In vivo antitumor activity of P39. hPD-1-knockin C57BL/6 mice bearing Lewis lung carcinoma (LLC) cells overexpressing hPD-L1 (LLC-hPD-L1) were treated with PBS, BMS202 (10 mg/kg) and P39 (10 and 25 mg/kg). The tumor growth was monitored (n = 6). (A) Ex vivo observation of the tumors from the treated mice. (B) Comparison of the weight of the tumors from the mice treated with PBS, BMS202 or P39. (C) Body weight of the treated mice was measured every 2 days. (D) Tumor volume was measured every 2 days. (E) Flow cytometry analysis of infiltrating CD8+ T cells (n = 6) frequency in BMS202 or P39 treated mice. (F and G) Flow cytometry detecting the IFN-γ (F) and GzmB level (G) in CD3+ CD8+ TILs from PBS, BMS202 or P39 treated tumors (n = 6). Data shown are mean value ± standard error of mean (SEM). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ns, no significant.