A big risk factor for sensitization and allergic diseases is susceptibility to animal allergens. The most significant animal allergens are derived from mammals, besides mites and cockroaches. The experiments on the allergenic properties of KUD975 were carried out on bisexual sexually mature albino guinea pigs weighing 300 ± 20 g. During the initial assessment of allergenic and mutagenic properties, the allergenic properties of KUD975 were studied by setting up an active skin anaphylaxis reaction. Mutagenicity in the test of induction of dominant lethal mutations was studied. For research, outbred male rats weighing 180-220 g KUD975 was administered intragastrically at a dose of 106 mg/kg, which corresponds to a 40-fold estimated therapeutic dose. Planting intact females at the rate of 3 heads for each male was performed weekly according to the stages of spermatogenesis. The study of the allergenic effect in the formulation of the reaction of active skin anaphylaxis in guinea pigs and mutagenicity in the test for the induction of dominant lethal mutations of the phenolic compound methyl ester (2 -((1hydroxy naphthalene-2-yl) thio) acetyl) -D-proline under the laboratory code KUD975 showed no signs of allergenicity and mutagenicity of compound KUD975. Given the results of this study, as well as the previously conducted study of toxicological safety, pharmacological activity, methyl ester (2 -((1hydroxy naphthalene-2-yl) thio) acetyl) -D-proline KUD-975 can be recommended for further study as a medicinal agent acting on arignase-2 for the treatment and prevention of a number of endothelium-associated diseases.