BACKGROUND

Recombinant human interleukin (rhIL)-7-hyFc (efineptakin alfa; NT-I7) is a potent T-cell amplifier, with two IL-7 molecules fused to IgD/IgG4 elements. rhIL-7-hyFc promotes extensive infiltration of CD8 T cells into the tumor, concurrently increasing the numbers of intratumoral PD-1CD8 T cells. The hIL-2/TCB2 complex (SLC-3010) inhibits tumor growth by preferential activation of CD122 (IL-2Rβ) CD8 T cells and natural killer cells, over regulatory T cells (Tregs). We investigated the underlying mechanisms of rhIL-7-hyFc and hIL-2/TCB2c antitumor activity and the potential synergistic efficacy, specifically focusing on tumor-specific CD8 cells within the tumor and the tumor-draining lymph nodes (tdLN).

METHODS

MC38 and CT26 tumor-bearing mice were administered with 10 mg/kg rhIL-7-hyFc intramuscularly and 0.9 mg/kg hIL-2/TCB2c intravenously. Anti-PD-1 monoclonal antibody was administered intraperitoneally three times at 3-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 tumors and tdLNs by flow cytometry.

RESULTS

Our data demonstrate that the combination of rhIL-7-hyFc and hIL-2/TCB2c increases efficacy and generates an immune-stimulatory tumor microenvironment (TME). The TME is characterized by an increased infiltration of tumor-specific CD8 T cells, and a decreased frequency of CD39TIM-3 Treg cells. Most importantly, rhIL-7-hyFc increases infiltration of a CD62LLy108 early progenitor population of exhausted CD8 T cells (T), which may retain long-term proliferation capacity and replenish functional effector CD8 T cells. hIL-2/TCB2c induces differentiation of CD62LLy108 T rapidly into CD101 terminally differentiated subsets (terminally exhausted T cell (T)). Our study also demonstrates that rhIL-7-hyFc significantly enhances the proliferation rate of T in the tdLNs, positively correlating with their abundance within the tumor. Moreover, rhIL-7-hyFc and hIL-2/TCB2c can overcome the limited therapeutic effectiveness of PD-1 blockade, culminating in the complete regression of tumors.

CONCLUSIONS

rhIL-7-hyFc can expand and maintain the progenitor pool of exhausted CD8 T cells, whereas hIL-2/TCB2c promotes their differentiation into T. Together, this induces an immune-stimulatory TME that improves the efficacy of checkpoint blockade.