The U.S. stock market witnessed a surge on May 23, 2025, as investors poured capital into biotechnology and nuclear energy sectors, triggering substantial gains across several mid-cap and growth-focused names. Amid favourable policy developments and clinical trial breakthroughs, the top ten gainers on the Nasdaq and NYSE posted double-digit percentage increases, reflecting strong institutional interest and sector rotation into defensives and innovation-led plays.
While the broader market remained steady, key outperformers were concentrated in healthcare and energy—specifically nuclear energy—as new regulatory developments in Washington signalled accelerated federal support for next-generation energy systems and oncology drug innovations. Analysts also flagged unusually high trading volumes in several names, pointing to large fund positioning and retail momentum driven by news catalysts and earnings-related commentary.
Why Did Merus N.V. (MRUS) Stock Rise on May 23, 2025?
Shares of Merus N.V. (NASDAQ: MRUS) climbed by an impressive 32.55% to close at $55.14 following the release of promising clinical trial data for its experimental cancer therapy petosemtamab, in combination with Merck’s Keytruda. The results from a head and neck cancer study showed a 79% one-year survival rate, sparking widespread investor enthusiasm. Analysts highlighted that such efficacy significantly outpaces standard-of-care benchmarks, with Needham & Company raising their price target to $88 and assigning a 60% probability of FDA approval. The news triggered strong inflows and made MRUS the day’s top gainer in percentage terms.
Why Did Regencell Bioscience (RGC) Stock Jump 26.85%?
Regencell Bioscience Holdings Limited (NASDAQ: RGC) surged 26.85% to $560.00 with no major public filings or press releases, suggesting the rally may be driven by speculative buying, social media chatter, or short-squeeze mechanics. The stock saw light volume (33,831 shares) but significant price action, raising questions about retail-driven volatility. RGC has historically been prone to sharp swings, and Friday’s move reflects renewed attention on smaller-cap biotech stocks, especially those with limited free floats and past volatility histories.
What Boosted Uranium Energy Corp. (UEC) by 25%?
Uranium Energy Corp. (NYSE American: UEC) gained 25.00% to close at $6.45 as nuclear-linked stocks rallied broadly in response to reports of new executive orders from the White House supporting nuclear power. These included directives aimed at expediting small modular reactor (SMR) approvals, boosting uranium stockpiles, and prioritising nuclear energy infrastructure. As a U.S.-focused uranium producer with near-term production capabilities, UEC attracted strong institutional inflows. Analysts believe UEC remains well-positioned as a pure-play proxy for American nuclear revitalisation policy.
Why Did Oklo Inc. (OKLO) Gain 23.04%?
Oklo Inc. (NYSE: OKLO) rose 23.04% to $48.87 amid heightened investor interest in advanced nuclear technologies. The company’s focus on microreactor design and clean fission energy has drawn increased attention after the federal government announced plans to fast-track nuclear reactor development on federal land. With high trading volumes (91.264 million shares), Oklo’s surge reflected a confluence of retail interest, policy-driven optimism, and analyst upgrades following visibility into its commercialization roadmap. Analysts highlighted Oklo as a structural long-term play within the evolving U.S. energy security framework.
What Drove United States Steel Corporation (X) Higher by 21.24%?
Shares of United States Steel Corporation (NYSE: X) jumped 21.24% to $52.01 after President Biden approved a strategic industrial partnership with Japan’s Nippon Steel. The transaction, projected to generate 70,000 jobs and retain U.S. Steel’s Pittsburgh headquarters, was received as a pro-labour, pro-growth policy move, calming earlier concerns about foreign control. Investors reacted to clarity around the deal’s terms, resulting in renewed momentum for the stock, which traded over 52.8 million shares—well above its 3-month average.
What Triggered NuScale Power Corporation’s (SMR) 19.43% Gain?
NuScale Power Corporation (NYSE: SMR) soared 19.43% to $30.24 as investor sentiment surged following Washington’s reaffirmation of support for small modular reactors (SMRs). NuScale, one of the most visible names in the SMR space, was seen as a direct beneficiary of proposed legislation that includes federal funding access, site permitting exemptions, and DoE-backed deployment pilots. The stock rallied sharply on institutional repositioning and saw volumes nearly six times its average, with hedge funds and energy ETFs likely participating.
Why Did Informatica Inc. (INFA) Rise by 17.45%?
Informatica Inc. (NYSE: INFA) advanced 17.45% to $22.55 after analysts reiterated bullish coverage amid strong enterprise software demand in the AI and cloud data management segment. While no company-specific news surfaced on Friday, the move was likely influenced by peer strength in the cloud analytics space, particularly with broader tech optimism and renewed CIO spending projections. The rally suggests that Informatica may benefit from tailwinds in enterprise data governance, with buy-side participants increasing exposure to data infrastructure names.
What Sparked NexGen Energy Ltd. (NXE) to Rise 14.71%?
NexGen Energy Ltd. (NYSE American: NXE) gained 14.71% to $6.24, tracking the broader uranium sector rally. As a leading uranium developer with projects in Saskatchewan’s Athabasca Basin, NexGen is widely viewed as a leveraged bet on uranium price appreciation. The stock rallied in sympathy with UEC and Cameco, driven by institutional flow into nuclear supply chain themes. NexGen’s lower market cap and high beta made it attractive for momentum traders seeking exposure to nuclear policy tailwinds.
Why Did Cameco Corporation (CCJ) Climb 11.13%?
Cameco Corporation (NYSE: CCJ) added 11.13% to $58.69 as part of the uranium sector rally. As one of the world’s largest uranium producers, Cameco was already on watchlists amid tightening global supply and rising reactor construction forecasts, particularly in Asia and Europe. Investors viewed Cameco as a safer, large-cap option to gain exposure to uranium’s comeback, especially in light of growing concerns around Russian fuel supply disruption. Analysts reiterated overweight positions, citing Cameco’s long-term contracts and proven reserves.
What Lifted BWX Technologies, Inc. (BWXT) by 11.03%?
BWX Technologies, Inc. (NYSE: BWXT) rose 11.03% to $119.49 amid the day’s nuclear stock rally, as the company provides critical nuclear components and fuel for both defence and civilian energy purposes. The company’s dual positioning across defence (submarine reactors, national labs) and energy (advanced reactors) made it a key gainer in Friday’s policy-driven uptrend. With a market cap above $10.9 billion, BWXT represents a rare crossover between energy and defence thematics, making it attractive to diversified institutional buyers.
Forward Outlook: Can the Nuclear and Biotech Momentum Continue?
Friday’s rally highlights the growing alignment between U.S. policy frameworks and equity market leadership. The convergence of regulatory support for clean energy, strategic industrial cooperation with allies, and major advances in oncology drug development could sustain interest in these sectors. Investors are likely to watch for follow-up actions such as Department of Energy funding announcements, FDA fast-track designations, and further macro tailwinds, including potential Fed pauses or stimulus reallocation.
While volatility in low-float biotech and energy names remains a risk, the strong volumes and sector breadth suggest this rally had deeper institutional participation. With major players like Merus, UEC, and BWXT now drawing buy-side attention, further re-rating could continue into June, especially ahead of mid-quarter earnings and sector conferences.
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