GSK has secured approval from the US Food and Drug Administration (FDA) for its severe asthma add-on maintenance therapy, Exdensur (depemokimab).

This means that the long-acting interleukin-5 (IL-5)-targeting monoclonal antibody (mAb) is now indicated for use in patients aged 12 years or older with severe asthma characterised by an eosinophilic phenotype.

The FDA's decision was based on the results of the Phase III SWIFT-1 (NCT04719832) and SWIFT-2 (NCT4718103) trials, which saw the therapy slash the prevalence of annualised asthma exacerbations by up to 58% over a 52-week treatment period.

At a twice-yearly dosing schedule, Exdensur also diminished asthma-linked hospitalisations, with 1% and 4% of patients enrolled onto the SWIFT-1 and 2 trials having to visit the hospital during the study period. This compares with 8% and 10% of patients receiving placebo, respectively.

Exdensur differs from other add-on maintenance therapies available to patients with severe asthma as it requires biannual dosing.

According to Kaivan Khavandi, senior vice-president and global respiratory, immunology and inflammation R&D head at GSK, Exdensur’s dosing edge could “redefine patient care” while further establishing the role of biologics in patients who face continued exacerbations despite treatment.

On 15 December, GSK also got approval for Exdensur from the Medicines and Healthcare Regulatory Agency (MHRA) in the UK, where it is indicated to treat patients with both asthma and severe chronic rhinosinusitis with nasal polyps.

Exdensur’s approval adds to GSK’s strong portfolio of respiratory medicines, which includes blockbuster COPD and add-on asthma therapy, Nucala (mepolizumab), which made £1.78bn ($2.37bn) for the UK-based pharma in 2024.

According to GlobalData’s Pharmaceutical Intelligence Center, this makes it the third best-selling severe asthma biologic during that year behind Sanofi and Regeneron’s Dupixent (dupilumab) and Novartis & Roche-owned Genentech’s Xolair (omalizumab).

Competition heats up in severe asthma

While Exdensur may be the first twice-yearly therapy to gain FDA approval in severe asthma, GSK will still face significant competition from other biologics approved in the indication.

This includes Sanofi and Regeneron’s biweekly IL-4 receptor alpha (IL-4Rα) blocker Dupixent, which has become the best-selling drug on the severe asthma market following its 2018 approval in the indication.

According to a patient-based forecast from GlobalData, Dupixent’s sales will continue to balloon – reaching a projected sales peak of $4.8bn in 2031 in asthma alone. The forecast also predicts that Exdensur’s 2031 sales will reach $935m.

Exdensur will also have to contend with Xolair, though the November 2025 expiry of its US patent formulation will likely see the drug’s profits fall dramatically over the next year.

Earlier this year, the FDA approved Celltrion's interchangeable Xolair biosimilar, Omlyclo, for severe asthma.