Keytruda, a medication developed by Merck & Co., was first approved by the U.S. Food and Drug Administration (FDA) for cancer treatment in 2014. Specifically, it was approved for the treatment of advanced melanoma in patients who had previously received other forms of therapy [1].

Keytruda, also known as pembrolizumab, is a type of drug called a programmed death receptor-1 (PD-1) blocking antibody. It works by helping the body's immune system fight cancer cells [2].

It's important to note that Keytruda has since been approved for the treatment of several other types of cancer, including certain types of lung, head and neck, and Hodgkin lymphoma [3].

Sources:

[1] "FDA approves new therapy for advanced melanoma." U.S. Food and Drug Administration. FDA.gov. September 4, 2014. Available at: <https://www.fda.gov/news-events/press-announcements/fda-approves-new-therapy-advanced-melanoma>.

[2] "Keytruda (pembrolizumab): Drug Information." RxList. RxList.com. February 15, 2022. Available at: <https://www.rxlist.com/keytruda-drug.htm>.

[3] "Keytruda (pembrolizumab): Side Effects, Interactions, Warning, Dosage & Uses." Drugs.com. Drugs.com. February 15, 2022. Available at: <https://www.drugs.com/keytruda.html>.

[4] "Keytruda (pembrolizumab) Patent Information." DrugPatentWatch. DrugPatentWatch.com. February 15, 2022. Available at: <https://www.drugpatentwatch.com/drugs/keytruda>.