Work

345 Neoantigen-targeted adoptive cell therapy in bladder cancer: feasibility of isolating and enriching tumor-reactive infiltrating lymphocytes

Year: 2026

Type: conference-abstract

Abstract: Background Advanced and recurrent bladder cancer presents a formidable clinical challenge with patients requiring radical cystectomy often facing poor long-term outcomes and diminished quality of life. While recent therapeutic advances have expanded options for non-muscle invasive bladder cancer (NMIBC), long term durable response rates are measured in only 50% of patients highlighting a critical need for novel, targeted interventions. Adoptive cell therapy (ACT) using tumor infiltrating lymphocytes (TIL) is a promising strategy, but standard bulk TIL products often suffer from a low frequency of tumor reactive T cells. Targeting patient-specific neoantigens can overcome this limitation by ensuring a highly potent, tumor restricted response. This study evaluates a platform to systematically identify, isolate and enrich neoantigen-reactive TIL from bladder tumors establishing a feasible and scalable framework for personalized cell-based immunotherapies.Methods Tumors and PBMC were collected from 15 bladder cancer patients under an IRB-approved study (Pro00037380). Initial TIL were expanded ex-vivo from tumor fragments using high-dose IL2 (Pre-REP). Whole exome and RNA sequencing identified patient specific neoantigens and autologous HLA-binding long peptides (25 aa; 42-200 peptides per patient) were manufactured. Patient derived B cells served as antigen presenting cells (APC’s) and were pulsed with neoantigen peptides. Pre-REP TIL were then co-cultured with the peptide-pulsed APC. Neoantigen reactive TIL were isolated via fluorescence activated cell sorting (FACS) based on upregulated surface expression of OX40 and 4-1BB. Sorted populations underwent a rapid expansion protocol (REP). Final neoantigen-enriched TIL were evaluated for specificity against neoantigen peptides by measuring 4-1BB/OX40 upregulation via flow cytometry and cytokine release/degranulation via the ELLA platform.Results TIL expanded in 15/15 (100%) of the available bladder tumor samples. Phenotypic analysis revealed CD4 + T cells were predominant across all pre-REP and expanded TIL samples. Following co-culture with peptide-pulsed autologous APC, TIL significantly upregulated OX40 and 4-1BB. In addition, robust expression of IFN-gamma, granzyme-B and TNF-alpha was measured in 10/15 (66%) samples. After FACS isolation of the OX40+/41BB+ TIL population and subsequent REP, specific reactivity against pooled neoantigen peptides were successfully confirmed in 11/15 (86%) of the expanded samples. Neoantigen reactivity to individual peptides within peptide pools was confirmed by IFN-gamma secretion.Conclusions Neoantigen-reactive TIL can be successfully isolated and robustly expanded from bladder tumors with notable predominant CD4 + T cell phenotype. This platform provides a strong therapeutic rationale and a scalable strategy to advance toward future clinical trials evaluating neoantigen-enriched adoptive cell therapies for patients with advanced bladder cancer.

Source: Journal for ImmunoTherapy of Cancer

DOI: 10.1136/jitc-2026-sitc2026.0345