Regeneron Pharmaceuticals Inc.’s plans to lower the price of its cholesterol-lowering medication Praluent sent shares of some of its rivals down in Monday premarket trade. Regeneron shares rose 1.6% premarket, while shares of its partner Sanofi slumped about 0.1%. Shares of Amgen Inc. , which makes another cholesterol drug in the same category of drugs, termed PCSK9 inhibitors, declined 0.85% in premarket trade, and shares of Esperion Therapeutics Inc. , which recently reported positive results for a cholesterol drug in development, plummeted 5.7% premarket. Another PCSK9 inhibitor developer, Medicines Company , had its shares rise 6.2% premarket; the company has said it plans to compete with established rivals on price. PCSK9 inhibitors have been shown to be effective for patients when lifestyle changes and low-priced statinshaven’t worked, but their high price tags have led to restrictions on insurance coverage. Alongside pricing changes, Regeneron also reported positive data in which its drug Praluent showed a 15% reduction in major adverse cardiac events relative to patients on the placebo. The decision to lower the price is a “‘landmark’ step here,” said Bernstein analyst Ronny Gal, adding “our 2 cents is that it was unavoidable and Regeneron has shown leadership here by stepping out to reality (and obtained an advantage over Amgen in the process).” Regeneron shares have dropped 10.5% over the last three months and Sanofi shares have dropped 8.1%, compared with a 4.6% rise in the S&P 500 .