title: Safety assessment of 4'-thio-beta-D-arabinofuranosylcytosine in the beagle dog suggests a drug-induced centrally mediated effect on the hypothalamic-pituitary-adrenal axis.
abstract: 4'-Thio-beta-D-arabinofuranosylcytosine (OSI-7836) is a nucleoside analogue with structural similarity to gemcitabine and cytarabine (ara-C). Myelosuppression, reversible transaminase elevations, and flu-like symptoms are common side effects associated with human use of gemcitabine and ara-C. Fatigue is also associated with the use of gemcitabine and OSI-7836 in humans. To better understand the toxicity of OSI-7836, subchronic studies were conducted in dogs. OSI-7836 was administered on days 1 and 8 or on days 1, 2, and 3 of a 21-day dose regimen. These schedules attempted to match clinical trial dosing regimens. Routine toxicity study end points demonstrated that OSI-7836 was primarily cytotoxic to the gastrointestinal tract, bone marrow, and testes; the myelotoxicity was mild and reversible. Plasma pharmacokinetics were dose-linear with an elimination half-life of 2.2 h. Follow-up single dose experiments in dogs assessed drug effects on lymphocyte subpopulations and on adrenal and thyroid function. Populations of T and B cells were equally reduced following OSI-7836 administration. There were no adverse effects on thyroid function, but there were marked reductions in circulating cortisol and adrenocorticotropic hormone concentrations suggesting a centrally mediated impairment of the hypothalamic-pituitary-adrenal axis. These findings show a toxicological profile with OSI-7836 similar to other nucleoside analogues and suggest that the beagle is a model for studying one possible cause of OSI-7836-related fatigue, impaired function of the hypothalamic-pituitary-adrenal axis.
authors.affiliation: OSI Pharmaceuticals, Inc., Boulder, Colorado 80301, USA.
authors.forename: Dorothy B
authors.initials: DB
authors.lastname: Colagiovanni
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Drolet
authors.forename: Larry
authors.initials: L
authors.lastname: Dihel
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Meyer
authors.forename: Karen
authors.initials: K
authors.lastname: Hart
authors.forename: Julie
authors.initials: J
authors.lastname: Wolf
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000633:toxicity*; D001087:Arabinonucleosides / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000633:toxicity*; D001772:Blood Cell Count; D004285:Dogs; D004353:Drug Evaluation, Preclinical; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010913:Pituitary-Adrenal System / Q000187:drug effects* / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000473:pathology; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism; D013974:Thyroxine / Q000097:blood
chemical_list: D000970:Antineoplastic Agents; D001087:Arabinonucleosides; D000324:Adrenocorticotropic Hormone; D013974:Thyroxine; D006854:Hydrocortisone; C411255:4'-thio-arabinofuranosylcytosine