PD-1 and IL-15 receptor

Class

PD-1-directed antibody-IL-15 fusion protein (immunocytokine)

Pathway

PD-1 checkpoint blockade combined with IL-15-driven NK/CTL/memory T-cell proliferation

PD-1 is an inhibitory receptor expressed on activated T cells that normally limits immune responses once a threat has been cleared, preventing excessive tissue damage. Tumors exploit this control point by expressing ligands that engage PD-1, suppressing the very T cells meant to attack them. Antibodies that block PD-1 interrupt this inhibitory signal, restoring T-cell activity. Interleukin-15 (IL-15) is a cytokine that drives proliferation and survival of natural killer (NK) cells and memory CD8+ T cells, populations central to sustained anti-tumor immunity. Fusing a PD-1-blocking antibody to an IL-15 component creates a bifunctional immunocytokine that simultaneously removes an inhibitory brake on T cells and delivers a proliferative signal to effector lymphocytes, an approach intended to produce a stronger and more durable immune response than checkpoint blockade or cytokine therapy alone. Because the antibody portion directs the molecule toward PD-1-expressing cells, IL-15 activity may be concentrated where checkpoint-inhibited lymphocytes reside, including within the tumor microenvironment. This mechanism is broadly relevant across solid and hematologic cancers in which immune evasion through checkpoint upregulation, combined with limited persistence of effector cells, restrains the benefit of checkpoint inhibition used in isolation.