Neurofunctional test batteries in safety pharmacology - Current and emerging considerations for the drug development process.

Regulatory guidelines recommend specialised safety pharmacology assessments in animals to characterise drug-induced effects on the central nervous system (CNS) prior to first-in-human trials, including the functional observational battery or Irwin test (here collectively termed neurofunctional assessments). These assessments effectively detect overtly neurotoxic drugs; however, the suitability of the in vivo assessments to readily detect more subtle drug effects on the nervous system has been questioned. A survey was formulated by an international expert working group convened by the (NC3Rs) to capture practice in CNS neurofunctional assessment tests and opinions on the perceived impact of in vivo test battery endpoints. Impact was defined as "the impact of measures alone/in combination on decision making in drug development or candidate selection when using the neurofunctional assessment". The results demonstrate that rodents are predominantly used for small molecule assessments, whereas non-rodents are frequently used to test biotherapeutics. Practice varied between respondents in terms of experimental design. Subsets of test battery endpoints were consistently considered highly impactful (e.g. convulsions, stereotypic behaviors); however, the perceived impact level of other endpoints varied depending whether drugs were designed for CNS targets. Many endpoints were considered to have no or minimal impact, whereas a subset of endpoints in CNS test batteries appears more impactful than others. A critical evaluation is required to assess whether the translational value of CNS in vivo safety pharmacology assessments could be increased by modifying or augmenting standard CNS test batteries. A revised approach to CNS safety assessment has the potential to reduce animal numbers without compromising patient safety.

Regulatory respiratory data refinement with reduced animal usage.

INTRODUCTION: Assessment of effects of potential drug candidates on the respiratory system is part of the regulatory preclinical safety assessment conducted prior to first in human trials (FTIH). Commonly, this is carried out utilizing head out plethysmography (HOP) or whole body plethysmography (WBP) which record only ventilatory parameters. When dosing via the inhaled route a more thorough respiratory assessment, including a direct measure of airway mechanics, is desirable. The aim of the present work was to improve the strategy for respiratory safety testing by a) evaluating a telemetered pleural pressure - HOP (PP-HOP) model and b) evaluating a crossover study design protocol in the WBP model to reduce variability and animal usage. METHODS: For the PP- HOP model, rats were surgically implanted with a telemetry device for measurement of pleural pressure. Animals were placed in HOP tubes and respiratory function assessed when exposed to methacholine at doses of 0 (saline only), 0.42, 1.6 and 3.8 mg/kg. WBP assessment was performed in rats in a crossover study design when treated with theophylline at doses of 0 (saline only), 3, 10 and 30 mg/kg. RESULTS: Data from the PP-HOP study confirmed the expected changes in ventilatory parameters and airway mechanics in response to inhaled methacholine, including an increase in pulmonary resistance and decrease in tidal volume. Data from the WBP crossover study demonstrated similar sensitivity and statistical power to detect changes in respiratory rate and tidal volume to a standard parallel group design. CONCLUSION: Measurement of PP-HOP in a stand-alone safety pharmacology study in conjunction with HOP assessment conducted as part of a toxicology study, represents an improved respiratory testing strategy for inhaled drugs. For compounds administered by other routes, we conclude that use of WBP using a crossover dosing design is a suitable alternative to parallel dosing groups, with a significant reduction in animal numbers and no loss of statistical power.

Evaluation of the PhysioTel™ Digital M11 cardiovascular telemetry implant in socially housed cynomolgus monkeys up to 16weeks after surgery.

INTRODUCTION: The novel PhysioTel™ Digital M11 telemetry implant was evaluated in socially housed monkeys with respect to both safety pharmacological cardiovascular (arterial blood pressure (BP), heart rate (HR) and electrocardiogram (ECG)) and toxicological (clinical pathology and histopathology) endpoints. METHODS: Telemetry and clinical pathology data were obtained repeatedly up to 16weeks after surgery in four female cynomolgus monkeys, followed by necropsy. Due to postsurgical complications, one spare animal was included and only toxicological endpoints from the affected (fifth animal) were reported. Continuous telemetry recordings were conducted at periods without dosing and after ascending doses of moxifloxacin (0, 10, 30, 100mg/kg) and L-NAME (0, 0.1, 1, 10mg/kg). Additionally, a retrospective power analysis was conducted based on baseline M11 implant data from 32 other animals. RESULTS: During periods without dosing, the cardiovascular endpoints were stable over time and within normal ranges. Moxifloxacin and L-NAME elicited the expected pharmacological responses with dose-dependent increase in QTca (8, 17, 22ms) and BP (mean BP: 12, 21, 34mmHg), respectively. Expected intravascular and tissue reactions were observed at the sites of the BP catheter and the transmitter. Signs of infection (localised to the transmitter implantation site with associated systemic effects) was noted in the fifth animal. No systemic pathologies were seen in any animals. Power analysis (80% power) indicated that the minimal differences which can be detected in a parallel group design (n=6) are 7mmHg (mean BP), 16bpm (HR), 12ms (QTca). DISCUSSION: The M11 implant provided stable, high quality ECG and BP data for a duration covering the length of sub-chronic repeated dose toxicity studies without important impact on toxicological endpoints. Adequate power in order to elucidate major treatment-related cardiovascular effects was demonstrated. However to avoid post-surgical complications the implantation procedures should be carefully considered before using the method.

Social housing of non-rodents during cardiovascular recordings in safety pharmacology and toxicology studies.

INTRODUCTION: The Safety Pharmacology Society (SPS) and National Centre for the Replacement, Refinement & Reduction of Animals in Research (NC3Rs) conducted a survey and workshop in 2015 to define current industry practices relating to housing of non-rodents during telemetry recordings in safety pharmacology and toxicology studies. The aim was to share experiences, canvas opinion on the study procedures/designs that could be used and explore the barriers to social housing. METHODS: Thirty-nine sites, either running studies (Sponsors or Contract Research Organisations, CROs) and/or outsourcing work responded to the survey (51% from Europe; 41% from USA). RESULTS: During safety pharmacology studies, 84, 67 and 100% of respondents socially house dogs, minipigs and non-human primates (NHPs) respectively on non-recording days. However, on recording days 20, 20 and 33% of respondents socially house the animals, respectively. The main barriers for social housing were limitations in the recording equipment used, study design and animal temperament/activity. During toxicology studies, 94, 100 and 100% of respondents socially house dogs, minipigs and NHPs respectively on non-recording days. However, on recording days 31, 25 and 50% of respondents socially house the animals, respectively. The main barriers for social housing were risk of damage to and limitations in the recording equipment used, food consumption recording and temperament/activity of the animals. CONCLUSIONS: Although the majority of the industry does not yet socially house animals during telemetry recordings in safety pharmacology and toxicology studies, there is support to implement this refinement. Continued discussions, sharing of best practice and data from companies already socially housing, combined with technology improvements and investments in infrastructure are required to maintain the forward momentum of this refinement across the industry.

A multi-site comparison of in vivo safety pharmacology studies conducted to support ICH S7A & B regulatory submissions.

INTRODUCTION: Parts A and B of the ICH S7 guidelines on safety pharmacology describe the in vivo studies that must be conducted prior to first time in man administration of any new pharmaceutical. ICH S7A requires a consideration of the sensitivity and reproducibility of the test systems used. This could encompass maintaining a dataset of historical pre-dose values, power analyses, as well as a demonstration of acceptable model sensitivity and robust pharmacological validation. During the process of outsourcing safety pharmacology studies to Charles River Laboratories, AstraZeneca set out to ensure that models were performed identically in each facility and saw this as an opportunity to review the inter-laboratory variability of these essential models. METHODS: The five in vivo studies outsourced were the conscious dog telemetry model for cardiovascular assessment, the rat whole body plethysmography model for respiratory assessment, the rat modified Irwin screen for central nervous system assessment, the rat charcoal meal study for gastrointestinal assessment and the rat metabolic cage study for assessment of renal function. Each study was validated with known reference compounds and data were compared across facilities. Statistical power was also calculated for each model. RESULTS: The results obtained indicated that each of the studies could be performed with comparable statistical power and could achieve a similar outcome, independent of facility. DISCUSSION: The consistency of results obtained from these models across multiple facilities was high thus providing confidence that the models can be run in different facilities and maintain compliance with ICH S7A and B.