Pembrolizumab vs Atezolizumab
## Overview
Pembrolizumab is an anti-PD-1 antibody; atezolizumab (Tecentriq) is an anti-PD-L1 antibody. This represents a mechanistic distinction: PD-1 blockade (pembrolizumab) removes inhibitory signals from T cells, while PD-L1 blockade (atezolizumab) targets the ligand on tumor cells and APCs.
## Mechanism of Action
Pembrolizumab: blocks PD-1 receptor on T cells, preventing both PD-L1 and PD-L2 binding. Atezolizumab: blocks PD-L1 on tumor/immune cells, preventing binding to PD-1 (maintaining PD-L2/PD-1 interaction intact). The clinical significance of sparing PD-L2 signaling is uncertain.
## Pharmacokinetics
Pembrolizumab: q3w or q6w IV. Atezolizumab: 1200 mg q3w IV (or 1680 mg q4w). Half-life of atezolizumab ~27 days.
## Key Indications
Pembrolizumab: melanoma, NSCLC (PD-L1+), urothelial, HNSCC, cervical, hepatocellular, endometrial, TMB-high, MSI-H (broad). Atezolizumab: NSCLC (TECENTRIQ), urothelial carcinoma, small-cell lung cancer (1L combination), hepatocellular carcinoma (IMBRAVE150 with bevacizumab), alveolar soft part sarcoma.
## Key Distinctions
Atezolizumab has a unique approval in hepatocellular carcinoma in combination with bevacizumab (IMbrave150), offering a non-sorafenib first-line option. Pembrolizumab + lenvatinib is an alternative HCC regimen. In NSCLC with EGFR/ALK alterations, atezolizumab combinations differ in evidence from pembrolizumab.
## Key Takeaways
- Pembrolizumab: anti-PD-1; blocks both PD-L1 and PD-L2; broader indications
- Atezolizumab: anti-PD-L1; unique HCC + bevacizumab approval; SCLC combination
- Both IgG4-based; similar irAE profiles
Заключение
Pembrolizumab has broader approval and is preferred for most solid tumors where PD-1/PD-L1 therapy is indicated. Atezolizumab is specifically preferred for HCC (atezolizumab + bevacizumab is a standard first-line regimen) and SCLC first-line combination. Companion diagnostic assays differ between the two.