LYP-IN-3 (compound D34) is a selective Lymphoid-tyrosine phosphatase (LYP) inhibitor (Ki=0.93 μM) that modulates the T-cell receptor (TCR) signaling pathway during tumor progression. It promotes T-cell activation, hinders M2 macrophage polarization, and increases PD-1/PD-L1 expression. When combined with PD-1/PD-L1 inhibitors, LYP-IN-3 may enhance cancer immunotherapy [1].