Evaluation of Therapeutics for Advanced-Stage Heart Failure and Other Severely-Debilitating or Life-Threatening Diseases.

Severely-debilitating or life-threatening (SDLT) diseases include conditions in which life expectancy is short or quality of life is greatly diminished despite available therapies. As such, the medical context for SDLT diseases is comparable to advanced cancer and the benefit vs. risk assessment and development of SDLT disease therapeutics should be similar to that of advanced cancer therapeutics. A streamlined development approach would allow patients with SDLT conditions earlier access to therapeutics and increase the speed of progression through development. In addition, this will likely increase the SDLT disease therapeutic pipeline, directly benefiting patients and reducing the economic and societal burden of SDLT conditions. Using advanced-stage heart failure (HF) as an example that illustrates the concepts applicable to other SDLT indications, this article proposes a streamlined development paradigm for SDLT disease therapeutics and recommends development of aligned global regulatory guidance.

Toxicokinetics and toxicity of atorvastatin in dogs.

HMG-CoA reductase inhibitors (e.g., statins) are an important clinical option to lower cholesterol and treat co-morbidities. Atorvastatin is the most prescribed statin and has obtained generic status. We recently had a clinical development program evaluating a combination of atorvastatin with a GPR119 agonist as a treatment for dyslipidemia, where toxicological evaluations in dogs were completed. There were several challenges related to selecting doses for atorvastatin, including understanding the dose-exposure relationship from different drug forms used by the innovator in their general toxicology studies, bioanalytical assays that did not separate and quantify parent from metabolites, and high variability in the systemic exposures following oral dosing. The studies in this report characterized the toxicokinetics and toxicity of atorvastatin in the dog for up to 13-weeks. Overall, there were no notable differences in the toxicokinetics of atorvastatin or the two active hydroxylated metabolites between the sexes at Week 13. However, systemic exposures were markedly lower at Week 13 compared to that observed at Week 4, suggesting induction of metabolism or reduced absorption from the gastrointestinal tract following oral dosing. Changes in laboratory chemistries included increased liver enzyme levels and lower cholesterol levels. Histopathologic evaluation revealed multifocal minimal to slight hemorrhages in the submucosa of the gallbladder; all findings were reversible. The information from these studies along with the existing clinical experience with atorvastatin can be used to design robust toxicology studies in dogs and reduce animal use.

alpha 2u-Globulin nephropathy, renal cell proliferation, and dosimetry of inhaled tert-butyl alcohol in male and female F-344 rats.

tert-Butyl alcohol (TBA) has been shown to cause kidney tumors in male rats following chronic administration in drinking water. The objective of the present study was to determine whether TBA induces alpha 2u-globulin (alpha 2u) nephropathy (alpha 2u-N) and enhanced renal cell proliferation in male, but not female, F-344 rats, and whether the dosimetry of TBA to the kidney is gender specific. Male and female F-344 rats were exposed to 0, 250, 450, or 1750 ppm TBA vapors 6 h/day for 10 consecutive days to assess alpha 2u-nephropathy and renal cell proliferation and for 1 and 8 days to evaluate the dosimetry of TBA following a single and repeated exposure scenario. Protein droplet accumulation was observed in kidneys of male rats exposed to 1750 ppm TBA, with alpha 2u-globulin immunoreactivity present in these protein droplets. A statistically significant increase in alpha 2u concentration in the kidney, as measured by an enzyme-linked immunosorbent assay, was observed in male rats exposed to 1750 ppm TBA with a exposure-related increase in renal cell proliferation. Renal alpha 2u concentration was positively correlated with cell proliferation in male rat kidney. No histological lesions or increased renal cell proliferation was observed in female rats exposed to TBA compared to controls. The TBA kidney:blood ratio was higher at all concentrations and time points in male rats compared with female rats, which suggests that TBA is retained longer in male rat kidney compared with female rat kidney. Together these data suggest that TBA causes alpha 2u-N in male rats, which is responsible for the male rat-specific increase in renal cell proliferation.

Identification of the 1-cyano-3,4-epithiobutane-derived urinary mercapturic acid N-acetyl-S-(4-cyano-2-thio-1-butyl)-cysteine in male Fischer 344 rats.

1-Cyano-3,4-epithiobutane (CEB), a naturally occurring nitrile derived from cruciferous plants, causes nephrotoxicity in male Fischer 344 rats. Nephrotoxicity induced by CEB is dependent on glutathione (GSH) conjugation and bioactivation. Conjugation with GSH and subsequent metabolism leads to the formation of specific urinary metabolites. The objectives of the present study were to identify CEB-derived urinary metabolites and quantify urinary non-protein thiols and thioethers in male Fischer 344 rats. Animals received 125 mg kg(-1) of CEB alone or following pretreatment with one of three selective inhibitors of GSH metabolism: acivicin, probenecid or aminooxyacetic acid. Total non-protein urinary thiol and urinary thioether concentrations were elevated in all treated groups at 12 and 24 h; however, elevations in non-protein thiols were not significantly greater in rats administered CEB alone as compared to negative controls. A single predominant urinary metabolite was identified as the CEB-derived mercapturic acid N-acetyl-S-(4-cyano-thio-1-butyl)-cysteine. Evidence for other CEB-derived metabolites was also demonstrated. These findings represent the identification of a unique compound and provide further evidence for the importance of GSH conjugation as a significant pathway in CEB metabolism.

Protection from 1-cyano-3,4-epithiobutane nephrotoxicity by aminooxyacetic acid and effect on xenobiotic-metabolizing enzymes in male Fischer 344 rats.

1-Cyano-3,4-epithiobutane (CEB), a naturally occurring nitrile derived from cruciferous plants, causes nephrotoxicity and increased renal glutathione (GSH) concentration in male F-344 rats. This CEB-induced nephrotoxicity is dependent on GSH conjugation and bioactivation. The objectives of the present study were to investigate the effect of CEB on several xenobiotic-metabolizing enzymes and to evaluate the effect of modulators of GSH transport and metabolism on CEB-induced nephrotoxicity and GSH concentration. Animals received 125 mg kg-1 CEB alone or following pretreatment with one of three selective inhibitors of GSH metabolism: acivicin, probenecid or aminooxyacetic acid. There were no significant alterations in epoxide hydrolase (EH), P-450, ethoxyresorufin O-deethylase (EROD) or pentoxyresorufin O-depentylase (PROD) enzyme activity, but renal glutamyl cysteine synthetase (GCS) activity was decreased at 12 and 24 h, as was renal glutathione S-transferase 4 h after CEB administration. Renal ECOD activity was also diminished at 24 h and at 12 and 24 h in liver. Aminooxyacetic acid (AOAA) abrogated the nephrotoxicity, the renal GSH-enhancing effect, and decreased GCS of CEB alone. These findings provide further evidence for the importance of GSH conjugation as a significant pathway in CEB metabolism and the role of a reactive thiol in nephrotoxicity and altered renal GSH.