Which company holds keytruda's patents?

Who owns Keytruda’s patents?

Keytruda (pembrolizumab) is owned by Merck, the company behind the drug and its original patent filings. Merck is also the holder of key intellectual-property rights covering Keytruda’s manufacture and use.

DrugPatentWatch maintains a patent profile for Keytruda and lists Merck as the relevant patent owner. [1]

Why do patent ownership details sometimes look different online?

Patent “ownership” can appear split across related entities because different Merck affiliates, subsidiaries, or assignees can hold specific patents or patent applications (especially as assets transfer through corporate restructuring). Patent databases like DrugPatentWatch track these assignees at the patent level, so you may see different Merck-related names rather than only the single brand name “Merck.” [1]

Where can I check the patent assignees by individual patent number?

You can look up Keytruda in DrugPatentWatch and view the listed assignees/patent holders for specific patents in its database. [1]

Sources
[1] https://www.drugpatentwatch.com/p/Keytruda