Leyden Labs reveals RIGImmune acquisition with Phase 1 data
Dutch biotech Leyden Labs has reported positive Phase 1 results for intranasal RIG-101 and disclosed that it acquired the drug’s developer, RIGImmune, earlier this year.
Why it matters: The acquisition expands Leyden Labs beyond the broadly protective nasal antibodies at the center of its pipeline into a second approach to mucosal protection: switching on the airway’s own antiviral defenses.
- RIG-101 is being developed initially to prevent respiratory viruses from triggering asthma exacerbations. The next test will be more meaningful: exposing patients with asthma to human rhinovirus under controlled conditions and seeing whether the drug actually protects them.
Zoom in: Leyden Labs said RIG-101 was safe and well tolerated across all tested doses in healthy volunteers and patients with asthma, including after daily intranasal dosing for up to seven days.
- In asthma patients, treatment induced type I and type III interferons and interferon-stimulated genes, consistent with its intended mechanism.
- The company did not disclose the number of participants in the completed cohorts, adverse-event rates or quantitative biomarker results.
- The clinical registry describes the program as a two-part, randomized, placebo-controlled Phase 1/2 trial targeting 82 participants at two UK sites. Part B will test RIG-101 against placebo in adults with asthma before and after challenge with rhinovirus RV-A16.
How it works: RIG-101 is part of a novel class of oligonucleotides called stem-loop RNA therapeutics (SLR) designed to activate RIG-I, an intracellular sensor of viral RNA that triggers innate antiviral responses including interferon production.
- The oligonucleotide is delivered directly to the respiratory mucosa using NEED, RIGImmune’s non-lipid nanoparticle delivery platform. US-based RIGImmune has reported preclinical activity against several respiratory RNA viruses, including rhinovirus, influenza and RSV.
The previously undisclosed acquisition: Leyden’s release also revealed for the first time that it bought RIGImmune earlier in 2026. The company did not disclose financial terms, but public filings provide considerably more detail.
- Alembic Pharmaceuticals, an early RIGImmune investor, states in its 2025/26 annual report that Leyden acquired RIGImmune under a share purchase agreement dated March 20, 2026. Alembic received 994,615 preferred shares and 1,032,592 common shares in Leyden Labs, valued at $6.68 million, as upfront consideration for its RIGImmune holding, plus undisclosed contingent payments tied to milestones. That figure doesn’t represent the total acquisition price but could point towards a transaction in company shares rather than cash. Alembic had been involved since 2021 with RIGImmune, when its initial investment gave it a 19.97% post-money stake in the company.
- In addition, Susan Sobolov, former President and COO of RIGImmune, is now CTO of Leyden Labs, which could also mean that the company’s technology will play an increasing role in Leyden Labs’ development strategy.
- Leyden Labs confirmed the acquisition in an email to European Biotechnology: “The acquisition is complementary to Leyden’s current approach and aligns nicely with the organizational mission. The acquisition occurred in the Spring of 2026.”
Backstory: RIGImmune was founded in 2020 by Yale professors Anna Marie Pyle and Akiko Iwasaki around stem-loop RNAs targeting RIG-I. In 2022, it acquired UK respiratory drug-delivery company SubIntro, combining the RNA technology with what became its NEED delivery platform, alongside financing from F-Prime Capital. RIGImmune later secured an exclusive Yale license covering its stem-loop technology and backing from the Gates Foundation.
Also notable: The deal came during a period of heavy fundraising for Leyden Labs. In June, the company added €40 million from investors including the EIC Fund, Invest-NL, the Gates Foundation and ClavystBio to fund its mucosal protection platform. That followed a €30 million financing in October 2025, a $70 million Series B earlier that year and €20 million in venture debt from the European Investment Bank.
What’s next: The rhinovirus challenge will be the key test for Leyden Labs. The trial registry currently estimates completion in February 2027.
