Background NT-I7 (efineptakin alfa; rhIL-7-hyFc) is a potent T-cell amplifier, with two IL-7 molecules fused to IgD/IgG4 elements. NT-I7 promotes extensive infiltration of CD8⁺ T cells to the tumor, concurrently increasing absolute numbers of PD-1⁺ CD8⁺ T cells in mice.^{1 2} Moreover, it expands central memory CD8⁺ T cells in tumors and tumor-draining lymph nodes. The hIL-2/TCB2 complex inhibits tumor growth by preferential activation of CD122 (IL-2Rβ)^high CD8⁺ T cells and NK cells, without stimulating Treg. Both cytokines belong to the common gamma-chain cytokine family and induce antitumor effects. We investigated the synergistic antitumor efficacy and mechanisms of NT-I7 in combination with hIL-2/TCB2c, with or without PD-1 inhibitor.

Methods MC38 and/or CT26 tumor-bearing mice were administered a single dose of 10 mg/kg NT-I7 intramuscularly (IM) and 0.9 mg/kg hIL-2/TCB2c intravenously (IV). Anti-PD-1 monoclonal antibody was administered intraperitoneally three times with three-day intervals at a dose of 5 mg/kg. Tumor volume was measured to assess efficacy. To compare the composition of immune cells between each monotherapy and the combination therapy, we analyzed tumor and tumor-draining lymph nodes (TDLN) by flow cytometry.

Results Our data demonstrated that the combination of NT-I7 and hIL-2/TCB2c synergistically inhibits tumor growth and generates an immune-stimulatory tumor microenvironment (TME). This TME was characterized by an increased infiltration of tumor-specific CD8⁺ T cells, and a decreased frequency of CD11b⁺ MDSCs and CD39^high TIM-3⁺ Treg cells, known to be highly immunosuppressive. Most importantly, NT-I7 increased infiltration of CD62L⁺Ly108⁺ early progenitor population of exhausted CD8⁺ T cells (T_PEX), which may retain long-term proliferation capacity and replenish functional effector CD8⁺ T cells. IL-2/TCB2c treatment induces differentiation of CD62L⁺Ly108⁺ T_PEX rapidly into CD101⁺ terminally differentiated subsets. Remarkably, our study demonstrated that NT-I7 significantly enhances the proliferation rate of CD8⁺ T_PEX as well as memory T cells in the tumor-draining lymph nodes (TDLNs), positively correlated with the abundance of T_PEX within the tumor. These findings strongly suggest that the expansion of T_PEX, following NT-I7 administration, originates from the TDLNs. Moreover, the addition of PD-1 blockade further enhances the therapeutic efficacy of NT-I7 plus hIL-2/TCB2c, leading to complete regression of tumors.

Conclusions NT-I7 dramatically and preferentially increased T_PEX and less exhausted T cells, while hIL-2/TCB2c induced the differentiation of these cells. These findings highlight that NT-I7 in combination with other immunotherapies, such as IL-2 and/or CPI, can enhance the anti-tumor efficacy.

References

1. Kim JH Kim, YM Kim, D Choi, SB Jo, HW Park, SW Hong, et al. Hybrid Fc-fused interleukin-7 induces an inflamed tumor microenvironment and improves the efficacy of cancer immunotherapy. Clinical & Translational Immunology 2020;9(9):1–16.

2. Lee JY, Lee E, Hong SW, Kim D, Eunju O, Sprent J, Im SH, Lee YJ, Surh CD. TCB2, a new anti-human interleukin-2 antibody, facilitates heterodimeric IL-2 receptor signaling and improves anti-tumor immunity. Oncoimmunology. 2019 Nov 4;9(1):1681869.