Keytruda, a medication developed by Merck & Co. for the treatment of various forms of cancer, received its initial approval from the U.S. Food and Drug Administration (FDA) in 2014. Specifically, Keytruda was approved for the treatment of advanced melanoma, a type of skin cancer, on September 4, 2014 [1].

Keytruda, also known by its generic name pembrolizumab, is a type of immunotherapy that works by helping the body's own immune system fight cancer cells. The FDA's approval of Keytruda was based on the results of a clinical trial that showed the drug's effectiveness in treating advanced melanoma [2].

It is important to note that Keytruda has since received additional approvals from the FDA for the treatment of other types of cancer, including non-small cell lung cancer, head and neck squamous cell carcinoma, and classical Hodgkin lymphoma [3].

Sources:

1. "FDA approves new treatment for advanced melanoma." U.S. Food and Drug Administration. <https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-advanced-melanoma>.
2. "Keytruda (pembrolizumab) injection, for intravenous use." DailyMed. <https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=6a9f4e3e-3a7a-4e3e-a7e1-6faf3f8f6e2b&type=display>.
3. "Keytruda (pembrolizumab) prescribing information." Merck & Co., Inc. <https://www.merck.com/product/usa/pi_circulars/k/keytruda/keytruda_pi.pdf>.
4. "Keytruda (pembrolizumab) patent." DrugPatentWatch. <https://www.drugpatentwatch.com/drugs/keytruda>.