Fig. 2: MTX-531 cotargets cellular EGFR and PI3K signaling in HNSCC CAL-33 and CAL-27 models.
a, Immunoblot analyses of EGFR and PI3K–mTOR pathway expression in CAL-33 cells treated for 2 h with MTX-531 over a broad dose range. The images are representative of three repetitions of the experiment. b, Pharmacodynamic activity of MTX-531 in CAL-33 tumor-bearing mice treated with a single oral dose of 100 mg kg−1. Immunoblot analyses of tumors isolated at the indicated time points (n = 3 tumors per group) (left) were quantified by densitometry analyses of phosphorylated kinase expression (right). Data are representative of two individual experiments and are presented as the mean ± s.e.m. c, Antitumor efficacy of MTX-531 against CAL-33 (left; n = 5 mice per group) or CAL-27 (right; n = 6 mice per group) xenografts. MTX-531 was dosed daily by oral gavage at the indicated dosage for 134 days (CAL-33) or 145 days (CAL-27) except for the 100 mg kg−1 arm of the CAL-33 study where dosing stopped after 37 days to monitor the durability of complete responders. Top, data are shown as the mean tumor volume ± s.e.m. An unpaired two-sided t-test was carried out to determine statistical significance. Bottom, the effects of treatment on survival were quantitated by euthanizing individual mice when tumor burden reached an equivalent size (1,000 mm3 for CAL-33 and 500 mm3 for CAL-27). A one-way analysis of variance (ANOVA) comparison among all groups was carried out to determine statistical significance. d, Antitumor efficacy of MTX-531 against advanced-stage CAL-33 xenografts. Daily treatment with MTX-531 (100 mg kg−1 per os (PO)) was initiated when mean tumor volumes reached ~500 mm³ (n = 10 mice per group). Top left, data are shown as the mean tumor volume ± s.e.m. Top right, the effects of treatment on survival were quantified by euthanizing individual mice when the tumor burden reached 1,000 mm³. Statistical differences in survival between the vehicle-treated and the MTX-531-treated group were determined using the log-rank (Mantel–Cox) test. The best individual response of MTX-531-treated mice (bottom left) is depicted in a waterfall plot (bottom right). **P < 0.01 and ****P ≤ 0.0001.
