Objective: Earlier works have reported on the effectiveness of the compounds of the group of substituted 5R1, 6R2, 3,4-thiadiasine-2-amines for treating experimental myocardial infarction, conditioned by the immune-modifying action of the compound. The purpose of this study was to evaluate the action of the L17 compound of the group of substituted 5R1, 6R2, 3,4-thiadiasine-2-amines on the extent of injury and the possible recurrence of experimental myocardial infarction by the dynamic assessment of transaminase activity in blood and myocardial homogenate (tissue). Methods: Modelling of myocardial infarction in rats was performed in accordance with the author's modification of the standard ligation model. Tissue enzyme activity of LDH and CK-MB was evaluated at days 1, 7, and 14. Results: According to the results, the decrease in LDH 1-2 activity in tissue (after experimental myocardial infarction) corresponded to the increase in enzyme activity in blood on the first day of the experiment...