Check out the companies making the biggest moves premarket: Regeneron Pharmaceuticals — The drugmaker fell more than 11% after its treatment for a skin cancer missed goals in a late-stage trial. Macy’s — The department store shares jumped nearly 4% in premarket after a regulatory filing revealed Berkshire Hathaway initiated a small position in the company, valued at roughly $55 million at the end of the first quarter. The stake is very small for the conglomerate, so many speculated it was bought by investment lieutenant Ted Weschler, who manages 6% of the equity portfolio. Dominion Energy — Shares popped more than 13% after a Bloomberg report said NextEra Energy is discussing a deal for the company with a valuation of $66 billion. The report added that a deal could be reached as soon as Monday. Bio Rad Laboratories — The stock jumped 13% following a Wall Street Journal report that activist Elliott Investment Management has built a sizable stake in the company. However, the exact size of the stake nor Elliott’s vision for the company were not detailed in the report. Arm Holdings — Shares were down 1% after a Bloomberg report Friday that a probe by the U.S. Federal Trade Commission is investigating if the company is illegally monopolizing parts of the chip market. Delta Air Lines — Shares were up more than 1% after a regulatory filing showed Berkshire Hathaway took a sizable stake in the airline, at a total of $2.6 billion . It comes six years after Warren Buffett moved Berkshire’s entire equity portfolio out of airlines. UnitedHealth — The insurer was off more than 3.5% after it was revealed in the same regulatory filing that Berkshire Hathaway had sold shares of some of the company in the first quarter. — CNBC’s Yun Li contributed reporting
