Today's biggest winners and losers in the stock market.

On this episode of Stock Movers:

- Seagate (STX) shares slumped as much as 8.3% after management comments at a JPMorgan conference sparked investor fears that the company won’t be able to keep up with soaring demand for memory chips. Chief Executive Officer Dave Mosley said building new factories would “take too long” and potentially set up the company with more capacity than it needs when asked during a Monday presentation whether Seagate plans to expand manufacturing capacity.

- NextEra (NEE) agreed to pay about $67 billion in stock for Dominion Energy in the biggest power acquisition ever, creating a giant utility extending from Florida to the artificial intelligence data centers clustered in Virginia. The scope of the transaction underscores how the spike in AI-driven power demand is pushing the utilities sector to seek ever-greater size and clout. The deal would position NextEra as the dominant utility in a region that’s struggling to meet the surge in electricity consumption. Dominion shares rose while NextEra shares fell.

- Regeneron Pharmaceuticals (REGN) shares sank more than 10%, most intraday since May 2025, after the drugmaker’s phase 3 data for fianlimab in metastatic melanoma fell short of expectations. Citi and Leerink analysts downgraded their ratings on the stock following the disappointing trial update. Regeneron’s experimental drug fianlimab couldn’t beat Merck & Co.’s established cancer blockbuster Keytruda in the study, Regeneron said late on Friday. Another head-to-head trial of the Regeneron compound versus Bristol-Myers Squibb Co.’s Opdualag continues.