Towards consensus practices to qualify safety biomarkers for use in early drug development

Magnitude of Urine Albumin and KIM-1 Changes Can be Used to Differentiate Glomerular Injury From Tubular Injury in Rats

Emerging urinary kidney safety biomarkers have been evaluated in recent years and have been shown to be superior to the serum parameters blood urea nitrogen (BUN) and creatinine (sCr) for monitoring kidney injury in the proximal tubule. However, their potential application in differentiating the location of the initial kidney injury (eg, glomerulus vs tubule) has not been fully explored. Here, we assessed the performance of two algorithms that were constructed using either an empirical or a mathematical model to predict the site of kidney injury using a data set consisting of 22 rat kidney toxicity studies with known urine biomarker and histopathologic outcomes. Two kidney safety biomarkers used in both models, kidney injury molecule 1 (KIM-1) and albumin (ALB), were the best performers to differentiate glomerular injury from tubular injury. The performance of algorithms using these two biomarkers against the gold standard of kidney histopathologic examination showed high sensitivity in differentiating the location of the kidney damage to either the glomerulus or the proximal tubules. These data support the exploration of such an approach for use in clinical settings, leveraging urinary biomarker data to aid in the diagnosis of either glomerular or tubular injury where histopathologic assessments are not conducted.

Activated SOX9+ renal epithelial cells promote kidney repair through secreting factors

A broad spectrum of lethal kidney diseases involves the irreversible destruction of the tubular structures, leading to renal function loss. Following injury, a spectrum of tissue-resident epithelial stem/progenitor cells are known to be activated and then differentiate into mature renal cells to replace the damaged renal epithelium. Here, however, we reported an alternative way that tissue-resident cells could be activated to secrete multiple factors to promote organ repair. At single-cell resolution, we showed that the resident SOX9+ renal epithelial cells (RECs) could expand in the acutely injured kidney of both mouse and human. Compared to other cells, the SOX9+ RECs overexpressed much more secretion related genes, whose functions were linked to kidney repair pathways. We also obtained long-term, feeder-free cultured SOX9+ RECs from human urine and analysed their secretory profile at both transcriptional and proteomic levels. Engraftment of cultured human SOX9+ RECs or injection of its conditional medium facilitated the regeneration of renal tubular and glomerular epithelium, probably through stimulating endogenous REC self-activation and mediating crosstalk with other renal cells. We also identified S100A9 as one of the key factors in the SOX9+ REC secretome. Altogether, the abilities to extensively propagate SOX9+ RECs in culture whilst concomitantly maintaining their intrinsic secretory capacity suggest their future application in cell-free therapies and regeneration medicine.

Early-Onset albuminuria and Associated Renal Pathology in Leucine-Rich Repeat Kinase 2 Knockout Rats

Activating mutations of the leucine-rich repeat kinase 2 (LRRK2) gene are associated with Parkinson disease (PD), prompting development of LRRK2 inhibitors as potential treatment for PD. However, kidney safety concerns have surfaced from LRRK2 knockout (KO) mice and rats and from repeat-dose studies in rodents administered LRRK2 inhibitors. To support drug development of this therapeutic target, we conducted a study of 26 weeks' duration in 2-month-old wild-type and LRRK2 KO Long-Evans Hooded rats to systematically examine the performance of urinary safety biomarkers and to characterize the nature of the morphological changes in the kidneys by light microscopy and by ultrastructural evaluation. Our data reveal the time course of early-onset albuminuria at 3 and 4 months in LRRK2 KO female and male rats, respectively. The increases in urine albumin were not accompanied by concurrent increases in serum creatinine, blood urea nitrogen, or renal safety biomarkers such as kidney injury molecule 1 or clusterin, although morphological alterations in both glomerular and tubular structure were identified by light and transmission electron microscopy at 8 months of age. Diet optimization with controlled food intake attenuated the progression of albuminuria and associated renal changes.

Urinary Metabolomics from a Dose-Fractionated Polymyxin B Rat Model of Acute Kidney Injury

BACKGROUND

Polymyxin B treatment is limited by kidney injury. We sought to identify Polymyxin B related urinary metabolomic profile modifications for early detection of polymyxin-associated nephrotoxicity.

METHODS

Samples were obtained from a previously conducted study. Male Sprague-Dawley rats received dose-fractionated polymyxin B (12mg/kg/day) once daily (QD), twice daily (BID), and thrice daily (TID) for three days with urinary biomarkers and kidney histopathology scores determined. Daily urine was analysed for metabolites via 1H NMR. Principal Components Analyses identified spectral data trends with orthogonal Partial Least Square Discriminant Analysis applied to classify metabolic differences. Metabolomes were compared across groups (i.e., those receiving QD, BID, TID, and control) using a mixed-effects models. Spearman correlation was performed for injury biomarkers and the metabolome.

RESULTS

A total of 25 rats were treated with Polymyxin B, and n=2 received saline, contributing 77 urinary samples. Pre-dosing samples clustered well, characterized by higher amounts of citrate, 2-oxoglutarate, and hippurate. Day 1 samples showed higher taurine; day 3 samples had higher lactate, acetate, and creatine. Taurine was the only metabolite significantly increased in both BID and TID compared to QD group. Day 1 taurine correlated with increasing histopathology scores (rho=0.4167, P=0.038) and KIM-1 (rho =0.4052, P=0.036); whereas KIM-1 on day one and day 3 did not reach significance with histopathology (rho=0.3248, P=0.11 and rho=0.3739, P=0.066).

CONCLUSIONS

Polymyxin B causes increased amounts of urinary taurine on day 1 which then normalizes to baseline concentrations. Taurine may provide one of the earlier signals of acute kidney damage caused by polymyxin B.

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.

Kidney Injury Monitoring in Tobramycin-Treated Rhesus Monkeys: Supplementing Urinary Kidney Biomarkers With Kidney Biopsy Gene Expression Profiling

Kidney biopsies are used sparingly to diagnose kidney injury in the clinic. Here we have conducted a small exploratory study to directly compare the low-grade kidney injury monitoring performance of serum safety biomarkers, novel urine safety biomarkers, microscopic histopathology and targeted gene expression alterations in kidney biopsy specimens in rhesus monkeys treated with tobramycin. Targeted gene expression increases were observed in the kidney biopsy samples and whole kidney sections for kidney injury molecule 1 (KIM-1), clusterin (CLU), osteopontin (OPN) messenger RNA transcripts. In addition, increases of the urinary kidney safety protein biomarkers including KIM-1, CLU, OPN were also observed. These increases in gene expression and urinary protein end point were in concordance with the eventual low-grade kidney lesions seen in terminal tissue sections. In contrast, conventional serum biomarkers blood urea nitrogen and serum creatinine were not as sensitive in monitoring kidney injury. Although these data do not support routinely adding kidney biopsies to regular toxicology studies, they provide evidence on the value and limitations of incorporating gene expression profiling on kidney biopsy specimens, further underscore the value of urinary kidney safety biomarkers for improved low-grade kidney injury monitoring, and open the door for future definitive studies.

Advanced preclinical models for evaluation of drug-induced liver injury - consensus statement by the European Drug-Induced Liver Injury Network [PRO-EURO-DILI-NET]

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) and one of the leading indications for liver transplantation in Western societies. Given the wide use of both prescribed and over the counter drugs, DILI has become a major health issue for which there is a pressing need to find novel and effective therapies. Although significant progress has been made in understanding the molecular mechanisms underlying DILI, our incomplete knowledge of its pathogenesis and inability to predict DILI is largely due to both discordance between human and animal DILI in preclinical drug development and a lack of models that faithfully recapitulate complex pathophysiological features of human DILI. This is exemplified by the hepatotoxicity of acetaminophen (APAP) overdose, a major cause of ALF because of its extensive worldwide use as an analgesic. Despite intensive efforts utilising current animal and in vitro models, the mechanisms involved in the hepatotoxicity of APAP are still not fully understood. In this expert Consensus Statement, which is endorsed by the European Drug-Induced Liver Injury Network, we aim to facilitate and outline clinically impactful discoveries by detailing the requirements for more realistic human-based systems to assess hepatotoxicity and guide future drug safety testing. We present novel insights and discuss major players in APAP pathophysiology, and describe emerging in vitro and in vivo pre-clinical models, as well as advanced imaging and in silico technologies, which may improve prediction of clinical outcomes of DILI.

Urinary miRNA Biomarkers of Drug-Induced Kidney Injury and Their Site Specificity Within the Nephron

Drug-induced kidney injury (DIKI) is a major concern in both drug development and clinical practice. There is an unmet need for biomarkers of glomerular damage and more distal renal injury in the loop of Henle and the collecting duct (CD). A cross-laboratory program to identify and characterize urinary microRNA (miRNA) patterns reflecting tissue- or pathology-specific DIKI was conducted. The overall goal was to propose miRNA biomarker candidates for DIKI that could supplement information provided by protein kidney biomarkers in urine. Rats were treated with nephrotoxicants causing injury to distinct nephron segments: the glomerulus, proximal tubule, thick ascending limb (TAL) of the loop of Henle and CD. Meta-analysis identified miR-192-5p as a potential proximal tubule-specific urinary miRNA candidate. This result was supported by data obtained in laser capture microdissection nephron segments showing that miR-192-5p expression was enriched in the proximal tubule. Discriminative miRNAs including miR-221-3p and -222-3p were increased in urine from rats treated with TAL versus proximal tubule toxicants in accordance with their expression localization in the kidney. Urinary miR-210-3p increased up to 40-fold upon treatment with TAL toxicants and was also enriched in laser capture microdissection samples containing TAL and/or CD versus proximal tubule. miR-23a-3p was enriched in the glomerulus and was increased in urine from rats treated with doxorubicin, a glomerular toxicant, but not with toxicants affecting other nephron segments. Taken together these results suggest that urinary miRNA panels sourced from specific nephron regions may be useful to discriminate the pathology of toxicant-induced lesions in the kidney, thereby contributing to DIKI biomarker development needs for industry, clinical, and regulatory use.

Machine Learning in Drug Discovery: A Review

This review provides the feasible literature on drug discovery through ML tools and techniques that are enforced in every phase of drug development to accelerate the research process and deduce the risk and expenditure in clinical trials. Machine learning techniques improve the decision-making in pharmaceutical data across various applications like QSAR analysis, hit discoveries, de novo drug architectures to retrieve accurate outcomes. Target validation, prognostic biomarkers, digital pathology are considered under problem statements in this review. ML challenges must be applicable for the main cause of inadequacy in interpretability outcomes that may restrict the applications in drug discovery. In clinical trials, absolute and methodological data must be generated to tackle many puzzles in validating ML techniques, improving decision-making, promoting awareness in ML approaches, and deducing risk failures in drug discovery.

Lack of synergistic nephrotoxicity between vancomycin and piperacillin/tazobactam in a rat model and a confirmatory cellular model

BACKGROUND

Vancomycin and piperacillin/tazobactam are reported in clinical studies to increase acute kidney injury (AKI). However, no clinical study has demonstrated synergistic toxicity, only that serum creatinine increases.

OBJECTIVES

To clarify the potential for synergistic toxicity between vancomycin, piperacillin/tazobactam and vancomycin + piperacillin/tazobactam treatments by quantifying kidney injury in a translational rat model of AKI and using cell studies.

METHODS

(i) Male Sprague-Dawley rats (n = 32) received saline, vancomycin 150 mg/kg/day intravenously, piperacillin/tazobactam 1400 mg/kg/day intraperitoneally or vancomycin + piperacillin/tazobactam for 3 days. Urinary biomarkers and histopathology were analysed. (ii) Cellular injury was assessed in NRK-52E cells using alamarBlue®.

RESULTS

Urinary output increased from Day -1 to Day 1 with vancomycin but only after Day 2 for vancomycin + piperacillin/tazobactam-treated rats. Plasma creatinine was elevated from baseline with vancomycin by Day 2 and only by Day 4 for vancomycin + piperacillin/tazobactam. Urinary KIM-1 and clusterin were increased with vancomycin from Day 1 versus controls (P < 0.001) and only on Day 3 with vancomycin + piperacillin/tazobactam (P < 0.001, KIM-1; P < 0.05, clusterin). The histopathology injury score was elevated only in the vancomycin group when compared with piperacillin/tazobactam as a control (P = 0.04) and generally not so with vancomycin + piperacillin/tazobactam. In NRK-52E cells, vancomycin induced cell death with high doses (IC50 48.76 mg/mL) but piperacillin/tazobactam did not, and vancomycin + piperacillin/tazobactam was similar to vancomycin.

CONCLUSIONS

All groups treated with vancomycin demonstrated AKI; however, vancomycin + piperacillin/tazobactam was not worse than vancomycin. Histopathology suggested that piperacillin/tazobactam did not worsen vancomycin-induced AKI and may even be protective.

A Review of Specific Biomarkers of Chronic Renal Injury and Their Potential Application in Nonclinical Safety Assessment Studies

A host of novel renal biomarkers have been developed over the past few decades which have enhanced monitoring of renal disease and drug-induced kidney injury in both preclinical studies and in humans. Since chronic kidney disease (CKD) and acute kidney injury (AKI) share similar underlying mechanisms and the tubulointerstitial compartment has a functional role in the progression of CKD, urinary biomarkers of AKI may provide predictive information in chronic renal disease. Numerous studies have explored whether the recent AKI biomarkers could improve upon the standard clinical biomarkers, estimated glomerular filtration rate (eGFR), and urinary albumin to creatinine ratio, for predicting outcomes in CKD patients. This review is an introduction to alternative assays that can be utilized in chronic (>3 months duration) nonclinical safety studies to provide information on renal dysfunction and to demonstrate specific situations where these assays could be utilized in nonclinical drug development. Novel biomarkers such as symmetrical dimethyl arginine, dickkopf homolog 3, and cystatin C predict chronic renal injury in animals, act as surrogates for GFR, and may predict changes in GFR in patients over time, ultimately providing a bridge from preclinical to clinical renal monitoring.

The Utility of Novel Urinary Biomarkers in Mice for Drug Development Studies

Novel urinary protein biomarkers have recently been identified and qualified in rats for the early detection of renal injury in drug development studies. However, there are few reports on the utility of these renal biomarkers in mice, another important and widely used preclinical animal species for drug development studies. The purpose of this study was to assess the value of these recently qualified biomarkers for the early detection of drug-induced kidney injury (DIKI) in different strains of mice using multiple assay panels. To this end, we evaluated biomarker response to kidney injury induced by several nephrotoxic agents including amphotericin B, compound X, and compound Y. Several of the biomarkers were shown to be sensitive to DIKI in mice. When measured, urinary albumin and neutrophil gelatinase-associated lipocalin were highly sensitive to renal tubular injury, regardless of the assay platforms, mouse strain, and nephrotoxic agents. Depending on the type of renal tubular injury, kidney injury molecule-1 was also highly sensitive, regardless of the assay platforms and mouse strain. Osteopontin and cystatin C were modestly to highly sensitive to renal tubular injury, but the assay type and/or the mouse strain should be considered before using these biomarkers. Calbindin D28 was highly sensitive to injury to the distal nephron in mice. To our knowledge, this is the first report that demonstrates the utility of novel urinary biomarkers evaluated across multiple assay platforms and nephrotoxicants in different mice strains with DIKI. These results will help drug developers make informed decisions when selecting urinary biomarkers for monitoring DIKI in mice for toxicology studies.

Evaluation of 10 Urinary Biomarkers for Renal Safety With 5 Nephrotoxicants in Nonhuman Primates

To date, there has been very little published data evaluating the performance of novel urinary kidney biomarkers in nonhuman primates (NHPs). To assess the biomarker performance and characterize the corresponding histomorphologic patterns of tubular renal injury in the NHP, several studies were conducted using mechanistically diverse nephrotoxicants including cefpirome, cisplatin, naproxen, cyclosporine, and a combination of gentamicin with everninomicin. An evaluation of 10 urinary biomarkers (albumin, clusterin, cystatin C, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, liver-type fatty acid-binding protein, N-acetyl-β-D-glucosaminidase, osteopontin, retinol binding protein 4 and total protein) was performed on urine collected from these studies. Each of these 5 treatments resulted in kidney proximal tubule injury of various severities. Histomorphologic features observed following treatment were generally consistent with analogous drug-induced changes in humans described in the literature. Most of the analyzed biomarkers were able to detect the injury earlier and with greater sensitivity than blood urea nitrogen and serum creatinine. Across all studies, KIM-1 and clusterin showed the highest overall performance. Differences in the patterns of biomarker responsiveness were noted among certain studies that may be informing tubular injury severity and recovery potential, underlying histopathologic processes, and prognosis. These findings demonstrate the utility of urinary kidney translational safety biomarkers in NHPs and provide additional supporting evidence for translating these biomarkers for use in clinical trial settings to further ensure patient safety.

Evaluation of biomarkers for in vitro prediction of drug-induced nephrotoxicity in RPTEC/TERT1 cells

There have been intensive efforts to identify in vivo biomarkers that can be used to monitor drug-induced kidney damage before significant impairment occurs. Kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, clusterin, β2-microglobulin and cystatin C (CysC) have been validated as clinical or preclinical biomarkers in urinary and plasma predictive of acute and chronic kidney injuries and diseases. A high-throughput in vitro assay predictive of nephrotoxicity could potentially be implemented in early drug discovery stage to reduce attrition at later stages of drug development. To assess the potential of these known in vivo biomarkers for in vitro evaluation of drug-induced nephrotoxicity, we selected four nephrotoxic agents (cisplatin, cyclosporin, aristolochic acid I and gentamicin) and detected their effects on the protein levels of nephrotoxic biomarkers in RPTEC/TERT1 cells. The protein levels of clusterin, CysC, GSTπ and TIMP-1 significantly increased in the conditioned media of RPTEC/TERT1 cells treated with cisplatin, cyclosporin, aristolochic acid I and gentamicin. The messenger RNA levels of clusterin, CysC, GSTπ and TIMP-1 also increased in RPTEC/TERT1 cells treated with cisplatin, cyclosporin, aristolochic acid I and gentamicin, indicating that drug-induced upregulation involves transcriptional activation. Taken together, the results clearly demonstrate that among the known in vivo nephrotoxic biomarkers, clusterin, CysC, GSTπ and TIMP-1 can be effectively used as in vitro biomarkers for drug-induced nephrotoxicity in RPTEC/TERT1 cells.

Biomarkers of Acute and Chronic Kidney Disease

The current unidimensional paradigm of kidney disease detection is incompatible with the complexity and heterogeneity of renal pathology. The diagnosis of kidney disease has largely focused on glomerular filtration, while assessment of kidney tubular health has notably been absent. Following insult, the kidney tubular cells undergo a cascade of cellular responses that result in the production and accumulation of low-molecular-weight proteins in the urine and systemic circulation. Modern advancements in molecular analysis and proteomics have allowed the identification and quantification of these proteins as biomarkers for assessing and characterizing kidney diseases. In this review, we highlight promising biomarkers of kidney tubular health that have strong underpinnings in the pathophysiology of kidney disease. These biomarkers have been applied to various specific clinical settings from the spectrum of acute to chronic kidney diseases, demonstrating the potential to improve patient care.

Urine kidney safety biomarkers improve understanding of indirect intra-renal injury potential in dogs with a drug-induced prerenal azotemia

Drug-induced kidney injury (DIKI) is a frequent occurrence in nonclinical drug development. It is well established that novel urine kidney safety biomarkers will outperform urea nitrogen (BUN) and serum creatinine (sCr) for monitoring direct drug injury to the kidney across numerous compounds spanning diverse mechanisms and efforts are underway for a formal regulatory clinical qualification. However, it remains unclear how these novel biomarkers will perform under prerenal azotemia when BUN and sCr are elevated but no intra-renal injury is suspected. This lack of knowledge is largely due to the dearth of such nonclinical animal models. We report here that treatment of dogs with a potent antihypertensive compound MK-5478 at a suprapharmacologic dose for up to 9 days results in the development of prerenal azotemia and, in some dogs, kidney toxicity through the dual sustained effects of MK-5478 as a nitric oxide donor and an angiotensin II receptor blocker (ARB). While conventional serum biomarkers BUN, and often sCr as well, were highly elevated in these dogs with or without kidney damage, urine kidney biomarkers clusterin (CLU) and neutrophil gelatinase-associated lipocalin (NGAL) showed increases only in dogs with kidney histopathologic changes following the sustained period of prerenal azotemia. Urine albumin (ALB) and total protein also tracked with kidney lesions but with less sensitivity. Thus, we present evidence for the first time that urine kidney safety biomarkers used together with BUN and sCr can distinguish intra-renal injury among dogs with prerenal azotemia while the conventional serum biomarkers alone are ambiguous, either being interpreted as false positives of kidney injury, or dismissed under circumstances as benign without appreciation for a threshold of impending injury.

Predictive Nephrotoxicity Profiling of a Novel Antifungal Small Molecule in Comparison to Amphotericin B and Voriconazole

BACKGROUND AND PURPOSE

Candida albicans is the major fungal species associated with superficial mucosal infections such as oral candidiasis as well as systemic mycoses with high morbidity and mortality. On top of the rising drug resistance, currently available antifungal agents have significant adverse effects. Nephrotoxicity is the major treatment complication associated with antifungal agents.Recently, we discovered a novel antifungal small molecule SM21 with promising antifungal activity. The present study aimed to comparatively evaluate the in vivo and in vitro nephrotoxicity of SM21 comparing with Amphotericin B and voriconazole.

EXPERIMENTAL APPROACH

Nephrotoxicity of SM21 and its analogue were comparatively evaluated with Amphotericin B (AmB) and voriconazole. Immortalized human kidney proximal tubule epithelial cells (HK-2) were used for in vitro analysis of nephrotoxicity using cytotoxicity assays and qPCR gene expression analysis (Kim-1/HAVcr-1, CASP3). Sprague Dawley (SD) rat model was used to evaluate the nephrotoxicity in vivo using classical (SCr and BUN) and next-generation kidney injury urinary biomarkers (Kim-1, CLU, ALB, NGAL, β2M, and Cys C) alongside histopathological and immunohistochemical standards.

KEY RESULTS

AmB treatment showed a stronger cytotoxic impact on HK-2 viability and gene expression of cell death markers (Kim-1/HAVcr-1, CASP3) compared with SM21 and SM21 analogue in vitro (P < 0.01). In vivo data further demonstrated that SM21 did not significantly increase classical as well as novel nephrotoxic biomarkers, and minimal renal tubular necrosis and abnormalities were observed (15 mg kg-1 BW/day).

CONCLUSIONS AND IMPLICATIONS

SM21 had a significantly better safety profile in terms of nephrotoxicity with no major tubular epithelial abnormalities observed in kidney cells and no augmentation of kidney injury biomarkers compared to AmB. Kim-1 and CLU were the most sensitive biomarkers for detection of AmB-induced kidney damage. Future clinical trials should consider inclusion of these novel biomarkers as early indicators of acute kidney injury in antifungal-induced nephrotoxicity.

Evaluation of Dose-Fractionated Polymyxin B on Acute Kidney Injury Using a Translational In Vivo Rat Model

We investigated dose-fractionated polymyxin B (PB) on acute kidney injury (AKI). PB at 12 mg of drug/kg of body weight per day (once, twice, and thrice daily) was administered in rats over 72 h. The thrice-daily group demonstrated the highest KIM-1 increase (P = 0.018) versus that of the controls (P = 0.99) and histopathological damage (P = 0.013). A three-compartment model best described the data (bias, 0.129 mg/liter; imprecision, 0.729 mg2/liter2; R2, 0.652,). Area under the concentration-time curve at 24 h (AUC24) values were similar (P = 0.87). The thrice-daily dosing scheme resulted in the most PB-associated AKI in a rat model.

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.

Changes in novel gastrointestinal and renal injury markers in the blood plasma of sheep following increasing intravenous doses of tolfenamic acid

The administration of high doses of non-steroidal anti-inflammatory drugs (NSAID), such as tolfenamic acid (TA), has undesirable effects on different organs. Some novel biomarkers have been reported that can determine the gastrointestinal and renal injury caused by a high dose of NSAIDs or other toxic substances. This study was aimed at determining the changes in gastrointestinal (TFF2 and HYP), renal (NGAL and KIM-1) and cardiac (cTn-I, CK-MB) injury markers after the use of increasing intravenous doses of TA in sheep. TA was administered intravenously to groups of six sheep each, at the dose levels of 0 (Group 0, i.e., G0), 2 (G2), 4 (G4), 8 (G8) and 16 (G16) mg/kg. The concentrations of the studied biomarkers were measured at 3, 9, 18 and 36 h after administration of TA. The TFF2 and NGAL concentrations in G16 were found to be significantly higher (P < 0.05) than in the other groups except for G8 at different sampling times. HYP concentration in G16 was observed to be significantly (P < 0.05) lower than that in all other groups at 36 h. KIM-1 level in G16 was significantly (P < 0.05) higher than in all other groups at different sampling times. An increase in the renal markers, KIM-1 and NGAL, in G8 was observed before any change in plasma creatinine and urea. The cardiac marker cTn-I in G16 was significantly (P < 0.05) higher than in other groups at different sampling times. The results showed that the novel biomarkers (HYP, TFF2, NGAL, and KIM-1) can be used to determine gastric and renal injury in sheep.

Investigating the Value of Urine Volume, Creatinine, and Cystatin C for Urinary Biomarkers Normalization for Drug Development Studies

Novel urinary protein biomarkers have recently been identified and qualified in rats for the early detection of renal injury in drug development studies. However, there seems to be no standardized normalization method for analyzing these urinary biomarkers, as some users normalize with urinary creatinine (uCr), urine volume (uVol), or leave biomarker un-normalized. More recently, urinary cystatin C is also emerging as a urinary biomarker normalizer, given some of its characteristics as a glomerular filtration marker. The purpose of this study was to identify an optimal drug-induced kidney injury biomarker normalization method that can be adopted more uniformly in the field. To this end, we compared the variability of uVol, urinary cystatin C, and Cr in healthy rats; we evaluated the sensitivity of the renal biomarkers to renal injury after normalization with uVol, uCr, and cystatin C in rats with cisplatin-induced renal injury. We showed that, over time, uCr was less variable than urinary cystatin C and uVol. When the renal biomarkers were normalized with the 3 normalizing end points, the biomarkers showed (1) least variability following normalization with Cr in healthy animals and (2) poor sensitivity when normalized with urinary cystatin C in animals with renal injury. Overall, the results suggested that uCr is better than urinary cystatin C and uVol for normalizing renal biomarkers in rats under controlled preclinical conditions. To our knowledge, this is the first report that compared the variability of uVol, cystatin C, and Cr in the context of renal biomarkers' normalization.

An in vitro method for nephrotoxicity evaluation using HK-2 human kidney epithelial cells combined with biomarkers of nephrotoxicity

The kidney is one of the major target organs for drug-induced toxicity. During drug development, the traditional markers of nephrotoxicity indicate only severe and late damage, which leads to high costs. The new biomarkers are needed for a more sensitive and reliable evaluation of nephrotoxicity, especially for the regulatory accepted and validated in vitro model. We developed an in vitro model based on the HK-2 cell using the biomarkers of nephrotoxicity as endpoints for the evaluation of nephrotoxicity. The predictive performance of the biomarkers including LDH, GGT, KIM-1, clusterin, CysC, NGAL, TIMP-1, GSTπ and osteopontin was evaluated with 22 well characterized compounds. The area under the curve (AUC) values of KIM-1, clusterin, CysC and osteopontin ranged between 0.79 and 0.84. The combination of clusterin, KIM-1 and/or osteopontin improved the AUC value (ranging between 0.88 and 0.95) compared to one biomarker. Taken together, these results suggest that the model based on the HK-2 cell using clusterin, osteopontin, CysC and KIM-1 as endpoints would allow the prediction of nephrotoxicity at early preclinical stages.

Performance Assessment of New Urinary Translational Safety Biomarkers of Drug-induced Renal Tubular Injury in Tenofovir-treated Cynomolgus Monkeys and Beagle Dogs

Newer urinary protein kidney safety biomarkers can outperform the conventional kidney functional biomarkers blood urea nitrogen (BUN) and serum creatinine (SCr) in rats. However, there is far less experience with the relative performance of these biomarkers in dogs and nonhuman primates. Here, we report urine protein biomarker performance in tenofovir-treated cynomolgus monkeys and beagle dogs. Tenofovir intravenous daily dosing in monkeys for 2 or 4 weeks at 30 mg/kg/day resulted in minimal to moderate tubular degeneration and regeneration, and tenofovir disoproxil fumarate oral dosing in dogs for 10 days at 45 mg/kg/day resulted in mild to marked tubular degeneration, necrosis, and regeneration. Among biomarkers tested, kidney injury molecule 1 (Kim-1) and clusterin (CLU) clearly outperformed BUN and SCr and were the most reliable in detecting the onset and progression of tenofovir-induced tubular injury. Cystatin C, retinol binding protein 4, β2-microglobulin, neutrophil gelatinase-associated lipocalin, albumin, and total protein also performed better than BUN and SCr and added value when considered together with Kim-1 and CLU. These findings demonstrate the promising utility of these urinary safety biomarkers in monkeys and dogs and support their further evaluation in human to improve early detection of renal tubular injury.

A multi-center preclinical study of gadoxetate DCE-MRI in rats as a biomarker of drug induced inhibition of liver transporter function

Drug-induced liver injury (DILI) is a leading cause of acute liver failure and transplantation. DILI can be the result of impaired hepatobiliary transporters, with altered bile formation, flow, and subsequent cholestasis. We used gadoxetate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), combined with pharmacokinetic modelling, to measure hepatobiliary transporter function in vivo in rats. The sensitivity and robustness of the method was tested by evaluating the effect of a clinical dose of the antibiotic rifampicin in four different preclinical imaging centers. The mean gadoxetate uptake rate constant for the vehicle groups at all centers was 39.3 +/- 3.4 s^-1 (n = 23) and 11.7 +/- 1.3 s^-1 (n = 20) for the rifampicin groups. The mean gadoxetate efflux rate constant for the vehicle groups was 1.53 +/- 0.08 s^-1 (n = 23) and for the rifampicin treated groups was 0.94 +/- 0.08 s^-1 (n = 20). Both the uptake and excretion transporters of gadoxetate were statistically significantly inhibited by the clinical dose of rifampicin at all centers and the size of this treatment group effect was consistent across the centers. Gadoxetate is a clinically approved MRI contrast agent, so this method is readily transferable to the clinic. Conclusion: Rate constants of gadoxetate uptake and excretion are sensitive and robust biomarkers to detect early changes in hepatobiliary transporter function in vivo in rats prior to established biomarkers of liver toxicity.

Polymer Therapeutics: Biomarkers and New Approaches for Personalized Cancer Treatment

Polymer therapeutics (PTs) provides a potentially exciting approach for the treatment of many diseases by enhancing aqueous solubility and altering drug pharmacokinetics at both the whole organism and subcellular level leading to improved therapeutic outcomes. However, the failure of many polymer-drug conjugates in clinical trials suggests that we may need to stratify patients in order to match each patient to the right PT. In this concise review, we hope to assess potential PT-specific biomarkers for cancer treatment, with a focus on new studies, detection methods, new models and the opportunities this knowledge will bring for the development of novel PT-based anti-cancer strategies. We discuss the various "hurdles" that a given PT faces on its passage from the syringe to the tumor (and beyond), including the passage through the bloodstream, tumor targeting, tumor uptake and the intracellular release of the active agent. However, we also discuss other relevant concepts and new considerations in the field, which we hope will provide new insight into the possible applications of PT-related biomarkers.

Current practices and future outlook on the integration of biomarkers in the drug development process

Over the last decade, there has been broad incorporation of translational biomarkers into the early drug development process to predict safety concerns, measure target engagement and monitor disease progression. One goal of translational biomarkers is to create a cycle whereby preclinical readouts influence candidate selection and subsequent clinical data are fed back into research to facilitate better decision making. Successes have been limited and not as broad in scope as desired. Collaborations between industry and regulators have increased the number of qualified biomarkers; but the process is lengthy and expensive. A high level overview of translational biomarkers as well as a discussion of some of the successes and failures encountered in development is discussed here.

Regulatory landscapes for biomarkers and diagnostic tests: Qualification, approval, and role in clinical practice

While the term 'biomarker' is relatively new, the concept is millennia old. However, with the introduction of new technologies to discover potential biomarkers comes the need to assess their utility and veracity for any given use. This is particularly true for the use of biomarkers to support regulatory decisions in medical product development. Hence the US Food and Drug Administration has developed processes for the qualification of biomarkers and other medical product development tools, processes that are underscored by recent legislation (i.e. the 21st Century Cures Act). In addition to these qualification processes, diagnostic tests that measure a biomarker may follow a process for regulatory decision through the processes that evaluate companion diagnostics. This mini-review provides an overview of these processes and their role in pharmaceutical development and clinical use. Impact statement This work summarizes very recent developments in the US FDA's biomarker qualification program. Furthermore, it contrasts biomarker qualification with companion diagnostic evaluation. As such, it will be highly informative for researches considering taking a biomarker discovery farther along the road to validation.

A Multiplatform Approach for the Discovery of Novel Drug-Induced Kidney Injury Biomarkers

Drug-induced kidney injury (DIKI) is a common toxicity observed in pharmaceutical development. We demonstrated the use of label-free liquid chromatography-mass spectrometry (LC-MS) and multiplex liquid chromatography-single reaction monitoring (LC-SRM) as practical extensions of standard immunoassay based safety biomarker assessments for identification of new toxicity marker candidates and for improved mechanistic understanding. Two different anticancer drugs, doxorubicin (DOX) and cisplatin (cis-diamminedichloridoplatinum, CDDP), were chosen as the toxicants due to their different modes of nephrotoxicity. Analyses of urine samples from toxicant treated and untreated rats were compared to identify biochemical analytes that changed in response to toxicant exposure. A discovery (label-free LC-MS) and targeted proteomics (multiplex LC-SRM) approach was used in combination with well established immunoassay experiments for the identification of a panel of urinary protein markers related to drug induced nephrotoxicity in rats. The initial generation of an expanded set of markers was accomplished using the label-free LC-MS discovery screen and ELISA based analysis of six nephrotoxicity biomarker proteins. Diagnostic performance of the expanded analyte set was statistically compared to conventional nephrotoxicity biomarkers. False discovery rate (FDR) analysis revealed 18 and 28 proteins from the CDDP and DOX groups, respectively, exhibiting significant differences between the vehicle and treated groups. Multiplex SRM assays were constructed to more precisely quantify candidate markers selected from the discovery screen and immunoassay experiments. To evaluate the sensitivity and specificity for each of the candidate biomarkers, histopathology severity scores were used as a benchmark for renal injury followed by receiver-operating characteristic (ROC) curve analysis on selected biomarkers. Further examination of the best performing analytes revealed relevant biological significance after consideration of anatomical localization and functional roles. In summary, the inclusion of mass spectrometry together with conventional ELISA based assays resulted in the identification of an expanded set of biomarkers with a realistic potential for providing additional beneficial information in mechanistic investigations of drug induced kidney injury and with similar responsiveness to conventionally applied indicators of renal injury.

Salt Selection Matters: Differential Renal Toxicity With MDV1634.Maleate Versus MDV1634.2HCl

Salt forms of pharmaceutical compounds can have unique pharmacokinetic and toxicity properties. MDV1634 was evaluated for neurology indication and also demonstrated blood pressure (BP)-lowering effects in nonclinical studies. During the chemistry manufacturing campaign, 2 salt forms, dihydrochloride (2HCl) and maleate (MAL), which improved chemical stability and water solubility of the free base were identified. MDV1634.MAL showed better chemical attributes and was evaluated in toxicology studies for further development. A 28-day oral toxicity study in dogs with MDV1634.MAL demonstrated partially reversible renal toxicity. Although MAL salt is generally regarded as safe, renal toxicity is sometimes observed in rats and dogs. To evaluate contribution of each salt form to renal toxicity and BP lowering, an additional 28-day study was conducted with MDV1634.2HCL and MDV1634.MAL, which included toxicokinetics, continuous BP measurement in a subset of dogs, and sensitive urinary biomarker evaluation for temporal monitorability and reversibility of potential renal findings. In the repeat study, both salt forms showed similar exposures during the dosing period, but renal tubular toxicity was observed only with MDV1634.MAL and not with MDV1634.2HCl. The renal findings with MDV1634.MAL included early urinary biomarker changes (increase in albumin, clusterin, β2 microglobulin, and neutrophil gelatinase-associated lipocalin); elevations in serum blood urea nitrogen and creatinine; and microscopic findings of partially reversible tubular basophilia, single cell necrosis, pigmentation, and mineralization. The renal findings in contrast to the BP findings were MAL-specific and considered not related to MDV1634, thereby under scoring the importance of salt forms in pharmaceutical development.

Promoting Adoption of the 3Rs through Regulatory Qualification

One mechanism to advance the application of novel safety assessment methodologies in drug development, including in silico or in vitro approaches that reduce the use of animals in toxicology studies, is regulatory qualification. Regulatory qualification, a formal process defined at the the U. S. Food and Drug Administration and the European Medicines Agency, hinges on a central concept of stating an appropriate "context of use" for a novel drug development tool (DDT) that precisely defines how that DDT can be used to support decision making in a regulated drug development setting. When accumulating the data to support a particular "context-of-use," the concept of "fit-for-purpose" often guides assay validation, as well as the type and amount of data or evidence required to evaluate the tool. This paper will review pathways for regulatory acceptance of novel DDTs and discuss examples of safety projects considered for regulatory qualification. Key concepts to be considered when defining the evidence required to formally adopt and potentially replace animal-intensive traditional safety assessment methods using qualified DDTs are proposed. Presently, the use of qualified translational kidney safety biomarkers can refine and reduce the total numbers of animals used in drug development. We propose that the same conceptual regulatory framework will be appropriate to assess readiness of new technologies that may eventually replace whole animal models.

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.

Biomarkers in Pharmaceutical Research

BACKGROUND

Biomarkers are important tools in drug development and are used throughout pharmaceutical research.

CONTENT

This review focuses on molecular biomarkers in drug development. It contains sections on how biomarkers are used to assess target engagement, pharmacodynamics, safety, and proof-of-concept. It also covers the use of biomarkers as surrogate end points and patient selection/companion diagnostics and provides insights into clinical biomarker discovery and biomarker development/validation with regulatory implications. To survey biomarkers used in drug development--acknowledging that many pharmaceutical development biomarkers are not published--we performed a focused PubMed search employing "biomarker" and the names of the largest pharmaceutical companies as keywords and filtering on clinical trials and publications in the last 10 years. This yielded almost 500 entries, the majority of which included disease-related (approximately 60%) or prognostic/predictive (approximately 20%) biomarkers. A notable portion (approximately 8%) included HER2 (human epidermal growth factor receptor 2) testing, highlighting the utility of biomarkers for patient selection. The remaining publications included target engagement, safety, and drug metabolism biomarkers. Oncology, cardiovascular disease, and osteoporosis were the areas with the most citations, followed by diabetes and Alzheimer disease.

SUMMARY

Judicious biomarker use can improve pharmaceutical development efficiency by helping to select patients most appropriate for treatment using a given mechanism, optimize dose selection, and provide earlier confidence in accelerating or discontinuing compounds in clinical development. Optimal application of biomarker technology requires understanding of candidate drug pharmacology, detailed modeling of biomarker readouts relative to pharmacokinetics, rigorous validation and qualification of biomarker assays, and creative application of these elements to drug development problems.

Evaluation of biomarkers for in vitro prediction of drug-induced nephrotoxicity: comparison of HK-2, immortalized human proximal tubule epithelial, and primary cultures of human proximal tubular cells

There has been intensive effort to identify in vivo biomarkers that can be used to monitor drug-induced kidney damage and identify injury before significant impairment occurs. Kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and human macrophage colony stimulating factor (M-CSF) have been validated as urinary and plasma clinical biomarkers predictive of acute and chronic kidney injury and disease. Similar validation of a high throughput in vitro assay predictive of nephrotoxicity could potentially be implemented early in drug discovery lead optimization to reduce attrition at later stages of drug development. To assess these known in vivo biomarkers for their potential for in vitro screening of drug-induced nephrotoxicity, we selected a panel of nephrotoxic agents and examined their effects on the overexpression of nephrotoxicity biomarkers in immortalized (HK-2) and primary (commercially available and freshly in-house produced) human renal proximal tubule epithelial cells. Traditional cytotoxicity was contrasted with expression levels of KIM-1, NGAL, and M-CSF assessed using ELISA and real-time quantitative reverse transcription PCR. Traditional cytotoxicity assays and biomarker assays using HK-2 cells were both unsuitable for prediction of nephrotoxicity. However, increases in protein levels of KIM-1 and NGAL in primary cells were well correlated with dose levels of known nephrotoxic compounds, with limited correlation seen in M-CSF protein and mRNA levels. These results suggest that profiling compounds against primary cells with monitoring of biomarker protein levels may have potential as in vitro predictive assays of drug-induced nephrotoxicity.

Recent Successes in the Identification, Development, and Qualification of Translational Biomarkers

The development of novel safety or efficacy biomarkers has increasingly been used to improve safety monitoring and minimize attrition during drug development; however, for new biomarkers, the failure rate can equal or exceed that of new chemical entities. Drug-induced kidney injury is recognized to occur throughout the drug development process, with histopathology considered to be the gold standard for preclinical toxicologic screening. Renal biomarkers used clinically are primarily biomarkers of renal function and are considered insensitive for the detection of drug-induced kidney injury during first-in-man studies, particularly for compounds known to induce renal injury in preclinical species. Recent efforts by public–private partnerships have led to unprecedented success in the identification, development, and qualification of several new translatable biomarkers of kidney injury in the rat. To optimize the chance of success in current and future biomarker efforts in preclinical species and man, selection and development of biomarkers should emphasize biological considerations including marker variability and biology in both health and disease. The research to support the qualification of novel renal safety markers for routine use in the clinical setting is currently underway, and results from this work are greatly anticipated.

Biomarkers of tobacco smoke exposure

Diseases and death caused by exposure to tobacco smoke have become the single most serious preventable public health concern. Thus, biomarkers that can monitor tobacco exposure and health effects can play a critical role in tobacco product regulation and public health policy. Biomarkers of exposure to tobacco toxicants are well established and have been used in population studies to establish public policy regarding exposure to second-hand smoke, an example being the nicotine metabolite cotinine, which can be measured in urine. Biomarkers of biological response to tobacco smoking range from those indicative of inflammation to mRNA and microRNA patterns related to tobacco use and/or disease state. Biomarkers identifying individuals with an increased risk for a pathological response to tobacco have also been described. The challenge for any novel technology or biomarker is its translation to clinical and/or regulatory application, a process that requires first technical validation of the assay and then careful consideration of the context the biomarker assay may be used in the regulatory setting. Nonetheless, the current efforts to investigate new biomarker of tobacco smoke exposure promise to offer powerful new tools in addressing the health hazards of tobacco product use. This review will examine such biomarkers, albeit with a focus on those related to cigarette smoking.

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.

Comparison between male and female Sprague-Dawley rats in the response of urinary biomarkers to injury induced by gentamicin

Differences were examined between male and female Sprague-Dawley rats in the response of 16 urinary biomarkers (measured using several assay platforms) to renal injury produced by gentamicin administered subcutaneously for 10 days at a dosage of 75 mg/kg. Urinary biomarkers expressed as fold difference from contemporaneous controls and renal histopathology were assessed after 3 and 10 doses. On day 4, minimal proximal tubular changes were observed microscopically in all males but no females; on day 11, more extensive and more severe injury was observed to a similar extent in all animals of both sexes. Modest increases (maximum 5-fold) in all urinary biomarkers (except epidermal growth factor [EGF], which was decreased) on day 4 and marked elevations (maximum 271-fold) on day 11 were seen consistently in both sexes. However, the magnitude of the increases differed between the sexes. On day 4, despite the lack of tubular injury, many biomarkers were more elevated in females than males but this rarely led to statistically significant sex differences; only 2 biomarkers (β2-microglobulin and total protein) showed a greater increase in males than females in line with the histopathology. On day 11, there were many more biomarkers that showed a statistically significant difference between the sexes in fold change with treatment; in line with the results on day 4, the majority of biomarkers were more increased in females than males. It remains unresolved if sex differences in the magnitude of biomarker response at injury threshold would lead to any difference in diagnostic interpretation between the sexes. These data highlight the need for publication of more studies using animals of both sexes to fully explore the influence of sex on the diagnostic performance of the novel biomarkers.

Assessment Standards

Histopathology generally represents the reference standard for performance evaluation of nonclinical biomarkers used to inform regulatory decision making. This study uses drug-induced nephrotoxicity in rats to evaluate histopathology methods utilized in biomarker performance assessments. Male Sprague-Dawley rats received a single dose of cisplatin (0.5–5.0 mg/kg, intraperitoneally) to produce mild renal injury. Animals were euthanized 72 hr postdose and perfusion fixed. Kidneys were processed for histology and stereology procedures. Kidney injury molecule-1 (Kim-1) was measured in urine and in kidney tissue. Digital slide images were generated and analyzed by pathologists after collaborating on a training set of glass slides and digital images. Image analysis identified immunohistochemistry (IHC)-defined tubular injury. Stereology methods yielded estimations of proximal tubular cell number and volume. Statistical relationships among data sets were determined using correlation coefficients. Receiver operator characteristic (ROC) analyses determined the effect of method on biomarker assessment. Urinary Kim-1 was strongly correlated with digital image analysis and secondarily to histopathology evaluations. Stereology demonstrated weak or no correlation to pathology and urinary Kim-1. In ROC analyses, semiquantitative evaluations determined higher values for urinary Kim-1 performance than did IHC-based qualitative digital analyses. Semiquantitative evaluation as used in this study was most predictive of urinary Kim-1 values.

The current status of biomarkers for predicting toxicity

INTRODUCTION

There are significant rates of attrition in drug development. A number of compounds fail to progress past preclinical development due to limited tools that accurately monitor toxicity in preclinical studies and in the clinic. Research has focused on improving tools for the detection of organ-specific toxicity through the identification and characterization of biomarkers of toxicity.

AREAS COVERED

This article reviews what we know about emerging biomarkers in toxicology, with a focus on the 2012 Northeast Society of Toxicology meeting titled 'Translational Biomarkers in Toxicology.' The areas covered in this meeting are summarized and include biomarkers of testicular injury and dysfunction, emerging biomarkers of kidney injury and translation of emerging biomarkers from preclinical species to human populations. The authors also provide a discussion about the biomarker qualification process and possible improvements to this process.

EXPERT OPINION

There is currently a gap between the scientific work in the development and qualification of novel biomarkers for nonclinical drug safety assessment and how these biomarkers are actually used in drug safety assessment. A clear and efficient path to regulatory acceptance is needed so that breakthroughs in the biomarker toolkit for nonclinical drug safety assessment can be utilized to aid in the drug development process.