Keytruda (pembrolizumab) is a brand-name intravenous infusion prescribed for certain types of cancer. It works by blocking the activity of specific receptors, which stops cancer cells from growing.

Keytruda allows your immune cells to fight cancer cells, slowing the progression of cancer growth.

Keytruda belongs to a group of drugs called programmed death receptor-1 (PD-1) inhibitors. Keytruda is also an immunotherapy. This means that it helps your immune system attack cancer cells.

Keytruda works by inhibiting (blocking) the activity of proteins called PD-L1 and PD-L2. These proteins bind to PD-1 receptors (binding sites) on both cancer cells and healthy cells.

Your immune system sees cancer cells as foreigners or invaders. When the PD-L1 and PD-L2 proteins bind to the PD-1 receptor, it sends a message to T cells (immune system cells): “Stop attacking invaders!” This allows cancer cells to continue growing without being attacked by the immune system.

Keytruda interrupts this process. The drug binds to PD-1 receptors, preventing PD-L1 and PD-L2 from binding.

By doing this, Keytruda allows T cells to perform their protective work and continue attacking cancer cells. This, in turn, prevents cancer from growing and spreading.

It depends. The timing of when Keytruda starts to work varies from person to person and may depend on the type and stage of cancer.

A doctor can help determine whether Keytruda is being effective. They may look for signs that Keytruda is working, such as:

  • decreased size or lack of growth in a tumor (using imaging tests)
  • changes in the levels of certain cancer biomarkers (using blood tests)
  • decrease in intensity or frequency of cancer symptoms, such as pain, fatigue, or difficulty breathing
  • improvement in overall health and quality of life

Keytruda stays in your system for up to 4 months after your last dose.

The drug has a half-life of 22 days. This means it takes your body 22 days to clear half of a Keytruda dose.

Due to Keytruda’s long-acting effects, certain precautions are recommended after treatment ends.

If you can become pregnant, experts recommend using birth control for 4 months after your last dose. They also recommend avoiding nursing for 4 months after your last dose.

Keytruda blocks two specific proteins from interacting with each other, which allows your immune system to inhibit the growth of cancer cells.

A doctor will confirm that Keytruda is working if a tumor stops growing or shrinks in size.

After stopping treatment, Keytruda takes about 4 months to clear from your system.

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