Anti-tumor activity of Man 9 x PS targeting immunotherapies in diffuse intrinsic pontine glioma (DIPG) and pancreatic cancers.

Abstract

2530 Background: Aberrant cell-surface glycans and lipids are attractive immunotherapy targets due to their stable tumor expression. High-mannose glycan mannose-9 (Man9), and phosphatidylserine (PS) are co-expressed across multiple malignancies and contribute to immune suppression. We developed Man9×PS-targeting effector immunotherapy platforms for the treatment of solid tumors, with a focus on pancreatic cancer and diffuse intrinsic pontine glioma (DIPG). Methods: The Man9×PS×CD3 trispecific T cell engager (TCE), VTRU200, was expressed and purified from CHO cells. The Man9×PS CAR T cell, VCAR300, was generated from murine splenic T cells transduced with a Man9×PS CAR-encoding viral vector. In vitro tumor cytotoxicity of VTRU200 was assessed using human T cells co-cultured with cell lines (PANC-1, AsPC-1) or patient-derived primary cultures (DIPG-008, DIPG-011) and compared with bispecific Man9×CD3 or PS×CD3 controls. Tumor selectivity and potential off-target binding were evaluated by immunohistochemistry (IHC) on pancreatic and breast tumors with matched normal tissues, and by immunofluorescence (IF) across a panel of 33 normal human tissues. In vivo dose escalation of VCAR300 was evaluated by bioluminescence imaging in a Panc02 murine orthotopic pancreatic tumor model. Cancer stem cell binding was verified by co-staining with anti-CD133 antibody. Previously, VTRU200 was evaluated in syngeneic, xenograft, and patient-derived xenograft (PDX) acute myeloid leukemia (AML) models, and VCAR300 persistence was tested in a pilot orthotopic pancreatic cancer model. Results: VTRU200 demonstrated potent, target-dependent cytotoxicity with 0.1-5 nM EC50 values across multiple solid tumor cell lines in the presence of human T cells. Cytotoxicity required engagement of both Man9 and PS, with additive effects relative to bispecific controls. IHC demonstrated strong staining in pancreatic and breast tumors with absence of staining in corresponding paired normal tissues, while there was no detectable reactivity across normal human tissue panels by IF. Consistent with prior AML studies showing robust anti-leukemic activity, VCAR300 exhibited high anti-tumor activity in vitro with an effector:target ratio at 50% maximum killing (ET50) of less than 1, and in a murine orthotopic pancreatic cancer model (25-fold reduction in tumor size after 2 weeks of treatment with 2x10 6 CAR T/mouse) with an excellent safety profile. Anti-tumor activity was associated with tumor stem cell targeting and release of inflammatory cytokines. Conclusions: Man9 x PS dual targeting is a promising strategy for treating solid tumors. VTRU200 and VCAR300 are potential therapeutic candidates with potent anti-tumor activity across multiple tumor types and impressive safety. Following a successful pre-IND interaction with the FDA, first-in-human studies are planned to initiate in 2027.