Esperion Therapeutics Inc. Shares of ESPR plunged nearly 56% in premarket trading on Thursday, the day after the company told investors it is in dispute about a milestone payment of up to $440 million for its cholesterol-lowering treatment candidate. Esperion said earlier this month that Nexletol reduced the risk of heart attack and other heart problems in people who cannot take statins. The company said in a securities filing that the milestone payment is tied to whether the European label for the pill includes cardiovascular risk reduction data; However, Daiichi Sankyo Co. Ltd.’s JP:4568 European…