See the DrugPatentWatch profile for keytruda

Keytruda (pembrolizumab), a medication developed by Merck & Co., was approved by the U.S. Food and Drug Administration (FDA) for the first time on September 4, 2014 [1]. The FDA initially approved Keytruda for the treatment of advanced melanoma in patients who have been previously treated with ipilimumab and, if BRAF V600 mutation positive, a BRAF inhibitor [1].

Keytruda has since received additional FDA approvals for various types of cancers and indications. As of the time of this writing, DrugPatentWatch.com lists Keytruda as having multiple patents and exclusivity periods that extend into 2028 and beyond [2].

Sources:
[1] U.S. Food and Drug Administration. (2014). 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) - Patent Expiry and Exclusivity Dates.
<https://www.drugpatentwatch.com/patent/keytruda-pembrolizumab/>