Cosibelimab — Drug Monograph

Brand names: Unloxcyt

Drug class: Checkpoint Inhibitor

Mechanism of Action

Human IgG1 monoclonal antibody targeting programmed death-ligand 1 (PD-L1). Cosibelimab blocks PD-L1 from engaging PD-1 and B7.1 (CD80), releasing inhibition of tumor-specific T cells. Unlike PD-L1 antibodies engineered to be effector-null, cosibelimab retains a functional Fc domain and can additionally recruit antibody-dependent cellular cytotoxicity (ADCC) against PD-L1-expressing tumor cells, providing a potential dual mechanism.

FDA Indications

• Metastatic cutaneous squamous cell carcinoma (mcSCC) or locally advanced cutaneous squamous cell carcinoma (lacSCC) in adults who are not candidates for curative surgery or curative radiation (approved December 13, 2024)

Common Side Effects

• Fatigue
• Musculoskeletal pain
• Rash
• Diarrhea
• Anemia
• Constipation
• Nausea
• Pruritus

Clinical Pearl

Cosibelimab-ipdl is a PD-L1 inhibitor for advanced cutaneous squamous cell carcinoma that is unresectable or not curable with radiation, giving an alternative to the PD-1 agents cemiplimab and pembrolizumab. Its retained Fc effector function (ADCC) distinguishes it mechanistically from effector-silent PD-L1 antibodies.

Related Therapies & Mechanisms

• Atezolizumab (Tecentriq) — Checkpoint Inhibitor
• Avelumab (Bavencio) — Checkpoint Inhibitor
• Cemiplimab (Libtayo) — Checkpoint Inhibitor
• Dostarlimab (Jemperli) — Checkpoint Inhibitor