Nucala (mepolizumab) is generally well tolerated by patients, with consistent safety data of up to 4.8 years in severe eosinophilic asthma1

Nucala is indicated as an add-on treatment for severe refractory eosinophilic asthma in adults, adolescents and children aged 6 years and older. The recommended dose of Nucala is 100mg SC once every 4 weeks in adults and adolescents 12 years and older. The licenced dose of Nucala in children aged 6-11 years is 40mg SC once every 4 weeks regardless of weight.2

The maximum exposure duration of mepolizumab in the phase 3 and open label extension studies was 4.8 years. A patient withdrawal range of 4 weeks to 4.8 years was observed in MENSA, SIRIUS, COSMOS and COSMEX.1

The long-term safety and immunogenicity profile of Nucala was similar to that observed in placebo-controlled severe asthma trials 1,3,4

Number of Nucala prescriptions in the UK

COSMEX: Most frequent on-treatment AEs and SAE (N=339)1

AEs occurring in ≥10% of the population, SAE occurring in >1 patient

On-treatment AEs, n(%)  
143 (42)
Asthma 77 (23)
Bronchitis 64 (19)
Upper respiratory tract infection 64 (19)
Sinusitis 62 (18)
Headache 57 (17)
Influenza 44 (13)
Back pain 42 (12)
On-treatment SAEs, n(%)  
34 (10)
Pneumonia 6 (2)
Nasal polyps 4 (1)
Respiratory tract infection
3 (<1)
Foot fracture 3 (<1)
Lower respiratory tract infection 2 (<1)
Osteonecrosis 2 (<1)
Diverticulitis 2 (<1)
Fracture 2 (<1)
Gastroesophageal reflux disease 2 (<1)
Hyponatraemia 2 (<1)
2 (<1)
  • COSMEX Study Design

    COSMEX Study design

    Diagrammatic representation of COSMEX study design. Treatment period of up to 172 weeks and N=339.

    DESCRIPTION: Multi-centre, open-label, long-term, single arm extension study assessing the safety and efficacy of Nucala in 339 patients with severe eosinophilic asthma who were given Nucala 100mg SC every 4 weeks in addition to SoC. COSMEX enrolled a subset of patients from COSMOS with a history of life-threatening or seriously debilitating asthma. There was no fixed treatment duration for COSMEX and all patients were given Nucala until they met protocol-defined stopping criteria. The median duration of Nucala treatment in COSMEX was 2.2 years (range 8 weeks-3.3 years); maximum exposure to Nucala for patients in COSMEX was up to 4.8 years.

    OBJECTIVES: The primary endpoints were adverse event frequency and annualised rate of exacerbations. FEV1, ACQ-5 score and daily OCS use were also assessed.

    ACQ-5, asthma control questionnaire; FEV1, forced exhalation volume in one second; OCS, oral corticosteroid; SC, subcutaneous; SoC, standard of care
    *As determined by the investigator


    1. Khurana, S. Clinical Therapeutics; 2019; 1-16.e5;

REALITI-A: Most frequent on-treatment AEs (N=823)7

AEs occurring in >3 events and SAE occurring in <1% of patients.

On Treatment AEs, n(%)  
33 (4%)
Pruritus 6 (<1%)
Fatigue 6 (<1%)
Influenza like illness 5 (<1%)
Nausea 5 (<1%)
Arthralgia 5 (<1%)
Myalgia 4 (<1%)
Back pain 3 (<1%)
Herpes zoster 3 (<1%)
Lethargy 3 (<1%)
Nasopharyngitis 3 (<1%)
  • REALITI-A Study Design

    REALITI-A Study Design

    Study Design: 2-years, global, prospective, observational, single-arm study2

    REALITI-A Study Design
      Total population (n=822)
    Age in years, mean (SD) 54.0 (13.6)
    Female % 63%
    Smoking history  

    Current smoker %


    Never smoked %


    Former smoker %

    Geometric mean blood eosinophil count, cells/μL (SD log) 350 (1.253)
    Mean duration of asthma in years (SD)  19.7 (15.7)
    Patients on maintenance OCS & 39%
    Daily mean OCS dose in mg/day (IQR) 10 (5.0, 15.0)
    Comorbidities %  

    Allergic Rhinitis 


    Chronic Rhinosinusitis


    Nasal Polyps


    REALITI-A is a 2-year study in adults aged 18 years and over. 

    The primary endpoint was the rate of clinically significant exacerbationsb at 12 months compared to the baseline rate in the 12 months prior to treatment.2

    aIf enrolment occurred before the index date, there was a variable-length run-in period in which patients continued with the same therapy; there was no run-in period when enrolment and index dates were the same day/when index date occurred before enrolment1; bClinically significant exacerbations: those requiring ED visit/hospitalisation and/or use/increased dose of OCS therapy1

    Real-world studies are designed to evaluate associations among variables and not to definitively establish causality. These limitations are important when interpreting results: lack of comparator arm, differences in patient populations and data collection vs. randomised controlled trials.

    SEA, severe eosinophilic asthma; SC, subcutaneous; SoC, standard-of-care.


    1. Harrison T, et al. Eur Respir J. 2020;56:2000151;
    2. Caruso C, Canonica GW, Patel M et al. International, prospective study of mepolizumab in severe asthma: REALITI-A at 2yrs. Abstract presented at ERS; 4-6 September 2022; Barcelona, Spain.


AE: adverse event; SAE: serious adverse event; SC: subcutaneous

  1. Khurana S et al. Clin Ther 2019; 41:2041-2056
  2. Nucala SmPC
  3. Ortega HG et al. N Engl J Med 2014; 371:1198-1207
  4. Khatri S, et al. J Allergy Clin Immunol 2019; 143:1742-1751.e7
  5. GlaxoSmithKline Data on File. REF-143003
  6. Caruso C, Canonica GW, Patel M, et al. International, prospective study of mepolizumab in severe asthma: REALITI-A at 2yrs. Abstract presented at ERS; 4-6 September 2022; Barcelona, Spain.
  7. GlaxoSmithKline Data on File. REF-165200


Adverse events should be reported. Reporting forms and information can be found at or search for MHRA Yellowcard in the Google Play or Apple App store. Adverse events should also be reported to GlaxoSmithKline on 0800 221 441

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January 2023 | PM-GB-MPL-WCNT-200031 (V6.0)