It has been reported that BIBR 1532 inhibited the reverse transcriptase of telomerase, hTERT, and shortened the length of the telomerase to suppress human cancer cell proliferation. In pre-B acute lymphoblastic leukemia cells, BIBR1532 suppressed c-Myc and hTERT expression in a concentration-dependent manner to inhibit telomerase activity, and high doses of BIBR1532 could induce apoptosis by elevating p73, Bax/Bcl-2 and caspase-3 activation. In NB4 leukemic cells, combined treatments with BIBR 1532 and arsenic trioxide suppressed cell proliferative capacity and inhibited telomerase activity probably via transcriptional suppression of c-Myc and hTERT.