Sanofis $1.4B Kymab Bet Falters as Asthma Drug Stumbles in Phase II

Title

Sanofi’s $1.4B Kymab Gamble Set Back as Asthma Drug Amlitelimab Misses Phase II Goal

Keywords

Sanofi
Kymab acquisition
amlitelimab
KY1005
asthma drug
Phase II clinical trial
immunology pipeline
OX40L antagonist
immune-mediated diseases
clinical trial failure
respiratory drug development

Key Facts

- Acquisition Overview:
Sanofi acquired UK-based Kymab in 2021 for up to $1.4 billion to strengthen its immunology and inflammatory disease pipeline, primarily for Kymab’s lead asset, amlitelimab (formerly KY1005), a monoclonal antibody targeting the OX40L immune regulator3 4 5 8.

- Asthma Setback:
In 2025, amlitelimab failed to achieve statistically significant improvement over placebo in reducing disease exacerbations for moderate-to-severe asthma patients in the Phase II TIDE-Asthma trial, particularly at the highest tested dose1 2 6 10.

- Subgroup Signal:
Despite missing the primary endpoint, amlitelimab showed promising efficacy in a biomarker-defined asthma subgroup (patients with high eosinophils and neutrophils), reducing exacerbations by over 70% at week 60—comparable to or exceeding market leaders like Dupixent and Tezspire1 6 10.

- Secondary Endpoints:
The drug delivered “nominally significant” yet “clinically meaningful” improvements in secondary measures such as lung function and asthma control, especially at medium doses1 6 10.

- Continued Development:
Sanofi and external analysts (e.g., Leerink Partners) still view amlitelimab as promising, citing its differentiated profile and durable effects. Plans are underway for a Phase III trial in asthma, as well as continued development for several other immune-mediated conditions1 6 10.

- Mechanism of Action:
Amlitelimab targets OX40L, a key regulator in the immune response, aiming to rebalance pro- and anti-inflammatory T cells without broadly suppressing immunity. This approach holds potential for various autoimmune and inflammatory disorders3 4 6 8.

- Pipeline and Indications:
Amlitelimab is also being investigated for atopic dermatitis (where it met endpoints in a prior Phase II trial), hidradenitis suppurativa, alopecia areata, celiac disease, and scleroderma. Its peak sales potential is estimated at over €5 billion, with the largest opportunity in atopic dermatitis1 6 10.

- Safety Profile:
The drug demonstrated an acceptable safety and tolerability profile in asthma and prior trials, with adverse events similar to placebo and mostly mild to moderate in severity6.

- Strategic Impact:
The setback in asthma is a significant blow to Sanofi’s ambitions in respiratory medicine, but the company remains committed to advancing amlitelimab as part of its broader strategy to become a leader in immunology and reduce reliance on external innovation4 8 10.

Comparison of Amlitelimab (Asthma, TIDE-Asthma Phase II) to Existing Asthma Therapies

| Feature | Amlitelimab (KY1005) | Dupixent (Sanofi/Regeneron) | Tezspire (Amgen/AstraZeneca) |
|---------------------------|------------------------------|-----------------------------|-------------------------------|
| Target | OX40 Ligand (OX40L) | IL-4/IL-13 | TSLP |
| Mechanism of Action | Immune regulation/rebalancing| Th2 pathway blockade | Epithelial cytokine blockade |
| Phase II Asthma Efficacy | Primary endpoint missed; >70% reduction in select subgroups at week 60 | 66–70% annualized exacerbation reduction in subgroups | 66–70% annualized exacerbation reduction in subgroups |
| Safety | Acceptable; mostly mild/moderate TEAEs | Well-established | Well-established |
| Dosing Frequency | Every 4 weeks (then 12 weeks)| Every 2 weeks | Every 4 weeks |
| Approved for Asthma | No (in development) | Yes | Yes |

Blockquote

“In asthma, amlitelimab shows potential as an effective, long-acting medicine, including in patients with moderate-to-severe heterogenous inflammation. If the preliminary effect we have seen is confirmed in phase 3 studies, amlitelimab could become a differentiated treatment option in asthma.”
— Houman Ashrafian, Sanofi Head of R&D6 10