Fig. 1

Schematic Overview of the Current TIL Production Protocol and Potential Improvements. Currently, surgically removed melanoma metastases are processed into single cell digest or smaller tumor pieces. At this point in production, direct selection of tumor reactive cells based on activation markers such as PD-1 or CD137, or CD8⁺ T cells or multimers can be applied. TIL outgrowth currently occurs in HD IL-2. Outgrowth of TIL could be improved in the presence of alternative cytokines such as IL-7, IL-15 or IL-21 or agonistic co-stimulatory antibodies such as CD137. In addition, a variation of gene modifications of homing or co-stimulatory factors can be applied. The current REP protocol consists of addition of activating soluble anti-CD3, HD IL-2 and irradiated feeders, but may be improved by addition of alternative cytokines such as IL-7, IL-15 and IL-21 and artificial feeders may be used. Also, the current REP time may be shortened. After REP, gene modification can also be applied. The infusion procedure of TIL to the patient currently consists of a conditioning lymphodepleting regimen, usually cyclophosphamide and fludarabine and administration of HD IL-2 following TIL infusion. However, multiple studies are being conducted with adjusted doses and treatment schedules of the lymphodepleting regimen and IL-2, as are studies being conducted with TIL as combination therapy to further potentiate the anti-tumor effect of TIL