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.

CNS Safety Screening Under ICH S7A Guidelines Requires Observations of Multiple Behavioral Units to Assess Motor Function.

In the adoption of behavior as a critical end point in safety pharmacology and neurotoxicity screening, federal regulatory agencies have shifted the predominating scientific perspective from pharmacology back to the experimental analysis of behavior (psychology). Nowhere is this more evident than in tier I safety assessment of the central nervous system (CNS). The CNS and peripheral nervous system have multiple behavioral units of general activity. A complete picture of the motor control neural pathways cannot be measured by any one single approach. The CNS safety protocols under International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use S7A are required to be conducted in accordance with Good Laboratory Practices by trained technical staff. The CNS safety assessments necessitate the inclusion of a thorough and detailed behavioral analysis of home cage activity, the response to handling, and transportation to and observations within an open-field apparatus with ancillary measures of basal muscle tone, muscle strength, and tremor in a functional observation battery, as well as quantitative measurements of 3-dimensional activity in an automated photobeam arena. Cost-cutting initiatives or a radical application of the "reduce use" principle of the 3 Rs only jeopardize the spirit, intent, and predictive validity of tier I safety testing assays dictated by current drug safety guidelines.

Extended recording of LMA in rats: Effects of IV catheters, "comfort jackets" and chamber lids on arterial blood gas parameters.

The standard infrared photobeam locomotor activity system has been used extensively in neurobiology and neuropharmacology to study the functional impact of direct manipulations of the nervous system. There is interest in using the activity monitors to assess the early stages of drug withdrawal in rodents. In a standard twice-daily dosing strategy animals would be dosed at 6:00 am and 5:00 pm for 15 to 30 days. There is interest in using the chambers to assess the early stages of the discontinuation syndrome. Placement of the rodents into the chambers following the scheduled sham or vehicle last dose of a 15- to 30-day subchronic dosing regimen (b.i.d., t.i.d., etc.) and monitoring overnight allows for a quantitative measure of the initial physiological homeostatic acclimation period during the lights-out period. By using the chambers there is no circadian dysrhythmia induced as an experimental confound and objectively verifiable data is generated during the period expected to correspond with the plasma drug levels approaching zero and the onset of discontinuation syndrome. We demonstrated that untreated "normal" rats showed a normal decelerating time-effect curve over the 12-hour monitoring period that was not compromised by restricted access to food and water. Arterial blood gas monitoring before and after 12 h of night-time activity chamber monitoring clearly demonstrated normal respiratory function with no clinical signs of any blood gas-based diagnosis of metabolic dysfunction.

Predicting the Need for a Tier II Ototoxicity Study From Early Renal Function Data.

History has established that many drugs, such as the antibiotics, chemotherapies, and loop diuretics, are capable of inducing both nephrotoxicity and ototoxicity. The exact mechanisms by which cellular damage occurs remain to be fully elucidated. Monitoring the indices of renal function conducted in the Food and Drug Administration's prescribed set of early investigational new drug (IND)-enabling studies may be the first signs of ototoxicity properties of the new drug candidate. In developing improved and efficacious new molecular entities, it is critically necessary to understand the cellular and molecular mechanisms underlying the potential ototoxic effects as early in the drug development program as possible. Elucidation of these mechanisms will facilitate the development of safe and effective clinical approaches for the prevention and amelioration of drug-induced ototoxicity prior to the first dose in man. Biomarkers for nephrotoxicity in early tier I or tier II nonclinical IND-enabling studies should raise an inquiry as to the need to conduct a full auditory function assay early in the game to clear the pipeline with a safer candidate that has a higher probability of continued therapeutic compliance once approved for distribution.

NOEL and NOAEL: A retrospective analysis of mention in a sample of recently conducted safety pharmacology studies.

INTRODUCTION: The concept of characterizing adversity in relation to administered test article dose and/or exposure within toxicology studies has long been considered a normal aspect of the drug safety evaluation enterprise. The typical way this is done in drug safety investigations is by examining study data, often with focus on clinical signs, clinical pathology and histopathology, to determine a No-Observable-Effect-Level (NOEL) and/or a No-Observable-Adverse-Effect-Level (NOAEL). Once established, these, with other information, may be used to identify a safe starting dose in human clinical trials. Although safety pharmacology (SP) is concerned to identify and characterize potentially "adverse" functional effects, NOEL, and particularly NOAEL, traditionally do not have application in SP study interpretation and reporting. METHODS: An anonymized survey of a contract research laboratory master schedule was undertaken to appreciate recent usage of these concepts in GLP (Good Laboratory Practice) cardiovascular, respiratory, and neurobehavioral safety studies. RESULTS: Results across the sample of studies (N = 635) generally confirmed application of appropriate dose selection strategies, as there was a very low proportion (<1%) of observed severe adverse events (antecedent observations ultimately associated with morbidity/mortality). Data further indicated either no mention of NOEL/NOAEL (50%), or alternately, explicit identification of NOEL (28%), or NOAEL (21%). The majority of times a NOAEL was identified, it was also the case that this coincided with the highest dose administered (e.g., there may have been drug-related findings, but these were considered non-adverse across the dose range). DISCUSSION: While the concept of adversity is certainly relevant to nonclinical SP studies, actual current practices appear to reflect a history which generally avoids toxicologically-oriented classifications such as NOAEL. Questions remain regarding the applicability of NOAELs to safety pharmacology studies, including, importantly, the specific circumstances under which such designations of adversity may be considered to add value to understandings of relative risk and risk mitigation in early human clinical trials.

In further defense of nonclinical abuse liability testing of biologics.

Risk assessment is not a choice. Drug Abuse Liability (DAL) is mandated under international and national drug control statutes for all drugs targeting the CNS. Once administered to humans many biologics may have long-lived or permanent physiological effects that make DAL testing arduous. We respond to premises of a recently published position on DAL testing of biologics by de Zafra et al. (2018). We propose that, at a minimum, Sponsors submitting a Biologics Licensure Application (BLA) must think "outside the box" and include differential study designs for the same three core small NME assays detailed in the current DAL guidelines (self-administration, drug discrimination, and dependence liability). Abuse liability testing for drug scheduling decisions for marketing approval are not excluded or limited from risk assessment analysis simply because the entity is a biologic. In fact, more robust study designs may be necessary to address alterations in the reinforcing and discriminative stimulus effects of common drugs of abuse, as well as the dependence liability of the biologic, itself.

Relative equivalence of CNS safety (FOB) assessment outcomes in male and female Wistar-Han and Sprague-Dawley rats.

In 2006 the National Toxicology Program (NTP) of the FDA shifted to the preferred use of Wistar-Han rats from the more commonly used Sprague-Dawley (SD) strain - and industry followed. While European laboratories preferred the Wistar-Han line, there was a paucity of relevant historical control data in many US research institutions for the new "industry standard" rat strain. In 2010 the NTP reversed its decision and shifted back to SD rats because of reproductive issues with the Wistar strain. For post hoc comparative analyses, we report minimal practical differences in Functional Observational Battery (FOB) data from a large sample of male and female Wistar-Han and SD rats. In summarizing data from the preclinical safety evaluations of the CNS effects of new drugs using the FOB, it is crucial to understand the value of not only how the functional expression of drug effects in the rat are predictive of the human response, but also how and why they differ. What we can predict from the behavioral and physiological response of the designated test system to drug administration is the foundation of "generalizability" to the human's response. Here, we conclude that the use of either SD or WH rat strains in standard CNS safety studies provide equivalent supportive data for CNS safety assessment required for IND approval under the harmonized guidelines.

"Not Everything That Shakes Is a Seizure": Making the Determination of Test Article-Induced Convulsions in Toxicology Studies.

Spontaneous unexpected events occasionally develop during the course of rodent preclinical toxicology studies. The presentation of serious adverse events on animal studies may require notification of these events to the Food and Drug Administration if the events are most likely the direct result of test article administration. Classical conditioning of emotional responses may occur over the course of a repeat-dose study and clinical observation calls of "convulsions" are reported to the study director and/or staff veterinarians. In the current heightened environment of most research laboratories related to general animal welfare issues, it is imperative to have an action plan that will help to elucidate the potential origins of these motor events. We provide 10 factors that should be considered to help the study director determine the most likely cause of these motor attacks as being organic or psychogenic in origin.

The gold-standard in preclinical abuse liability testing: It's all relative.

All new molecular entities (NMEs) with targeted or indirect effects on the central nervous system (CNS) must be evaluated for their abuse liability as a part of their nonclinical development plan. Inherently key in the drug control review is the term "relative abuse liability". The basis for determination of drug control is critically dependent on the nonclinical assessment of the reinforcing attributes of the NME in animals (rat is the regulatory preferred species) in a standard operant conditioning paradigm. Pharmaceutical representatives without a background in behavioral analysis or operant conditioning models must weigh through conceptually-intriguing language and constructs that accurately convey and communicate the relative potential for abuse to drug regulatory experts in the field. Effective statutory language in the preclinical assessment of relative abuse liabilities for schedule control status reviews must be 1) specific; 2) concise; 3) familiar to the regulators; 4) unambiguous; 5) constructive; and 6) formalized with respect to both international and national drug control policies. In this review we attempt to define and highlight the importance of the statutory language used to report self-administration study results to both parties engaged in NDA approval process.

A predictive index of biomarkers for ictogenesis from tier I safety pharmacology testing that may warrant tier II EEG studies.

Three significant contributions to the field of safety pharmacology were recently published detailing the use of electroencephalography (EEG) by telemetry in a critical role in the successful evaluation of a compound during drug development (1] Authier, Delatte, Kallman, Stevens & Markgraf; JPTM 2016; 81:274-285; 2] Accardi, Pugsley, Forster, Troncy, Huang & Authier; JPTM; 81: 47-59; 3] Bassett, Troncy, Pouliot, Paquette, Ascaha, & Authier; JPTM 2016; 70: 230-240). These authors present a convincing case for monitoring neocortical biopotential waveforms (EEG, ECoG, etc) during preclinical toxicology studies as an opportunity for early identification of a central nervous system (CNS) risk during Investigational New Drug (IND) Enabling Studies. This review is about "ictogenesis" not "epileptogenesis". It is intended to characterize overt behavioral and physiological changes suggestive of drug-induced neurotoxicity/ictogenesis in experimental animals during Tier 1 safety pharmacology testing, prior to first dose administration in man. It is the presence of these predictive or comorbid biomarkers expressed during the requisite conduct of daily clinical or cage side observations, and in early ICH S7A Tier I CNS, pulmonary and cardiovascular safety study designs that should initiate an early conversation regarding Tier II inclusion of EEG monitoring. We conclude that there is no single definitive clinical marker for seizure liability but plasma exposures might add to set proper safety margins when clinical convulsions are observed. Even the observation of a study-related full tonic-clonic convulsion does not establish solid ground to require the financial and temporal investment of a full EEG study under the current regulatory standards. PREFATORY NOTE: For purposes of this review, we have adopted the FDA term "sponsor" as it refers to any person who takes the responsibility for and initiates a nonclinical investigations of new molecular entities; FDA uses the term "sponsor" primarily in relation to investigational new drug application submissions.

The drug discrimination assay: Interpretative value of partial generalization for drug schedule control actions.

The U.S. Food & Drug Administration (FDA) has issued a final guidance document on the preclinical determination of abuse potential that must be conducted in animals for all new molecular entities (NMEs) submitted for a new drug application (NDA). Under statutory restrictions government guidance documents serve only as a guide or an expression of the agency's current thinking on the topic. Guidelines do not legally bind the agency or its registrants to any content in the guidance. There are no statutory (legal) descriptions of what study designs or methodology must be submitted to the Drug Enforcement Administration with respect to drug scheduling review. This paper describes the utility of an alternate method used, worldwide, to assess the internal subjective effects of drugs to predict the abuse liability that provides additional information to address the relative aspects of that liability.

Method of data interpretation for the determination of abuse liability in rodent self-administration studies under the FDA guidance document.

All new molecular entities that enter the CNS and exert an activity in the brain must be assessed for abuse liability prior to a New Drug Application approval by the US Food and Drug Administration. One element of the screening process is the assessment of the reinforcing properties of the drug candidate using the regulatory-preferred species, the rat. We describe one method of data review from the standard rat IV SA study design that can be used to conclude the relative abuse liability of the new drug entity. While we do not claim the process as the only way to review or interpret the data, we believe the steps described highlight a process that the pharmaceutical development team can use as a starting point for a discussion during study protocol development.

Repeated "Day 1" FOB testing in ICH S7A safety assessment protocols: The influence of within- and between-session learning.

A large number of CNS safety assessment studies using the standard Functional Observational Battery (FOB) are conducted each year at Contract Research Organizations throughout the globe. Study design characteristics are as varied as the Sponsors for whom they are contracted. Gender inclusion, sample sizes, and timing of the FOBs are generally negotiated during protocol development. The ICH S7A guidelines describe a dose-effect study design for CNS safety assessment to be conducted prior to the first dose administration in man. Additionally, some Sponsors attempt to use the CNS safety FOB to establish both time- and dose-related acute behavioral effects of their compound in this single critical safety study. In this review, we highlight the confounding influences of multiple postdose FOBs (Day 1) versus the more standard, single FOB scheduled near systemic Cmax of the compound. Within- and between-session learning, combined with changes in vigilance/alertness/fatigue in both the animals and raters, can limit the generalizability of the FOB to accurately assess CNS effects under the current guidelines. Rationale is provided as to the tenuous nature of conducting simultaneous time- and dose-effect behavioral assessments as part of the core safety pharmacology programs.

Small Compartment Toxicity: CN VIII and Quality of Life: Hearing Loss, Tinnitus, and Balance Disorders.

Life experiences, industrial/environmental exposures, and administration of Food and Drug Administration (FDA)-approved drugs may have unintended but detrimental effects on peripheral and central auditory pathways. Most relevant to the readership of this journal is the role that drug treatments approved by the FDA as safe and effective appear to interact with 3 independent modes of toxicity within the small compartment of the ear. What may seem to be trivial drug-induced toxicity has the potential to change important measures of quality of life and functional capacity of mid- to late-life patients. Drugs meant to treat can become the source of interference in the activities of daily living, and as a result, treatment compliance may be jeopardized. Ototoxicity has been defined as the tendency of certain therapeutic agents and other chemical substances to cause functional impairments and cellular degeneration of the tissues of the inner ear resulting in hearing loss. However, one of the largest contributors to hospitalizations is fall-related injuries in the elderly patients associated with disorders of vestibular function linked to progressive and drug-induced toxicities. Tinnitus affects 35 to 50 million adults representing approximately 25% of the US population, with 12 million seeking medical care and 2 to 3 million reporting symptoms that were severely debilitating. This review is intended to highlight these targets of neurotoxicity that threaten the usefulness of drug treatments deemed safe and effective prior to access by the general public.

The standardized functional observational battery: Its intrinsic value remains in the instrument of measure: The rat.

The International Conference on Harmonisation's (ICH) Tripartite Guideline on Safety Pharmacology Studies for Human Pharmaceuticals has adopted the requirement that each new test substance must be tested for effects on the central nervous system prior to "first dose in man". This assessment is required to measure, at a minimum, the effects of the substance on general motor activity, behavioral changes, coordination, sensory/motor reflex responses, and body temperatures. To achieve this goal, ICH S7A recommends a neurobehavioral assessment (usually a functional observational battery (FOB) or modified Irwin test), which is generally undertaken in the rat. There seems to be a growing lack of consensus on the value of the FOB to determine CNS safety. This review highlights the importance of the time, effort and cost of training technicians to familiarize with their instrument of measure, so that each observer is better able to identify and document very subtle changes in behavior that will serve to increase the reliability and validity of these assays with respect to CNS safety assessments.

Preclinical assessment of abuse liability of biologics: In defense of current regulatory control policies.

Current regulatory policies of both the US Food and Drug Administration and Drug Enforcement Administration do not delineate automatic exceptions for biologics with respect to preclinical assessments for abuse liability of all new entities. As defined in current guidance documents and drug control policies, an exception may be given upon thorough review of available data, therapeutic target and in consultation with the Controlled Substances Staff within the Center for Drug Evaluation and Research of the FDA, but a blanket exception for all biological entities is not currently available. We review the abuse liability testing of four known biologics with definitive positive abuse liability signals in the three core abuse liability assays, self-administration, drug discrimination, and dependence potential described in the FDA draft guidance document. Interestingly, while all four examplars have positive abuse liability signals in all three assays, two of these biologics are controlled under the Comprehensive Drug Abuse and Control Act (CSA, 1970) and the other two are not currently controlled. Admittedly, these four biologics are small molecule entities. However, there is no reference to "molecular size" in the legally-binding statutory definition of biologics under the FD&C act or in the Controlled Substances Act. Neither of these drug control policy mandates have a bifurcated control status in which to make exceptions based solely on molecular size. With the current pharmaceutical focus on new technologies, such as "Trojan Horses", targeting the active transport of large molecule entities directly into the CNS, an argument to automatically exempt new molecular entities solely on molecular size is untenable. We argue that for the safety and health of general public the current regulatory control status be maintained until definitive criteria for exceptions can be identified and amended to both the FD&CA and CSA, if warranted.

The failure to detect drug-induced sensory loss in standard preclinical studies.

Over the years a number of drugs have been approved for human use with limited signs of toxicity noted during preclinical risk assessment study designs but then show adverse events in compliant patients taking the drugs as prescribed within the first few years on the market. Loss or impairments in sensory systems, such as hearing, vision, taste, and smell have been reported to the FDA or have been described in the literature appearing in peer-reviewed scientific journals within the first five years of widespread use. This review highlights the interactive cross-modal compensation within sensory systems that can occur that reduces the likelihood of identifying these losses in less sentient animals used in standard preclinical toxicology and safety protocols. We provide some historical and experimental evidence to substantiate these sensory effects in and highlight the critical importance of detailed training of technicians on basic ethological, species-specific behaviors of all purpose-bred laboratory animals used in these study designs. We propose that the time, effort and cost of training technicians to be better able to identify and document very subtle changes in behavior will serve to increase the likelihood of early detection of biomarkers predictive of drug-induced sensory loss within current standard regulatory preclinical research protocols.

Utility of the auditory brainstem response evaluation in non-clinical drug safety evaluations.

INTRODUCTION: The Food and Drug Administration (FDA) requires thorough evaluation of the potential safety hazards of all new drugs, food additives, and therapeutic devices that are intended for human use. Drugs that are otically administered (i.e., ear drops), or are known to systemically distribute to the inner ear, require additional specialized safety testing to ensure that the drug does not permanently impair auditory function. METHODS: To properly determine a drug's impact on auditory function, the FDA's Center for Drug Evaluation and Research requires the use of the Auditory Brainstem Response (ABR) evaluation. The ABR evaluation uses auditory stimuli evoked potentials to assess function by establishing minimum intensity thresholds. These thresholds can be monitored following drug treatment to determine an impact on hearing loss. This review discusses methodical considerations for conducting ABR evaluations as they apply to specialized drug safety studies. Alternative assays are discussed and compared to the utility of the ABR evaluation. CONCLUSIONS: The ABR evaluation provides reliable and sensitive measures of hearing function that are suitable for definitive drug safety evaluations or hazardous risk assessments.

Abuse liability assessment of hydrocodone under current draft regulatory guidelines.

INTRODUCTION: The abuse liability of hydrocodone was assessed in male Sprague-Dawley rats under the European Medicines Agency, the International Commission on Harmonisation, and the U.S. Food & Drug Administration draft guidelines for the non-clinical investigation of the dependence potential of medicinal products. METHODS: Self-administration, drug discrimination, and repeat-dose two week dependence liability studies were conducted to compare hydrocodone to the prototypical opiates, morphine and oxycodone. RESULTS: Hydrocodone was self-administered, produced an opiate-like subjective discriminative generalization profile and produced a significant discontinuation syndrome following abrupt treatment cessation that was quantitatively and qualitatively similar to morphine and/or oxycodone. CONCLUSION: Hydrocodone has abuse liability more similar to Schedule II opiates than other Schedule III compounds currently controlled under the U.S. Controlled Substance Act.

Background variability in standard clinical pathology biomarkers in beagle dogs instrumented with chronic indwelling telemetry devices.

INTRODUCTION: Contemporary best practice recommendations in preclinical cardiovascular safety assessment promote 3Rs principles. This includes the employment of within-subjects experimental designs to evaluate discrete, acute doses of investigational new drugs, as well as the maintenance of stock colonies of appropriate large animal test systems. Such colony species are often tested repeatedly on independent studies with provision of appropriate recovery periods and requisite health status evaluations (e.g., physical examinations, electrocardiographic assessments, clinical pathology evaluations). METHODS: To investigate the utility of the often reiterative process of pre- or inter-study clinical pathology testing to help ascertain health status of non-naïve, telemetered canines (beagle dogs), the present study collated the results of a randomly selected set of animals approximately every three months for a period of three years. RESULTS: Although occasionally a few routine hematology or clinical chemistry endpoints did demonstrate evidence of systematic trending over time, none of the observed fluctuations fell outside the range of expected biological variability, nor would have prevented assignment of any given animal to study. DISCUSSION: The present findings illustrate a high degree of consistency in routinely assessed clinical pathology parameters during the course of chronic telemetry instrumentation in the canine, including relative to historical control data in healthy, experimentally naïve animals of the same species and source, maintained under analogous laboratory conditions. The data suggest that routine assessment of such parameters for the purposes of facilitating judgments concerning suitability for study may represent a pursuit of little overall value, and which may be reasonably accomplished based on alternative, observation-based screening procedures.