Expanded PBS Listing for Pembrolizumab

The Pharmaceutical Benefits Scheme (PBS) listing for pembrolizumab has been expanded to include squamous cell carcinoma of the head and neck.

Pembrolizumab is also PBS subsidised for the treatment of some forms of:

• Malignant melanoma;
• Hodgkin lymphoma;
• Non-small cell lung cancer;
• Urothelial cancer;
• Primary mediastinal B-cell lymphoma;
• Deficient mismatch repair (dMMR) colorectal cancer; and
• Squamous cell carcinoma of the oral cavity, pharynx, or larynx.

Pembrolizumab is a monoclonal antibody with a high affinity against the programmed death 1 (PD‑1) receptor. Ligands that bind to PD-1 receptors include PD-L1 and PD-L2, with PD-L1 overexpressed on some cancer cells. Activation of the PD-1 pathway negatively regulates T-lymphocyte activity and helps tumours evade host immunity. Therefore, pembrolizumab’s inhibition of the PD-1 receptor can reactivate tumour-specific cytotoxic T-cells and enhance anti-tumour immunity.

The KEYNOTE-048 trial investigated the safety and efficacy of pembrolizumab in recurrent or metastatic squamous cell carcinoma of the head and neck. Patients were randomly assigned to receive pembrolizumab alone, pembrolizumab with chemotherapy (5-fluorouracil and a platinum), or cetuximab with chemotherapy (5-fluorouracil and a platinum). The trial authors conclude that pembrolizumab plus chemotherapy is an appropriate first-line option for recurrent or metastatic head and neck cancer, and pembrolizumab monotherapy is an appropriate option in this patient group where tumours express PD-L1.

The most frequently reported adverse events in the pembrolizumab monotherapy group were fatigue, anaemia, and constipation. Common adverse events in the pembrolizumab plus chemotherapy group include anaemia, nausea, constipation, neutropenia, and thrombocytopenia.