UnitedHealth Group Inc.'s (UNH) stock plunged over 5% in pre-market trading on Thursday after the healthcare giant reported mixed fourth-quarter results and provided its 2025 outlook amid lingering fallout from a recent cyberattack and heightened regulatory risks around its pharmacy benefit management business.

For the fourth quarter of 2024, UnitedHealth reported earnings of $5.98 per share, beating analysts' expectations of $6.73 per share. However, revenue of $100.81 billion fell short of the $101.6 billion estimate, sending shares lower in early trading.

The company affirmed its full-year 2025 guidance, forecasting revenue between $450 billion and $455 billion and adjusted earnings per share of $29.50 to $30.00. While the earnings outlook was in line with expectations, the revenue projection suggests potential headwinds ahead.

UnitedHealth's quarterly results and outlook were overshadowed by the fallout from a December cyberattack that disrupted operations and led to the tragic death of UnitedHealthcare CEO Brian Thompson. The incident sparked a public outcry against the insurance industry, fueling concerns about potential regulatory changes that could impact UnitedHealth's business model.

Additionally, the company faces growing scrutiny over its Optum pharmacy benefit management (PBM) unit, with lawmakers and critics calling for reforms to curb the role of PBMs in the drug pricing process. President-elect Donald Trump has threatened to "knock out" PBMs, posing a risk to UnitedHealth's Optum Rx business.

While UnitedHealth's earnings beat expectations, the revenue miss and uncertainty surrounding regulatory risks and the cyberattack aftermath weighed on investor sentiment, contributing to the stock's sharp decline in pre-market trading.