Imetelstat Sodium (GRN163L) is a telomerase template antagonist with in vitro and in vivo activity in a variety of tumor model systems. Telomerase is an enzyme that is active primarily in tumor cells and is crucial for the indefinite growth of tumor cells. Inhibition of telomerase may result in antineoplastic effects. High telomerase levels and short telomere lengths correlate with other markers of poor prognosis in patients with chronic lymphoproliferative disease.