Keytruda is a monoclonal antibody — a protein that binds to specific ligands — developed by Merck and used in cancer therapy. Keytruda works by increasing the immune system’s ability to help detect and fight tumor cells.

Keytruda binds to specific receptors present on the surface of immune cells called programmed cell death 1 (PD-1) and blocks their interaction with their ligands, PD-L1 and PD-L2. Under normal circumstances, PD-1 constitutes an immune checkpoint that prevents the immune response from attacking the body’s own cells. Thus, blocking the PD-1 receptor with Keytruda activates the immune system, particularly the tumor-killing T-lymphocytes, allowing them to destroy cancer cells.

Keytruda FDA Approval Status

The U.S. Food and Drug Administration (FDA) initially approved Keytruda in October 2015, as a second-line treatment — or one used after tumor progression has continued under traditional treatments — for metastatic non-small cell lung cancer (NSCLC), with high PD-L1 expression determined by an FDA-approved diagnostic test (PD-L1 IHC 22C3 pharmDx).

This was expanded in October, 2016, when the FDA approved Keytruda to be used as a first-line treatment for NSCLC. This approval has two indications. The first is metastatic NSCLC with high PD-L1 expression without EGFR (epidermal growth factor receptor) or ALK (anaplastic lymphoma kinase) mutations and no prior chemotherapy treatment. The second is metastatic NSCLC with PD-L1 expression where the disease progressed during or after platinum-based chemotherapy, NSCLC patients who have EGFR or ALK mutations must have received FDA-approved therapies prior to receiving Keytruda.

The FDA has put Keytruda on an accelerated approval track as a first-line combo treatment for metastatic non-squamous NSCLC alongside Alimta (pemetrexed) or Paraplatin (carboplatin) as a first-line therapy. Unlike the previous FDA approval, this treatment can be applied regardless of the patients’ PD-L1 levels. On the accelerated approval track, the treatment can be prescribed to patients, but continued FDA approval will depend on the results of ongoing clinical trials.

On May 23, 2017, Keytruda became the first drug to be granted accelerated approval to treat tumors based on a genetic marker as opposed to location. This is for the treatment of unresectable or metastatic solid tumors with the biomarkers microsatellite instability high (MSI-H) or mismatch repair deficient (dMMR). The approval was based on five KEYNOTE clinical trials, including 149 patients with 15 cancer types. Most were colorectal tumors, but one patient had small cell lung cancer, which could lead to potential advancements in the future.

Drug indications

Your doctor will usually perform tests to make sure Keytruda is the best treatment for you. If so, the drug will be given as a 30-minute intravenous infusion every three weeks for the approved indications until the disease progresses or reaches unacceptable toxicity levels. The drug is supplied in 100 mg single-dose vials.

Keytruda can pass into urine and other body fluids, so avoid contact with such fluids for at least 48 hours after receiving a dose.

Side effects

Keytruda can cause the immune system to attack normal organs and tissues in the body, resulting in serious or fatal side effects.

Some patients have had severe infusion-related reactions to Keytruda, such as chills, shortness of breath, itching, flushing or fever. The drug has also caused severe immune-related adverse effects including inflammation of the liver, lungs and endocrine organs (pituitary gland, thyroid gland and pancreas). Other side effects include colon inflammation and kidney problems. Common adverse reactions are fatigue, rash, itchiness, diarrhea, nausea and joint pain.

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