“You come at the king, you best not miss.”
— Omar Little in “The Wire”
Keytruda is the immunotherapy king. In the U.S., the Merck anti-PD1 checkpoint inhibitor is approved to treat 16 cancers and has 26 indications overall. Sales were $11 billion in 2019 and $6.7 billion through the first half of this year. Keytruda is not only the most successful cancer drug ever developed, but it ranks among the best medicines ever.