 Agents which block PCSK9 can lower LDL particle concentrations.The first two PCSK9 inhibitors, alirocumab and evolocumab, were approved as once every two week injections, by the U.S. Food and Drug Administration in 2015 for lowering LDL-particle concentrations when statins and other drugs were not sufficiently effective or poorly tolerated.The cost of these new medications, , was $14,000 per year at full retail; judged of unclear cost effectiveness by some.