Steroid-sparing benefits of biologic use in hypereosinophilic syndrome and substantial disease burden across subtypes.

Background: Limited data exist on the burden of myeloproliferative, lymphocytic and idiopathic subtypes of hypereosinophilic syndrome (M-HES, L-HES and I-HES) and the characteristics of patients with HES receiving biologic therapies. This analysis aimed to further characterize these subtypes and explore the impact of biologics in a real-world European setting.

Methods: This was a post hoc subgroup analysis of a retrospective, non-interventional, chart review (GSK ID: 214657) across five European countries. Index date was first clinical visit during January 2015-December 2019 (after or at time of HES diagnosis). Patients with HES aged ≥6 years with ≥1-year follow-up from index were included. Demographics, disease characteristics, diagnostic assessments, comorbidities, types of treatment, clinical manifestations, clinical outcomes and HES-related healthcare resource utilization were summarized for HES overall and subtypes. Oral corticosteroid (OCS) use and clinical manifestations/outcomes were assessed 12-months pre- and post-biologics.

Results: The analysis included 280 patients with I-HES (n = 155), M-HES (n = 66), L-HES (n = 42) and chronic eosinophilic leukemia (n = 2). The most common clinical manifestations were fatigue (54.2% I-HES, 52.4% L-HES, 42.4% M-HES), skin itch (36.4% M-HES, 35.7% L-HES, 33.5% I-HES) and pain (31.0% L-HES, 30.3% M-HES, 27.1% I-HES). Biologic use was highest with L-HES (64.3%), followed by I-HES (43.9%) and M-HES (34.8%). Clinical response rates were highest for the I-HES subtype (75.5%; 66.7% L-HES, 63.6% M-HES). Hospitalizations were highest for L-HES (45.2%; 30.3% M-HES, 25.8% I-HES). The annualized rate of OCS prescriptions reduced by 56.8% (0.44-0.19 per person-year) and the proportion of patients with ≥1 clinical response increased 3.6-fold (6.5%-23.4%) between the pre- and post-biologics periods.

Conclusions: All HES subtypes had a substantial disease burden and were commonly associated with fatigue, skin itch and pain. I-HES appeared to be more responsive to treatment than L-HES and M-HES. Biologic use for HES led to more patients experiencing clinical responses and was OCS-sparing.