Effect of andecaliximab (anti-MMP9) on proteolysis of IL-7 in vitro, TCR diversity in mice, and serum IL-7 in gastric cancer patients in combination with chemotherapy.

Abstract

101 Background: Andecaliximab (andeca) is a monoclonal antibody that selectively inhibits matrix metalloproteinase 9 (MMP9). IL-7 selectively enhances the proliferation and survival of naïve, memory, and effector T-cells (but not regulatory T-cells) in the periphery. Previous clinical trials with systemic recombinant IL-7 therapy increased TCR diversity. In the disease setting, elevated circulating IL-7 may be due to a compensatory increase in IL-7 production as demonstrated in mice upon inhibition of IL-7 signaling. Methods: An in vitro screen, in which recombinant active human MMP9 was incubated with > 140 human recombinant folded proteins, identified IL-7 as the most efficient substrate of MMP9. Results: IL-7 proteolysis occurred between A128:L129. IL-7 proteolysis altered the global protein structure, evidenced by a loss of cooperative unfolding observed with intact IL-7 (intrinsic fluorescence, Tm = 59.3o C). Mouse MMP9 proteolyzed mouse IL-7 in vitro. In the orthotopic syngeneic NeuT mouse model, MMP9 inhibition reduced tumor growth (p = 0.0005). In a 7-day NeuT study, anti-MMP9 alone improved TCR diversity (decreased clonality) within tumor-infiltrating T-cells (Dunnett’s p = 0.0083). Further, anti-MMP9 and anti-PDL1 co-treatment promoted an increase in CD3+ cells (p = 0.01), CD4+ T cells (p = 0.006), and CD8+ T cells (p = 0.013) concomitant with a decrease in tumor-associated CD25+ FoxP3+ regulatory T cells (p = 0.04) in the tumor. In gastric cancer patient serum, pro-MMP9 (p < 0.0001), active MMP9 (p < 0.0001), and IL-7 (p < 0.0001) were higher than healthy controls. Serum IL-7 levels were normalized upon treatment with andeca plus mFOLFOX6 (N = 40; FDR-corrected p < 0.001) in a Phase I gastric cancer study. Conclusions: MMP9 proteolyzed IL-7 in vitro. Specific MMP9 inhibition in a mouse tumor model improved TCR diversity. Andeca +mFOLFOX6 therapy normalized serum IL-7 levels, which could be due to andeca, chemotherapy, or disease resolution. The functional implications of IL-7 proteolysis by MMP9 in gastric cancer are currently under investigation.