A new study published in the Journal of Allergy and Clinical Immunology found that a common genetic variant — present in roughly 60% of the population — may significantly reduce how well mepolizumab works in children with asthma. The culprit is a variant in the SERPINE1 gene, which causes the body to produce more of a protein called PAI1 during viral illness, leading to greater airway scarring and a weaker antiviral response.

What makes this finding especially notable is that when mepolizumab is given to children with this variant, it appears to stimulate additional inflammatory pathways that damage the airway — pathways the drug doesn't block. In children without the variant, these changes don't occur. Researchers analyzed nasal samples and data from children aged 6–17 with exacerbation-prone asthma from prior studies.

Key Takeaways:

• Children with the SERPINE1 variant may experience worse asthma outcomes on mepolizumab compared to those without it
• The drug may activate unblocked inflammatory pathways in these patients, potentially limiting its therapeutic benefit
• These findings could help clinicians identify which children may need alternative treatment strategies earlier in their care

Why it matters: With 60% of the population carrying this variant, the implications for pediatric asthma care are significant. This research is a meaningful step toward precision medicine — tailoring asthma treatment to a child's individual genetic profile rather than a one-size-fits-all approach.