Sanofi Pauses Phase 2 Trial of Monoclonal Antibody SAR445399 in Chronic Lung Disease

Sanofi has suspended a phase 2 clinical trial evaluating SAR445399, a monoclonal antibody, in adults with non-cystic fibrosis bronchiectasis (NCFB), a chronic lung disease.¹ The trial was first submitted to the clinical trials registry on April 17, 2026, and its listing was updated to "suspended" on July 28, 2026, indicating that enrollment or dosing has stopped while the company reviews next steps.² The suspension was reported as officially registered on July 29, 2026, the day before Sanofi's second-quarter earnings call.¹ A company spokesperson told Fierce Biotech the decision was made "as part of a company-wide portfolio review for strategic business reasons" and was not related to safety concerns.¹

How does SAR445399 work, and what was the trial testing?

SAR445399 is an anti-interleukin-1 receptor 3 (IL-1R3) monoclonal antibody developed to block the interleukin-1, -33, and -36 cytokine pathways, mechanisms implicated in chronic immune-related dermatologic and respiratory diseases.¹ The suspended phase 2 study was a randomized, double-blind, placebo-controlled trial designed to measure reduction in mucus plug score following treatment with SAR445399 compared with placebo, in adults ages 18 to 80 with NCFB.¹ NCFB is a chronic lung condition affecting roughly half a million people in the US and more than one million people globally, and it currently has limited approved treatment options; Insmed's brensocatib became the first FDA-approved therapy specifically for the condition in August 2025.¹

Why is this happening now?

The pause comes amid a broader pipeline reassessment under Sanofi's new chief executive officer, Belén Garijo, who took over in late April 2026 following the departure of former CEO Paul Hudson.¹ According to BioSpace, Garijo has described the effort as a "very rigorous portfolio prioritization process" and has said the company is evaluating its late-stage portfolio based on scientific merit, long-term value potential, and risk profile, though she noted Sanofi does not have a fixed target number of programs to discontinue.³ The SAR445399 pause follows a string of other recent Sanofi pipeline actions: the company discontinued the oral TNFR1 inhibitor balinatunfib last week after it failed to significantly ease psoriasis severity in a mid-stage study, and late last month halted all but one ongoing study of the investigational antibody amlitelimab following disappointing Phase III results in atopic dermatitis, taking a €952 million ($1.1 billion) impairment charge in the process.¹

What is the status of Sanofi's broader immunology pipeline?

Sanofi's pipeline page currently lists SAR445399 under mid-stage development for hidradenitis suppurativa, a study the company has said remains open and recruiting; the company has no listed pipeline entry for the drug in NCFB specifically.¹ SAR445399, first disclosed by Sanofi in 2023, had also been explored across other chronic immune-related indications given IL-1R3's role in dermatologic and respiratory disease pathways.¹ The amlitelimab decision was particularly notable given the drug came to Sanofi through its $1.4 billion acquisition of Kymab in 2021, and the company had hoped the OX40-ligand antibody would help offset Dupixent's approaching patent cliff.¹

What happens next?

Sanofi has not indicated whether the SAR445399 NCFB trial will resume, be formally discontinued, or be replaced by a redesigned study, and the company had not provided additional comment as of the most recent reporting.¹ The broader portfolio review remains ongoing under Garijo's leadership, and further trial or program decisions are expected as Sanofi continues assessing its late-stage assets against its updated strategic criteria.³

References

1. Kansteiner F. Sanofi suspends chronic lung disease phase 2 study, tied to "strategic business reasons." Fierce Biotech. August 5, 2026. Accessed August 6, 2026.
2. Sanofi pauses key bronchiectasis trial, raising questions for SNY investors. TipRanks. August 2026. Accessed August 6, 2026.
3. Sanofi's new CEO wants more "realistic view" of Phase 3 go/no-go decisions. BioSpace. July 2026. Accessed August 6, 2026.