In January 2017, a US Federal Court ordered a ban on the sale of Praluent, a PCSK9 inhibitor (used for lowering cholesterol) developed by pharmaceutical companies Sanofi and Regeneron, after rival company, Amgen, accused them of patent infringement. This ban comes on the heels of Pfizer’s decision to discontinue global clinical trials of their own PCSK9 inhibitor, bococizumab, after reports of increased adverse events such as immunogenicity (the patient’s immune system fighting the drug) and lack of efficacy compared to PCSK9 inhibitors already on the market.

PCSK9 inhibitors (proprotein convertase subtilisin/kexin type 9) are a relatively new class of cholesterol-lowering medications that are used to treat patients at risk for cardiovascular disease with elevated LDL-C (Low-Density Lipoprotein-Cholesterol — i.e. “bad” cholesterol)*. LDL-C is considered “bad” cholesterol because it can form plaques and block arteries (atherosclerosis). The goal of treating patients with elevated LDL-C is to prevent major adverse cardiovascular events (MACE) such as heart attacks (myocardial infarction) and strokes.

The ban of Praluent and the discontinuation of bococizumab leave only one PCSK9 inhibitor on the market in the United States: Amgen’s Repatha. In order to give Sanofi and Regeneron time to appeal, the ban will take place 30 days after the ruling. There is still the possibility of Amgen settling for royalties on Praluent’s sales, which were expected to be $2 billion by 2020.

*More explanation on how PCSK9 inhibitors work

“Bad” cholesterol is removed from the bloodstream by proteins found on the surface of cells called “LDL-C receptors”. PCSK9 can bind to these receptors which removes them from the surface of the cell. Thus, PCSK9 lowers the cell’s capability in removing cholesterol. PCSK9 inhibitors block PCSK9 from binding to these receptors, thereby allowing them to do their job of removing cholesterol.