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Integrating nonclinical in vitro, in silico, and in vivo datasets holistically can improve hazard characterization and risk assessment. In pharmaceutical development, cardiovascular liabilities are a leading cause of compound attrition. Prior to clinical studies, functional cardiovascular data are generated in single-dose safety pharmacology telemetry studies, with structural pathology data obtained from repeat-dose toxicology studies with limited concurrent functional endpoints, eg, electrocardiogram via jacketed telemetry. Relationships between datasets remain largely undetermined. To address this gap, a cross-pharma collaboration collated functional and structural data from 135 compounds. Retrospective functional data were collected from good laboratory practice conscious dog safety pharmacology studies: effects defined as hemodynamic blood pressure or heart rate changes. Morphologic pathology findings (mainly degeneration, vacuolation, inflammation) from related toxicology studies in the dog (3-91 days repeat-dosing) were reviewed, harmonized, and location categorized: cardiac muscle (myocardium, epicardium, endocardium, unspecified), atrioventricular/aortic valves, blood vessels. The prevalence of cardiovascular histopathology changes was 11.1% of compounds, with 53% recording a functional blood pressure or heart rate change. Correlations were assessed using the Mantel-Haenszel Chi-square trend test, identifying statistically significant associations between cardiac muscle pathology and (1) decreased blood pressure, (2) increased heart rate, and between cardiovascular vessel pathology and increased heart rate. Negative predictive values were high, suggesting few compounds cause repeat-dose cardiovascular structural change in the absence of functional effects in single-dose safety pharmacology studies. Therefore, observed functional changes could prompt moving (sub)chronic toxicology studies forward, to identify cardiovascular liabilities earlier in development, and reduce late-stage attrition., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Purpose: The oral prodrug of gemcitabine LY2334737 is cleaved systemically to gemcitabine; the mechanism responsible for hydrolysis is unknown. LY2334737 cytotoxicity was tested in the NCI-60 panel; mining of microarray expression data identified carboxylesterase (CES) as a top hydrolase candidate. Studies examined whether CES is responsible for hydrolysis and whether cellular CES expression confers prodrug sensitivity., Experimental Design: Human recombinant CES isozymes were assayed for LY2334737 hydrolysis. Stable CES-overexpressing HCT-116 transfectants and a SK-OV-3 knockdown were prepared. Cell lines were tested for drug sensitivity and CES expression by quantitative real time-PCR (qRT-PCR), Western blotting, and immunohistochemical staining. Bystander cytotoxicity studies were conducted with GFP-tagged PC-3 cells as the reporter cell line. Therapeutic response of the HCT-116 transfectants was evaluated in xenografts., Results: Of 3 human CES isozymes tested, only CES2 hydrolyzed LY2334737. Five cell lines that express CES2 responded to LY2334737 treatment. LY2334737 was less cytotoxic to a SK-OV-3 CES2 knockdown than parental cells. The drug response of CES2-transfected HCT-116 cells correlated with CES2 expression level. Bystander studies showed statistically greater PC-3-GFP growth inhibition by LY2334737 when cells were cocultured with CES2 and not mock transfectants. Oral treatment of xenograft models with 3.2 mg/kg LY2334737 once a day for 21 days showed greater tumor growth inhibition of CES2 transfectant than the mock transfectant (P ≤ 0.001)., Conclusions: CES2 is responsible for the slow hydrolysis of LY2334737. Because intact prodrug circulates at high plasma levels after oral LY2334737 administration, improved response rates may be observed by tailoring LY2334737 treatment to patients with CES2 tumor expression., (©2012 AACR.)