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Stock Markets May 18, 2026 10:32 AM

Dominion, Regeneron Lead a Broad Swath of Market-Cap Movers as Stocks Swing

Large winners and losers span sectors from energy and biotech to semiconductors amid deal and partnership headlines

By Leila Farooq SNDK AMAT GEV ORCL KLAC

Monday's trading session produced notable swings across large, mid and small-cap stocks. Energy and pharma names saw strong moves tied to corporate transactions and partnerships, while several semiconductor and technology-related companies posted double-digit declines. The market featured distinct winners such as Dominion Resources and Roblox, and steep losers including a number of small-cap names.

Dominion, Regeneron Lead a Broad Swath of Market-Cap Movers as Stocks Swing
SNDK AMAT GEV ORCL KLAC

Key Points

  • Monday's session produced pronounced moves across market-cap segments, with both double-digit gains and losses reported.
  • Notable corporate developments included Regeneron's partnership with Parabilis involving $125 million upfront and NextEra Energy's announced all-stock acquisition of Dominion Energy, which corresponded with significant stock moves.
  • Sectors most visibly impacted included energy, pharmaceuticals/biotech, semiconductors and technology-related industrials.

Equities moved unevenly on Monday as individual company developments and other factors drove sharp gains and losses across market-capitalization tiers. Below are the principal movers of the day, organized by market-cap category and including the percent changes reported for each security.

Mega-cap movers (Market Cap: $200B+ USD)

  • SanDisk Corp-Exch (SNDK) -5.67%
  • Applied Materials Inc (AMAT) -5.17%
  • GE Vernova LLC (GEV) -4.91%
  • Oracle Corp (ORCL) -3.4%
  • KLA-Tencor Corp (KLAC) -2.7%
  • Caterpillar (CAT) -2.51%
  • Avago Technologies (AVGO) -1.86%

Large-cap stock movers (Market Cap: $10B-$200B USD)

  • Regeneron Pharmaceuticals (REGN) -10.67% - Regeneron partners with Parabilis under a deal featuring $125 million upfront
  • Applied Optoelectronics (AAOI) -10.9%
  • Li Auto Inc (LI) -10.02%
  • Lumentum Holdings Inc (LITE) -9.55%
  • Powell Industries (POWL) -8.68%
  • Tower Semiconductor (TSEM) -8.44%
  • Vicor Corp (VICR) -7.65%
  • GS Acquisition A (VRT) -8.01%
  • Dominion Resources (D) +10.04% - NextEra Energy to acquire Dominion Energy in an all-stock deal
  • Roblox Corp (RBLX) +9.98%

Mid-cap stock movers (Market Cap: $2B-$10B USD)

  • Aehr Test Systems (AEHR) -15.08%
  • Generate Biomedicines Inc (GENB) -15.13%
  • Colonnade Acquisition (OUST) -14.66%
  • Lightwave Logic Inc (LWLG) -12.97%
  • SNXX (SNXX) -11.96%
  • Plug Power (PLUG) -11.08%
  • Bio-Rad Laboratories Inc (BIO) +11.59%
  • Fly Leasing Ltd (FLY) +6.68%
  • Brady Corp (BRC) +13.59% - shares rise after beating estimates and raising guidance

Small-cap stock movers (Market Cap: $300M-$2B USD)

  • China Merchants Holdings Pacific (CAEP) -32.0%
  • RoboStrategy (BOT) -29.16%
  • Willow Lane Acquisition (BRUN) -19.75%
  • AAOX (AAOX) -21.29%
  • Roth CH Acquisition V (NUAI) -18.55%
  • Julong Holding Ltd (JLHL) +21.24%
  • TECO Energy Inc-Exch (TE) +18.08%
  • CC Neuberger Principal Holdings II (GETY) +18.25%
  • Autolus Therapeutics (AUTL) +14.12% - Byondis forms a scientific advisory board related to its ADC pipeline
  • Acxiom Inc (RAMP) +27.48% - LiveRamp stock surges on a fourth quarter beat

These movements span multiple sectors, with particular activity noted in energy, pharmaceuticals/biotech, semiconductors, and certain technology-related names. Reported corporate actions and results - including strategic partnerships, acquisitions and earnings outcomes - were cited in connection with several of the larger moves.

Risks

  • Deal-related uncertainty - The announced all-stock acquisition involving Dominion Energy and NextEra Energy highlights transactional risk for shareholders in the energy sector.
  • Partnership and pipeline execution - Regeneron's partnership terms and Byondis' advisory board formation for ADC work underscore the execution risk in the pharmaceuticals and biotech sectors.
  • Earnings and guidance sensitivity - Companies reporting beats or guidance changes, such as Brady Corp and LiveRamp (RAMP), illustrate the potential for sizeable share-price volatility tied to reported results.

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