Check out the companies making headlines in premarket trading. UnitedHealth — Shares dropped 7% in the premarket Tuesday after the company announced it was suspending its 2025 outlook due to higher-than-expected medical expenditures. UnitedHealth also announced CEO Andrew Witty was stepping down, effective immediately, for personal reasons. Stephen Hemsley will replace Witty as chief executive. Rigetti Computing — Shares tumbled 11.4% after the quantum computing firm recorded $1.5 million for first-quarter revenue, below the $2.6 million consensus forecast from analysts polled by FactSet. Coinbase — Shares rallied 9.2% following the announcement that the crypto trading platform will join the S & P 500 , taking effect before trading on May 19. Coinbase will replace Discover Financial Services . Hertz Global Holdings — The rental car stock sank nearly 9% after first-quarter results came in worse than expected. Hertz reported an adjusted loss of $1.12 per share on $1.81 billion of revenue. Analysts surveyed by LSEG were looking for a loss of 97 cents per share and $2 billion of revenue. The company said it had $1.2 billion in liquidity at the end of March. Simon Property Group — The real estate investment trust slid 2% despite first-quarter revenue topping expectations. Simon saw $1.37 billion, while analysts predicted $1.36 billion, per LSEG. Under Armour — Shares of the athletic goods and apparel company added 2.2% after Under Armour beat revenue expectations for its fiscal fourth quarter and lifted its adjusted earnings per share guidance for the fiscal first quarter. Sea Limited — The consumer internet stock surged 14.1% after adjusted EBITDA for the first quarter surpassed forecasts. Sea posted $946.5 million, beating the FactSet consensus of $710.9 million. The company reported $4.84 billion in revenue, missing Wall Street's prediction $4.91 billion. Boeing — Shares moved 1.5% higher following a Bloomberg report that China has lifted its ban on Boeing deliveries. Domestic airlines and government agencies are being told this week that deliveries can resume, the report said, citing people familiar with the matter. Valero Energy — Shares of the oil refiner ticked 1% higher on the heels of Goldman Sachs' upgrade to buy from neutral. Goldman said Valero can benefit from an improving backdrop and more attractive supply-and-demand trends. Calumet — The special product producer jumped 2.2% following Bank of America's initiation at a buy rating. The bank said Calumet shares can see sizable upside through growth in the biofuels business. — CNBC's Pia Singh, Jesse Pound and Fred Imbert contributed reporting