STRO-001 therapy demonstrates preclinical efficacy against CD74 expressing NOMO-1 AML cell line and primary AML cells. (A) Flow cytometric analysis of CD74 cell surface expression on K562 and NOMO-1 cell lines. (B) In vitro cytotoxicity of STRO-001 against K562 and NOMO-1 cells. Cells were treated with increasing doses of STRO-001 alone (blue) or excess of naked antibody SP7219 (1 uM, red). After 3 days of continuous exposure, viability was assessed by Cell Titer-Glo assay. Data are normalized to untreated controls. Error bars denote standard deviation from 2 technical replicates at each dose. Experiments were repeated at least twice (supplemental Figure 5). (C) Top, experimental schema evaluating STRO-001 in vivo efficacy in NOMO-1 xenograft model. Bottom, leukemia burden measured by bioluminescence (IVIS) imaging in NOMO-1 xenograft mice untreated (left) or treated with STRO-001 at 3 mg/kg weekly for 3 weeks (right). Shown are representative timepoints. N = 5 mice per group. X denotes death. (D) Kaplan-Meier survival curves of NOMO-1 xenografts untreated or treated with STRO-001. N = 5 per group. Statistical differences in survival were evaluated using Log-rank Mantel-Cox. (E) Flow cytometric analysis of CD74^- (AML-4) and CD74⁺ AML patient specimens (AML-5-7). (F) In vitro cytotoxicity of STRO-001 primary AML specimens. Cells were treated as described above. Error bars denote standard deviation from 3 technical replicates at each dose. (G) Experimental design to assess in vivo activity of STRO-001 against a PDX model transplanted with a primary AML sample, AML-7. Peripheral blood was obtained every other week following the last dose of STRO-001, bone marrow aspirate was obtained 4 and 13 weeks after transplant. (H) Percent AML cells in the bone marrow at indicated weeks following leukemia injection determined by flow cytometry. (I) Kaplan-Meier survival curves of PDX mice untreated (n = 3) or treated with STRO-001 (n = 3). Statistical differences in survival were evaluated using Log-rank Mantel-Cox.