Is there a role for the no observed adverse effect level in safety pharmacology?

In nonclinical toxicology the highest dose or exposure without test article-related adverse effects, known as the No Observed Adverse Effect Level (NOAEL), is a variable that may be determined. In safety pharmacology the vast majority of the endpoints measured are quantitative numeric functional endpoints such as changes in heart rate, blood pressure or respiratory frequency, endpoints that are usually not assessed using a defined framework of adversity. Therefore, we asked the question: is there a role for the NOAEL in safety pharmacology? To help answer this question, we conducted a survey via the Safety Pharmacology Society. We found that within safety pharmacology there is no formal definition of adversity and no guidance on defining NOAEL. We also found, perhaps unsurprisingly, there is no agreed rubric for using a NOAEL in safety pharmacology and we learned that the NOAEL is not a requirement in order to progress a new investigational drug through the regulatory process. Thus, a summary label such as NOAEL lacks nuance and disregards context in relation to the nature and the severity of the safety pharmacology findings. Consequently, defining 'adversity' and determining a NOAEL in safety pharmacology studies are not recommended since the range of functional endpoints investigated do not conform to a binary 'toxic/non-toxic' rubric. Focusing on describing test article-related effects on safety pharmacology endpoints, using reasoned arguments as part of an integrated risk assessment, will ensure that the clinical pharmacologists and regulatory bodies see a clear description of relevant findings at each dose or exposure level.

Response of safety pharmacologists to challenges arising from the rapidly evolving changes in the pharmaceutical industry.

This commentary highlights and expands upon the thoughts conveyed in the lecture by Dr. Alan S. Bass, recipient of the 2017 Distinguished Service Award from the Safety Pharmacology Society, given on 27 September 2017 in Berlin, Germany. The lecture discussed the societal, scientific, technological, regulatory and economic events that dramatically impacted the pharmaceutical industry and ultimately led to significant changes in the strategic operations and practices of safety pharmacology. It focused on the emerging challenges and opportunities, and considered the lessons learned from drug failures and the influences of world events, including the financial crisis that ultimately led to a collapse of the world economies from which we are now recovering. Events such as these, which continue to today, challenge the assumptions that form the foundation of our discipline and dramatically affect the way that safety pharmacology is practiced. These include the latest scientific and technological developments contributing to the design and advancement of safe medicines. More broadly, they reflect the philosophical mission of safety pharmacology and the roles and responsibilities served by safety pharmacologists. As the discipline of Safety Pharmacology continues to evolve, develop and mature, the reader is invited to reflect on past experiences as a framework towards a vision of the future of the field.

A Historical View and Vision into the Future of the Field of Safety Pharmacology.

Professor Gerhard Zbinden recognized in the 1970s that the standards of the day for testing new candidate drugs in preclinical toxicity studies failed to identify acute pharmacodynamic adverse events that had the potential to harm participants in clinical trials. From his vision emerged the field of safety pharmacology, formally defined in the International Conference on Harmonization (ICH) S7A guidelines as "those studies that investigate the potential undesirable pharmacodynamic effects of a substance on physiological functions in relation to exposure in the therapeutic range and above." Initially, evaluations of small-molecule pharmacodynamic safety utilized efficacy models and were an ancillary responsibility of discovery scientists. However, over time, the relationship of these studies to overall safety was reflected by the regulatory agencies who, in directing the practice of safety pharmacology through guidance documents, prompted transition of responsibility to drug safety departments (e.g., toxicology). Events that have further shaped the field over the past 15 years include the ICH S7B guidance, evolution of molecular technologies leading to identification of new therapeutic targets with uncertain toxicities, introduction of data collection using more sophisticated and refined technologies, and utilization of transgenic animal models probing critical scientific questions regarding novel targets of toxicity. The collapse of the worldwide economy in the latter half of the first decade of the twenty-first century, continuing high rates of compound attrition during clinical development and post-approval and sharply increasing costs of drug development have led to significant strategy changes, contraction of the size of pharmaceutical organizations, and refocusing of therapeutic areas of investigation. With these changes has come movement away from dedicated internal safety pharmacology capability to utilization of capabilities within external contract research organizations. This movement has created the opportunity for the safety pharmacology discipline to come "full circle" and return to the drug discovery arena (target identification through clinical candidate selection) to contribute to the mitigation of the high rate of candidate drug failure through better compound selection decision making. Finally, the changing focus of science and losses in didactic training of scientists in whole animal physiology and pharmacology have revealed a serious gap in the future availability of qualified individuals to apply the principles of safety pharmacology in support of drug discovery and development. This is a significant deficiency that at present is only partially met with academic and professional society programs advancing a minimal level of training. In summary, with the exception that the future availability of suitably trained scientists is a critical need for the field that remains to be effectively addressed, the prospects for the future of safety pharmacology are hopeful and promising, and challenging for those individuals who want to assume this responsibility. What began in the early part of the new millennium as a relatively simple model of testing to assure the safety of Phase I clinical subjects and patients from acute deleterious effects on life-supporting organ systems has grown with experience and time to a science that mobilizes the principles of cellular and molecular biology and attempts to predict acute adverse events and those associated with long-term treatment. These challenges call for scientists with a broad range of in-depth scientific knowledge and an ability to adapt to a dynamic and forever changing industry. Identifying individuals who will serve today and training those who will serve in the future will fall to all of us who are committed to this important field of science.

Evaluation of drug-induced QT interval prolongation in animal and human studies: a literature review of concordance.

Evaluating whether a new medication prolongs QT intervals is a critical safety activity that is conducted in a sensitive animal model during non-clinical drug development. The importance of QT liability detection has been reinforced by non-clinical [International Conference on Harmonization (ICH) S7B] and clinical (ICH E14) regulatory guidance from the International Conference on Harmonization. A key challenge for the cardiovascular safety community is to understand how the finding from a non-clinical in vivo QT assay in animals predicts the outcomes of a clinical QT evaluation in humans. The Health and Environmental Sciences Institute Pro-Arrhythmia Working Group performed a literature search (1960-2011) to identify both human and non-rodent animal studies that assessed QT signal concordance between species and identified drugs that prolonged or did not prolong the QT interval. The main finding was the excellent agreement between QT results in humans and non-rodent animals. Ninety-one percent (21 of 23) of drugs that prolonged the QT interval in humans also did so in animals, and 88% (15 of 17) of drugs that did not prolong the QT interval in humans had no effect on animals. This suggests that QT interval data derived from relevant non-rodent models has a 90% chance of predicting QT findings in humans. Disagreement can occur, but in the limited cases of QT discordance we identified, there appeared to be plausible explanations for the underlying disconnect between the human and non-rodent animal QT outcomes.

Discovery of liver-targeted inhibitors of stearoyl-CoA desaturase (SCD1).

Inhibitors based on a benzo-fused spirocyclic oxazepine scaffold were discovered for stearoyl-coenzyme A (CoA) desaturase 1 (SCD1) and subsequently optimized to potent compounds with favorable pharmacokinetic profiles and in vivo efficacy in reducing the desaturation index in a mouse model. Initial optimization revealed potency preferences for the oxazepine core and benzylic positions, while substituents on the piperidine portions were more tolerant and allowed for tuning of potency and PK properties. After preparation and testing of a range of functional groups on the piperidine nitrogen, three classes of analogs were identified with single digit nanomolar potency: glycine amides, heterocycle-linked amides, and thiazoles. Responding to concerns about target localization and potential mechanism-based side effects, an initial effort was also made to improve liver concentration in an available rat PK model. An advanced compound 17m with a 5-carboxy-2-thiazole substructure appended to the spirocyclic piperidine scaffold was developed which satisfied the in vitro and in vivo requirements for more detailed studies.

Safety pharmacology in 2010 and beyond: survey of significant events of the past 10 years and a roadmap to the immediate-, intermediate- and long-term future in recognition of the tenth anniversary of the Safety Pharmacology Society.

In recognition of the tenth anniversary of the Safety Pharmacology Society (SPS), this review summarizes the significant events of the past 10years that have led to the birth, growth and evolution the SPS and presents a roadmap to the immediate-, intermediate- and long-term future of the SPS. The review discusses (i) the rationale for an optimal non-clinical Safety Pharmacology testing, (ii) the evolution of Safety Pharmacology over the last decade, (iii) its impact on drug discovery and development, (iv) the merits of adopting an integrated risk assessment approach, (v) the translation of non-clinical findings to humans and finally (vi) the future challenges and opportunities facing this discipline. Such challenges include the emergence of new molecular targets and new approaches to treat diseases, the rapid development of science and technologies, the growing regulatory concerns and associated number of guidance documents, and the need to train and educate the next generation of safety pharmacologist.

Exploratory drug safety: a discovery strategy to reduce attrition in development.

Identification of novel new molecules which hold the greatest promise of safe and effective therapies remains a continuous challenge to the pharmaceutical industry. This has led the industry to implement strategies for identification of the most promising candidates during the discovery phase and for their safe and expeditious advancement through development. Testing for potential liable properties in the discovery phase has included the evaluation of major areas of pharmaceutics that have led to failure such as its physical and pharmaceutical properties, drug metabolism and pharmacokinetic characteristics, various safety endpoints including pre-development safety pharmacology, general toxicology and genetic toxicology and interrogation of counter-screen data to identify off-target affinities (i.e., receptors, ion channels, transporters, kinases, etc.) that pose a concern. Amongst the many important areas of concern is the potential for toxicities of the major organ systems. To mitigate this concern, a strategy pursued is to identify the prominent toxicological properties of the candidate prior to its recommendation for development. The results of these studies in discovery allow exclusion of the candidate before the expenditure of resources and time typical of development. In addition, the discovery phase toxicology studies serve to address key questions that may have arisen from the study of another molecule, the phenotypic profile from pre-clinical models where the therapeutic target has been genetically modified or concerns that have been raised as a result of other investigations. Importantly, the results of the exploratory drug safety studies will be used by the sponsor to judge the potential risks associated with continued pursuit of a potential development candidate. In many ways, pre-clinical toxicological investigations in discovery serve the important objective of identifying the most promising candidates to progress into development and onto registration.

Measuring the risk of torsades de pointes: electrocardiographic evaluation of PNU-142093 in conscious cynomolgus non-human primates using restraint and non-restraint procedures.

OBJECTIVE: Drug-induced torsades de pointes (TdP) arrhythmia is a serious public health concern that has significantly slowed the advancement of promising new therapeutic agents to the marketplace. Modeling for the potential to produce TdP has relied in part on the surrogate biomarker QT interval prolongation, measured in vivo in animals and in the clinic in man. This study was a comparison of the effects of PNU-142093, a selective 5HT1D-serotonin receptor agonist, on QT interval prolongation under restraint and non-restraint conditions in conscious cynomolgus non-human primates. METHODS: Lead II electrocardiograms (ECG) were collected following an oral single-dose (non-restraint conditions using radio-telemetry) and single- and multiple-doses for 14 days (restraint conditions using electrodes applied to the surface) at doses of 0, 5, 15, and 25 mg/kg. ECG were collected from non-restrained animals predose and for up to 5 hrs, and again at 7 hrs, postdose on 4 different days in a Latin-square crossover design; N=4/sex/dose level. ECG were collected from restrained animals on days 1, 7, and 13, predose and at approximately 4 hrs postdose; N=2/sex/group. RESULTS: Non-restrained animal heart rate ranged from 159+/-22.1 to 168+/-21.4 beats/minute when compared to restrained animal heart rate (ranging from 242+/-17.2 to 246+/-11.5 beats/minute), suggesting that non-restrained animals were under less stress. In non-restrained animals, PNU-142093 produced a non-dose related decrease in heart rate, associated with a dose-related increase in QT and QTc (QT interval corrected for changes in heart rate) intervals, which was accompanied by alterations in T-wave morphology (e.g., widening and notching of the T wave). In restrained non-human primates, PNU-142093 had no effect on heart rate or ECG morphology on any day of dosing and no statistically significant effect on QT or QTc intervals on days 1 or 7 of dosing. By day 13 there were statistically significant increases in QT and QTc intervals at 15 and 25 mg/kg. The increase in QTc interval in restrained animals on day 13 was 29+/-12 and 30+/-19 msec at 15 and 25 mg/kg/day, respectively, and that in non-restrained animals was 65+/-23 and 73+/-28 msec. DISCUSSION: These data demonstrate an ability to detect problematic drugs in conscious cynomolgus non-human primates using both restraint and non-restraint procedures. They further show that the sensitivity of these assays to identify this signal of cardiac risk is significantly improved under the condition of non-restraint.

Benchmarking safety pharmacology regulatory packages and best practice.

INTRODUCTION: The objectives of this survey were to obtain a global information update regarding current industry perspectives that describe Safety Pharmacology programs as they relate to the ICH S7A and S7B regulatory guidelines but also to obtain a broader perspective of other practises practices in the field currently used by companies. Preliminary findings were presented at the 7th Annual Meeting of the Safety Pharmacology Society (SPS) (Edinburgh, Scotland, Sept 19-21, 2007). METHODS: The survey was distributed by the SPS to 125 pharmaceutical companies. Survey topics included (a) an update on ICH S7A and S7B practices, (b) frontloading Safety Pharmacology studies prior to selection of candidate drugs, (c) abuse and dependence-liability studies and (d) an extended evaluation of industry practises practices as assessed by Contract Research Organizations (CROs). RESULTS: Respondents (>94%) include GLP core battery (CV, CNS and respiratory) studies in the drug package submitted to regulatory agencies, and approximately 40% also submit studies on gastrointestinal and renal function. Respondents to the ICH S7B aspects indicate approximately 98% include the hERG assay and QT interval (in vivo) data in submissions, 63% include APD in vitro data and another 23% APD in vivo and other cardiac channel data (26%). SP frontloading is performed by 78% of all responding companies. Respondents indicate that 39% of these non-GLP CV studies are conducted before lead optimization (LO) and 85% during LO and before candidate drug selection. The hERG, CNS selectivity binding screens and rodent behavioral studies are frontloaded by 100%, 90% and 74% of respondents. Responding CROs (26) were surveyed on the services offered including Irwin or Functional Observational Battery (FOB) tests (70%), respiratory studies (85%), in vivo telemeterized dogs (69%) and in vitro CV studies (50%). Only 38% of SP studies are combined with toxicology studies at the CROs. DISCUSSION: The survey results indicate that ICH S7A core battery studies are implemented by most of the responding companies with a clear trend of an enhanced submission of renal and GI studies. The impact of ICH S7B is clear since, all respondents assess cardiac repolarization using cellular hERG (I(Kr)) and whole animal (QT interval) assays as a component of their safety assessment. Responses indicate a diversity of approaches for conducting abuse liability studies, which primarily use the methods of self-administration and drug discrimination. While early SP frontloading of studies seems to vary, the methods used appear to be generic to some extent and include in vitro 'off-target' evaluations and in vivo tests to determine the potential for CNS and cardiovascular issues.

Scientific review and recommendations on preclinical cardiovascular safety evaluation of biologics.

Biological therapeutic agents (biologicals), such as monoclonal antibodies (mAbs), are increasingly important in the treatment of human disease, and many types of biologicals are in clinical development. During preclinical drug development, cardiovascular safety pharmacology studies are performed to assess cardiac safety in accord with the ICH S7A and S7B regulations that guide these studies. The question arises, however, whether or not it is appropriate to apply these guidelines, which were devised primarily to standardize small molecule drug testing, to the cardiovascular evaluation of biologicals. We examined the scientific literature and formed a consensus of scientific opinion to determine if there is a rational basis for conducting an in vitro hERG assay as part of routine preclinical cardiovascular safety testing for biologicals. We conclude that mAb therapeutics have very low potential to interact with the extracellular or intracellular (pore) domains on hERG channel and, therefore, are highly unlikely to inhibit hERG channel activity based on their targeted, specific binding properties. Furthermore, mAb are large molecules (>140,000 Da) that cannot cross plasma membranes and therefore would be unable to access and block the promiscuous inner pore of the hERG channel, in contrast with typical small molecule drugs. Consequently, we recommend that it is not appropriate to conduct an in vitro hERG assay as part of a preclinical strategy for assessing the heart rate corrected QT interval (QTc) prolongation risk of mAbs and other types of biologicals. It is more appropriate to assess QTc risk by integrating cardiovascular endpoints into repeat-dose general toxicology studies performed in an appropriate non-rodent species. These recommendations should help shape future regulatory strategy and discussions for the cardiovascular safety pharmacology testing of mAbs as well as other biologicals and provide guidance for the preclinical cardiovascular evaluation of such agents.

ILSI-HESI cardiovascular safety subcommittee dataset: an analysis of the statistical properties of QT interval and rate-corrected QT interval (QTc).

INTRODUCTION: The Health and Environmental Sciences Institute of the International Life Sciences Institute (ILSI/HESI) Cardiovascular Safety Subcommittee outlined a set of in vivo telemetry studies to determine how well this preclinical model identified compounds known to cause torsades de pointes (TdP) and prolong QT interval in humans. In the original analysis of these data, QT, QTcB (Bazett model), QTcF (Fridericia model), and QTcQ (animal-specific model) were evaluated. We further evaluate the statistical properties of these measurements, using a method that can properly account for the sources of variability in the dataset. METHODS: The ILSI/HESI telemetry studies were conducted as a double Latin square design where eight dogs each received a vehicle control and three dose levels of a compound on four separate dosing days. We statistically analyzed the QT/QTc intervals using a repeated measures analysis of covariance and evaluate the powers for QT, QTcF and QTcQ based on simulations. RESULTS: The analyses for QTcF and QTcB intervals show that all six compounds which were known to cause TdP in humans were identified as positive and all six compounds known to be free of TdP events in their clinical use had no statistically significant treatment-related effects, while the analyses for QTcQ identified all positive compounds except pimozide. The power analysis shows that the method can detect a 7% increment of QT, a 5% increment of QTcF, and a 4% increment of QTcQ, with greater than 80% of power when n=8. DISCUSSION: We describe a repeated measures procedure to perform statistical analysis of covariance on Latin square designs and show that it can be used to detect meaningful changes in the analysis of QT/QTc intervals.

ILSI-HESI cardiovascular safety subcommittee initiative: evaluation of three non-clinical models of QT prolongation.

INTRODUCTION: Drugs that delay cardiac repolarization pose potential safety risks to patients and cause serious regulatory concern because of the link between QT interval prolongation and the potentially fatal arrhythmia torsades de pointes (TdP). Predicting which drugs will cause TdP is an inexact and difficult science. The utility of non-clinical assays was not well understood due in part to variability in methods, species, and consistency in the assays reported in the literature. The Health and Environmental Sciences Institute of the International Life Sciences Institute (ILSI/HESI) outlined a set of studies to determine how well selected commonly used non-clinical assays identified compounds known to cause TdP and prolong QT interval in humans. METHODS: Compounds known to prolong ventricular repolarization and compounds considered safe by years of clinical use were tested in three assays: HERG ionic current, Purkinje fiber repolarization, and in vivo QT studies in conscious telemeterized dogs. RESULTS: The data from each of these assays demonstrate that compounds that may pose a proarrhythmia risk for patients can be distinguished from those that are considered safe. DISCUSSION: Taken collectively, the in-vitro and in-vivo preclinical results can be integrated to develop an accurate preclinical risk assessment to support clinical safety.

Validation of a motor activity system by a robotically controlled vehicle and using standard reference compounds.

INTRODUCTION: A series of experiments were undertaken to evaluate the accuracy, precision, specificity, and sensitivity of an automated, infrared photo beam-based open field motor activity system, the MotorMonitor v. 4.01, Hamilton-Kinder, LLC, for use in a good laboratory practices (GLP) Safety Pharmacology laboratory. METHODS: This evaluation consisted of two phases: (1) system validation, employing known inputs using the EM-100 Controller Photo Beam Validation System, a robotically controlled vehicle representing a rodent and (2) biologic validation, employing groups of rats treated with the standard pharmacologic agents diazepam or D-amphetamine. The MotorMonitor's parameters that described the open-field activity of a subject were: basic movements, total distance, fine movements, x/y horizontal ambulations, rearing, and total rest time. These measurements were evaluated over a number of zones within each enclosure. RESULTS: System validation with the EM-100 Controller Photo Beam Validation System showed that all the parameters accurately and precisely measured what they were intended to measure, with the exception of fine movements and x/y ambulations. Biologic validation using the central nervous system depressant diazepam at 1, 2, or 5 mg/kg, i.p. produced the expected dose-dependent reduction in rat motor activity. In contrast, the central nervous system stimulant D-amphetamine produced the expected increases in rat motor activity at 0.1 and 1 mg/kg, i.p, demonstrating the specificity and sensitivity of the system. DISCUSSION: Taken together, these studies of the accuracy, precision, specificity, and sensitivity show the importance of both system and biologic validation in the evaluation of an automated open field motor activity system for use in a GLP compliant laboratory.

Drugs effects on ventricular repolarization: a critical evaluation of the strengths and weaknesses of current methodologies and regulatory practices.

A growing number of drugs and drug combinations inhibit cardiac potassium ion conductance and ventricular repolarization, and increase cardiac APD, QT interval, and risk of potentially fatal TdP. The past decade has seen an explosion of research advances into the mechanism of action underpinning these observations, and an unprecedented level of collaboration between academia, industry, and regulatory authorities to define effective strategies for accurate prediction of increased TdP risk (if any) in humans, based upon nonclinical and/or clinical endpoints. Because the incidence of TdP is so very low, even for drugs for which the association is known, the risk can only be assessed based upon surrogate markers (signals) in in vitro and in vivo non-clinical studies as well as in clinical trials. In this article, we review both the strengths and weaknesses of current methodologies and regulatory practices for assessment of TdP risk for pharmaceuticals.

Challenges and lessons learned since implementation of the safety pharmacology guidance ICH S7A.

The International Conference on Harmonization, Topic S7A guidance (ICH S7A) on safety pharmacology for human pharmaceuticals has been in effect for 3 years in Europe, the United States and Japan. Surveys of the pharmaceutical industry, regulatory agencies and the audience attending the 4th Annual Meeting of the Safety Pharmacology Society have helped identify and address areas of controversy, as well as those challenges that have emerged since implementation of the guidance worldwide. Overall, ICH S7A has been successfully implemented. The guidance provides for "Good Laboratory Practice" compliant "safety pharmacology core battery" of studies that are generally performed prior to first administration to humans. The approach is science-driven and specifies the use of robust and sophisticated in vitro and/or in vivo assays. There are, however, some areas that require further refinement/clarification such as the specifics of study design including the selection of dose/concentration, choice of species, modeling of the temporal pharmacodynamic changes in relation to pharmacokinetic profile of parent drug and major metabolites, use of an appropriate sample size, statistical power analysis as a means of demonstrating the sensitivity of the model system, testing of human-specific metabolites and demonstrating not only the model's sensitivity, but also its specificity for predicting adverse events in humans. There was also discussion of when these studies are needed in relation to the clinical development plan. Representatives from the pharmaceutical industry and regulatory agencies see the implementation of ICH S7A as a major step forward towards identifying the risk to Phase 1 and 2 volunteers and patients. It remains to be seen, however, whether and in what ways the ICH S7A-based strategy will contribute to the modification of the integrated risk assessment during the latter stages of clinical development or once drugs have been introduced to the marketplace.