The FDA approved Lipfendra (enlicitide) , the first-ever oral PCSK9 inhibitor — a daily pill that slashes LDL ("bad") cholesterol by up to 60% in patients already on statins. For over a decade, PCSK9 drugs only existed as expensive injectables (Amgen's Repatha, Sanofi's Praluent), keeping them out of reach for millions. Merck's once-daily pill changes that for the roughly 1 in 4 U.S. adults with high LDL cholesterol.

Side effects: Must be taken on an...