Sally Robinson

A European pharmaceutical company initiative challenging the regulatory requirement for acute toxicity studies in pharmaceutical drug development.

Regulatory guidelines indicate acute toxicity studies in animals are considered necessary for pharmaceuticals intended for human use. This is the only study type where lethality is mentioned as an endpoint. The studies are carried out, usually in rodents, to support marketing of new drugs and to identify the minimum lethal dose. A European initiative including 18 companies has undertaken an evidence-based review of acute toxicity studies and assessed the value of the data generated. Preclinical and clinical information was shared on 74 compounds. The analysis indicated acute toxicity data was not used to (i) terminate drugs from development (ii) support dose selection for repeat dose studies in animals or (iii) to set doses in the first clinical trials in humans. The conclusion of the working group is that acute toxicity studies are not needed prior to first clinical trials in humans. Instead, information can be obtained from other studies, which are performed at more relevant doses for humans and are already an integral part of drug development. The conclusions have been discussed and agreed with representatives of regulatory bodies from the US, Japan and Europe.

Overcoming the barriers to the uptake of nonclinical microsampling in regulatory safety studies.

Toxicokinetic analysis is an essential part of nonclinical drug development. Advances in bioanalytical techniques have opened up the potential to use smaller sample volumes (microsamples) to assess drug exposure in blood, plasma and/or serum. Microsampling can increase the amount of nonclinical safety information available, improve its validity by linking toxic effects to drug exposure in individual animals and represents the most significant opportunity to reduce animal use in toxicology studies in the short term. In May 2013, a workshop was held with 80 delegates from 33 companies with the aim of sharing information and knowledge on microsampling technologies. This article covers the discussions at the workshop, current practice in the industry, regulatory experiences and the future direction of microsampling across drug development.

Opportunities to minimise animal use in pharmaceutical regulatory general toxicology: A cross-company review

Toxicity studies in animals are carried out to identify the intrinsic hazard of a substance to support risk assessment for humans. In order to identify opportunities to minimise animal use in regulatory toxicology studies, a review of current study designs was carried out. Pharmaceutical companies and contract research organisations in the UK shared data and experience of standard toxicology studies (ranging from one to nine months duration) in rodents and non-rodents; and carcinogenicity studies in the rat and mouse. The data show that variation in study designs was primarily due to (i) the number of animals used in the main study groups, (ii) the use of animals in toxicokinetic (TK) satellite groups, and (iii) the use of animals in off-treatment recovery groups. The information has been used to propose a series of experimental designs where small adjustments could reduce animal use in practice, while maintaining the scientific objectives.

Functional assessments in repeat-dose toxicity studies: the art of the possible

Clinical and nonclinical safety liabilities remain a major cause of adverse drug reactions, candidate drug attrition, delays during development, labelling restrictions, non-approval, and product withdrawal. Many of the toxicities are functional in nature and/or in origin. Whereas pharmacological responses tend to be fairly rapid in onset, and are therefore detectable after a single dose, some diminish on repeated dosing, whereas others increase in magnitude and therefore can be missed or underestimated in single-dose safety pharmacology studies. Functional measurements can be incorporated into repeat-dose toxicity studies, either routinely or on an ad hoc basis. Drivers for this are both scientific (see above), and regulatory (e.g., ICH S6, S7, S9). There are inherent challenges in achieving this: the availability of suitable technical and scientific expertise in the test facility; unsuitable laboratory conditions; use of simultaneous (as opposed to staggered) dosing; requirement for toxicokinetic sampling; unsuitability of certain techniques (e.g., use of anaesthesia; surgical implantation; food restriction); equipment availability at close proximity; sensitivity of the methods to detect small, clinically relevant, changes. Nonetheless, ‘fit-for-purpose’ data can still be acquired without requiring additional animals. Examples include assessment of behaviour, sensorimotor, visual, and autonomic functions, ambulatory ECG and blood pressure, echocardiography, respiratory, gastrointestinal, renal and hepatic functions. This is entirely achievable if functional measurements are relatively unobtrusive, both with respect to the animals and to the toxicology study itself. Careful pharmacological validation of any methods used, and establishing their detection sensitivity, is vital to ensure the credibility of generated data.

Cross-Sector Review of Drivers and Available 3Rs Approaches for Acute Systemic Toxicity Testing

Acute systemic toxicity studies are carried out in many sectors in which synthetic chemicals are manufactured or used and are among the most criticized of all toxicology tests on both scientific and ethical grounds. A review of the drivers for acute toxicity testing within the pharmaceutical industry led to a paradigm shift whereby in vivo acute toxicity data are no longer routinely required in advance of human clinical trials. Based on this experience, the following review was undertaken to identify (1) regulatory and scientific drivers for acute toxicity testing in other industrial sectors, (2) activities aimed at replacing, reducing, or refining the use of animals, and (3) recommendations for future work in this area.

Target organ toxicities in studies conducted to support first time in man dosing: An analysis across species and therapy areas

An analysis of target organ toxicities in first time in man (FTiM) toxicity studies for 77 AstraZeneca candidate drugs (CDs) was conducted across a range of therapy areas. In the rodent, the most frequently affected organ was the liver followed by adrenal glands, kidney, spleen, bone marrow and thymus. In non-rodent, liver and thymus were the most frequently affected organs, followed closely by the testis and GI tract. The profile of affected organs was largely similar across the therapy areas of respiratory and inflammation, cardiovascular/gastrointestinal and CNS/pain. The oncology/infection therapy area differed with a larger range of organs affected. For the 75 CDs for which both rodent and non-rodent studies were conducted, new target organs were identified in non-rodents for 43 of the CDs. Notably, the changes seen only in non-rodents included organ systems of high relevance for human risk assessment such as the liver, male reproductive tissues and CNS. Additionally, profiles were similar for those CDs that progressed into human trials and those that did not. Overall, our data provide new insights into drug toxicity profiles in pre-clinical species and additionally confirm the value of using non-rodents as a second species in toxicity testing to support human safety.

Assessment of toxicological effects of blood microsampling in the vehicle dosed adult rat

UNLABELLED Historically, satellite groups are often used for rodent toxicokinetic profiling because of the haematological consequences of blood sampling. If microsampling is shown to be toxicologically benign, its adoption in rat studies would enable comparison of exposure and toxicity in individual animals (as happens in non-rodent studies) as well as obviating need for satellite groups. METHODS Groups of 10 male (200-300g) and female (150-250g) rats aged 10weeks were vehicle dosed and either left unsampled, conventional blood volume sampled (6×200μL) or microsampled (6×32μL) on Days 1 and 14. At termination on Day 15, clinical pathology plus liver and spleen weights and histopathology were obtained. RESULTS All clinical pathology parameters were within background range. However, compared to unsampled controls, conventional volume sampled rats showed a statistically significant (p<0.001) decrease in haemaglobin, haematocrit and red blood cell count, an increase in reticulocytes (at least p<0.01), increased AST and GLDH and, in males only, an increase in monocytes and neutrophils. In contrast, microsampled animals showed no changes except for a slight, toxicologically insignificant decrease in haemoglobin concentration (15.0g/dL compared to the unsampled group mean of 14.4g/dL) in females (p<0.05) and a small increase in monocytes (p<0.05) in males. CONCLUSION Microsampling of adult rats is possible without adverse toxicological consequences.

A global pharmaceutical company initiative: An evidence-based approach to define the upper limit of body weight loss in short term toxicity studies

Short term toxicity studies are conducted in animals to provide information on major adverse effects typically at the maximum tolerated dose (MTD). Such studies are important from a scientific and ethical perspective as they are used to make decisions on progression of potential candidate drugs, and to set dose levels for subsequent regulatory studies. The MTD is usually determined by parameters such as clinical signs, reductions in body weight and food consumption. However, these assessments are often subjective and there are no published criteria to guide the selection of an appropriate MTD. Even where an objective measurement exists, such as body weight loss (BWL), there is no agreement on what level constitutes an MTD. A global initiative including 15 companies, led by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), has shared data on BWL in toxicity studies to assess the impact on the animal and the study outcome. Information on 151 studies has been used to develop an alert/warning system for BWL in short term toxicity studies. The data analysis supports BWL limits for short term dosing (up to 7days) of 10% for rat and dog and 6% for non-human primates (NHPs).

Recommendations from a global cross-company data sharing initiative on the incorporation of recovery phase animals in safety assessment studies to support first-in-human clinical trials.

An international expert group which includes 30 organisations (pharmaceutical companies, contract research organisations, academic institutions and regulatory bodies) has shared data on the use of recovery animals in the assessment of pharmaceutical safety for early development. These data have been used as an evidence-base to make recommendations on the inclusion of recovery animals in toxicology studies to achieve scientific objectives, while reducing animal use. Recovery animals are used in pharmaceutical development to provide information on the potential for a toxic effect to translate into long-term human risk. They are included on toxicology studies to assess whether effects observed during dosing persist or reverse once treatment ends. The group devised a questionnaire to collect information on the use of recovery animals in general regulatory toxicology studies to support first-in-human studies. Questions focused on study design, the rationale behind inclusion or exclusion and the impact this had on internal and regulatory decisions. Data on 137 compounds (including 53 biologicals and 78 small molecules) from 259 studies showed wide variation in where, when and why recovery animals were included. An analysis of individual study and programme design shows that there are opportunities to reduce the use of recovery animals without impacting drug development.

Reducing pre-clinical blood volumes for toxicokinetics: toxicologists, pathologists and bioanalysts unite

Blood samples are taken from animals during general toxicology, reproductive toxicology and safety pharmacology studies with pharmaceutical and non-pharmaceutical chemicals to demonstrate that the compound is present in the groups of animals being tested and to understand how the degree of systemic exposure may be linked to any toxicological effects observed. The blood (plasma or serum) concentration data generated from each sample are used to derive toxicokinetic (TK) data and regulatory guidance dictates generally how and when these data are needed during compound development. A number of OECD and ICH documents [1–6] indicate the value of relating achieved exposure to toxicological findings and how this provides useful information for estimating safety margins for clinical trials and for supporting dose level selection for chronic toxicity studies. For pharmaceuticals, typically, a full concentration profile is needed at the start and end of a study, but there is some variation between organizations in the number of samples taken to generate a profile and whether all or selected control animals are sampled [7]. For non-pharmaceutical chemicals, the use of TK in toxicology studies is not generally required in the registration processes but is considered beneficial [8–10]. There are differences across industry sectors in how TK data are generated and used, but the advantages of monitoring exposure in toxicity studies are frequently discussed and agreed [11,12]. From a risk assessment perspective for non-pharmaceutical chemicals, actual animal exposure to parent and metabolites may be used to unravel the relevance of toxicological findings to human health, regardless of how the TK profile is generated (e.g. steady state determinations in dietary studies versus PK-like profiling in oral gavage studies) [13]. Other uses include comparing ‘external’ and ‘systemic’ “no observed adverse effect levels” across studies, setting an internal reference dose or chemical-specific uncertainty factors, enabling the use of physiologically based pharmacokinetic modeling [11]. Exposure data are useful where different doses, species, strains, gender and life stages are compared at the end of a toxicology program [14].