Series B Funded Biotechnology Startups
The 50 most recent Series B rounds in biotechnology span February through November 2025, with disclosed amounts ranging from $3M (iVeena, Salt Lake City) t…
The 50 most recent Series B rounds in biotechnology span February through November 2025, with disclosed amounts ranging from $3M (iVeena, Salt Lake City) to $600M (Kailera Therapeutics, Waltham). Cambridge, Massachusetts is the densest single hub: Strand Therapeutics ($153M, August 2025), ARTBIO ($132M, July 2025), AIRNA ($155M, April 2025), and PAQ Therapeutics ($39M, May 2025) all closed there. South San Francisco contributed two of the set's largest rounds — Kardigan at $254M in October 2025 and NewLimit at $130M in May 2025.
International activity accounts for roughly a third of the dataset. Three Netherlands-based companies — The Protein Brewery (Breda), Revyve (Wageningen), and Salvia BioElectronics (Eindhoven) — raised rounds between $28M and $60M. Spain produced three closes including Splice Bio at $135M (Barcelona) and ARTHEx Biotech in Valencia, while France contributed BrainEver, Osivax, and EG 427. October 2025 was the most active single month, with seven rounds closing including Kailera's $600M.
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Frequently asked
What are the largest Series B rounds in this data?
Kailera Therapeutics (Waltham, Massachusetts) leads at $600M, raised October 19, 2025. Kardigan (South San Francisco) closed the second-largest at $254M on October 13, 2025. AIRNA (Cambridge, Massachusetts) raised $155M in April 2025, and Strand Therapeutics (also Cambridge) raised $153M in August 2025, with Splice Bio (Barcelona) at $135M in June 2025 rounding out the top five.
Which US cities are most active for Series B biotech funding?
Cambridge, Massachusetts has the highest concentration, with Strand Therapeutics, ARTBIO, PAQ Therapeutics, and AIRNA all closing rounds between April and August 2025. South San Francisco follows with Kardigan ($254M) and NewLimit ($130M). California more broadly spans Brisbane, Sunnyvale, Emeryville, San Diego, Newark, and San Francisco across this dataset.
How significant is European activity in Series B biotech rounds?
16 of the 50 companies are headquartered in Europe. The Netherlands leads with three rounds — The Protein Brewery (Breda), Revyve (Wageningen), and Salvia BioElectronics (Eindhoven). France contributed three rounds (BrainEver, Osivax, EG 427) and Spain three (Splice Bio, Seqera, ARTHEx Biotech), with Switzerland, the UK, Denmark, Belgium, and Ireland each contributing one or two.
What does the round size distribution look like at this stage?
Disclosed amounts span from $3M (iVeena, Salt Lake City) to $600M (Kailera Therapeutics). Seven rounds closed above $100M: Kailera, Kardigan, AIRNA, Strand Therapeutics, Splice Bio ($135M), ARTBIO ($132M), and NewLimit ($130M). One company — Olaris (Framingham, Massachusetts, April 2025) — raised at an undisclosed amount.
What time period does this data cover, and when was deal flow highest?
The earliest round shown is Auron Therapeutics (Wellesley, Massachusetts) at $27M on February 4, 2025; the most recent is Gate Bioscience (Brisbane, California) at $65M on November 13, 2025. October 2025 was the busiest single month, with seven rounds closing including Kailera's $600M, Kardigan's $254M, Peptilogics' $78M, Ansa Biotechnologies' $45M, BridGene Biosciences' $28M, OXCCU's $28M, and Salus BioMed's $7M.
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