Anti-PD-L1 antibodies (Atezolizumab, Durvalumab, Avelumab) block PD-L1 from binding both PD-1 and CD80 (B7-1), disrupting two inhibitory interactions simultaneously. They leave PD-1/PD-L2 signaling intact. Anti-PD-1 antibodies (Pembrolizumab, Nivolumab) block PD-1 from interacting with both PD-L1 and PD-L2 but do not affect the PD-L1/CD80 interaction. Additionally, the Fc engineering differs: Atezolizumab and Durvalumab have silenced Fc effector functions to avoid depleting PD-L1-expressing immune cells, while Avelumab retains native IgG1 ADCC activity.

Two scoring systems are used: Tumor Proportion Score (TPS) counts the percentage of viable tumor cells with partial or complete membrane PD-L1 staining; Combined Positive Score (CPS) includes PD-L1-positive tumor cells, lymphocytes, and macrophages divided by total viable tumor cells, multiplied by 100. The choice of scoring system and positivity cutoff varies by tumor type and specific checkpoint inhibitor indication. For research-grade IHC, our anti-PD-L1 antibodies are validated on FFPE sections with recommended Tris-EDTA pH 9.0 antigen retrieval.

Soluble PD-L1 is a shed or cleaved form of PD-L1 found in serum and plasma. Elevated sPD-L1 levels have been associated with poor prognosis and reduced response to checkpoint immunotherapy in multiple cancer types. Our PD-L1 ELISA kit quantifies sPD-L1 in human serum, plasma, and cell culture supernatants, making it suitable for both preclinical biomarker studies and clinical sample analysis.

For competitive ELISA-based blocking assays, use PD-L1-Fc chimera coated on plates paired with biotinylated PD-1 as the detection ligand. For cell-based reporter assays, PD-L1-expressing stable cell lines co-cultured with PD-1-expressing reporter cells provide a more physiologically relevant readout. For SPR/BLI kinetics of anti-PD-L1 candidates, use Avi-tagged or biotinylated PD-L1 ECD for oriented surface immobilization.

All three are anti-human PD-L1 antibodies but differ in isotype and Fc engineering. Atezolizumab is a humanized IgG1 with N297A mutation (Fc-silent). Durvalumab is a human IgG1 with L234F/L235E/P331S mutations (Fc-silent). Avelumab is a fully human IgG1 with wild-type Fc that retains ADCC activity, which may contribute to its anti-tumor mechanism. Our research-grade biosimilars replicate these differences and are suitable for head-to-head analytical comparability studies.