Pembrolizumab vs Durvalumab
## Overview
Pembrolizumab is an anti-PD-1 antibody; durvalumab (Imfinzi) is an anti-PD-L1 antibody with a specific niche in unresectable stage III NSCLC (following definitive chemoradiotherapy) established by the PACIFIC trial.
## Mechanism of Action
Pembrolizumab: anti-PD-1 (blocking PD-L1 and PD-L2). Durvalumab: anti-PD-L1 IgG1 with engineered Fc (no ADCC), blocking PD-L1 from binding both PD-1 and CD80 (B7.1).
## Key Clinical Indication: PACIFIC Trial
The PACIFIC trial (durvalumab maintenance after concurrent chemoradiotherapy for unresectable stage III NSCLC) demonstrated 33% improvement in OS and significant PFS benefit. This specific indication — stage III NSCLC post-CRT maintenance — is where durvalumab has its strongest evidence and is essentially the standard of care globally.
## Pharmacokinetics
Durvalumab: 10 mg/kg q2w or 1500 mg q4w IV, half-life ~17 days. Pembrolizumab: longer half-life (~26 days), q3w or q6w.
## Other Durvalumab Indications
Durvalumab + tremelimumab (CTLA-4 inhibitor) + chemotherapy for NSCLC (POSEIDON regimen). Durvalumab in bladder cancer, SCLC (CASPIAN trial), and biliary tract cancer (TOPAZ-1).
## Key Takeaways
- Durvalumab: definitive niche in unresectable stage III NSCLC post-CRT (PACIFIC trial)
- Pembrolizumab: broader first-line use in metastatic NSCLC and other tumor types
- Both anti-PD-(L)1 agents with similar irAE profiles
結論
Durvalumab is the standard-of-care agent for unresectable stage III NSCLC following chemoradiotherapy (PACIFIC trial). Pembrolizumab is the dominant agent for metastatic/first-line NSCLC and most other solid tumors. Their clinical niches are largely complementary rather than directly competitive.