L3D10 treatment delays growth of established tumors in human CTLA-4 knock-in mice. MC38 tumor cells were injected subcutaneously into the human CTLA-4 knock-in mice. At 10 to 14 days after tumor injection, when the tumors reached a mean diameter of 8 mm, the mice were injected with either L3D10 or control Ig every 4 days for 4 weeks. (A) Growth kinetics of established tumors in mice treated with either control IgG or L3D10 (n = 9). Data shown are means and SEM of tumor volumes. The volumes of large holes caused by necrosis in some mice were subtracted. Student t tests were used to compare the tumor size at each time point; those with P < .05 are indicated with an asterisk (*), whereas those with P < .01 are indicated with 2 asterisks (**). (B) Kaplan-Meier survival curves of mice that received control IgG or L3D10. A log-rank test revealed that L3D10 significantly prolonged mouse survival (P = .011).