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Two young cynomolgus macaques (Macaca fascicularis) given a small molecule kinase inhibitor ((S)-4-((2-(5-chloro-2-fluorophenyl)-5-isopropylpyrimidin-4-yl)amino)-N-(2-hydroxypropyl)nicotinamide [SCIO-120]) via nasogastric intubation gavage, once-daily for 21 days at 400 mg/kg/day, developed an unusual epithelial proliferative process in the renal parenchyma. Morphological and immunohistochemical characterization of the lesions confirmed an invasive malignant epithelial neoplasm (carcinoma). A similar renal neoplasm was seen in a third macaque after a 14-day exposure to a second kinase inhibitor in the same chemical series ((S) 4-((2-(5-chloro-2-fluorophenyl)-5-methoxypyrimidin-4-yl)amino)-N-cyclopropylnicotinamide [SCIO-974]). Despite remarkably short latency periods, exposure to these kinase inhibitors was likely causally associated with the induction of the renal tumors, as renal carcinomas are exceedingly rare spontaneously in macaques. Both SCIO-120 and SCIO-974 were designed as potent TGFβR1 inhibitors (IC50s 37 and 39 nM, respectively). SCIO-120 and SCIO-974 inhibited additional kinases, most notably closely related ALK4 (IC50 = 34  and 20 nM, respectively), c-Jun n-Terminal kinase 3 (JNK3, IC50 = 10 and 20 nM, respectively), and Fms-related tyrosine kinase 1 (29  and 76 nM, respectively). TGFβR1 has been specifically implicated in epithelial proliferative disorders, including neoplasia. Neither SCIO-120 nor SCIO-974 was genotoxic based on bacterial reverse mutation and/or clastogenicity screening assays. The rapid appearance of renal carcinomas in primates following short-term treatment with nongenotoxic kinase inhibitors is remarkable and suggests that the compounds had noteworthy tumor-enhancing effects, hypothetically linked to their TGFβR1 inhibition activity. These observations have implications for mechanisms of carcinogenesis and TGFβR1 biology., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Immunohistochemical staining for the lysosome-associated membrane protein 2 (LAMP-2) has been proposed previously as an alternative to electron microscopy to identify hepatic phospholipidosis. This study used LAMP-2 immunohistochemistry (IHC) to diagnose phospholipidosis in rats exhibiting renal tubular injury. Rats were administered toreforant, a histamine H4 receptor antagonist by oral gavage at a dose of 3, 10, or 100 mg/kg/d for 6 months. Hematoxylin and eosin staining revealed renal tubular epithelial cell vacuolation, hypertrophy, degeneration, and luminal dilation in the 100 mg/kg/d group animals. Renal tubular injury was confirmed using kidney injury marker 1 (KIM-1) IHC. The involvement of phosopholipidosis in the renal injury was investigated by LAMP-2. Adipophilin IHC was included to differentiate phospholipidosis from lipidosis. Increased LAMP-2 staining was observed in the 100 mg/kg/d group animals when compared to vehicle group animals. Lysosome-associated membrane protein-2 staining was most prominent in the outer stripe of the outer medulla where KIM-1 staining was also most prominent. By contrast, adipophilin staining was not increased. Phospholipidosis was also confirmed by electron microscopy. These data support the use of LAMP-2 IHC as a diagnostic tool and suggest an association between phospholipidosis and the renal tubular injury caused by toreforant.

The discovery of the histamine H 4 receptor (H 4 R) provided a new avenue for the exploration of the physiological role of histamine, as well as providing a new drug target for the development of novel antihistamines. The first step in this process was the identification of selective antagonists to help unravel the pharmacology of the H 4 R relative to other histamine receptors. The discovery of the selective H 4 R antagonist JNJ 7777120 was vital for showing a role for the H 4 R in inflammation and pruritus. While this compound has been very successful as a tool for understanding the function of the receptor, it has drawbacks, including a short in vivo half-life and hypoadrenocorticism toxicity in rats and dogs, that prevented advancing it into clinical studies. Further research let to the discovery of JNJ 39758979, which, similar to JNJ 7777120, was a potent and selective H 4 R antagonist and showed anti-inflammatory and anti-pruritic activity preclinically. JNJ 39758979 advanced into human clinical studies and showed efficacy in reducing experimental pruritus and in patients with atopic dermatitis. However, development of this compound was terminated due to the occurrence of drug-induced agranulocytosis. This was overcome by developing another H 4 R antagonist with a different chemical structure, toreforant, that does not appear to have this side effect. Toreforant has been tested in clinical studies in patients with rheumatoid arthritis, asthma, or psoriasis. In conclusions there have been many H 4 R antagonists reported in the literature, but only a few have been studied in humans underscoring the difficulty in finding ligands with all of the properties necessary for testing in the clinic. Nevertheless, the clinical data to date suggests that H 4 R antagonists can be beneficial in treating atopic dermatitis and pruritus.

Canagliflozin is an SGLT2 inhibitor used for the treatment of type 2 diabetes mellitus. Studies were conducted to investigate the mechanism responsible for renal tubular tumors and pheochromocytomas observed at the high dose in a 2-year carcinogenicity study in rats. At the high dose (100mg/kg) in rats, canagliflozin caused carbohydrate malabsorption evidenced by inhibition of intestinal glucose uptake, decreased intestinal pH and increased urinary calcium excretion. In a 6-month mechanistic study utilization of a glucose-free diet prevented carbohydrate malabsorption and its sequelae, including increased calcium absorption and urinary calcium excretion, and hyperostosis. Cell proliferation in the kidney and adrenal medulla was increased in rats maintained on standard diet and administered canagliflozin (100mg/kg), and in addition an increase in the renal injury biomarker KIM-1 was observed. Increased cell proliferation is considered as a proximal event in carcinogenesis. Effects on cell proliferation, KIM-1 and calcium excretion were inhibited in rats maintained on the glucose-free diet, indicating they are secondary to carbohydrate malabsorption and are not direct effects of canagliflozin., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Cisplatin (CDDP) is known to produce renal proximal tubule injury. Various renal biomarkers have been related to CDDP nephrotoxicity in previous research, but the temporal and spatial relationship of these biomarkers to injury reversal has not been well defined. In this study, the progression and reversal of renal histopathology findings relative to serum and urinary biomarker changes were examined during a 4-week postdose period following single intraperitoneal administration of CDDP (1 mg/kg) or 0.9% saline. Degeneration, vacuolation, inflammation, and regeneration of the S3 segment of proximal tubules were evident 72 hours following CDDP administration. Tubular degeneration and regeneration were also observed at 1 and 1.5 weeks but at lower incidences and/or severity indicating partial reversal. Complete histologic reversal was observed by 2 weeks following CDDP administration. Urinary kidney injury molecule 1 (KIM-1), α-glutathione-S-transferase (α-GST), and albumin levels increased at 72 hours postdosing, concurrently with the earliest histologic evidence of tubule injury. Changes in urinary KIM-1 correlated with KIM-1 immunostaining in the proximal tubular epithelial cells. No significant changes in serum biomarkers occurred except for a minimal increase in urea nitrogen at 1.5 weeks postdosing. Of the novel renal biomarkers examined, urinary KIM-1, α-GST, and albumin showed excellent concordance with CDDP-induced renal injury progression and reversal; and these biomarkers were more sensitive than traditional serum biomarkers in detecting early, acute renal tubular damage confirmed by histopathology. Furthermore, urinary KIM-1, α-GST, and albumin outperformed other biomarkers in correlating with the time of maximum histologic injury.

A 28-day study was conducted to evaluate changes in urinary cytokine/chemokine expression levels in dogs with renal injury due to administration of cisplatin. Animals (n=17) were administered cisplatin at 0.75 mg/kg/day (i.v.) for five consecutive days. Urine/serum were collected at pre-dosing, 4h post-dosing and on days 2, 3, 4, 8, 10, 14, 16, 18, 21, 23, 25, 28 and unscheduled terminations. Animals were euthanized when serum creatinine (sCr) levels measured at ≥ 1.9 mg/dL, indicating significant loss of renal function (decreased glomerular filtration rate). Relevant clinical observations included lethargy and dehydration. Pre-study sCr levels ranged from 0.6 to 0.8 mg/dL; on days 1 through 4, sCr levels ranged from 0.5 and 1.1mg/dL; and terminal sCr levels ranged from 0.6 and 6.6 mg/dL. Histologically, cisplatin-related renal changes were characterized as proximal tubule dilatation, vacuolization, degeneration, regeneration, and interstitial inflammation. Increased interleukin (IL)-2, IL-8, monocyte chemoattractant protein-1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GMCSF) and keratinocyte-derived chemokine (KC) occurred on days 3 through 4. Increased IL-7 occurred on day 4. This study showed for the first time that inflammatory cytokines/chemokines in urine positively identified acute renal tubular injury in dogs at time points earlier than sCr, a traditional marker of nephrotoxicity., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The first formal qualification of safety biomarkers for regulatory decision making marks a milestone in the application of biomarkers to drug development. Following submission of drug toxicity studies and analyses of biomarker performance to the Food and Drug Administration (FDA) and European Medicines Agency (EMEA) by the Predictive Safety Testing Consortium's (PSTC) Nephrotoxicity Working Group, seven renal safety biomarkers have been qualified for limited use in nonclinical and clinical drug development to help guide safety assessments. This was a pilot process, and the experience gained will both facilitate better understanding of how the qualification process will probably evolve and clarify the minimal requirements necessary to evaluate the performance of biomarkers of organ injury within specific contexts.