- Leyden Labs has raised 40 million euros from the Gates Foundation, EIC Fund, Invest-NL, and ClavystBio to advance its pan-influenza nasal spray through clinical trials.
- The Gates Foundation joins as a first-time investor, with a specific mandate to expand access to Leyden’s products in low- and middle-income countries.
- The raise brings Leyden Labs’ total funding to over $336M, making it one of the best-capitalised respiratory virus biotechs outside the US.
Flu vaccines have been around for 80 years. They still don’t work well enough for the elderly, the immunocompromised, or anyone exposed to a strain that emerged after the annual reformulation window. Leyden Laboratories thinks a nasal spray can do better, and just closed a €40 million round to prove it.
The Dutch biotech announced the round from the European Innovation Council Fund, Dutch national investment institution Invest-NL, the Bill & Melinda Gates Foundation, and Singapore-linked life sciences investor ClavystBio. The EIC Fund, Invest-NL, and ClavystBio are returning backers. The Gates Foundation joins for the first time.
“This financing represents much more than capital. It signals confidence in our scientific approach, our team, and our mission to fundamentally improve how the world protects itself against respiratory viruses,” says Koenraad Wiedhaup, founder and chief executive of Leyden Labs.
The respiratory virus infection drugs market stands at $23.8 billion in 2026 and is forecast to reach $35.2 billion by 2031, growing at an 8.1% annual rate, according to Mordor Intelligence. Within that, monoclonal antibodies are the fastest-growing treatment modality at a 9.2% annual rate.
Why a nasal spray and why now
Founded in 2020 and headquartered in Leiden, Netherlands, Leyden Labs is developing what it calls a Mucosal Protection Platform: a pipeline of nasal sprays that deliver broadly protective antibodies directly to the lining of the nose and throat, where airborne viruses first enter the body.
Its lead programme, PanFlu, is built around CR9114, a human monoclonal antibody licensed exclusively from Janssen Pharmaceuticals that protects against influenza A and B. PanFlu is currently in clinical development.
The startup works by targeting conserved regions of viruses, meaning the antibodies are designed to remain effective even when new variants emerge. The nasal spray format means patients can self-administer immediately, without waiting for seasonal reformulations.
Critically, because the approach does not depend on the body generating its own immune response, it can protect people with weakened immune systems who often can’t benefit from conventional vaccines.
Peers working on systemic respiratory protection include AstraZeneca and Sanofi, whose RSV monoclonal antibody, nirsevimab, has demonstrated 88–90% real-world effectiveness and holds a significant market share. Pfizer and Moderna are developing next-generation mRNA flu vaccines.
While those programmes protect against specific viruses delivered by injection, Leyden’s platform aims to cover full viral families intranasally — and to work regardless of immune function.
European science story becomes a global access play
The entry of the Gates Foundation reshapes the strategic read on this round. The foundation’s mandate is specific: it will fund work to identify and implement strategies to optimise access to Leyden’s pipeline in low- and middle-income countries: markets where seasonal flu and pandemic-scale outbreaks cause the most deaths and where conventional vaccine distribution regularly fails.
EIC Fund support was granted through its Strategic Technologies for Europe Platform, short for STEP.
“Leyden Labs represents the kind of breakthrough biotechnology innovation the EIC STEP Scale Up initiative was designed to support. This investment was made because we believe Leyden Labs’ novel approach to protect against respiratory viruses has the potential to make a meaningful impact on global public health while reinforcing Europe’s leadership in biotechnology innovation,” says Hermann Hauser, member of the EIC Fund Board.
Invest-NL’s investment principal Ineke Cazander adds, “To turn breakthrough innovations into solutions that benefit society, companies need access to patient capital. As the national promotional institution of the Netherlands, we are pleased to support Leyden Labs in that journey.”
This round follows a strong run of financing activity. Leyden raised $70M in a Series B in January 2025, a €20M venture debt facility from the European Investment Bank in June 2025, and €30M from EIC Fund and Invest-NL in October 2025. The new capital will advance PanFlu through clinical development and fund Leyden’s broader mucosal pipeline targeting coronaviruses and other respiratory viruses. Total funding now exceeds $336M, according to PitchBook.
The company has 78 employees and has not disclosed a post-round valuation or target headcount.
The clinical timeline for respiratory antibody programmes remains the central risk. Approval processes are long, and the flu sector has seen promising antibody candidates stall before reaching patients. With the Gates Foundation now requiring a credible LMIC access plan alongside clinical milestones, Leyden carries a dual mandate: prove the science works, and prove the world can actually reach it.
