shares of esperion therapeutics inc espr plunged about 56 in premarket trading on thursday the day after the company told investors that there is a dispute about a million milestone payment for its cholesterollowering treatment candidate worth up to 440 million esperion said earlier this month that nexletol reduced the risk of heart attack and other heart issues in people who can’t take statins the company said in a securities filing that the milestone payment is tied to whether cardiovascular risk reduction data is included in the european label for the pill however daiichi sankyo co ltd’s jp4568 european