Toxicological studies on bestatin. III. Chronic toxicity test and recovery study in beagle dogs.

Chronic toxicity and its recovery of bestatin (NK421) was studied in both sexes of 28 Beagle dogs. At dose levels of 96, 38.4 and 15.4 mg/kg, NK421 was administered orally to dogs for 540 successive days. Control dogs were treated orally with 2 g/dog of corn starch. Each group consisted of 3 males and 3 females, and 2 males and 2 females were added to the 38.4 mg/kg group for a recovery test of 35 days. As general signs, anorexia, abnormal feces (loose stool, diarrhea, mucous stool), loss of activity, loss of lustre in fur, decoloration of the visible mucosa and emaciation were transiently observed in a early stage in 1 male and 1 female of the 96 mg/kg group. In correlation with these signs, slight anemia appeared hematologically, and the increased alkaline phosphatase activity and the decreased albumin ratio in serum protein fractions were observed biochemically. Except for the slight abnormal findings observed in the liver of the above 2 dogs, no significant changes were histopathologically noticed in any organ of all the dogs examined. The maximum non-toxic dose of NK421 in this study is estimated to be 38.4 mg/kg in dogs.