Pembrolizumab

Pembrolizumab, sold under the brand name Keytruda, is a humanized monoclonal antibody, more specifically a PD-1 inhibitor, used in cancer immunotherapy to treat many types of cancer. It is administered by slow intravenous injection.
Common side effects include fatigue, musculoskeletal pain, decreased appetite, itchy skin, diarrhea, nausea, rash, fever, cough, difficulty breathing, constipation, pain, and abdominal pain. It is an IgG4 isotype antibody that blocks a protective mechanism of cancer cells, allowing the immune system to destroy them. It targets the programmed cell death protein 1 receptor of lymphocytes.
Pembrolizumab was approved for medical use in the United States in 2014. It is on the World Health Organization's List of Essential Medicines. A fixed-dose combination of pembrolizumab and berahyaluronidase alfa, was approved for medical use in the United States in September 2025.

Medical uses

In the United States, pembrolizumab is indicated for the treatment of melanoma, non-small cell lung cancer, malignant pleural mesothelioma, head and neck squamous cell cancer, classical hodgkin lymphoma, primary mediastinal large B-cell lymphoma, urothelial cancer, microsatellite instability-high or mismatch repair deficient cancer, microsatellite instability-high or mismatch repair deficient colorectal cancer, gastric cancer, esophageal cancer, cervical cancer, hepatocellular carcinoma, biliary tract cancer, merkel cell carcinoma, renal cell carcinoma, endometrial carcinoma, tumor mutational burden-high cancer, cutaneous squamous cell carcinoma, and triple-negative breast cancer.
, pembrolizumab is used via intravenous infusion to treat inoperable or metastatic melanoma, metastatic non-small cell lung cancer in certain situations, as a first-line treatment for metastatic bladder cancer in people who cannot receive cisplatin-based chemotherapy and have high levels of PD-L1, as a second-line treatment for head and neck squamous cell carcinoma, after platinum-based chemotherapy, for the treatment of people with refractory classic Hodgkin lymphoma, and recurrent locally advanced or metastatic esophageal squamous cell carcinoma.
For non-small cell lung cancer, pembrolizumab is used in combination with chemotherapy or by itself as a first-line treatment if the cancer expresses PD-L1 and the cancer has no mutations in EGFR or in ALK; if chemotherapy has already been administered, then pembrolizumab can be used as a second-line treatment, but if the cancer has EGFR or ALK mutations, agents targeting those mutations should be used first. Assessment of PD-L1 expression must be conducted with a validated and approved companion diagnostic.
In 2017, the US Food and Drug Administration approved pembrolizumab for any unresectable or metastatic solid tumor with certain genetic anomalies. This was the first time the FDA approved a cancer drug based on tumor genetics rather than tissue type or tumor site; therefore, pembrolizumab is a so-called tissue-agnostic drug.
In the European Union, pembrolizumab is indicated for:

the treatment of advanced melanoma in adults as monotherapy.
the adjuvant treatment of adults with Stage III melanoma and lymph node involvement who have undergone complete resection as monotherapy.
the first-line treatment of metastatic non-small cell lung carcinoma in adults whose tumors express PD-L1 with a ≥ 50% tumor proportion score with no EGFR or ALK positive tumor mutations as monotherapy.
the first-line treatment of metastatic non-squamous non-small cell lung cancer in adults whose tumors have no EGFR or ALK positive mutations in combination with pemetrexed and platinum chemotherapy.
the first-line treatment of metastatic squamous non-small cell lung cancer in adults in combination with carboplatin and either paclitaxel or nab-paclitaxel.
the treatment of locally advanced or metastatic non-small cell lung cancer in adults whose tumors express PD-L1 with a ≥ 1% TPS and who have received at least one prior chemotherapy regimen. People with EGFR or ALK positive tumor mutations should also have received targeted therapy before receiving Keytruda as monotherapy.
the treatment of adults with relapsed or refractory classical Hodgkin lymphoma who have failed autologous stem cell transplant and brentuximab vedotin, or who are transplant-ineligible and have failed BV as monotherapy.
the treatment of locally advanced or metastatic urothelial carcinoma in adults who have received prior platinum-containing chemotherapy as monotherapy.
the treatment of locally advanced or metastatic urothelial carcinoma in adults who are not eligible for cisplatin-containing chemotherapy and whose tumors express PD L1 with a combined positive score ≥ 10 as monotherapy.
the first-line treatment of metastatic or unresectable recurrent head and neck squamous cell carcinoma in adults whose tumors express PD-L1 with a CPS ≥ 1 as monotherapy or in combination with platinum and 5-fluorouracil chemotherapy.
the treatment of recurrent or metastatic head and neck squamous cell carcinoma in adults whose tumors express PD-L1 with a ≥ 50% TPS and progressing on or after platinum-containing chemotherapy as monotherapy.
the first-line treatment of advanced renal cell carcinoma in adults in combination with axitinib.

In June 2020, the US FDA approved an indication for pembrolizumab as the first-line treatment for people with unresectable or metastatic microsatellite instability-high or mismatch repair deficient colorectal cancer. The approval marks the first immunotherapy approved for that population in the US as a first-line treatment and which is administered to people without also giving chemotherapy.
In March 2021, the US FDA approved pembrolizumab in combination with platinum and fluoropyrimidine-based chemotherapy to treat metastatic or locally advanced esophageal or gastroesophageal carcinoma in people who are not candidates for surgical resection or definitive chemoradiation. Efficacy was evaluated in KEYNOTE-590, a multicenter, randomized, placebo-controlled trial that enrolled 749 participants with metastatic or locally advanced esophageal or gastroesophageal junction carcinoma who were not candidates for surgical resection or definitive chemoradiation.
In May 2021, the US FDA approved pembrolizumab in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy for the first-line treatment of people with locally advanced unresectable or metastatic HER2 positive gastric or gastroesophageal junction adenocarcinoma. Approval was based on the prespecified interim analysis of the first 264 participants of the ongoing KEYNOTE-811 trial, a multicenter, randomized, double‑blind, placebo‑controlled trial in participants with HER2‑positive advanced gastric or gastroesophageal junction adenocarcinoma who had not previously received systemic therapy for metastatic disease.
In July 2021, the US FDA approved pembrolizumab for high-risk, early-stage, triple-negative breast cancer in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery. The FDA also granted regular approval to pembrolizumab in combination with chemotherapy for people with locally recurrent unresectable or metastatic triple-negative breast cancer whose tumors express PD-L1 as determined by an FDA-approved test.
In November 2021, the US FDA approved pembrolizumab for the adjuvant treatment of people twelve years of age and older with stage IIB or IIC melanoma following complete resection.
In November 2021, the US FDA approved pembrolizumab for the adjuvant treatment of renal cell carcinoma for people at intermediate-high or high risk of recurrence following nephrectomy. Approval was based on KEYNOTE-564, a multicenter, randomized, double-blind, placebo-controlled trial in 994 participants with intermediate-high or high risk of recurrence of RCC, or M1 no evidence of disease.
In March 2022, the US FDA approved pembrolizumab for the treatment of advanced endometrial cancer.
In January 2023, the US FDA approved pembrolizumab for adjuvant treatment following resection and platinum-based chemotherapy for stage IB, II, or IIIA non-small cell lung cancer.
In October 2023, the US FDA approved pembrolizumab to be used with gemcitabine and cisplatin for locally advanced unresectable or metastatic biliary tract cancer.
In January 2024, the US FDA approved pembrolizumab, in combination with chemoradiotherapy for the treatment of people with FIGO 2014 Stage III-IVA cervical cancer.
In June 2024, the US FDA approved pembrolizumab with carboplatin and paclitaxel, followed by single-agent pembrolizumab, for adults with primary advanced or recurrent endometrial carcinoma.
In September 2024, the US FDA approved pembrolizumab with pemetrexed and platinum chemotherapy as first-line treatment of unresectable advanced or metastatic malignant pleural mesothelioma.
In March 2025, the US FDA granted traditional approval to pembrolizumab with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy for the first-line treatment of adults with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma whose tumors express PD-L1. Pembrolizumab previously received accelerated approval for this indication in May 2021. Efficacy was evaluated in KEYNOTE-811, a multicenter, randomized, double-blind, placebo-controlled trial enrolling 698 participants with HER2-positive advanced gastric or GEJ adenocarcinoma not previously treated with systemic therapy for metastatic disease. Among the 698 participants, 594 had tumors expressing PD-L1 with a CPS ≥1 using the PD-L1 IHC 22C3 pharmDx kit. Participants were randomized to pembrolizumab 200 mg or placebo, in combination with trastuzumab and either fluorouracil plus cisplatin or capecitabine plus oxaliplatin.
In June 2025, the US FDA approved neoadjuvant and adjuvant pembrolizumab for resectable locally advanced head and neck squamous cell carcinoma. The FDA approved pembrolizumab for adults with resectable locally advanced head and neck squamous cell carcinoma whose tumors express PD-L1 as determined by an FDA-approved test, as a single agent as neoadjuvant treatment, continued as adjuvant treatment in combination with radiotherapy with or without cisplatin after surgery, and then as a single agent. It is the first approval for head and neck squamous cell carcinoma in six years and the first overall perioperative approval for locally advanced head and neck squamous cell carcinoma.
In November 2025, the US FDA approved pembrolizumab or pembrolizumab and berahyaluronidase alfa with enfortumab vedotin as neoadjuvant treatment followed by adjuvant treatment after cystectomy for adults with muscle invasive bladder cancer who are ineligible for cisplatin.