Sargramostim increases survival when dosed beginning 48 h after TBI. Panel A: After TBI to achieve LD_50–60/60, 15 of 36 (41.7%) control-treated (dashed line), 28 of 36 (77.8%) sargramostim-treated (solid line) non-human primates survived to day 60 (P = 0.0018, Fisher's exact one-sided). The median survival time for the control group is 20 days. The median survival time for the sargramostim group is not estimable. Comparison of the two survival curves indicated a significant difference in favor of the sargramostim-treated group (P=0.0023). Cox proportional hazards model has a hazard ratio (sargramostim versus control) of 0.31 (95% CI, 0.14–0.70). Panel B: After TBI to achieve LD_70–80/60, 3 of 18 control-treated and 11 of 18 sargramostim-treated non-human primates survived to day 60 (P = 0.0076, Fisher's exact one-sided). The median survival time for the control group is 16 days. The median survival time for the sargramostim group is not estimable. Comparison of the two survival curves indicated a significant difference in favor of the sargramostim group (P=0.0036). The Cox proportional hazards model has a hazard ratio (sargramostim versus control) of 0.29 (95% CI, 0.12–0.73). LD_50–60/60, lethal radiation dose for 50–60% within 60 days postirradiation; LD_70–80/60, lethal radiation dose for 70–80% within 60 days postirradiation. TBI = total-body irradiation.