a,⁎, Simon Authier a, Michael Stonerook b, Michael J. Curtis c a b c
CiToxLAB Research Inc., 445 Armand Frappier, Laval, QC H7V 4B3, Canada Columbia, MO, United States Cardiovascular Division, Rayne Institute, St Thomas' Hospital, London SE17EH, UK
a r t i c l e
i n f o
Article history: Received 27 May 2015 Received in revised form 28 May 2015 Accepted 29 May 2015 Available online xxxx
a b s t r a c t The relative importance of the discipline of safety pharmacology (which integrates physiology, pharmacologyand toxicology) has evolved since the incorporation of the Safety Pharmacology Society (SPS) as an entity on August 10, 2000. Safety pharmacology (SP), as a synthesis of these other fields of knowledge, is concerned with characterizing the safety profile (or potential undesirable pharmacodynamic effects) of new chemical entities (NCEs) and biologicals. Initially focused on the issue of drug-induced QT prolongation it has developed into an important discipline over the past 15 years with expertise beyond its initial focus on torsades de pointes (TdP). It has become a repository for interrogation of models for drug safety studies and innovative non-clinical model development, validation and implementation. Thus, while safety pharmacology consists of the triumvirate obligatory cardiovascular, central nervous system (CNS) and respiratory system core battery studies it also involves assessing drug effects on numerous other physiological systems (e.g., ocular, auditory, renal, gastrointestinal, blood, immune) leveraging emerging new technologies in a wide range of non-clinical drug safety testing models. As with previous editorials that preface the themed issue on safety pharmacology methods published in the Journal of Pharmacological and Toxicological Methods (JPTM), we highlight here the content derived from the most recent (2014) SPS meeting held in Washington, DC. The dynamics of the discipline remain fervent and method development, extension and refinement are reflected in the content. This issue of the JPTM continues the tradition of providing a publication summary of articles (reviews, commentaries and methods) with impact on the discipline of safety pharmacology. © 2015 Elsevier Inc. All rights reserved.
1. Current status of manuscript submissions to SP issue of JPTM During the last SPS meeting, diverse scientific topics were discussed in a series of symposia composed of internationally-recognized scientists. The sessions encompassed core-battery related topics such as models for the assessment of cardiac function and dysfunction and provided an overview of the central nervous system. However, interesting new topics were introduced such as non-cardiac ion channels and models used in the assessment of peripheral neuropathy and altered autonomic function. While the zebrafish (Sushi or Science?) continues to be a model advocated for use in early safety studies, other thoughtprovoking topics included ‘Nausea and Vomiting: Not a Gagging Matter’ and ‘Should the Sleep State be a Target for Safety Pharmacology?’ The meeting concluded with an important session that provided an update as well as pharmaceutical and regulatory perspectives on the Comprehensive In Vitro Proarrhythmia Assay (CIPA) currently in development. As in previous years, manuscript submissions as content for the focused issue of JPTM are almost as diverse as the nature of the discipline itself but have generally been comprised of topics consistent with those ⁎ Corresponding author. E-mail address: [email protected] (M.K. Pugsley).
safety issues concerning both the pharmaceutical industry as well as regulatory authorities. An overview of the topics that have been published in JPTM can be seen in Fig. 1. When we compared the other vital core battery components (i.e., the CNS and respiratory organ systems) to the cardiovascular system they were a small component of the overall meeting content, unless perhaps some impending regulatory document was to be issued, otherwise they lagged behind in terms of prevalence. Surprisingly there is a marked increase in the number of articles in this issue that examine and investigates CNS drug safety methods and include topics that range from abuse liability and auditory function to methods applied to the assessment of seizure risk. 2. The Diplomate In Safety Pharmacology certification Authier et al. (2015) provide a comprehensive overview of the development and implementation of the Diplomate in Safety Pharmacology (DSP) certification program. The article describes the process by which candidates can obtain certification in understanding of the principles and practice of SP, as has been done by other professional scientific disciplines such as the American Board of Toxicology (ABT) or Society for Toxicologic Pathology (STP). The article outlines advantages to certification including authentication of the discipline within the overall
http://dx.doi.org/10.1016/j.vascn.2015.05.013 1056-8719/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
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Fig. 1. Publication trends for manuscripts that have been published in the annual focused issue of the Journal of Pharmacological & Toxicological Methods. Included are the total number of articles published each year and the nature of the content. Trends for paper were segregated based upon content and whether it involved core battery studies, i.e., the CNS, cardiovascular or respiratory system. Trends are also shown for content related to Supplemental Safety Pharmacology studies (i.e., renal or GI), whether surveys were published as well as recent manuscripts involved in characterizing pluripotent cardiac (iPSC-CM) stem cells and animal welfare.
pharmaceutical community and with regulatory authorities; it encourages participation in SPS activities by other professionals (toxicologists, clinicians, academics) who wish to broaden their professional expertise and it provides an opportunity for candidates to strengthen their fundamental scientific knowledge, consolidate their understanding of regulatory guidelines and stimulate the sharing of methods and model development in the form of publications and presentations on relevant topics in SP. In order to become a DSP the candidates must successfully complete a certification exam conducted at the annual SPS meeting. The DSP exam material consists primarily of information pertinent to the conduct of vital function core battery studies (CNS, cardiovascular, respiratory), supplemental SP studies (renal/urinary, gastrointestinal, autonomics, blood), understanding Regulatory Guidelines (ICHS7A, ICHS7B) as well as relevant cross-functional knowledge (e.g., physiology, pharmacology, biochemistry, pathology, and statistics). 3. Methods used to evaluate CNS function in SP Gauvin, Dalton, and Baird (in press) explored the application (for future studies) of the standard infrared photobeam locomotor activity system. This method is a quantification system used to assess behavior over long time intervals and there is much interest to apply such a system during the investigation of drug withdrawal in rodents. Since locomotor activity in the rat is considered a highly sensitive measure of behavior and a highly reliable index of withdrawal intensity, it is thought that such a system can be used by safety pharmacologists to assist in the determination of the potential abuse liability of a new chemical entity (NCE). The authors showed that minimal differences occur in general animal activity between experimentally-naïve rats and animals that have had surgery and are jacketed in order to implant femoral catheters. They also assessed arterial blood gas monitoring in order to compare whether there were differences in pulmonary function and metabolism between these groups. All the parameters that were assessed appeared stable for the 12 hour monitoring period. A current topic of interest to the CNS community involves the assessment of the seizure risk of an NCE. Metea, Litwak, and Arrezzo (2015) provide a comprehensive review of the non-clinical methods that can be used in the assessment of seizure risk. Discussion regarding in vitro pharmacological profiling, in silico modeling as well as pro-convulsant models (i.e., chemical convulsants, chronic kindling, electroshock) are included in the review and it highlights the strengths and limitations of the use of the electroencephalogram (EEG) patterns that can be
obtained in non-clinical studies. Importantly, the authors highlight appropriate species selection for seizure liability studies and methods of EEG collection methods and data analysis reporting from non-clinical animal models, both of which are essential components of the conduct of proper SP studies. In a second paper, Gauvin, McComb, Code, Dalton, and Baird (2015) characterize the abuse liability of the narcotic analgesic hydrocodone (4,5α-epoxy-3-methoxy-17-methylmorphinan-6-one). Hydrocodone is one of the first FDA approved opioids (in 1943 as Hycodon) and remains one of the most frequently prescribed opioids within the US (as Vicodin or hydrocodone/acetaminophen). In 2007 it was reported that the US consumed 99% of the worldwide supply of the narcotic (Ocampo, 2009; US DEA, 2014a). A review of the US DEA apparent aggregate production quota showed that 99,625 kg of hydrocodone was produced for use in the US in 2014 (US DEA Diversion Control, 2014). Hydrocodone, regardless of the amount or other constituents contained within the formulation, remains a Schedule II compound (US DEA, 2014b). The authors compared the effects of hydrocodone to morphine and oxycodone in a series of self-administration, drug discrimination, and repeat-dose two week dependence liability studies with interesting results. Gilbert, Sgro, Modlin, Wheat, and Kallman (in press) provide a brief communication that effectively describes the patency and longevity of an i.v. self-administration model using rats. The authors explain the improvements in methods they made regarding femoral catheter implantation and examine, chronologically, the number of skin button repairs and catheter replacement surgeries that were needed in animals trained to respond to injections of a reinforcement drug under a fixed ratio schedule. The authors tested 4 different skin button types in the study and conclude with outlining the usefulness of one particular type of skin button for use in long duration (N6 months) safety studies. This is a very informative paper that reduces study duration and increases efficiency by improving upon non-clinical surgical methods. Abernathy, Gauvin, Tapp, Yoder, and Baird (2015) provide a very interesting review article that highlights the auditory system and the possible impact a drug can have on function. It should be known, and may be surprising, that over 700 drugs (or their combinations) have a potential risk for effects on the human auditory system (Cary, Clarke, & Delic, 1997). In the ICH S7A guideline (US FDA, 2001) under section 2.8.1 entitled ‘Follow-up Studies For Safety Pharmacology Core Battery’ it describes (in subsection 2.8.1.1) some additional central nervous system studies including “Behavioral pharmacology, learning and memory, ligand-specific binding, neurochemistry, visual, auditory and/or electrophysiology examinations”. The nature of these types of studies provides a greater depth of understanding than can be provided by the core battery studies on vital functions. Thus, otic drugs either administered within the ear itself or are systemically bioavailable and distribute to the auditory system must be assessed with regard to their safety profile using special study methods. The effects of novel drugs that may impact auditory function need to be evaluated for effects on components of the external ear (i.e., auditory canal and tympanic membrane), middle ear (i.e., the malleus, incus and stapes) as well as the inner ear (i.e., cochlea, organ of Corti, or hair cells) and the vestibulocochlear nerve. The US FDA requires that such drugs be evaluated with the Auditory Brainstem Response (ABR) (US FDA, 2008). As Abernathy et al. (2015) outline, the ABR is an auditory evoked potential that assesses function and drug effects on function by establishing minimum intensity thresholds. These thresholds can then be monitored and changes reflect the impact of dysfunction that develops with drug administration. Drug effects can be either conductive, i.e., changes that occlude the sound conduction pathways in the external or middle ear, or sensorineural, i.e., central hearing impairment occurs due to changes or damage to the inner ear components. The authors discuss the components of the test and outline suggestions regarding conduct of auditory function studies in non-clinical species and conclude that ABR is suitable for use in drug safety evaluations.
Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
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4. Cardiovascular methods in safety pharmacology assessment The article by Morrissette et al. (in press) describes a number of standard correction methods, routinely used in safety pharmacology studies, to determine what best corrects drug-induced QT changes for heart rate in an anesthetized guinea pig model. This is a very well assembled series of studies. While the content is quite familiar to most safety pharmacologists, the nature of the compounds that were tested in the system to ‘stress’ the QT-HR relationship includes ivabradine and ephedrine infusions along with atrial pacing and dofetilide, D,L-sotalol and verapamil administration. The correction formulas used included Bazett (QT / (RR)1/2), Fridericia (QT / (RR)1/3) and Van de Water (QT − 0.0871{60 / (HR) − 1}) in order to determine the best fit formula for the conditions assessed. The authors found that the best fit correction formula was dependent upon the HR range to which it was applied, as one might anticipate, but the authors also remind us that researchers need to identify and understand the study/ model conditions under which the test article is being assessed as these can dramatically affect heart rate. Ideally these details should be known prior to the conduct of the study. Kremer et al. (in press) evaluate the Jacketed External Telemetry (JET™) system in male and female dogs in combination with an implanted miniature blood pressure transmitter (the JET-BP Add-on). They examined the tolerability, functionality, and sensitivity of this combined study design by testing low and high doses of etilefrine (a sympathomimetic amine used in the treatment of orthostatic hypotension), sotalol and hydralazine. The authors found that the pharmacological responses of all the positive controls were dose related as desired. Interestingly they conducted a retrospective power analysis (of a noncentral t-distribution at a power of 0.8 and a significance level of 0.05) which confirmed that the study design (6 dogs/sex/group) permitted detection and statistical differentiation of minor (5–15%) changes in the ECG and blood pressure measurements. Importantly, an anatomical and clinical pathology assessment did not provide any untoward findings that would prevent the use of this system in toxicology studies. Kaiser, Tichenor, Regalia, York, and Holzgrefe (2015) provide a timely paper that outlines the effects of different types of social environments on heart rate and ECG variables in primates using the Jacketed External Telemetry (JET™) system. The authors used several different social housing paradigms and evaluated the influence of each social situation on heart rate. There are few published accounts describing either animal or scientific compromise in cardiovascular safety studies resulting from efforts to socially house the animals. Previously, Klumpp, Trautmann, Markert, and Guth (2006) published on optimizing the experimental environment for the conduct of dog telemetry studies. These authors showed differences in HR and BP with dogs depending upon the cage configuration and group composition during the study. Readers are referred to the US Dept. of Agriculture website (http://awic.nal.usda.gov/research-animals/laboratory-animal-species/ nonhuman-primates) where there are a number of documents that describe “The Welfare of Nonhuman Primates Used in Research” as outlined in the European Commission, Scientific Committee on Animal Health and Animal Welfare. The 2002 report at the site includes information about various enrichment aspects such as social housing, animal training, and provision of visual barriers. This is a timely paper that outlines the effects of different types of social environments on heart rate in jacketed primates and places this issue into the safety pharmacology realm. The authors use several different social housing paradigms and evaluate the influence of that social situation on heart rate and the EKG. Xing et al. (2015) provide a very informative paper that is similarly well timed regarding optimizing animal housing conditions during the conduct of safety pharmacology studies. The paper nicely reviews EKG data obtained from jacketed male and female primates and the effects of moxifloxacin, the clinically used positive thorough QT study (TQT) control drug. The authors examined whether group housing of primates, rather than single housing, was feasible and whether this change
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in housing conditions from a standard, accepted study design would impact the data collected. An assessment of statistical power was also conducted. The authors found that group housing was associated with significantly lower heart rates and the PR and QT intervals on the corresponding EKGs were significantly higher (at the multiple time points assessed) compared to when animals were singly housed. Moxifloxacin increased QT and QTc intervals, as anticipated, but did not differentially affect HR or the PR interval under either housing condition. Conduct of the statistical power analysis suggested that group housing did not negatively impact the magnitude of detectable changes in EKG measures and rather, better power was achieved under group housing conditions. The study concludes that group housing conditions for primates should be considered when conducting EKG assessments in safety pharmacology (or toxicology) studies. Wallis, Gharanei, and Maddock (in press) provide a very interesting and timely literature review article on cardiac contractility. Currently work is ongoing by those in the pharmaceutical industry and contract research organizations through consortia such as the Health and Environmental Sciences Institute (HESI) to evaluate measures of cardiac inotropy (i.e., + dP/dtmax or the QA interval) and lusitropy (− dP/ dtmax or tau) as additional functional physiological endpoints to examine drug safety within the conduct of the safety pharmacology evaluation of a NCE (Sarazan, Kroehle, & Main, 2012; Pierson et al., 2013; Guth et al., 2015). The paper outlines the concordance between ex vivo assays ranging from perfused Langendorff whole hearts or tissues (ventricles, atria or papillary muscle) isolated from hearts from many different species. The authors conclude with appraisal of the usefulness of using in vitro assays as a sensitive hazard identification assay for assessing drug effects on cardiac contractility. 5. In silico safety pharmacology methods In their paper, Williams and Mirams (2015) provide an overview of their available open source software and web portal that permits safety pharmacologists (and others) to input data that they have for blockade of the proposed CIPA in channels (IKr, ICaL, INa, IKs, IK1 and Ito) to conduct simulations using different mathematical models. The models available include the Ten Tusscher and Panfilov (2006), Grandi, Pasqualini, and Bers (2010), O'Hara, Virág, Varró, and Rudy (2011) and human stemcell derived myocyte (Paci, Hyttinen, Aalto-Setala, & Severi, 2013). The web portal can be found at https://chaste.cs.ox.ac.uk/ActionPotential. Users can input their own data as suggested by the authors using human IC50 values for channel block derived from full, or extrapolated, concentration–response curves. The program will then determine effects on the cardiac AP and whether there is a potential for development of aberrant rhythms. The software program provides a simple means for examination of drug effects on the CIPA ion channels in response to the CIPA initiative and allows the user access to emerging technology with applicability to cardiac electrophysiology simulations. 6. Stem cells and safety pharmacology Current alternative screening models and methods under consideration by the safety pharmacology and regulatory communities for the CIPA initiative include human stem cells in which hERG (IKr) as well as other cardiac ion currents such as the fast inward sodium (INa), calcium (ICaL) and additional potassium currents (IK1 and IKs) can be assessed in totality (Pugsley, Authier, & Curtis, 2008; Pugsley, Dalton, Authier, & Curtis, 2014). Thus, rather than examining drug effects on heterogeneously expressed human ion channel isoforms in HEK or CHO cell lines (as is current practice) to characterize drug safety, the safety pharmacology and scientific community is investigating applicability of human induced pluripotent stem cells (Peng, Lacerda, Kirsch, Brown, & Bruening-Wright, 2010). Induced pluripotent stem cell cardiac myocytes (iPSC-CMs) of somatic origin continue to be evaluated for all aspects of their electrophysiological potential (Tanaka et al., 2009;
Please cite this article as: Pugsley, M.K., et al., The shifting landscape of safety pharmacology in 2015, Journal of Pharmacological and Toxicological Methods (2015), http://dx.doi.org/10.1016/j.vascn.2015.05.013
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Gibson, Yue, Bronson, Palmer, & Numann, 2014). In this issue of the Journal, Asakura et al. (2015) conduct a very comprehensive assessment in the characterization of the electrophysiological effects of drugs (E4031, moxifloxacin, terfenadine, and aspirin) on cardiac stem cells using multi-electrode array (MEA) systems. As the authors note, the MEA system is frequently used in such assessments but the optimal experimental conditions (i.e., filter frequency, cell plating density etc.) have not been completely defined. Extracellular field potentials (FPs) were recorded from iPS cell-derived cardiomyocyte (iCell® hiPSC-CM) sheets at 0.1 or 1 Hz in the absence and presence of drugs. Studies also examined the relationship between FPs and cardiac action potentials (APs) by simultaneous recording both parameters using the FluoVolt™ membrane potential dye. The authors conclude that FP waveform amplitudes increase with increasing plate density of cells and that FP can be used to assess the QT effects of novel drugs but electrophysiological study conditions should be defined in order to produce consistent, reliable data. Rast et al. (2015) describe the use of an integrated platform that incorporates multi-well field potential (FP) recording methods with the use of Fura-2-based calcium transient ratiometry. The cells used are human induced pluripotent stem cell derived cardiomyocytes (hi-PSC-CM). The authors tested a number of calcium channel blockers (verapamil, diltiazem and nifedipine) and the calcium-SR storage blocker ryanodine as well as calcium channel agonists (FPL 64176 and BAY K 8644). A physiological assessment was also made using (±)isoprenaline and the M2 agonist, arecaidine propargyl ester. This study is a definite first for safety pharmacology since it combines complementary in vitro methods with a potential for use in development of the CIPA initiative currently ongoing between the pharmaceutical industry, contract research organizations and regulatory authorities (FDA) (Sager, Gintant, Turner, Pettit, & Stockbridge, 2014). The authors describe the technical difficulties associated with resolution and matching of calcium transients with the FP but show that the combined technology platforms provides for advanced interpretation of the FPs recorded in terms of drug effects on cellular calcium modulation. 7. A best practices survey on renal safety pharmacology Benjamin et al. (2015) conducted a survey designed to investigate current best practices with regard to assessment of drug-induced renal toxicity. The survey was designed to determine the strategies that are taken by industry scientists to investigate observed renal toxicity in either single safety pharmacology or repeat dose toxicology studies. It also attempted to ascertain the nature of any mechanistic studies that might be conducted and whether the validation of drug-induced kidney injury (DIKI) biomarkers was impactful for drug safety assessments. The survey showed that renal safety pharmacology studies are not frequently conducted but that urinary measurements are most commonly conducted with repeat-dose toxicity studies. Not surprisingly, there was an indication of a lack of consistent use of DIKI biomarkers in urinary safety studies. 8. Summary As in the past, safety pharmacology continues to seek to provide validation and refine methods for use in preclinical hazard identification of NCE adverse effect liability. It does so in accordance with the scientific methods that rapidly progress with technological advances for functional measures. Additionally safety pharmacology seeks to organize and strategize the implementation of methods according to the guidance issued by the ICH while aiming to maximize translational value of the data acquired in hope of better predictivity in drug discovery and development. At the same time, through publication of its works, it seeks to globally inform safety pharmacologists and those involved in drug safety assessment.
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