Pivotal trial: Study design1

Study 200622


Up to 4 weeks

with stable regimen of hypereosinophilic 

syndrome (HES) therapy


32 weeks; N=108

1:1 Randomization

NUCALA 300 mg SC + stable HES therapy (n=54)

Placebo + stable HES therapy (n=54)

Administered every 4 weeks


20 weeks

NUCALA (n=102)

32-week, multicenter, randomized, double blind, placebo-controlled, parallel-group study comparing NUCALA 300 mg SC to placebo, each added to stable HES therapy in 108 patients aged ≥12 years with HES.


Key inclusion criteria

  • Diagnosed with HES* ≥ 6 months prior to baseline
  • Blood eosinophil counts ≥ 1000 cells/µL during screening
  • ≥2 HES flares in the past 12 months
  • At least one of these HES flares must not have been related to a decrease in therapy during the 4 weeks prior to the flare

Key exclusion criteria

  • Patients with non-hematologic secondary HES (eg, drug hypersensitivity, parasitic helminth infection, HIV infection, non-hematologic malignancy)
  • Patients with FIP1L1-PDGFRA kinase-positive HES

Stable HES therapy

  • Existing HES therapy, which included but was not limited to chronic or episodic corticosteroids, immunosuppressants, or cytotoxic therapy

Primary endpoint results:

Proportion of patients who experienced HES flares(s) during the 32-week study or withdrew. NUCALA 28% vs placebo 56%, P=0.002


Select secondary endpoints:

Time to first flare, change from baseline in Brief Fatigue Inventory Item 3 at Week 32


*HES diagnosis was based on signs or symptoms of organ system involvement and/or dysfunction that could be directly related to blood eosinophilia of >1500 eosinophils/μL on ≥2 occasions, and/or tissue eosinophilia.

Historical flares for study entry criteria were defined as documented HES-related worsening of clinical symptoms or blood eosinophil counts requiring an escalation in treatment.

HES flare defined as a worsening of clinical signs/symptoms or increased eosinophils (on ≥ 2 occasions), resulting in an escalation/addition of oral corticosteroids (OCS) or cytotoxic or immunosuppressive therapy.


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Clinical efficacy

Review the clinical trial data on HES flares

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