Pilot study on the treatment with thioproline of 24 small animals with tumors

Thioproline (thiazolidine-4-carboxylic acid) was administered in a 16-week trial by either IM or subcutaneous routes to 23 dogs and 1 cat with solid tumors (12 animals) and incompletely excised malignant tumors (12 animals). Acute partial responses were observed in 3 of the 12 animals with solid tumors. In a mammary gland carcinoma and oral fibrosarcoma, there was tumor enlargement by the 4th day of drug therapy followed by partial regression. Drug activity appeared to be directed against tumor blood supply. Tumor progression occurred in 11 of the 12 other animals (incompletely excised tumors). Although 4 of 5 dogs with intranasal tumors were alive and relatively free of tumorous signs at 9 months or more after surgical operation was done, there was no microscopic evidence of reverse transformation or cytostatic activity in the 2 intranasal tumors that were reoperated upon. There was no hematologic or biochemical toxicosis noted. Apparent pain from injection and abscess formation were the most frequent complications from parenteral administration and would preclude using this method on a long-term basis.