An introduction to pembrolizumab (Keytruda®) and its common usage and dosage.👀👀👀

Pembrolizumab is a monoclonal antibody. It is a programmed death receptor-1 (PD-1) blocker. The PD-1 receptor expressed by T cells binds to its ligands PD-L1 and PD-L2, thereby inhibiting T cell proliferation and cytokine production. PD-1 ligands are upregulated in some tumor cells. Signaling in this pathway can help inhibit active T cell immune surveillance of tumors. Pembrolizumab can bind to the PD-1 receptor. Blocking the binding of PD-1 to PD-L1 and PD-L2 will relieve the suppression of immune responses mediated by the PD-1 pathway. Therefore, the growth of tumor cells will also be inhibited. Pembrolizumab can be used clinically to treat a variety of cancers.

Common Pediatric Usage and Dosage of Pembrolizumab:

Indications	Usual dose for adults	Usual dose for children
Melanoma	For the treatment of unresectable or metastatic melanoma that has failed first-line therapy   200 mg once every three weeks or 400 mg once every six weeks until disease progression or unacceptable toxicity, or up to 12 months.	For adjuvant treatment of melanoma in children 12 years and older.   2 mg/kg every 3 weeks, up to 200 mg. Until disease progression, unacceptable toxicity, or up to 12 months.
Non-small cell lung cancer (NSCLC)	It is used as a first-line monotherapy for locally advanced or metastatic non-small cell lung cancer with negative epidermal growth factor receptor (EGFR) gene mutation and negative anaplastic lymphoma kinase (ALK) as assessed by PD-L1 tumor proportion score (TPS) ≥ 1%. It is used in combination with carboplatin and paclitaxel for the first-line treatment of patients with metastatic squamous non-small cell lung cancer.   The recommended dose for monotherapy or combination chemotherapy is 200 mg once every three weeks or 400 mg once every six weeks.   Monotherapy or combination chemotherapy: until disease progression or unacceptable toxicity, or up to 24 months.   Adjuvant monotherapy: until disease progression or unacceptable toxicity, or up to 12 months.   For resectable non-small cell lung cancer, if it is given on the same day as chemotherapy, it should be given before chemotherapy. Neoadjuvant combination chemotherapy for 12 weeks or until disease progression that precludes radical surgery or unacceptable toxicity, followed by pembrolizumab as a single-agent adjuvant therapy after surgery for 39 weeks or until disease recurrence or unacceptable toxicity.
Esophageal cancer	Pembrolizumab is used in combination with fluorouracil and platinum chemotherapy for the first-line treatment of patients with locally advanced, unresectable or metastatic esophageal or gastroesophageal junction cancer. Pembrolizumab can also be used to treat patients with locally advanced or metastatic esophageal squamous cell carcinoma (ESCC) whose tumors express PD-L1 (CPS ≥ 10) and who have failed previous first-line systemic therapy.   The recommended dose for monotherapy or in combination with chemotherapy is 200 mg once every three weeks or 400 mg once every six weeks until disease progression or unacceptable toxicity, or up to 24 months. If pembrolizumab is administered on the same day as chemotherapy, it should be administered before chemotherapy.
Classical Hodgkin's lymphoma (cHL)	Recommended monotherapy dose: 200 mg once every three weeks or 400 mg once every six weeks until disease progression or unacceptable toxicity, or up to 24 months. (For patients with cHL, an additional 400 mg dose is recommended every six weeks.)	2 mg/kg once every 3 weeks, up to a maximum of 200 mg, until disease progression or unacceptable toxicity, or up to 24 months.
Primary mediastinal large B-cell lymphoma (PMBCL)	Recommended monotherapy dose: 200 mg once every three weeks or 400 mg once every six weeks until disease progression or unacceptable toxicity, or up to 24 months. (For adult patients with PMBCL, an additional 400 mg dose is recommended every six weeks.)	2 mg/kg once every 3 weeks, up to a maximum of 200 mg, until disease progression or unacceptable toxicity, or up to 24 months.
Urothelial carcinoma	Pembrolizumab is indicated for the treatment of patients with locally advanced or metastatic urothelial carcinoma who are not eligible for cisplatin-containing chemotherapy. Pembrolizumab is indicated for the treatment of patients with BCG-unresponsive, high-risk, non-muscle invasive bladder cancer (NMIBC) with carcinoma in situ (CIS) with or without papillary tumors who are not eligible or who choose not to undergo cystectomy.   Recommended dose: 200 mg every three weeks or 400 mg every six weeks until persistent or recurrent high-risk urothelial carcinoma, disease progression, or unacceptable toxicity, or up to 24 months.
High-microsatellite instability/mismatch repair deficiency cancer	Recommended monotherapy dose: 200 mg once every three weeks or 400 mg once every six weeks until disease progression or unacceptable toxicity, or up to 24 months.	2 mg/kg once every 3 weeks, up to a maximum of 200 mg, until disease progression or unacceptable toxicity, or up to 24 months.
Gastric cancer	Pembrolizumab can be used as first-line treatment for patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma.   Pembrolizumab should be given before trastuzumab and chemotherapy. The dose is 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.
Cervical cancer	Pembrolizumab can be used with or without bevacizumab for the treatment of patients with persistent, recurrent, or metastatic cervical cancer whose tumors express PD-L1 (CPS ≥ 1).   Pembrolizumab should be given before bevacizumab. The dose is 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.
Hepatocellular carcinoma (HCC)	Pembrolizumab is used to treat hepatocellular carcinoma in patients who have received prior sorafenib or oxaliplatin-containing chemotherapy.   Recommended dose for monotherapy: 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.
Merkel cell carcinoma (MCC)	Pembrolizumab is used to treat adult patients with recurrent locally advanced or metastatic Merkel cell carcinoma.   Recommended dose: 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.	Pembrolizumab is used to treat pediatric patients with Merkel cell carcinoma.   2 mg/kg once every 3 weeks, up to a maximum of 200 mg, until disease progression or unacceptable toxicity, or up to 24 months.
Renal cell carcinoma (RCC)	Pembrolizumab is indicated as first-line treatment for adult patients with advanced renal cell carcinoma. Adjuvant treatment for patients with renal cell carcinoma who are at intermediate or high risk of recurrence after nephrectomy or nephrectomy and resection of metastatic disease   200 mg every three weeks or 400 mg every six weeks.   Combined with oral axitinib (5 mg twice a day) or lenvatinib (20 mg once a day). When pembrolizumab is used in combination with axitinib, it may be considered to increase the dose of axitinib above the initial dose of 5 mg at intervals of six weeks or longer.   Duration of monotherapy: until disease progression or unacceptable toxicity or up to 12 months.   Duration of Combination Therapy: Until disease progression or unacceptable toxicity or Pembrolizumab is given for up to 24 months.
Endometrial cancer	Pembrolizumab combined with lenvatinib can be used in patients with non-MSI-H pMMR advanced endometrial cancer who have disease progression after prior systemic therapy and are not suitable for curative surgery or radiotherapy: 200 mg once every three weeks or 400 mg once every six weeks, combined with lenvatinib 20 mg once daily, until disease progression or unacceptable toxicity or pembrolizumab for up to 24 months.   Monotherapy can be used to treat patients with MSI-H/dMMR advanced endometrial cancer who have disease progression after prior systemic therapy and are not candidates for curative surgery or radiation therapy in any setting: 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.
High tumor mutation burden cancer	Pembrolizumab is indicated for the treatment of adult patients with unresectable or metastatic solid tumors with high tumor mutational burden (TMB-H, ≥10 mutations/megabase/Mb) who have progressed after prior therapy and have no satisfactory alternative treatment options.   Recommended dose for monotherapy: 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.	Pembrolizumab can be used to treat pediatric cancers with high tumor mutation burden.   Recommended dose: 2 mg/kg once every 3 weeks, up to a maximum of 200 mg, until disease progression or unacceptable toxicity, or up to 24 months.
Cutaneous squamous cell carcinoma (cSCC)	Pembrolizumab can be used to treat patients with recurrent or metastatic cSCC or locally advanced cSCC that is not curable with surgery or radiation therapy.   Recommended dose for monotherapy: 200 mg every three weeks or 400 mg every six weeks until disease progression or unacceptable toxicity or up to 24 months.
Triple-negative breast cancer (TNBC)	Pembrolizumab can be used in combination with neoadjuvant chemotherapy and continued as an adjuvant pembrolizumab monotherapy after surgery in patients with early-stage, high-risk TNBC whose tumors express PD-L1 (CPS ≥ 20) as assessed by a well-validated test.   In neoadjuvant therapy, patients should receive pembrolizumab 200 mg every three weeks for eight times or 400 mg every six weeks for four times, or until disease progression precluding radical surgery or unacceptable toxicity, followed by adjuvant pembrolizumab monotherapy. In adjuvant monotherapy, pembrolizumab is given at 200 mg every three weeks for nine times or 400 mg every six weeks for five times, or until disease relapse or unacceptable toxicity.   If patients have disease progression that precludes radical surgery or experience intolerable pembrolizumab-related toxicity during neoadjuvant therapy, they should not continue to receive adjuvant pembrolizumab monotherapy.

No dose adjustment is required for patients with mild hepatic impairment, mild or moderate renal impairment, and the elderly.