The incidence of multidrug resistance (MDR) during cancer chemotherapy is a major challenge for treatment. With the aim of identifying drugs that are capable of targeting treatment‑resistant cancer cells, the present study evaluated the efficacy of GMZ‑1 in cancer chemotherapy using K562/A02, an MDR leukemia cell line. Cell viability and apoptosis were measured by MTT assay and flow cytometry/Giemsa staining, respectively. The expression levels of the MDR protein 1 (MDR1) gene transcript and protein in K562/A02 cells were determined by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. GMZ‑1 suppressed the viability of various human cancer cell lines and induced apoptosis in the K562/A02 cell line in a time‑ and concentration‑dependent manner. GMZ‑1 toxicity may be associated with a decrease in MDR gene expression. These findings demonstrated that GMZ‑1 may have efficacy as a potential antitumor drug to overcome leukemia cell resistance to apoptosis induced by chemotherapy.