Employing novel pan-cancer targets for immunotherapy in leukemias and solid tumors.

2582 Background: Acute myeloid leukemia (AML) and many solid tumors are difficult to treat. Tumor-associated protein targets that are the focus of cancer immunotherapy research are prone to on-target, off-tumor toxicity and antigen-negative relapse due to mutation or downregulation. Targeting cancer-specific markers less susceptible to resistance is key for safer therapies. Our research explores high mannose (Man 9) oligosaccharides and phosphatidylserine (PS) as non-protein targets. Man9 glycans are absent on healthy cells but are present in cancers like AML, breast, colon, and lung. PS, exposed during malignant transformation, is found on colon, prostate, and brain tumors. Methods: We have engineered trispecific T cell engagers (Man9/PS/CD3) to target Man9 and/or PS-positive cancers. We tested solid tumor cell lines (pancreatic, lung, colorectal) via flow cytometry and found that the dual affinity molecule (Man 9 x PS) had high binding to many solid tumors (Table 1). We assessed their efficacy in vivo and specificity using glycan microarray, and immunohistochemistry to confirm tumor specificity and predict favorable safety profiles. Results: Flow cytometry showed that our therapeutic molecules specifically bind to AML cells and various solid tumors while sparing healthy tissues. Glycan microarrays confirmed selective binding to abnormal glycans on cancer cells. Immunohistochemistry of FFPE tissues indicated tumor specificity and enrichment on cancer stem cells. In vitro studies (coculture of luciferase-transduced target cells with activated CD8+ T cells in the presence of absence of the T cell engager) demonstrated strong anti-leukemia activity against AML cell lines, with IC50 values of 5–10 pM. In vivo studies in human CD3 transgenic mice treated with intravenous doses of VTRU200 (Man9 x PS x CD3) showed significant therapeutic responses, based on in vivo bioluminescence imaging. Conclusions: Our data supports Man9 and PS as promising non-protein targets for pan-cancer immunotherapy. The dual targeting approach with T cell engagers reduces on-target, off-tumor toxicity and antigen-negative relapse, advancing a first-in-class Man9 x PS x CD3 trispecific T cell engager. We have also designed and validated a bispecific (Man9 x PS) chimeric antigen receptor (CAR) and research is ongoing for CAR-T therapy for pancreatic cancer. With IND-enabling studies underway, we aim to advance this breakthrough immunotherapy for AML and other cancers, targeting an IND submission within 18 months. Cell type Man9/PS positivity (%) Sample size Mouse AML (cell line) 75-80 2 Human AML (cell line) 54-100 9 Human adult AML (primary) 35-98 8 Human pediatric AML (primary) 31-87 7 Human pediatric ALL (primary) 80-97 3 Human MM (cell line) 88-99.9 2 Human DLBCL (cell line) 56-93 3 Human pancreatic cancer (cell line) 46-95 3 Human colorectal cancer (cell line) 66-98 2 Human lung cancer (cell line) 82 1