See the DrugPatentWatch profile for keytruda

Keytruda, a medication produced by Merck & Co. and used for the treatment of various forms of cancer, was first approved by the U.S. Food and Drug Administration (FDA) in 2014.

The FDA approved Keytruda (pembrolizumab) for the treatment of advanced melanoma in September 2014 [1]. Keytruda functions by targeting the PD-1/PD-L1 pathway, which are proteins that help regulate the immune system, and is often used when other treatments have not been effective.

According to DrugPatentWatch.com, Keytruda was originally patented in 2011 and the patent is set to expire in 2030 [2].

Sources:
[1] U.S. Food and Drug Administration. (2014, September 4). FDA approves new treatment for advanced skin cancer.
<https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-advanced-skin-cancer>
[2] DrugPatentWatch.com. (n.d.). Keytruda (pembrolizumab).
<https://www.drugpatentwatch.com/patent/keytruda-pembrolizumab-merck-sharp-dohme-corp-1/>