Check out the companies making headlines before the bell: Pharmaceutical stocks — Shares of U.S. companies in the pharmaceutical industry fell after President Donald Trump said late Tuesday that he is going to announce ” very shortly a major tariff on pharmaceuticals .” Pfizer and Merck shares each dropped more than 4%, while Eli Lilly shed more than 3%. Apple — Shares fell more than 2% in the premarket, continuing to drop after a four-day losing streak that cost the tech giant roughly 25% of its market value. The iPhone maker has been hit hardest among the “Magnificent Seven” companies because of Apple’s reliance on China. Retailers — Many retail stocks fell before market open amid uncertainty about the potential effect of sweeping tariffs on trade partners and after China announced retaliatory tariffs on U.S. goods. Target , Best Buy and Home Depot shares each slid about 3%. Walmart — Shares of the big-box retailer shed 1% after Walmart pulled its outlook for operating income in the first quarter, saying it wants to “maintain flexibility to invest in price as tariffs are implemented.” The company still expects sales to grow 3% to 4% during the three-month period. Automakers — Shares of automakers fell as the Trump administration’s tariffs on dozens of countries came into effect overnight. Ford and General Motors slipped 3% and 2%, respectively. Constellation Energy — The energy provider’s stock moved almost 2% higher following an upgrade at Citi to buy from neutral. The bank said Constellation’s recent slide has created a compelling risk/reward. Peabody Energy — The coal miner’s stock jumped nearly 13% premarket after Trump signed a series of executive orders Tuesday to support the industry. Peabody is also reviewing its deal with Anglo American to purchase Australian assets after a mine fire. — CNBC’s Sean Conlon, Sarah Min, Spencer Kimball and Michelle Fox contributed reporting.