Sustained low disease activity during long-term mepolizumab treatment in FIP1L1::PDGFRA-negative hypereosinophilic syndrome: a multicenter real-world study
Abstract
Background Mepolizumab reduces relapses and glucocorticoid exposure in hypereosinophilic syndrome (HES), but evidence on long-term effectiveness remains limited. Growing consensus emphasizes sustained low disease activity over single-timepoint response in chronic inflammatory diseases. Objective To evaluate the long-term safety and effectiveness of mepolizumab in HES using a pragmatic definition of Eosinophilic Low Disease Activity State (EoLDAS). Methods We conducted a retrospective multicenter study of 67 patients with glucocorticoid-responsive FIP1L1::PDGFRA -negative HES treated with mepolizumab between 2003 and 2022 through clinical trials or compassionate use programs. Clinical manifestations, blood eosinophil counts, treatments, and serious adverse events were assessed at three-month intervals. EoLDAS was defined as absence of relapse, an absolute eosinophil count <0.5×10 9 /L (complete hematologic response, [CHR]), and a prednisone dose ≤5 mg/day. Results After a median follow-up of 51 months, 12 patients (18%) relapsed and CHR was maintained during a median of 93% of visits. Patients spent a median of 79% (IQR, 40–88) of follow-up visits in EoLDAS, and 51% maintained EoLDAS for at least 75% of visits. Poor EoLDAS attainment (<25% of visits; n=11) was associated with lymphocytic HES and more prior treatment lines. Extending mepolizumab dosing intervals was associated with modest increases in eosinophil counts, but not with relapse or increased glucocorticoid exposure. No serious adverse event was considered related to mepolizumab. Conclusion Mepolizumab provided sustained long-term disease control with low glucocorticoid exposure in FIP1L1::PDGFRA -negative HES. EoLDAS offers a pragmatic measure of longitudinal disease control that warrants prospective validation and may inform future treat-to-target strategies.
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BibTeX
@article{chevalier2026sustained,
title = {{Sustained low disease activity during long-term mepolizumab treatment in FIP1L1::PDGFRA-negative hypereosinophilic syndrome: a multicenter real-world study}},
author = {Kevin Chevalier and François Barde and Stanislas Faguer and Nathalie Freymond and Zakaria Lahmar and Arnaud Bourdin and Dorine Canu and Antoine Neel and Lucile Grange and Camille Taille and Alpha Oumar Diallo and Divi Cornec and Daniele Belgodere and Bernard Bonnotte and Pascal Chanez and Camille Ravaiau and Sébastien Trouiller and Julien Seneschal and Félix Ackermann and Ibrahim Marroun and Emmanuel Ledoult and Julien Rohmer and Guillaume Lefevre and Matthieu Groh and Jean-Emmanuel Kahn},
journal = {Journal of Allergy and Clinical Immunology: In Practice},
year = {2026},
month = oct,
doi = {10.1016/j.jaip.2026.09.021},
url = {https://hal.science/hal-05776378v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Sustained low disease activity during long-term mepolizumab treatment in FIP1L1::PDGFRA-negative hypereosinophilic syndrome: a multicenter real-world study
AU - Kevin Chevalier
AU - François Barde
AU - Stanislas Faguer
AU - Nathalie Freymond
AU - Zakaria Lahmar
AU - Arnaud Bourdin
AU - Dorine Canu
AU - Antoine Neel
AU - Lucile Grange
AU - Camille Taille
AU - Alpha Oumar Diallo
AU - Divi Cornec
AU - Daniele Belgodere
AU - Bernard Bonnotte
AU - Pascal Chanez
AU - Camille Ravaiau
AU - Sébastien Trouiller
AU - Julien Seneschal
AU - Félix Ackermann
AU - Ibrahim Marroun
AU - Emmanuel Ledoult
AU - Julien Rohmer
AU - Guillaume Lefevre
AU - Matthieu Groh
AU - Jean-Emmanuel Kahn
PY - 2026
DA - 2026/10/03
JO - Journal of Allergy and Clinical Immunology: In Practice
DO - 10.1016/j.jaip.2026.09.021
UR - https://hal.science/hal-05776378v1
AB - Background Mepolizumab reduces relapses and glucocorticoid exposure in hypereosinophilic syndrome (HES), but evidence on long-term effectiveness remains limited. Growing consensus emphasizes sustained low disease activity over single-timepoint response in chronic inflammatory diseases. Objective To evaluate the long-term safety and effectiveness of mepolizumab in HES using a pragmatic definition of Eosinophilic Low Disease Activity State (EoLDAS). Methods We conducted a retrospective multicenter study of 67 patients with glucocorticoid-responsive FIP1L1::PDGFRA -negative HES treated with mepolizumab between 2003 and 2022 through clinical trials or compassionate use programs. Clinical manifestations, blood eosinophil counts, treatments, and serious adverse events were assessed at three-month intervals. EoLDAS was defined as absence of relapse, an absolute eosinophil count <0.5×10 9 /L (complete hematologic response, [CHR]), and a prednisone dose ≤5 mg/day. Results After a median follow-up of 51 months, 12 patients (18%) relapsed and CHR was maintained during a median of 93% of visits. Patients spent a median of 79% (IQR, 40–88) of follow-up visits in EoLDAS, and 51% maintained EoLDAS for at least 75% of visits. Poor EoLDAS attainment (<25% of visits; n=11) was associated with lymphocytic HES and more prior treatment lines. Extending mepolizumab dosing intervals was associated with modest increases in eosinophil counts, but not with relapse or increased glucocorticoid exposure. No serious adverse event was considered related to mepolizumab. Conclusion Mepolizumab provided sustained long-term disease control with low glucocorticoid exposure in FIP1L1::PDGFRA -negative HES. EoLDAS offers a pragmatic measure of longitudinal disease control that warrants prospective validation and may inform future treat-to-target strategies.
SN - 2213-2198
SN - 2213-2201
ER -