TTI-CD200 delays disease progression in low-risk ALL. Cells from 4 MRD low-risk ALL patients (51-53, 63) were inoculated into NSG mice. Once engraftment reached >0.1%, mice received 4 doses of isotype control IgG4 or TTI-CD200 (50 mg/kg) intravenously at 72-hour intervals (gray boxes represent treatment duration). Human cell levels (CD45, CD10, and CD200) were measured in PB once per week and in bone marrow (BM) at termination. Patients 51 and 53 had low levels of CD45, so CD10 was used for measuring engraftment. Lines in PB graphs represent individual mice. Data in BM graphs represent mean ± SD. *P ≤ .05; **P ≤ .01; ***P ≤ .001; ****P ≤ .0001.