TRSC-05 Tumor Reactive T Cells From the Cerebrospinal Fluid in Melanoma Leptomeningeal Disease

BACKGROUND Leptomeningeal disease (LMD) is a devastating complication from cancer, with a median survival of 6-8 weeks. The incidence of LMD is highest in melanoma (5-25%) carrying the worst prognosis. Adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TILs) showed complete and durable responses in patients with advanced metastatic melanoma. CSF-derived T cell populations in LMD shift to more exhausted phenotypes compared to extracranial and brain metastases. Adoptive T cell transfer can be a novel therapeutic approach to treat melanoma LMD (M-LMD). Our goal is to optimize CSF-derived tumor reactive T cell expansion in M-LMD and assess their anti-tumoral response. METHODS Cells from CSF from M-LMD patients (n=6) were plated following established TIL culture protocols to determine optimal expansion conditions i.e.: 1) 6000 IU/mL IL-2, 2) IL-2+OKT3, 3) IL-2+anti-4-1BB agonistic antibody, 4) IL-2+IL-7+IL-15+IL-21, 5) IL-2+anti-CD3/CD28 human dynabeads, & 6) IL-2+anti-CD3/CD28/CD137 human dynabeads. After 4 weeks, T cells were propagated via REP and phenotyped. T cells were co-cultured with HLA-matched melanoma cell lines and IFN-y levels evaluated. TCR beta seq was done at different times point of expansion and peripheral T cells. RESULTS After initial culture in IL-2, 61.9% of samples showed increased cell yield with an average 101.68-fold expansion (range 2.35-1054). PreREP T cells were predominantly CD4+ (45.7%). REP was 100% success rate (mean 187.47-fold expansion). Post-REP flow cytometry revealed similar results. M-LMD T cells were highly functional, producing substantial levels of IFN-y in response to HLA-matched cells. Anti-CD3/CD28 produced a larger expansion of T cells with higher levels of IFN-y. TCR beta sequencing results are pending. CONCLUSIONS Therapies for LMD patients are desperately needed. Results demonstrate successful expansion of T cells ex vivo from CSF in M-LMD. Results raise potential to use autologous CSF-derived T cells as therapeutic strategy for patients with LMD.