The cellular effects of aurumacryl (a drug based on gold polyacrylate, which previously showed significant antitumor activity in vivo against solid tumors in mice) were studied in the model of the MCF7 stable cell line of human breast carcinoma. It was found that aurumacryl possesses cytotoxic and cytostatic effects on tumor cells. The dose-dependent cytotoxic effect of aurumacryl is expressed as the death of 60% of tumor cells after incubation with aurumacryl at a dose of 1 mg/mL for 24 h. The proliferation kinetics of the surviving fraction of tumor cells also undergoes significant changes, which is expressed in the predominant accumulation of the cells (93%) in the G0 phase of proliferative rest and in a significant decrease in the number of proliferating cells to 7%. These data could be interpreted as evidence of the loss of the reproductive ability of the surviving cells after treatment with aurumacryl.