Helion's $425M Fusion Round Leads Slowdown in Mega-Deals

Helion Energy secured a $425 million Series F investment, pushing the fusion technology company's valuation to $5.4 billion. The Everett, Washington-based firm, which has now accumulated over $1 billion in total funding, counts Lightspeed Venture Partners, SoftBank Vision Fund 2, and Sam Altman among its investors. The company previously closed a $500 million Series E in November 2021.

Helion's latest capital raise underscores investor enthusiasm for alternative energy solutions as electricity demand surges from artificial intelligence and other technological developments. The startup has already signed a power purchase agreement with Microsoft to supply electricity from its fusion facility beginning in 2028, and inked a customer agreement with Nucor to construct a power plant in the 2030s. Polaris, Helion's seventh generation prototype, recently entered operation and is expected to produce the first electricity generated from fusion. According to Crunchbase data, this round ranks as the second-largest in the fusion industry over the past year, trailing only Pacific Fusion's $900 million Series A led by General Catalyst in October.

The broader funding landscape showed signs of deceleration this week. Only three startups achieved nine-figure rounds, and companies needed roughly $60 million in capital to appear on the top 10 list. This marks a notable shift from the year's strong opening for large megarounds.

Top 10 Funding Rounds

1. Helion Energy: $425 million Series F (energy)
2. ElevenLabs: $180 million round led by Iconiq Growth and Andreessen Horowitz (artificial intelligence)
3. Openly: $123 million equity financing plus $70 million debt led by Eden Global Partners (insurance)
4. Atalanta Therapeutics: $97 million Series B co-led by EQT Life Sciences and Sanofi Ventures (biotech)
5. Mercor: $75 million round led by Felicis 1 (human resources)
6. Veir: $75 million Series B led by Munich Re Ventures (power grid)
7. Castelion: $100 million Series A including $30 million venture debt from Silicon Valley Bank, led by Lightspeed Venture Partners (defense)
8. Helicore Biopharma: $65 million Series A co-led by OrbiMed and Versant Ventures (biotech)
9. Smart Wires: $65 million investment with participation from BP Energy Partners (electronics)
10. Rad AI: $60 million round led by Transformation Capital (health care)

ElevenLabs, a Brooklyn-based voice artificial intelligence company, raised $180 million at a $3.3 billion valuation. The startup, founded in 2022, has now accumulated $281 million in total funding. The round came approximately one year after the company secured an $80 million Series B at unicorn valuation. ElevenLabs provides creators and enterprises with software to synthesize voices across numerous languages.

Openly, a Boston-based insurtech platform serving independent insurance agents, closed $123 million in equity financing alongside $70 million in debt, both led by Eden Global Partners. The company, which streamlines homeowners insurance processes and improves underwriting and claims management, has raised nearly $431 million since its 2017 founding. Eden Global Partners also led the company's $100 million Series D in 2023.

Atalanta Therapeutics, a Boston-based biotech firm employing RNA interference to treat neurological conditions, completed a $97 million Series B co-led by EQT Life Sciences and Sanofi Ventures. The company will deploy the capital toward clinical development of RNAi therapies targeting KCNT1-related epilepsy and Huntington's disease. Founded in 2018, Atalanta has raised $207 million total.

San Francisco-based recruiting startup Mercor raised $75 million in a round led by Felicis 1, achieving a $2 billion valuation. The company initiated fundraising in December, and the final amount could grow further. Since its 2023 founding, Mercor has raised nearly $109 million.

Veir, a Woburn, Massachusetts-based developer of superconducting technology for artificial intelligence data centers and utilities, closed a $75 million Series B led by Munich Re Ventures. The company, founded in 2019, has accumulated nearly $112 million in funding.

Castelion, an El Segundo, California-based defense manufacturer, raised $100 million in a Series A combining debt and equity. The startup develops what it describes as "affordable, mass-produced hypersonic long-range strike weapons" functioning as a "non-nuclear deterrent." Lightspeed Venture Partners led the round, which included $30 million in venture debt from Silicon Valley Bank. Defense technology has attracted significant investor attention recently, following major funding announcements by companies like Anduril Industries and Helsing. Other recent defense and critical infrastructure deals include Chaos Industries' $145 million Series B, Firehawk Aerospace' $60 million Series C, and Onebrief's $50 million Series B.

Helicore Biopharma, a South San Francisco-based biopharmaceutical company focused on obesity treatment and related conditions, emerged from stealth with $65 million in Series A funding co-led by OrbiMed and Versant Ventures.

Smart Wires, a Durham, North Carolina-based company developing power grid solutions, raised $65 million in a new investment featuring participation from BP Energy Partners. Founded in 2010, the company has raised $248 million total.

Rad AI, a San Francisco-based artificial intelligence-powered radiology firm, reportedly closed a $60 million round led by Transformation Capital at a $525 million valuation. The company, founded in 2018, has raised over $140 million.

Big global deals

The largest deal outside the United States originated from the Iberian Peninsula. TravelPerk, a Spain-based platform for managing business travel, raised $200 million in a Series E at a $2.7 billion valuation.

Methodology

This analysis examined the largest announced funding rounds in the Crunchbase database for U.S.-based companies during the seven-day period from January 25 to January 31. While the database captures most announced rounds, some reporting delays may occur as deals are disclosed later in the week.