Here's a classic drug development story: a promising new therapy works great in one or two diseases, but then it hits a wall in a third. That's the update from Sanofi SA (SNY) on its experimental drug lunsekimig.
The company reported Phase 2 data Tuesday showing the drug delivered meaningful improvements for patients with asthma and nasal polyps. But in a separate study for the skin condition atopic dermatitis, it missed its main goal. It's a reminder that biology is complicated, and a drug that tackles inflammation in the lungs doesn't automatically fix it on the skin.
Strong Outcomes In Asthma Study
First, the good news. In the Phase 2b AIRCULES trial for moderate-to-severe asthma, lunsekimig hit both its primary and key secondary endpoints. The drug led to statistically significant reductions in asthma exacerbations—those scary flare-ups—and improved lung function, as measured by a test called pre-bronchodilator forced expiratory volume (FEV1).
This is a population of patients who often have persistent symptoms even with standard treatments, so a new option that targets the underlying inflammatory pathways could be a big deal.
Positive Results In Nasal Polyp Study
The good news extended to the nose. In the Phase 2a DUET study for chronic rhinosinusitis with nasal polyps, lunsekimig achieved its primary endpoint by reducing nasal polyp size. Key secondary measures improved too, including nasal congestion scores and imaging-based assessments. This suggests the drug's mechanism might work across related inflammatory conditions that affect the airways.
Atopic Dermatitis Study Misses Goal
Now for the "but." Results from the exploratory Phase 2b VELVET study in atopic dermatitis were mixed. The trial did not meet its primary endpoint, which measured the percentage improvement in eczema severity scores.
It wasn't a total loss—patients showed gains in secondary measures, including higher rates of skin clearance. So there's some clinical activity there, just not enough to clear the primary hurdle. Sometimes in drug trials, you get a hint of efficacy that tells you to keep going or to tweak the approach. Other times, it's a sign to move on.
Sanofi Safety Profile
Across all the studies, lunsekimig showed a generally favorable safety profile. Common side effects included respiratory infections, headaches, and reactions at the injection site. Serious events occurred at similar rates to placebo.
The drug is a bispecific Nanobody, which is a fancy way of saying it's engineered to block two inflammatory drivers at once: TSLP and IL-13. Both are implicated in asthma and related diseases, so hitting them simultaneously is the whole idea.
Sanofi Ongoing Development
Lunsekimig is still moving through the clinic. Ongoing studies include the Phase 2 AIRLYMPUS trial in high-risk asthma and Phase 3 trials named PERSEPHONE and THESEUS. The path forward likely focuses on the respiratory wins while figuring out what, if anything, to do about the skin result.
Competitive Landscape
This news lands in a busy field. Back in May 2025, Regeneron Pharmaceuticals Inc. (REGN) and Sanofi reported mixed data from two COPD trials for their drug itepekimab. Their blockbuster drug Dupixent, however, scored an FDA approval for COPD in November 2024, its sixth U.S. indication.
More recently, in January, Upstream Bio Inc. (UPB) shared positive Phase 2 results for its severe asthma drug verekitug, showing it cut asthma attacks by 56% with quarterly dosing.
And just a few months ago in December 2025, the FDA approved GSK plc's (GSK) drug Exdensur (depemokimab-ulaa) as an add-on maintenance treatment for severe asthma—a drug that only needs two doses a year.
So, Sanofi's lunsekimig is trying to carve out space in a market where competitors are already having success and where the bar for convenience and efficacy keeps getting higher.
As for the stock reaction, Sanofi shares were up 0.95% at $48.05 in premarket trading Tuesday, according to market data.
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