PD-1/PD-L1-IN-44 (Compound 22) selectively inhibits the PD-1/PD-L1 protein with an IC50 of 1.21 nM. In animal models, PD-1/PD-L1-IN-44 effectively suppressed tumor growth and increased CD8+ cell infiltration without exhibiting toxicity.

PD-1/PD-L1-IN-44 exhibits non-specific toxicity with an IC 50 value greater than 20 μM in MDA-MB231, H1299, HCT116, and A549 cell lines. At a concentration of 10 μM over 48 hours, PD-1/PD-L1-IN-44 effectively inhibits the proliferation of A549 cells in A549/PBMC T cell co-cultures, achieving an inhibition rate of up to 76.5%.

PD-1/PD-L1-IN-44, administered at a dose of 10 mg/kg intraperitoneally (i.p.) once daily for 21 days, significantly inhibited tumor growth in 4T1 model mice. The formulation of the drug consists of 5% dimethyl sulfoxide, 10% castor oil, and 85% saline solution.