In the target animal safety study presented below, PALLADIA was demonstrated to have a narrow margin of safety; dogs being treated with PALLADIA should be monitored for adverse reactions which may indicate a dose adjustment is required. Two dogs in the 6 mg/kg group were euthanized for clinical toxicities on Days 23 and 27 of the study, respectively.
Toceranib was administered orally to 20 male and 20 female adult Beagle dogs (approximately 2 years of age) at doses of 0 mg/kg (placebo, 12 dogs), 2 mg/kg (0.5×, 8 dogs), 4 mg/kg (1×, 12 dogs), or 6 mg/kg (1.5×, 8 dogs) once every other day for 13 consecutive weeks without dose interruption. Toceranib caused weight loss, decreased feed consumption, pancreatic, gonadal, adrenal, muscle, and hematopoietic changes.
Feed consumption was decreased in the 6 mg/kg group compared to placebo, with the largest difference in means occurring at Day 35. Decrease in body weights in the 4 mg/kg group were seen at Day 31 and in the 6 mg/kg group at Day 15 compared with placebo and continued through the study. Dose related lameness, observed almost exclusively in the hind limbs, and limb pain was greater in all treatment groups as compared to placebo, with the 6 mg/kg group demonstrating the highest incidence. Stiffness and weakness were noted to occur almost exclusively in the 6 mg/kg group. Redness of oral mucosa was observed in all treatment groups. One dog in the 4 mg/kg group had oral ulcerations and one dog in the 6 mg/kg group had skin ulcerations, both with bacterial infections present. Diarrhea or soft stool were seen in all four groups.
Hematology analyses showed decreases in hematocrit, hemoglobin, and erythrocyte count and a decrease in reticulocyte count in the 4 and 6 mg/kg groups that tended to recover sufficiently to limit further erythrocyte count decreases. White blood cell counts were significantly lower across the study in all treated groups compared to placebo, primarily due to a decrease in neutrophils. Lymphocytes decreased to a lesser degree, especially at the low dose. Eosinophils and basophils showed marked, persistent decreases. Monocytes were not affected.
Platelet counts increased slightly in 4 and 6 mg/kg groups. Increases were observed in fibrinogen in the 4 and 6 mg/kg group.
Increases were observed in aspartate aminotransferase, creatine kinase, and serum phosphorus concentrations in the 4 and 6 mg/kg groups. Increases in alkaline phosphatase were seen in the 6 mg/kg group. An increase in amylase was seen in one dog in each of the treatment groups. An increase in serum potassium was seen in one dog in the 6 mg/kg group. Increases in lactate dehydrogenase and globulins were observed in the 6 mg/kg group.
Treatment-related microscopic changes included slight to marked reduction in cellularity of sternal and femoral bone marrow. There was a corresponding mild extramedullary hematopoiesis, mainly erythropoiesis, in the spleen. In the pancreas, dose-related slight to moderate acinar degranulation, characterized by diffuse loss of zymogen granules, occurred. In the adrenal glands, minimal cortical congestion/hemorrhage occurred at all doses, with suggestive dose-relationship. Adrenal cortical vacuolation was noted with low frequency in all groups. Dose related changes were noted in reproductive organs of both sexes. Males showed a dose-related germ cell depletion, tubular vacuolation, and reductions in numbers of mature spermatozoa. In females, ovaries showed a reduced incidence of mature/regressing corpora lutea and an increased incidence of small follicles.
Two dogs (one male, one female) in the 6 mg/kg group were euthanized for treatment-related clinical toxicities on Days 23 and 27 of the study, respectively. Onset of the terminal syndrome was seen as markedly reduced feed intake and melena. Over the following 9 days, the decreased feed intake progressed to near-complete anorexia and hematochezia appeared. Weight loss, lethargy, hindlimb lameness and weakness were observed. The following clinical pathology results are consistent with changes seen in the other dogs in the 6 mg/kg group as well as changes due to the dogs' debilitated conditions just prior to euthanasia. Both dogs had increases in total protein, globulins, phosphorus, cholesterol, triglycerides and fibrinogen. One dog had pancytopenia, decreased hematocrit, hemoglobin, reticulocytes, albumin, and PT and increased bands. Hematuria was also present. The other dog also had decreased lymphocytes, eosinophils, chloride, and sodium and increases in RBC, hematocrit, hemoglobin, platelets, ALP, amylase, creatinine, BUN, magnesium, potassium, and total bilirubin. Clotting profile showed a decreased PT and increased in PTT in both dogs. These dogs showed lymphoid depletion in lymph nodes, thymus, and gut-associated lymphatic tissues and mild to marked gastrointestinal lesions in addition to the microscopic findings described in animals surviving to the end of the study. These two dogs also had lesions in the gastrointestinal tract, kidneys, pancreas, pituitary gland and adrenal glands.