Fig. 6: Soquelitinib synergizes with immune checkpoint blockade therapy.

a Soquelitinib in combination with anti-programmed cell death receptor one (PD1) and anti-cytotoxic T lymphocyte antigen four (CTLA4) induces long-term anti-tumor immunity in the CT26 tumor model. Treatment with solution-formulated soquelitinib alone (30 mg/kg) or suboptimal dose of anti-PD1 (25 μg/mouse) and anti-CTLA4 (25 μg/mouse) resulted in an incomplete inhibition of tumor growth, whereas triple combination therapy exhibited durable anti-tumor response even after treatment was terminated for more than 2 weeks. n = 8 per group. Representative of two independent experiments is shown. b Soquelitinib treated T cells in blood display an increase in CXCR3 cell surface expression. Representative histogram overlays of CXCR3 expression on CD4+ and CD8+ T cells from blood samples (Left) and summary graphs of CXCR3 geometric mean fluorescence intensity (gMFI) in CD4+ and CD8+ T cells (Right). n = 7–8 per group. c In the presence of checkpoint inhibitors, soquelitinib induces an increase in Tbet+ CD4 T cells in the TME. Representative flow plot of Tbet-expressing CD4+ TILs (Left), and enumeration of CD4+Tbet+ cells after normalization for tumor size (Right). n = 3 per group. d Soquelitinib enhances granzyme (GZMB) production in CD8+ TILs. Granzyme B + CD8 T cells are expressed as the absolute numbers of granzyme B + CD8 + T cells per mm³ of tumors. n = 4 per group. Blood samples (b) or tumors (c, d) were collected from the CT26 tumor-bearing animals treated with either control chow, anti-PD1+anti-CTLA4 or triple combination therapy with soquelitinib chow (300 mg/kg/day) for 10 days and sacrificed one day after treatment. (e) Soquelitinib in combination with checkpoint blockade inhibitors reduces surface expression of exhaustion markers in the CT26 tumor model. Representative histogram overlays of indicated exhaustion marker expression in CD8+TILs from the CT26-tumor bearing mice treated with either isotype antibody plus vehicle control, dual combination, and triple combination are shown (Top). Treatment schedule was the same as shown in panel A. Tumors were harvested 8 days following the last dose of soquelitinib treatment. Summary graph of exhaustion marker expression is shown (Bottom). N = 4 per group. Graphs were drawn using Graphpad Prism. Histograms were created by Flowjo. NS not significant, *p ≤ 0.05, **p ≤ 0.005, and ***p ≤ 0.001. Data displayed as means ± SEM. Results are representative of two independent experiments. SQL soquelitinib.