How Leyden Labs is revolutionizing flu protection with its intranasal antibody spray

March 20, 2026

32 min episode · 2 min read

Its Intranasal Antibody Spray

Episode

32 min

Read time

2 min

Topics

Science & Discovery

AI-Generated Summary

Published Mar 26, 2026

Key Takeaways

✓Vaccine efficacy gap: Traditional flu vaccines average only 13% effectiveness against infection and perform even worse in elderly and immunocompromised populations — the groups most at risk. Leyden Labs' passive immunity approach bypasses this limitation entirely by delivering pre-formed antibodies directly into the nasal cavity, making protection independent of the recipient's immune system function.
✓Broad-spectrum antibody coverage: Leyden Labs' lead asset, PanFlu, uses the CR9114 antibody to neutralize all influenza A and B strains, with in vitro data also showing activity against C and D strains. This breadth means the spray does not require annual reformulation to match circulating strains, unlike conventional seasonal flu vaccines targeting only three subtypes.
✓Mucosal delivery mechanics: Administering antibodies intranasally coats the upper respiratory tract before viral replication begins, blocking infection at the portal of entry. Published data in Science Translational Medicine confirmed antibodies remain structurally intact and biologically active inside the human nose, resolving a key scientific uncertainty about whether nasal enzymes would degrade the molecules.
✓Preclinical efficacy validation: In nonhuman primate challenge studies using high-dose H1N1 administered intranasally, daily PanFlu spray produced sustained antibody trough levels and prevented viral replication in the upper respiratory tract. Consistent protection was also demonstrated across H5N1 and influenza B strains in mouse models, supporting progression into Phase 2 human trials.
✓Pandemic preparedness application: Because the spray delivers broad pre-existing antibody coverage, it can be stockpiled and distributed to households before a pandemic strain is identified. Leyden Labs received €20 million from the European Investment Bank via HERA, the EU's pandemic preparedness body, specifically to develop this rapid-response capability against novel influenza and coronavirus outbreaks.

What It Covers

Koenraad Wiedhaup, co-founder and CEO of Leyden Labs, and CSO Clarissa Kosch explain how their intranasal antibody spray delivers broad-spectrum protection against influenza and coronaviruses directly at the nasal entry point, addressing critical gaps left by traditional vaccines, backed by newly published preclinical data and €50 million in European funding.

Key Questions Answered

•Vaccine efficacy gap: Traditional flu vaccines average only 13% effectiveness against infection and perform even worse in elderly and immunocompromised populations — the groups most at risk. Leyden Labs' passive immunity approach bypasses this limitation entirely by delivering pre-formed antibodies directly into the nasal cavity, making protection independent of the recipient's immune system function.
•Broad-spectrum antibody coverage: Leyden Labs' lead asset, PanFlu, uses the CR9114 antibody to neutralize all influenza A and B strains, with in vitro data also showing activity against C and D strains. This breadth means the spray does not require annual reformulation to match circulating strains, unlike conventional seasonal flu vaccines targeting only three subtypes.
•Mucosal delivery mechanics: Administering antibodies intranasally coats the upper respiratory tract before viral replication begins, blocking infection at the portal of entry. Published data in Science Translational Medicine confirmed antibodies remain structurally intact and biologically active inside the human nose, resolving a key scientific uncertainty about whether nasal enzymes would degrade the molecules.
•Preclinical efficacy validation: In nonhuman primate challenge studies using high-dose H1N1 administered intranasally, daily PanFlu spray produced sustained antibody trough levels and prevented viral replication in the upper respiratory tract. Consistent protection was also demonstrated across H5N1 and influenza B strains in mouse models, supporting progression into Phase 2 human trials.
•Pandemic preparedness application: Because the spray delivers broad pre-existing antibody coverage, it can be stockpiled and distributed to households before a pandemic strain is identified. Leyden Labs received €20 million from the European Investment Bank via HERA, the EU's pandemic preparedness body, specifically to develop this rapid-response capability against novel influenza and coronavirus outbreaks.

Notable Moment

Wiedhaup reframes the pandemic preparedness argument by pointing out that a nasal spray with pre-built broad protection could be shipped directly to people's homes at the first sign of an outbreak — potentially keeping economies open without waiting for a strain-matched vaccine to be developed and distributed.

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