Translational Toxicology and the Work of the Predictive Safety Testing Consortium

Circulating microRNAs as promising testicular translatable safety biomarkers: current state and future perspectives

Drug-induced testicular injury (DITI) is one of the often-observed and challenging safety issues seen during drug development. Semen analysis and circulating hormones currently utilized have significant gaps in their ability to detect testicular damage accurately. In addition, no biomarkers enable a mechanistic understanding of the damage to the different regions of the testis, such as seminiferous tubules, Sertoli, and Leydig cells. MicroRNAs (miRNAs) are a class of non-coding RNAs that modulate gene expression post-transcriptionally and have been indicated to regulate a wide range of biological pathways. Circulating miRNAs can be measured in the body fluids due to tissue-specific cell injury/damage or toxicant exposure. Therefore, these circulating miRNAs have become attractive and promising non-invasive biomarkers for assessing drug-induced testicular injury, with several reports on their use as safety biomarkers for monitoring testicular damage in preclinical species. Leveraging emerging tools such as 'organs-on-chips' that can emulate the human organ's physiological environment and function is starting to enable biomarker discovery, validation, and clinical translation for regulatory qualification and implementation in drug development.

Study on the Mechanism of Bu-Shen-He-Mai Granules in Improving Renal Damage of Ageing Spontaneously Hypertensive Rats by Regulating Th17 Cell/Tregs Balance

Methods

Blood pressure and urine biochemical indices were recorded. Renal blood flow was evaluated by renal ultrasonography. Transmission electron microscopy (TEM) and HE staining were used to assess kidney and spleen morphology. Renal fibrosis was assessed using Masson staining. Serum levels of IL-6, IL-10, and IL-17A were measured using ELISAs. The density of RORγ and Foxp3 in the spleen was observed by immunofluorescence staining. The levels of Th17 cells and Tregs in blood were detected via flow cytometry. Transcriptome sequencing was performed to screen the targets of BSHM granules in hypertensive kidneys.

Results

BSHM granules decreased SBP by 21.2 mm·Hg and DBP by 8.8 mm·Hg in ageing SHRs (P < 0.05), decreased the levels of urine mALB, β2-Mg, and NAG (P < 0.01), and improved renal blood flow and arteriosclerosis. BSHM granules increased IL-10 expression (P < 0.05) while decreasing IL-6 (P < 0.01) and IL-17A (P < 0.05) levels. BSHM granules improved Foxp3 density and the number of Tregs (P < 0.01) and reduced RORγt density and the number of Th17 cells (P < 0.01). Transcriptome sequencing identified 747 differentially expressed (DE) mRNAs in kidneys after BSHM treatment. GO analysis suggested that BSHM granules act through immunoregulation.

Conclusions

BSHM granules attenuated hypertensive renal damage in ageing SHRs, by significantly increasing Tregs and decreasing Th17 cells.

Evaluation of Renal Biomarkers, Including Symmetric Dimethylarginine, following Gentamicin-Induced Proximal Tubular Injury in the Rat

Symmetric dimethylarginine (SDMA) is an excretory renal function biomarker shown to correlate well with glomerular filtration rate in dogs, cats, humans, and rats. The objectives of this study were to determine utility of serum SDMA as a renal biomarker in a rat model of gentamicin-induced renal injury and to provide validation of a commercially available SDMA immunoassay for rat serum. Rats were randomly assigned to one of three dose levels of gentamicin (20, 50, or 100 mg/kg) or a vehicle control group and dosed once daily by subcutaneous injection for either four or ten days. Serum and urine renal biomarker evaluation, including serum SDMA, hematologic and serum biochemical analysis, urinalysis, and histologic examination of kidney, were performed. Before biologic validation, analytic validation of the SDMA immunoassay for rat serum was performed, including assessment of assay accuracy, precision, analytical sensitivity, linearity, analyte stability, and interference testing. Among markers of excretory renal function, SDMA and serum creatinine increased earliest and at the lowest gentamicin concentrations and were significantly increased in both the 50- and 100- mg/kg dose levels in the four- and ten-dose treatment groups compared with controls. Time- and dose-dependent increases were noted for all urinary biomarkers investigated in this study, with microalbumin being most responsive and osteopontin least responsive for detection of gentamicin-induced injury across dose levels and schedules investigated. The SDMA immunoassay met all set quality requirements assessed in analytical validation. This study is the first to investigate performance of serum SDMA compared with other excretory renal function markers in a rat gentamicin acute toxicity model. In this study, serum SDMA was an earlier biomarker for detection of gentamicin-induced toxicity than serum cystatin C, BUN, and creatinine clearance. The SDMA immunoassay provides a reliable commercially available assay for future renal investigations in rat models.

A Performance Evaluation of Liver and Skeletal Muscle-Specific miRNAs in Rat Plasma to Detect Drug-Induced Injury

Liver and skeletal muscle-specific microRNAs (miRNAs) are currently being evaluated as novel plasma biomarkers that may out-perform or add value to the conventional liver injury biomarkers alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and to the skeletal muscle injury biomarkers AST and creatine kinase (CK). A comprehensive evaluation was conducted to assess the relative performance of these miRNAs to detect and distinguish liver from muscle tissue injury. The performance of miR-122 and miR-192 for liver and miR-1, miR-133a, miR-133b, and miR-206 for skeletal muscle was compared with 10 enzymatic or protein biomarkers across 27 compounds causing specific types of tissue injury in rat. Receiver operator characteristic analyses were performed comparing the relative sensitivity and specificity of each of the biomarkers in individual animals with histopathology observations of necrosis and/or degeneration in various organs. All of the miRNAs outperformed ALT, AST, and/or CK in studies with either liver or skeletal muscle injury and demonstrated superior specificity in organs without type-specific injury (eg, liver biomarkers assessed with compounds that cause skeletal muscle injury). When additional protein biomarkers were included, glutamate dehydrogenase, arginase I, alpha-glutathione S-transferase for liver and skeletal troponin I, myosin light chain 3, fatty acid-binding protein 3, and creatine kinase M isoform for skeletal muscle, the miRNAs demonstrated equal or superior performance to the extended panel. Taken together, this comprehensive evaluation demonstrates that these novel miRNA toxicity biomarkers outperform and add value with respect to sensitivity and specificity over ALT, AST in monitoring the liver and over CK for monitoring skeletal muscle drug-induced injury.

The significance of combined detection of CysC, urinary mAlb and β2-MG in diagnosis of the early renal injury in pregnancy-induced hypertension syndrome

Objective

To elaborate the significance of combined detection of cystatin C, urinary micro-albumin (mAlb) and β₂-microglobulin (β₂-MG) in diagnosis of the early renal injury in pregnancy-induced hypertension syndrome.

Methods

A total of 120 patients with pregnancy-induced hypertension syndrome who were admitted to this hospital for treatment between November 2015 and October 2018 were enrolled as subjects, and divided into the control group (without complication of renal injury, n = 76) and the observation group (with complication of renal injury, n = 44) according to the complications of early renal injury. Furthermore, 60 patients who participated in the antenatal care in this hospital were enrolled as the normal subjects (normal group). Automatic biochemistry analyzer was utilized to measure CysC, urinary mAlb and β₂-MG in serum to evaluate the specificity, sensitivity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of single or combined measurements of these indexes in diagnosis of the early renal injury in pregnancy-induced hypertension syndrome.

Results

In the observation group, the levels of CysC, urinary mAlb and β₂-MG were higher than those in the control group, while the levels in the normal group were the lowest (P < 0.05). Combined measurement of CysC, urinary mAlb and β₂-MG showed a higher accuracy (90.0%) in diagnosis of the early renal injury in pregnancy-induced hypertension syndrome than the single measurements, and the difference had statistical significance (P < 0.05). Besides, the sensitivity, specificity, PPV and NPV of the combined measurements were 94.59%, 87.30%, 81.40% and 94.49%, slightly higher than the single measurements, with no statistical significance in differences (P > 0.05).

Conclusion

CysC, urinary mAlb and β₂-MG can reflect the renal injury effectively, and the combined measurements shows potent accuracy in diagnosis of the early renal injury in pregnancy-induced hypertension syndrome, thereby providing the scientific evidence for early diagnosis and stipulation of rational therapeutic regimen and improving the pregnancy outcome.

Comparative Performance of Urinary Biomarkers for Vancomycin-Induced Kidney Injury According to Timeline of Injury

Urinary biomarkers are superior to serum creatinine for defining onset and extent of kidney injury. This study classifies the temporal predictive ability of biomarkers for vancomycin-induced kidney injury (VIKI) as defined by histopathologic damage. Male Sprague-Dawley rats (n = 125) were randomized to receive 150 to 400 mg/kg of body weight/day vancomycin via once or twice daily intraperitoneal injection over 1, 3, or 6 days. Urine was collected once during the 24 h prior to euthanasia or twice for rats treated for 6 days. Receiver operating characteristic (ROC) curves were employed to assess the urinary biomarker performances of kidney injury molecule 1 (KIM-1), clusterin, osteopontin (OPN), cystatin C, and neutrophil gelatinase-associated lipocalin (NGAL) to predict histopathologically defined VIKI (using a national standard pathological assessment scheme from hematoxylin and eosin stained kidneys). Urinary KIM-1, clusterin, and OPN outperformed cystatin C and NGAL with regard to sensitivity and specificity. For the earliest injury, urinary KIM-1 (area under the receiver operating characteristic curve [AUC], 0.662; P < 0.001) and clusterin (AUC, 0.706; P < 0.001) were the most sensitive for predicting even low-level histopathologic damage at 24 h compared to NGAL. KIM-1 and clusterin are the earliest and most sensitive predictors of VIKI. As injury progresses, KIM-1, clusterin, and OPN best define the extent of damage.

Evaluation of Vancomycin Exposures Associated with Elevations in Novel Urinary Biomarkers of Acute Kidney Injury in Vancomycin-Treated Rats

Vancomycin has been associated with acute kidney injury (AKI). However, the pharmacokinetic/toxicodynamic relationship for AKI is not well defined. Allometrically scaled vancomycin exposures were used to assess the relationship between vancomycin exposure and AKI. Male Sprague-Dawley rats received clinical-grade vancomycin in normal saline (NS) as intraperitoneal (i.p.) injections for 24- to 72-h durations with doses ranging 0 to 200 mg/kg of body weight divided once or twice daily. Urine was collected over the protocol's final 24 h. Renal histopathology was qualitatively scored. Urinary biomarkers (e.g., cystatin C, clusterin, kidney injury molecule 1 [KIM-1], osteopontin, lipocalin 2/neutrophil gelatinase-associated lipocalin 2) were assayed using a Luminex xMAP system. Plasma vancomycin concentrations were assayed by high-performance liquid chromatography with UV detection. A three-compartment vancomycin pharmacokinetic model was fit to the data with the Pmetrics package for R. The exposure-response in the first 24 h was evaluated using Spearman's nonparametric correlation coefficient (rs) values for the area under the concentration-time curve during the first 24 h (AUC0-24), the maximum concentration in plasma during the first 24 h (Cmax0-24 ), and the lowest (minimum) concentration in plasma after the dose closest to 24 h (Cmin0-24 ). A total of 52 rats received vancomycin (n = 42) or NS (n = 10). The strongest exposure-response correlations were observed between AUC0-24 and Cmax0-24 and urinary AKI biomarkers. Exposure-response correlations (rs values) for AUC0-24, Cmax0-24 , and Cmin0-24 were 0.37, 0.39, and 0.22, respectively, for clusterin; 0.42, 0.45, and 0.26, respectively, for KIM-1; and 0.52, 0.55, and 0.42, respectively, for osteopontin. However, no differences in histopathological scores were observed. Optimal sampling times after administration of the i.p. dose were 0.25, 0.75, 2.75, and 8 h for the once-daily dosing schemes and 0.25, 1.25, 14.5, and 17.25 h for the twice-daily dosing schemes. Our observations suggest that AUC0-24 or Cmax0-24 correlates with increases in urinary AKI biomarkers.

Adult vertebrate behavioural aquatic toxicology: Reliability and validity

Current advances in the ability to assay adult aquatic vertebrate behaviour are potentially very useful to aquatic toxicologists wishing to characterise the effects of pollutants on behaviour, cognition or neurodevelopment. This review considers two specific challenges faced by researchers wishing to exploit these technologies: maximising reliability and validity. It will suggest two behavioural procedures, with the potential for automation and high-throughput implementation, which can be used to measure social cohesion and anxiety, two areas of interest in behavioural aquatic toxicology. In addition, the review will make recommendations about how these procedures (and others) could be carried out to maximise reliability and validity.

The use of surrogate endpoints in regulating medicines for cardio-renal disease: opinions of stakeholders

Aim

There is discussion whether medicines can be authorized on the market based on evidence from surrogate endpoints. We assessed opinions of different stakeholders on this topic.

Methods

We conducted an online questionnaire that targeted various stakeholder groups (regulatory agencies, pharmaceutical industry, academia, relevant public sector organisations) and medical specialties (cardiology or nephrology vs. other). Participants were enrolled through purposeful sampling. We inquired for conditions under which surrogate endpoints can be used, the validity of various cardio-renal biomarkers and new approaches for biomarker use.

Results

Participants agreed that surrogate endpoints can be used when the surrogate is scientifically valid (5-point Likert response format, mean score: 4.3, SD: 0.9) or when there is an unmet clinical need (mean score: 3.8, SD: 1.2). Industry participants agreed to a greater extent than regulators and academics. However, out of four proposed surrogates (blood pressure (BP), HbA1c, albuminuria, CRP) for cardiovascular outcomes or end-stage renal disease, only use of BP for cardiovascular outcomes was deemed moderately accurate (mean: 3.6, SD: 1.1). Specialists in cardiology or nephrology tended to be more positive about the use of surrogate endpoints.

Conclusion

Stakeholders in drug development do not oppose to the use of surrogate endpoints in drug marketing authorization, but most surrogates are not considered valid. To solve this impasse, increased efforts are required to validate surrogate endpoints and to explore alternative ways to use them.

Nonclinical Safety Biomarkers of Drug-induced Vascular Injury

Better biomarkers are needed to identify, characterize, and/or monitor drug-induced vascular injury (DIVI) in nonclinical species and patients. The Predictive Safety Testing Consortium (PSTC), a precompetitive collaboration of pharmaceutical companies and the U.S. Food and Drug Administration (FDA), formed the Vascular Injury Working Group (VIWG) to develop and qualify translatable biomarkers of DIVI. The VIWG focused its research on acute DIVI because early detection for clinical and nonclinical safety monitoring is desirable. The VIWG developed a strategy based on the premise that biomarkers of DIVI in rat would be translatable to humans due to the morphologic similarity of vascular injury between species regardless of mechanism. The histomorphologic lexicon for DIVI in rat defines degenerative and adaptive findings of the vascular endothelium and smooth muscles, and characterizes inflammatory components. We describe the mechanisms of these changes and their associations with candidate biomarkers for which advanced analytical method validation was completed. Further development is recommended for circulating microRNAs, endothelial microparticles, and imaging techniques. Recommendations for sample collection and processing, analytical methods, and confirmation of target localization using immunohistochemistry and in situ hybridization are described. The methods described are anticipated to aid in the identification and qualification of translational biomarkers for DIVI.

Translational research into species differences of endocrine toxicity via steroidogenesis inhibition by SMP-028--for human safety in clinical study

SMP-028 is a drug candidate developed for the treatment of asthma. In a 13-week repeated dose toxicity study of SMP-028 in rats and monkeys, differences of endocrine toxicological events between rats and monkeys were observed. In rats, these toxicological events mainly consisted of pathological changes in the adrenal, testis, ovary, and the other endocrine-related organs. On the other hand, in monkeys, no toxicological events were observed. The goal of this study is to try to understand the reason why only rats, but not monkeys, showed toxicological events following treatment with SMP-028 and to eventually predict the possible toxicological effect of this compound on human endocrine organs. Our results show that SMP-028 inhibits neutral cholesterol esterase more strongly than other steroidogenic enzymes in rats. Although SMP-028 also inhibits monkeys and human neutral cholesterol esterase, this inhibition is much weaker than that of rat neutral cholesterol esterase. These results indicate (1) that the difference in endocrine toxicological events between rats and monkeys is mainly due to inhibition of steroidogenesis by SMP-028 in rats, not in monkeys, and (2) that SMP-028 may not affect steroidogenesis in humans and therefore might cause no endocrine toxicological events in clinical studies.

Translational immunologic safety evaluation: a perspective

Although translational research is a rapidly evolving area of biomedical sciences, translational immunologic safety evaluation has so far attracted only very limited attention. Assays and animal models have been developed to identify immunotoxic hazards related to immunosuppression, but less attention has been paid to immunostimulation, hypersensitivity, and autoimmunity. Some of these assays and models are recommended by regulatory bodies, even though it is as yet unsure to what extent they can predict the potential of, or lack of, new chemical entities and drug candidates for inducing significant immunotoxic effects. A translational approach should attempt to standardize and validate those models, assays, and biomarkers that could be used in regulatory non-clinical safety studies as well as clinical studies. Beyond translational immunologic safety, immune monitoring during clinical studies is intended to identify and evaluate potential immune safety issues not seen in non-clinical studies. Based on this overview of the current knowledge, it can be concluded that much remains to be done to conduct translational studies helpful to enhance the immunologic safety of drugs and chemicals.

Predicting and preventing acute drug-induced liver injury: what's new in 2010?

IMPORTANCE OF THE FIELD

The field of drug-induced liver injury (DILI) continues to expand in terms of global registries and with new agents added every year. Given the need to improve on our current methods of preclinical testing and monitoring for DILI during both clinical trials and in the post-approval setting, there is increasing research aimed at better understanding why injury occurs and who is most susceptible. To this end, the active pursuit of biomarkers that will predict injury prior to its occurrence and genetic testing that can identify individuals at risk of DILI continue to be at the forefront.

AREAS COVERED IN THIS REVIEW

While alanine aminotransferase (ALT) testing remains the workhorse of biochemical monitoring, it only detects hepatic injury after it has occurred and, therefore, is not a true predictor. The utility and shortcomings of ALT and other liver tests are reviewed along with a synopsis of several other candidate biomarkers that are being studied. In addition, we review the recent data supporting testing for genetic predisposition to DILI and how identifying clinical risk factors may translate into better means for preventing DILI.

WHAT THE READER WILL GAIN

We update the basis on which age and gender are considered risk factors for DILI, and review the latest reports detailing the association of several candidate genes and the development of DILI in a susceptible patient. Human leukocyte antigen-B*5701 is closely linked to the hypersensitivity reaction seen with abacavir, and such screening has been successfully incorporated into HIV treatment around the globe and offers the promise that testing for other genetic markers will soon become a routine part of clinical practice. At present, candidate genes conferring specific susceptibility to DILI have been identified for a relatively few agents (e.g., flucloxacillin, amoxicillin-clavulanate, ximelagatran and isoniazid), but many more are under study. Preventing DILI often comes down to avoiding the use of potentially hepatotoxic drugs in certain situations, and we review the clinical scenarios in which this is most relevant.

TAKE HOME MESSAGE

Given the number and range of studies aimed at identifying predictors of DILI, the focus of this review is to summarize what we consider to be the most relevant new information published on the topics of clinical and genetic factors that predispose to DILI, the use of biomarkers as predictors of acute DILI, along with advances in prevention strategies.

A panel of urinary biomarkers to monitor reversibility of renal injury and a serum marker with improved potential to assess renal function

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

Urinary clusterin, cystatin C, beta2-microglobulin and total protein as markers to detect drug-induced kidney injury

Earlier and more reliable detection of drug-induced kidney injury would improve clinical care and help to streamline drug-development. As the current standards to monitor renal function, such as blood urea nitrogen (BUN) or serum creatinine (SCr), are late indicators of kidney injury, we conducted ten nonclinical studies to rigorously assess the potential of four previously described nephrotoxicity markers to detect drug-induced kidney and liver injury. Whereas urinary clusterin outperformed BUN and SCr for detecting proximal tubular injury, urinary total protein, cystatin C and beta2-microglobulin showed a better diagnostic performance than BUN and SCr for detecting glomerular injury. Gene and protein expression analysis, in-situ hybridization and immunohistochemistry provide mechanistic evidence to support the use of these four markers for detecting kidney injury to guide regulatory decision making in drug development. The recognition of the qualification of these biomarkers by the EMEA and FDA will significantly enhance renal safety monitoring.

Urinary biomarkers trefoil factor 3 and albumin enable early detection of kidney tubular injury

The capacities of urinary trefoil factor 3 (TFF3) and urinary albumin to detect acute renal tubular injury have never been evaluated with sufficient statistical rigor to permit their use in regulated drug development instead of the current preclinical biomarkers serum creatinine (SCr) and blood urea nitrogen (BUN). Working with rats, we found that urinary TFF3 protein levels were markedly reduced, and urinary albumin were markedly increased in response to renal tubular injury. Urinary TFF3 levels did not respond to nonrenal toxicants, and urinary albumin faithfully reflected alterations in renal function. In situ hybridization localized TFF3 expression in tubules of the outer stripe of the outer medulla. Albumin outperformed either SCr or BUN for detecting kidney tubule injury and TFF3 augmented the potential of BUN and SCr to detect kidney damage. Use of urinary TFF3 and albumin will enable more sensitive and robust diagnosis of acute renal tubular injury than traditional biomarkers.

Personalized healthcare: how to improve outcomes by increasing benefit and decreasing risk through the use of biomarkers

The use of personalized healthcare is beginning to show promise as a means of increasing benefit and decreasing risk for patients, but much work needs to be done in order to fully exploit the advances in medical science that have occurred over the last 30 years. In particular, molecular approaches that aim to characterize patient individuality must be combined with genetic approaches to capture the promise of this potential revolution in the practice of medicine.

Genomic and metabolomic advances in the identification of disease and adverse event biomarkers

Incomplete knowledge of tissue pathogenesis is hampering the identification of biomarkers for the appropriate therapeutic targets to prevent or inhibit disease processes, and the prediction and diagnosis of injury due to disease and adverse events of drug therapy. The revolution in genomics and metabolomics, combined with advanced bioinformatics and computational methods for mining such large, complex data sets, are beginning to provide critical insights into tissue injury. Such results will move us closer to the promise of personalized medicine.

The Critical Path Institute's approach to precompetitive sharing and advancing regulatory science

Many successful large industries, such as computer-chip manufacturers, the cable television industry, and high-definition television developers,(1) have established successful precompetitive collaborations focusing on standards, applied science, and technology that advance the field for all stakeholders and benefit the public.(2) The pharmaceutical industry, however, has a well-earned reputation for fierce competition and did not demonstrate willingness to share data or knowledge until the US Food and Drug Administration (FDA) launched the Critical Path Initiative in 2004 (ref. 3).

Kidney injury molecule-1 outperforms traditional biomarkers of kidney injury in preclinical biomarker qualification studies

Kidney toxicity accounts both for the failure of many drug candidates as well as considerable patient morbidity. Whereas histopathology remains the gold standard for nephrotoxicity in animal systems, serum creatinine (SCr) and blood urea nitrogen (BUN) are the primary options for monitoring kidney dysfunction in humans. The transmembrane tubular protein kidney injury molecule-1 (Kim-1) was previously reported to be markedly induced in response to renal injury. Owing to the poor sensitivity and specificity of SCr and BUN, we used rat toxicology studies to compare the diagnostic performance of urinary Kim-1 to BUN, SCr and urinary N-acetyl-beta-D-glucosaminidase (NAG) as predictors of kidney tubular damage scored by histopathology. Kim-1 outperforms SCr, BUN and urinary NAG in multiple rat models of kidney injury. Urinary Kim-1 measurements may facilitate sensitive, specific and accurate prediction of human nephrotoxicity in preclinical drug screens. This should enable early identification and elimination of compounds that are potentially nephrotoxic.