Selective expansion of T-cell receptor engineered T cells with increased stem-like phenotypes using neoantigen stimulation.

backgroundAdoptive transfer of T-cell receptor-engineered T cells (TCR-T cells) has shown promising efficacy in solid tumor treatment, but achieving clinical benefit typically requires infusion of tens of billions of cells. The commonly used rapid expansion protocol (REP), based on the CD3-agonistic OKT3 antibody and irradiated allogeneic feeder cells, exponentially expands tumor-infiltrating lymphocytes (TILs). However, the effect of REP on TCR-T cell frequency and phenotype remains unclear. This study aimed to evaluate the impact of REP on TCR-T cells and to assess the potential of a neoantigen-specific stimulation platform, NeoExpand, as a strategy to selectively expand TCR-T cells with favorable phenotypes.

methodsWe compared the effects of REP and NeoExpand on the frequency, yield, and phenotype of TCR-T cells engineered against shared neoantigens. Various autologous antigen-presenting cell (APC) types, including dendritic cells and bulk peripheral blood mononuclear cells (PBMCs), were tested as stimulators in NeoExpand. Additionally, we combined NeoExpand with CD3 activation, with or without allogeneic feeders, to improve scalability. The role of exogenous interleukin (IL)-21 in shaping TCR-T cell phenotypes was also investigated.

resultsREP impaired the frequency and phenotype of TCR-T cells, particularly CD4

conclusionsThese findings demonstrate that NeoExpand enables selective expansion of TCR-T cells while preserving favorable phenotypes and scalability. The approach supports further clinical evaluation of NeoExpand as a strategy to generate high-quality TCR-T cell products for adoptive cell therapy.