Testing paradigm for prediction of development-limiting barriers and human drug toxicity

What can nanosafety learn from drug development? The feasibility of "safety by design"

"Safety by design" (SbD) is an intuitively appealing concept that is on the rise within nanotoxicology and nanosafety research, as well as within nanotechnology research policy. It leans on principles established within drug discovery and development (DDD) and seeks to address safety early, as well as throughout product development. However, it remains unclear what the concept of SbD exactly entails for engineered nanomaterials (ENMs) or how it is envisioned to be implemented. Here, we review the concept as it is emerging in European research and compare its resemblance with the safety testing and assessment practices in DDD. From this comparison, it is clear that "safety" is not obtained through DDD, and that SbD should be considered a starting point rather than an end, meaning that products will still need to progress through thorough safety evaluations and regulation. We conclude that although risk reduction is clearly desirable, the way SbD is currently communicated tends to treat safety as an inherent material property and that this is fundamentally problematic as it represents a recasting and reduction of societal issues into technical problems. SbD therefore faces a multitude of challenges, from practical implementation to unrealistic stakeholder expectations.

Human engineered heart tissue as a model system for drug testing

Drug development is time- and cost-intensive and, despite extensive efforts, still hampered by the limited value of current preclinical test systems to predict side effects, including proarrhythmic and cardiotoxic effects in clinical practice. Part of the problem may be related to species-dependent differences in cardiomyocyte biology. Therefore, the event of readily available human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CM) has raised hopes that this human test bed could improve preclinical safety pharmacology as well as drug discovery approaches. However, hiPSC-CM are immature and exhibit peculiarities in terms of ion channel function, gene expression, structural organization and functional responses to drugs that limit their present usefulness. Current efforts are thus directed towards improving hiPSC-CM maturity and high-content readouts. Culturing hiPSC-CM as 3-dimensional engineered heart tissue (EHT) improves CM maturity and anisotropy and, in a 24-well format using silicone racks, enables automated, multiplexed high content readout of contractile function. This review summarizes the principal technology and focuses on advantages and disadvantages of this technology and its potential for preclinical drug screening.

Biokinetics in repeated-dosing in vitro drug toxicity studies

The aim of the EU FP7 Predict-IV project was to improve the predictivity of in vitro assays for unwanted effects of drugs after repeated dosing. The project assessed the added benefit of integrating long-lived in vitro organotypic cell systems with 'omics' technologies and in silico modelling, including systems biology and pharmacokinetic assessments. RPTEC/TERT1 kidney cells, primary rat and human hepatocytes, HepaRG liver cells and 2D and 3D primary brain cultures were dosed daily or every other day for 14 days to a selection of drugs varying in their mechanism of pharmacological action. Since concentration-effect relationships not only depend on the activity of the drug or the sensitivity of the target, but also on the distribution of compounds in the in vitro system, the concentration of a selection of drugs in cells, microtitre plate plastic and medium was measured over time. Results, reviewed in this paper, indicate that lipophilic drugs bind significantly to plastic labware. A few drugs, including less lipophilic drugs, bind to cell-attachment matrices. Chemicals that reach high concentrations in cells, including cyclosporin A and amiodarone, significantly accumulate over time after repeated dosing, partly explaining their increased toxicity after repeated dosing, compared to a single dose.

Exploratory toxicology as an integrated part of drug discovery. Part I: Why and how

Toxicity and clinical safety have major impact on drug development success. Moving toxicological studies into earlier phases of the R&D chain prevents drug candidates with a safety risk from entering clinical development. However, to identify candidates without such risk, safety has to be designed actively. Therefore, we argue that toxicology should be fully integrated into the discovery process. We describe our strategy, including safety assessment of novel targets, selection of chemical series without inherent liabilities, designing out risk factors and profiling of candidates, and we discuss considerations regarding what to screen for. We aim to provide timely go/no-go decisions (fail early) and direction to the discovery teams, by steering away from safety risk (showing what will not fail).

Drug safety testing paradigm, current progress and future challenges: an overview

Early assessment of the toxicity potential of new molecules in pharmaceutical industry is a multi-dimensional task involving predictive systems and screening approaches to aid in the optimization of lead compounds prior to their entry into development phase. Due to the high attrition rate in the pharma industry in last few years, it has become imperative for the nonclinical toxicologist to focus on novel approaches which could be helpful for early screening of drug candidates. The need is that the toxicologists should change their classical approach to a more investigative approach. This review discusses the developments that allow toxicologists to anticipate safety problems and plan ways to address them earlier than ever before. This includes progress in the field of in vitro models, surrogate models, molecular toxicology, 'omics' technologies, translational safety biomarkers, stem-cell based assays and preclinical imaging. The traditional boundaries between teams focusing on efficacy/ safety and preclinical/ clinical aspects in the pharma industry are disappearing, and translational research-centric organizations with a focused vision of bringing drugs forward safely and rapidly are emerging. Today's toxicologist should collaborate with medicinal chemists, pharmacologists, and clinicians and these value-adding contributions will change traditional toxicologists from side-effect identifiers to drug development enablers.

Predictive Toxicology Approaches for Small Molecule Oncology Drugs

A daunting, unmet medical need exists for effective oncology chemotherapies, with cancer deaths in 2009 to exceed 560,000 in the United States alone. Because of the rapid demise of the majority of cancer patients with metastatic disease, oncology drug development must follow a much different paradigm than therapeutic candidates for less onerous diseases. The majority of drug candidates in development today are targeted at cancer therapy. Many of these candidate chemotherapeutic agents are active against novel targets, often presenting unique toxicological profiles. Since many of these novel targets are not unique to cancer cells, therapeutic margins may not exist. Decision making, in this event, is among the most challenging that any pharmaceutical toxicologist/pathologist or regulator will face. Nonclinical development scientists must compress timelines to present therapeutic options for cancer patients who have failed conventional therapy. In support of this goal, the U. S. Food and Drug Administration has created an oncology-specific paradigm for nonclinical testing and has introduced strategies to accelerate development and approval of successful candidates. Pharmaceutical toxicology testing strategies must not only satisfy regulation as the minimal expectation, but also attempt to reduce the current high attrition rates for oncologic candidates. A successful toxicology testing strategy represents the substance of this treatise.

The future of drug safety testing: expanding the view and narrowing the focus

Drug safety remains a high profile issue at a time when the cost and time required to develop a new drug are at an all time high. Balancing risk against the expected clinical benefit is the primary purpose of preclinical and clinical testing. We offer an expanded view on the application of predictive strategies and technologies to early safety decisions and suggestions to narrow the focus for improving preclinical safety testing to the problems that contribute most to adverse drug reactions.

Future of ToxicologyMechanisms of Toxicity and Drug Safety: Where Do We Go from Here?

Recent high-profile drug withdrawals increase the pressure on regulators and the pharmaceutical industry to improve preclinical safety testing. Understanding mechanisms of drug toxicity is an essential step toward improving drug safety testing by providing the basis for mechanism-based risk assessments. Nonetheless, despite several decades of research on mechanisms of drug-induced toxicity and the application of various new technologies to preclinical safety assessment, the overall impact on preclinical safety testing has been modest. Assessing the risk of exposing humans to new drug candidates still depends on preclinical testing in animals, which in many, but not all cases, predicts outcomes in humans accurately. The following offers a perspective on the challenges and opportunities facing efforts to improve preclinical safety testing and outlines gaps and needs that must be addressed. A case is built for focusing solutions on defined problems within the current safety testing paradigm rather than imposing wholesale change. Targets for application of new technologies, including in silico screening, biomarkers, surrogate assays and 'omic technologies, are outlined. Improving drug safety testing will depend on improving the application of mechanism-based risk assessment but will also require improving public and private collaborations in order to focus research regarding the mechanism of drug-induced toxicity on the most important problems.