Abstract 877: Targeting pancreas cancer liver metastases with B7-H3 tri-specific killer engager and regional delivery of placental-derived NK cellular therapy

Abstract Introduction: Pancreatic cancer (PDAC) is a dismal disease characterized by early metastases to the liver and poor overall survival. The success of natural killer (NK) cell therapies for solid tumors has been limited in part due to inadequate cytotoxicity and homing to sites of disease. We set out to evaluate the function of placental-derived NK cells in combination with a tri-specific killer engager (TriKE) targeting B7-H3 with ability to engage CD16 and express IL-15, critical components for NK cytotoxicity against B7-H3-expressing PDAC cells. We also investigated the effect of regional delivery as a method to enhance liver engraftment with the goal of combining regionally delivered placenta NK cells with B7-H3 TriKE platform to treat pancreatic cancer liver metastases. Materials and Methods: B7-H3 IHC staining was performed on 84 patient samples from resected PDAC to quantify expression on primary tumors. Human NK cells were isolated from human placenta and expanded ex vivo using the established K562.cl9mIL21 feeder line and IL-2. Phenotype was evaluated by flow cytometry and functional assessment by PANC-1 killing with or without B7-H3 TriKE. Nanoparticle labelled and unlabeled ex vivo activated NK cells were adoptively transferred into immunodeficient mice via either tail vein (IV) or portal vein (PV) injection and liver and spleen engraftment was assessed by ultrasound-guided photo-acoustic imaging and flow cytometry. Results: B7-H3 (>1% expression) was detected on 76/84 (90%) primary resected PDAC samples and median H-score was 12 (range 0-132). In vitro, PANC-1 cells showed 99% expression of B7-H3. Ex vivo expanded placenta NK cells were >90% CD16 positive and showed cytotoxicity against PANC-1 cells after 4 and 8 hours at 10:1 effector-to-target ratio. Addition of B7-H3 TriKE enhanced cytotoxicity in placenta NK cells, at both time points (4 hr: 51.2% ±2.0 vs 27.7% ± 3.0, P < 0.01; 8 hr: 76.7% ± 2.6 vs 56.6% ± 2.1, P < 0.01). 24 hours after administration, in vivo imaging analysis showed a 2.7-fold higher signal from PV compared to IV in the liver. This was confirmed by flow cytometry with administration by PV having showed significantly higher liver engraftment compared to IV (human CD45 positivity 23.6% ± 7.6 vs 8.8% ± 4.5, P = 0.03), while spleen engraftment was minimal and not significantly different between PV and IV administration (0.7% ± 0.4 vs 0.3% ± 0.2). Conclusion: B7-H3 is expressed on both primary human PDAC and the PANC-1 cell line representing a logical target for novel therapeutic strategies. Ex vivo expanded placenta NK cells demonstrate cytotoxicity against PDAC which is further enhanced through the B7-H3 TriKE. Regional delivery by portal venous administration results in increased liver engraftment and represents a viable and rational strategy for targeting PDAC liver metastases. Citation Format: Megan Purl, Tasneem Mukarrama, Jinhwan Kim, Sylvia M. Cruz, Jeffrey S. Miller, Martin Felices, William J. Murphy, Robert J. Canter, Sean J. Judge. Targeting pancreas cancer liver metastases with B7-H3 tri-specific killer engager and regional delivery of placental-derived NK cellular therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 877.