Interesting history of Keytruda from Forbes... https://www.forbes.com/sites/davidshaywitz/2017/07/26/the-startling-history-behind-mercks-new-cancer-blockbuster/#49d835d7948d
it is remarkable (and astounding) that as 'effed up a company as Merck is, they always somehow manage to get some unbelievably lucky break, in this case the ascension of Keytruda as the #1 Cancer killer...This allows Merck to charge whatever outrageous price the market will bear, "Cuz you want to live a little longer dontcha'?" This drug will literally carry the company for years moving forward, and keep Merck a viable drug outfit... unreal...the most corrupt screwed up organization out there, and they always end up winning no matter what...
The article traces how Keytruda was discovered by Organon, later acquired by Schering-Plough, in turn acquired by Merck, where the R&D geniuses killed the program, only to resurrect it after Bristol-Myers started reporting promising data!