Potent and selective inhibitor of native and recombinant human telomerase (IC50 values of ca. 100 nM), capable of inducing senescence in human cancer cells. BIBR1532 is a mixed-type non-competitive inhibitor of the human telomerase reverse transcriptase and human telomerase RNA components with similar potency primarily by interfering with the processivity of the enzyme. BIBR 1532 defines a novel class of mixed-type non-competitive telomerase inhibitor with mechanistic similarities to non-nucleosidic inhibitors of HIV1 reverse transcriptase.