P-08.09 Robust ex-vivo expansion of tumour-infiltrating lymphocytes from ovarian cancer biopsies using dendritic cells derived from the leukemic cell line DCOne

<h3>Background</h3> Adoptive cell therapy with tumour-infiltrating lymphocytes (TILs) in metastatic melanoma patients has demonstrated remarkable and durable anti-tumour responses even where prior therapies as checkpoint inhibitors had failed1, 2. Next to melanoma, TIL therapy is investigated for a broad range of solid tumours, such as breast cancer, lung cancer, and ovarian cancers 3, 4, 5. Nevertheless, the translation of TIL therapy to other cancer types remains challenging with a major limitation to produce sufficient quantities of TILs using current laborious and lengthy manufacturing process. Moreover, the availability of tumour-tissues the only source of TILs is also a major bottleneck, particularly in late-stage cancer patients. In this study we describe a novel and robust method to generate TILs from tumour samples from ovarian cancer patients using dendritic cells derived from leukemic cell line DCOne (DCOne mDC). <h3>Materials and Methods</h3> Patient TILs were isolated from fresh ovarian tumour biopsies obtained during surgery. Biopsies were cut into pieces of &lt;1 mm3 and digested overnight with collagenase and DNAse. Cells were centrifuged over a Ficoll-Plaque gradient and lymphocytes were isolated and cryopreserved in liquid nitrogen until further use. TILs were stimulated with either high dose of IL-2 or with DCOne mDC in the presence of IL-2 up to maximum of 28 days to obtain young TILs. Young TILs were further expanded for 14 days rapid expansion protocol (REP) using irradiated allogeneic PBMC as feeder cells in the presence of anti-CD3 antibody and IL-2. Purity, viability, phenotype and functionality of expanded TILs was assessed pre- and post-REP expansion. <h3>Results</h3> TILs cultured in the presence of DCOne mDC and IL-2 resulted in at least average of 5-fold higher expansion up to day 28 compared to IL-2 cultures. Furthermore, the young TILs expanded in the presence of DCOne mDC contained mainly CD3+ cells with a larger proportion of CD8+ T cells than CD4+ T cells compared to IL-2 cultures. Both CD4 and CD8 cells expanded in DCOne cultures were effector memory T cells. Furthermore, increased expansion of TILs from DCOne cultures was also observed in REP phase compared to IL-2 TILs. The DCOne mDC expanded TILs showed increased IFN-g+effector T cells post-PHA stimulation. <h3>Conclusions</h3> The presented data indicate that DCOne-derived mature DC are best equipped with the ability to promote strong ex vivo expansion of TILs with effector memory phenotype from patient-derived ovarian cancer biopsies. These data provide basis to expand the use of DCOne -derived mDC in the TIL manufacturing process of variety of difficult to expand tumour types providing optimism to treat more patients with successfully and timely manufactured TIL product. <b>S. Kaur Singh:</b> A. Employment (full or part-time); Modest; Mendus AB. <b>H. Zuo:</b> A. Employment (full or part-time); Modest; Mendus AB. <b>J. Naik:</b> A. Employment (full or part-time); Modest; Mendus AB. <b>W. Iwema:</b> None. <b>A. Plat:</b> None. <b>N. van Rooij:</b> None. <b>H. Nijman:</b> None. <b>M. de Bruyn:</b> None. <b>A. Karlsson-Para:</b> A. Employment (full or part-time); Modest; Mendus AB.