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Screening a novel class of anticoagulants for multi‐organ toxicity using Fischer 344 rats: involvement of clinical and anatomic pathologists in the early drug development process
Author(s) -
Schultze A. Eric,
Sullivan John M.
Publication year - 2007
Publication title -
veterinary clinical pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.537
H-Index - 51
eISSN - 1939-165X
pISSN - 0275-6382
DOI - 10.1111/j.1939-165x.2007.tb00198.x
Subject(s) - toxicity , partial thromboplastin time , medicine , prothrombin time , phospholipidosis , pharmacology , drug , pathology , drug development , hematology , coagulation , chemistry , biochemistry , phospholipid , membrane
Background: Veterinary clinical and anatomic pathologists play a critical role in assessing the safety of new molecules. The process for evaluation of candidate molecules in drug discovery may vary markedly, depending on the unique characteristics of the compound class. Objectives: The goal of this report is to describe the evaluation process for assessing the potential toxicity of 2 anticoagulant compounds that were representative of molecules tested in early screening studies in Fisher rats, and to use these studies as an example of the strategic approach used by veterinary pathologists in pharmaceutical safety assessment. Methods: Groups of 3 rats were given vehicle alone or one of several doses of compound A or B by oral gavage daily for 4 consecutive days. Survival; clinical signs; body and organ weight measurements; hematologic, coagulation, and clinical biochemical testing; and gross and histologic findings at necropsy were assessed. Transmission electron microscopy was used to characterize unique findings in the liver of rats treated with compound B. Results: Both compounds caused dose‐dependent prolongation of the prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin clotting time (TCT). Hepatobiliary and intestinal toxicity were identified by alterations in serum chemistry data, and by histopathologic findings. Electron microscopy and tissue inorganic phosphorus analysis revealed phospholipidosis in rats treated with compound B. Conclusions: Pharmacologically mediated or “on target” effects for these molecules were characterized by dose‐progressive prolongation of the PT, APTT, and TCT. Nonpharmacologically mediated or “off‐target” toxicity consisted of hepatoxicity and enterotoxicity. These liabilities required that scientists alter the original molecular scaffold to reach the desired therapeutic target and minimize toxicity.