Immune checkpoint inhibitors (ICIs) block CTLA‐4, PD‐1 and PD‐L1, or other molecules that control antitumour activities of lymphocytes. These products are associated with a broad array of immune‐related toxicities affecting a variety of organs, including the liver. ICI‐associated immune‐mediated hepatitis (IMH) ranges in severity between mild and life‐threatening and is marked by findings that bear both similarities as well as differences with idiopathic autoimmune hepatitis. Hepatotoxic events are often detected in clinical trials of ICIs that are powered for efficacy. Risk levels for ICI‐induced liver injury may be impacted by the specific checkpoint molecule targeted for treatment, the ICI dose levels, and the presence of a pre‐existing autoimmune diathesis, chronic infection or tumour cells which infiltrate the liver parenchyma. When patients develop liver injury during ICI treatment, a prompt assessment of the cause of injury, in conjunction with the application of measures to optimally manage the adverse event, should be made. Strategies to manage the risk of IMH include the performance of pretreatment liver tests with regular monitoring during and after ICI treatment and patient education. Using Common Terminology Criteria for Adverse Events developed at the National Cancer Institute to measure the severity level of liver injury, recommended actions may include continued ICI treatment with close patient monitoring, ICI treatment suspension or discontinuation and/or administration of corticosteroids or, when necessary, a non‐steroidal immunosuppressive agent. The elucidation of reliable predictors of tumour‐specific ICI treatment responses, as well as an increased susceptibility for clinically serious immune‐related adverse events, would help optimize treatment decisions for individual patients.

In the United States (US), the risk of hepatotoxicity linked to the widespread use of certain herbal products has gained increased attention among regulatory scientists. Based on current US law, all dietary supplements sold domestically, including botanical supplements, are regulated by the Food and Drug Administration (FDA) as a special category of foods. Under this designation, regulatory scientists do not routinely evaluate the efficacy of these products prior to their marketing, despite the content variability and phytochemical complexity that often characterizes them. Nonetheless, there has been notable progress in the development of advanced scientific methods to qualitatively and quantitatively measure ingredients and screen for contaminants and adulterants in botanical products when hepatotoxicity is recognized.

A workshop was convened to discuss best practices for the assessment of drug-induced liver injury (DILI) in clinical trials. In a breakout session, workshop attendees discussed necessary data elements and standards for the accurate measurement of DILI risk associated with new therapeutic agents in clinical trials. There was agreement that in order to achieve this goal the systematic acquisition of protocol-specified clinical measures and lab specimens from all study subjects is crucial. In addition, standard DILI terms that address the diverse clinical and pathologic signatures of DILI were considered essential. There was a strong consensus that clinical and lab analyses necessary for the evaluation of cases of acute liver injury should be consistent with the US Food and Drug Administration (FDA) guidance on pre-marketing risk assessment of DILI in clinical trials issued in 2009. A recommendation that liver injury case review and management be guided by clinicians with hepatologic expertise was made. Of note, there was agreement that emerging DILI signals should prompt the systematic collection of candidate pharmacogenomic, proteomic and/or metabonomic biomarkers from all study subjects. The use of emerging standardized clinical terminology, CRFs and graphic tools for data review to enable harmonization across clinical trials was strongly encouraged. Many of the recommendations made in the breakout session are in alignment with those made in the other parallel sessions on methodology to assess clinical liver safety data, causality assessment for suspected DILI, and liver safety assessment in special populations (hepatitis B, C, and oncology trials). Nonetheless, a few outstanding issues remain for future consideration.

Marketed pharmaceuticals are evaluated for safety by the US Food and Drug Administration (FDA) throughout the life cycle of the products. The FDA uses data from controlled clinical trials, from postmarketing case reports reported to the FDA's Adverse Event Reporting System, from epidemiological studies, and from registries to evaluate the safety of approved products. For some products, including some products used in dermatologic medicine, risks become apparent during the postmarketing period that require additional measures beyond product labeling and routine pharmacovigilance. The FDA continues to seek additional tools to assess risk, including pharmacogenomic biomarkers for adverse drug reactions and the use of large medical record and epidemiological databases for the systematic detection and characterization of drug-associated safety outcomes.

Two overarching goals tied to a futuristic vision of personalized medicine are to maximize individually derived benefits from available therapeutic drugs or biological agents and identify a reliable set of predictors of toxic outcomes to optimally manage a patient's treatment-related risk. This article will primarily address the second of these goals with a specific focus on challenges faced in the development of pharmacogenomic markers that would be used by practitioners to predict individual susceptibility to serious adverse drug reactions. The potential complexity of polygenic modifiers of risk for certain adverse drug reactions and demographic diversity in the prevalence of genomic variants pose significant challenges in the development of useful predictive biomarkers. Implementing rigorous scientific and logistical strategies to address these will be crucial in order to achieve meaningful success.