<p>Pharmacological studies were conducted to evaluate the specific </p><p>activity of new cytostatics obtained from local plant-based raw materials </p><p>of Madagascar periwinkle within the framework of the applied project FZ-</p><p>202007215 entitled “Development of an Industrial Technology for Antitumor </p><p>Drugs Based on Catharanthus roseus Raw Materials”. The cytotoxic activity of </p><p>the substance “Katarkans” and the individually isolated compound ajmalicine </p><p>against various tumor cell lines was experimentally assessed using specific </p><p>methods. Ehrlich ascites carcinoma (EAC), an animal model of breast cancer, was </p><p>used as an experimental tumor model. It is a rapidly growing, undifferentiated </p><p>malignant neoplasm with highly aggressive behavior and is widely used in </p><p>cancer research. A high cytostatic index was observed for both samples: 75% for </p><p>“Katarkans” and 70% for ajmalicine. An increase in the activity of ajmalicine </p><p>when used in combination as part of concomitant therapy was also observed. </p><p>The evaluation of the tested agents led to the conclusion that the proposed </p><p>cytostatics – “Katarkans”, ajmalicine, and their combinations – require further </p><p>investigation as potential pharmaceutical agents for the prevention and </p><p>treatment of oncological diseases.</p>