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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
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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
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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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