Pembrolizumab is
**Pembrolizumab is a monoclonal antibody targeting PD-1 receptor, used in the treatment of various cancers.**
**Core Concept**
Pembrolizumab is a checkpoint inhibitor that works by targeting the PD-1 receptor on T cells. This receptor is normally involved in the suppression of the immune response to prevent autoimmune diseases. However, in the context of cancer, tumor cells can exploit this mechanism by expressing PD-L1, a ligand that binds to PD-1, leading to immune suppression.
**Why the Correct Answer is Right**
Pembrolizumab binds to PD-1, blocking its interaction with PD-L1 and preventing the suppression of T-cell responses. This allows the immune system to recognize and attack cancer cells more effectively. Pembrolizumab is used in the treatment of various types of cancer, including melanoma, non-small cell lung cancer, and head and neck cancer. It has shown significant clinical efficacy in these diseases, with improved overall survival and response rates.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pembrolizumab does not target CTLA-4, another checkpoint receptor involved in immune suppression.
**Option B:** This option is incorrect because pembrolizumab is not a tyrosine kinase inhibitor, which is a different class of cancer therapy.
**Option C:** This option is incorrect because pembrolizumab is not a chemotherapy agent, which works by directly killing rapidly dividing cells.
**Clinical Pearl / High-Yield Fact**
Pembrolizumab has been shown to have a favorable side effect profile compared to traditional chemotherapy, with fewer toxicities and improved quality of life for patients. However, it can cause immune-related adverse events, such as pneumonitis and colitis, which require careful monitoring and management.
**Correct Answer: C. Pembrolizumab is a monoclonal antibody targeting PD-1 receptor, used in the treatment of various cancers.**