Objectives: The aim of this study was to demonstrate the effect of a synthetically derived inhibitor from the thieno[2,3-b]pyridine group on cell apoptosis of SK-OV-3 and OVCAR-3 cell lines of human ovarian cancer. It is hypothesized that after the treatment of tumor cell lines with an inhibitor, the percentage of cells in early, late, and early and late apoptosis together will increase. Materials and methods: Using MTT method, optimal concentration of inhibitor was determined with whom ovarian cancer cells of SK-OV-3 and OVCAR-3 cell lines were treated for 48 h. After adding annexin V and propidium iodide, the cells were analyzed by flow cytometer to obtain the percentage of cells in early, late and early and late apoptosis in total in treated and untreated cancer cells, and a graphical representation of the cells is also obtained. Results: They are represented as the percentage of early and late apoptosis and surviving cells. The effect of inhibitor resulted in a statistically significant increase in apoptotic cells of the SK-OV-3 cell line in early, late and early and late apoptosis in total compared to untreated cells. Similar results were recorded for the OVCAR-3 cell line, where a statistically significant increase in apoptotic cells was also recorded compared to untreated cells. Conclusions: The treatment of ovarian cancer cells with newly synthesized thieno[2,3-b]pyridine led to a statistically significant increase in the percentage of cells in early, late and early and late apoptosis in total compared to untreated cells. These results are not negligible, and the compound is potentially important for the further investigation in the cancer therapy field.