GRN163 reduced telomerase activity in neoplastic B-cell lines and primary MM cells. GRN163 treatment for 14 days decreased telomerase activity in 2 representative MM cell lines (CAG TRF, 2.7 kb; U266 TRF, 9.0 kb) in a dose-dependent and telomere-independent manner compared with vehicle (PBS) and 227 (mismatch oligonucleotide) controls. GRN163 treatment (10 μM) for 24 hours also decreased telomerase activity in CD138⁺ cells from 2 MM patients.