Systemic GRN163 treatment decreased tumor telomerase levels and inhibited the growth of myeloma xenografts in mouse models. NOD/SCID mice were inoculated with 10 × 10⁶ CAG myeloma cells by way of a subcutaneous route. When tumor volumes approached 100 mm³, mice were divided into 2 groups of 5 to 8 mice per group. (A) Mean tumor volumes ± SE (bars) in animals treated with daily intraperitoneal PBS (♦) or GRN163 (▪) (50 mg/kg per day) for 3 weeks (PBS vs GRN163 on day 23; P ≤ .19) are shown. (B) Representative telomerase activity in tumor xenografts harvested from animals after 14 and 21 treatment days, respectively, is also displayed.