Since reaching the market a decade ago, PCSK9 inhibitors have not lived up to their lofty expectations. | The FDA has approved Merck's internally developed cholesterol-lowering treatment Lipfendra for adults with hypercholesterolemia, or high levels of "bad" cholesterol. The drug, which is the first oral PCSK9 inhibitor to reach the market, has been pegged with peak annual sales potential of $5 billion.

The speedy clearance of Lipfendra is an important milestone for Merck and the result of a controversial voucher program put in place by former commissioner Marty Makary.

Merck and the FDA announced the approval of enlicitide 20 mg as an add-on to diet and exercise to lower LDL in adults with hypercholesterolemia and those with heterozygous…