Preclinical development of tumor-infiltrating lymphocyte therapy for metastatic colorectal cancer.

Abstract

95 Background: Immunotherapy has become an effective cancer therapy, particularly in the case of checkpoint blockade and adoptive T-cell therapy (ACT). ACT exploits the presence of tumor-infiltrating lymphocytes (TIL) by exponentially expanding their numbers ex vivo and re-infusing them into the patient in an autologous setting. With the effectiveness of TIL therapy already well established in multiple phase II studies in melanoma, there is a push to translate it to other cancers in need of improved therapies. Colorectal cancer (CRC) is a cancer where the presence of TIL has been strongly correlated with increased survival. Metastatic CRC (mCRC) has a poor outcome with median overall survival of less than 3 years. At present anti-PD1 therapy is only active in the small subset of mCRC patients (4%) that are MSI-high. We sought to evaluate the ability to generate and characterize TIL from patients with mCRC to provide a rationale for future TIL therapy in this disease. Methods: To assess the feasibility of utilizing TIL ACT for this patient population, we characterized the immune infiltrate of mCRC, TIL growth from tumor fragments (n = 24), as well as the TIL repertoire (n = 4) and anti-tumor potential in samples with available autologous tumor target. Results: Flow cytometry analysis detected a CD4-rich T-cell infiltration at the tumor site as well as a scarce yet activated CD8+ TIL population. The outgrowth of CD8+ TIL from tumor fragments in media containing IL-2 was potentiated by the addition of an agonistic 4-1BB antibody (Urelumab, BMS). Additionally, the use of a 4-1BB mAb improved the likelihood of growing TIL (63% [14/24] to 83% [20/24]) and increased the total yield of TIL grown. T-cell receptor sequencing showed enrichment in the tumor of CD8+ T-cell clones shared between the blood and tumor, suggesting selective expansion at the tumor site. Using IFNγ ELISPOT, CD8+ TIL from one patient with an MSS tumor were found to be reactive against a peptide derived from mutated TP53R116W restricted to HLA-B*39:01. Conclusions: It is possible to expand CD8+ T cells from microsatellite stable (MSS) mCRC that are able to target tumor antigens. Although preliminary, the initial data suggest the feasibility of TIL therapy for mCRC.