Oncogenicity studies of taltirelin tetrahydrate (TA-0910) by oral (GAVAGE) administration in CD-1 mice and CD rats

Oncogenicity studies of taltirelin tetrahydrate (TA-0910), a new thyrotropin-releasing hormone (TRH) analogue, were carried out on CD-1 mice and CD rats. Groups of 60 male and 60 female CD-1 mice received TA-0910, by oral gavage, at dosages of 5, 15 or 50 mg/kg/day. Treatment continued for a minimum period of 104 weeks. Groups of 55 male and 55 female CD rats received TA-0910, by oral gavage, at dosages of 20, 60 or 200 mg/kg/day. Treatment continued for a minimum period of 90 or 94 weeks for males and females, respectively. Of the treatment-related behavioral changes noted, the majority were considered to be directly related to the known pharmacological activity of the test substance and, as such, to be of questionable direct toxicological significance. In mice, there was no evidence of a treatment-related effect on the incidence of neoplasms. In rats, slightly higher incidences of pituitary adenoma, in males given 60 or 200 mg/kg/day, and thyroid follicular adenoma, in females given 200 mg/kg/day, were noted. However, in neither case was statistical significance attained in pair-wise comparisons, and the incidences were within expectation from background data. There was no evidence of any oncogenic potential of TA-0910 in these studies.