CD64+ fibroblast-targeted vilanterol and a STING agonist augment CLDN18.2 BiTEs efficacy against pancreatic cancer by reducing desmoplasia and enriching stem-like CD8+ T cells.

Objective: The objective of this study is to improve the efficacy of CLDN18.2/CD3 bispecific T-cell engagers (BiTEs) as a promising immunotherapy against pancreatic ductal adenocarcinoma (PDAC).

Design: Humanised hCD34⁺/hCD3e⁺, Trp53^R172HKras^G12DPdx1-Cre (KPC), pancreas-specific Cldn18.2 knockout (KO), fibroblast-specific Fcgr1 KO and patient-derived xenograft/organoid mouse models were constructed. Flow cytometry, Masson staining, Cell Titer Glo assay, virtual drug screening, molecular docking and chromatin immunoprecipitation were conducted.

Results: CLDN18.2 BiTEs effectively inhibited early tumour growth, but late-stage efficacy was significantly diminished. Mechanically, the Fc fragment of BiTEs interacted with CD64⁺ cancer-associated fibroblasts (CAFs) via activation of the SYK-VAV2-RhoA-ROCK-MLC2-MRTF-A-α-SMA/collagen-I pathway, which enhanced desmoplasia and limited late-stage infiltration of T cells. Molecular docking analysis found that vilanterol suppressed BiTEs-induced phosphorylation of VAV2 (Y172) in CD64⁺ CAFs and weakened desmoplasia. Additionally, decreased cyclic guanosine-adenosine monophosphate synthase/stimulator of interferon genes (STING) activity reduced proliferation of TCF-1⁺PD-1⁺ stem-like CD8⁺ T cells, which limited late-stage effects of BiTEs. Finally, vilanterol and the STING agonist synergistically boosted the efficacy of BiTEs by inhibiting the activation of CD64⁺ CAFs and enriching proliferation of stem-like CD8⁺ T cells, resulting in sustained anti-tumour activity.

Conclusion: Vilanterol plus the STING agonist sensitised PDAC to CLDN18.2 BiTEs and augmented efficacy as a potential novel strategy.