Keytruda represents almost half of Merck’s sales, and a new formulation could fend off rivals

As patent protection for the cancer juggernaut Keytruda approaches a critical juncture, Merck & Co. won’t give up market share without a fight. The company revealed this week that a subcutaneous version of the drug — along with chemotherapy — was as effective in a late-stage trial as the original recipe, which is infused intravenously.