Last reviewed 2026-04-22 · How we verify

A166

A166 is an anti-PD-L1 monoclonal antibody that blocks the interaction between PD-L1 on tumor cells and PD-1/B7.1 on immune cells, thereby restoring anti-tumor immune responses.

A166 is an anti-PD-L1 monoclonal antibody that blocks the interaction between PD-L1 on tumor cells and PD-1/B7.1 on immune cells, thereby restoring anti-tumor immune responses. Used for Non-small cell lung cancer, Other solid tumors (under investigation in Phase 3).

At a glance

Mechanism of action

By inhibiting the PD-L1/PD-1 axis, A166 removes the immunosuppressive signal that tumors use to evade T-cell recognition and killing. This checkpoint inhibition allows cytotoxic T lymphocytes to recognize and eliminate cancer cells more effectively. The drug is being developed by Sichuan Kelun-Biotech as a potential immunotherapy for various solid tumors.

Approved indications

• Non-small cell lung cancer
• Other solid tumors (under investigation in Phase 3)

Common side effects

• Fatigue
• Decreased appetite
• Immune-related adverse events
• Infusion-related reactions

Key clinical trials

• A Study of A166 in Patients With HER2-Positive Unresectable or Metastatic Breast Cancer (PHASE2)
• A Study of A166 in Patients With Advanced Solid Malignant Tumors (PHASE1)
• A Study of A166 Versus Trastuzumab Emtansine (T-DM1) in Patients With HER2-Positive Unresectable or Metastatic Breast Cancer Previously Treated With Trastuzumab and Taxane Therapy (PHASE3)
• Study of A166 in Patients With Relapsed/Refractory Cancers Expressing HER2 Antigen or Having Amplified HER2 Gene (PHASE1, PHASE2)
• HER2-positive Breast Cancer Project Initiated by Investigators (PHASE2)

Primary sources

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