PD-1/PD-L1-IN-29 (S4-1) is a potent PD-1/PD-L1 inhibitor with an IC 50 value of 6.1 nM. PD-1/PD-L1-IN-29 binds PD-L1 and disrupts PD-1/PD-L1 interactions, induces PD-L1 dimerization and internalization, improves its localization to the endoplasmic reticulum, and promotes PD-L1 entry into the endoplasmic reticulum. PD-1/PD-L1-IN-29 has anticancer activity. In Vitro PD-1/PD-L1-IN-29(S4-1) (10 or 20 μM, 48 h) can increase the cytotoxicity of PBMCs against A375 tumor cells by blocking PD-1/PD-L1 interaction and restoring the activation state of PBMCs, with little direct killing effect on tumor cells. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo PD-1/PD-L1-IN-29(S4-1)(10 or 25 mg/kg, i.p., 12 days) significantly inhibits tumour growth in the MC38 colorectal tumour mouse model, as observed in both the low and high dose groups (10 and 25 mg/kg), with inhibition rates of 65.9% and 88.8% respectively . The pharmacokinetic parameters of PD-1/PD-L1-IN-29(S4-1) in mice Parameters iv (5 mg/kg) po (50 mg/kg) T 1/2 (h) 9.78 4.77 T max (h) 0.08 0.92 C max (ng/mL) 6290 260.67 AUC 0-t (h*ng/mL) 3466.58/td> 808.04 AUC 0-∞ (h*ng/mL) 3566.62 830.34 CL (mL/h/kg) 1404.22 - MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid