Introduction

• Keytruda is the brand name of pembrolizumab. It is a prescription anti-cancer immunotherapy medicine.
• It was first approved in the United States in 2014.
• It is given mainly as:
  • an intravenous injection
  • and, in the U.S., a newer subcutaneous formulation called Keytruda Qlex for eligible solid-tumor indications.

Generic name

• The generic name of Keytruda is pembrolizumab.

Drug class

• Keytruda is a PD-1 blocking antibody.
• It belongs to the broader class of immune checkpoint inhibitors used in oncology.

How it works

• Pembrolizumab works by blocking the PD-1 receptor on immune cells.
• By blocking PD-1, it prevents some cancers from switching off the immune response, thereby helping the immune system attack cancer cells more effectively.

Main purpose

• Keytruda is used to treat many different cancers, not just one disease.
• Depending on the cancer type, it may be used:
  • alone
  • with chemotherapy
  • with targeted therapy
  • or in perioperative / neoadjuvant / adjuvant settings in some cancers.

Cancers for which it is used

• Current official prescribing information lists Keytruda across multiple cancers, including examples such as:
  • melanoma
  • non-small cell lung cancer
  • head and neck squamous cell carcinoma
  • classical Hodgkin lymphoma
  • primary mediastinal large B-cell lymphoma
  • urothelial cancer
  • esophageal cancer
  • triple-negative breast cancer
  • cervical cancer
  • endometrial carcinoma
  • gastric / gastroesophageal junction cancers
  • certain MSI-H / dMMR tumors.

Biomarker relevance

• In several indications, use of Keytruda depends on tumor biomarkers such as:
  • PD-L1 expression
  • MSI-H
  • dMMR
  • sometimes other tumor-specific eligibility criteria.
• This means it is not simply given for all patients with a particular cancer; eligibility can depend on test results.

Route of administration

• The standard Keytruda product is given by intravenous infusion.
• The U.S. also has Keytruda Qlex, a subcutaneous injection formulation containing pembrolizumab and berahyaluronidase alfa-pmph.

Common dosing pattern

• Official U.S. dosing commonly includes:
  • 200 mg every 3 weeks, or
  • 400 mg every 6 weeks for the IV formulation in many adult indications.
• Dosing and duration vary by indication, age group, combination regimen, and whether treatment is curative-intent or metastatic.

Why Keytruda is important

• Keytruda became one of the most important modern cancer drugs because it helped expand the role of immunotherapy in cancer treatment.
• Its importance lies in shifting treatment in many cancers from only killing tumor cells directly to also activating the immune system against the tumor. This is a medical inference supported by its PD-1 mechanism and broad approvals.

Major side-effect principle

• Because Keytruda activates the immune system, it can also make the immune system attack normal organs and tissues.
• The most important safety concept is therefore immune-mediated adverse reactions.

Important serious side effects

• Official safety information warns about serious immune-related problems affecting organs such as:
  • lungs (pneumonitis)
  • intestines (colitis)
  • liver (hepatitis)
  • hormone glands such as thyroid, pituitary, adrenal glands, pancreas
  • kidneys (nephritis)
  • skin
  • and other organ systems.
• These side effects can sometimes become severe or life-threatening if not recognised early.

Infusion and injection reactions

• Keytruda can also cause infusion-related reactions with IV use.
• The subcutaneous formulation can also have administration-related or hypersensitivity-type issues in line with product safety warnings.

Use in pregnancy

• Official prescribing information warns that Keytruda can harm an unborn baby.
• Contraception and pregnancy-related counseling are important where relevant.

Monitoring importance

• Patients on Keytruda usually need monitoring for:
  • symptoms of immune toxicity
  • blood tests
  • liver and kidney function
  • endocrine function in appropriate settings.
• This is because some side effects may first appear as lab abnormalities before obvious symptoms. This is a standard clinical inference supported by the warning framework in the label.

Recent development

• A recent major development is the U.S. approval of Keytruda Qlex in September 2025 as a subcutaneous version for approved adult and pediatric solid-tumor indications of IV pembrolizumab.
• The U.S. prescribing information was also updated in February 2026 for both IV Keytruda and Keytruda Qlex.

Key points to remember

• Keytruda = pembrolizumab.
• It is a PD-1 inhibitor / immune checkpoint inhibitor.
• It is used in many cancers, often depending on biomarkers and treatment setting.
• It may be given alone or in combination with other cancer treatments.
• The biggest safety issue is immune-related side effects affecting normal organs.
• A subcutaneous formulation called Keytruda Qlex is now approved in the U.S. for relevant solid-tumor indications.

Conclusion

• Keytruda is one of the most important modern cancer immunotherapy medicines.
• Its significance lies in using the immune system to fight cancer, but it also requires careful patient selection and close monitoring because immune activation can cause serious side effects.