MI-63 and dFdC inhibit tumor growth in vivo. (A) Severe combined immunodeficiency mice were inoculated with Granta-519 cells subcutaneously and monitored until tumors were established. Five mice per group were then injected intraperitoneally with vehicle, MI-219 daily for 2 weeks, dFdC (GEM) every third day for 2 weeks, or both agents using the same schedules but at a 50% dose reduction. Tumor volumes were measured 3 times per week and are plotted as a function of time in the top panel. Statistically significant differences are defined as *P < .05 relative to the vehicle control and as #P < .05 relative to MI-219 alone. In the bottom panel, the average tumor growth rate per day was calculated, and the P values of each group are shown relative to the vehicle group, as well as to MI-219 alone, or dFdC alone.