Comparative Effectiveness Study of Mepolizumab Versus Omalizumab

Great than or equal to (>=) 2 consecutive medical or pharmacy claims for the same biologic agent (either mepolizumab or omalizumab) on or after January 1, 2019

The first observed claim will be defined as the index date and the second claim must occur within 6 months of the index date

• >=12 months of Medicare FFS continuous clinical activity prior to the index date (baseline period)

Continuous clinical activity will be defined as consecutive quarters with >=1 medical and >=1 pharmacy claim

• >=2 diagnoses of asthma on separate visits in any position during the baseline period or on the index date
• >=1 asthma exacerbation during the baseline period or on the index date
• >=18 years of age at the index date

While most Medicare FFS beneficiaries are aged >=65 years, some younger adults qualify for Medicare due to disability or specific medical conditions. Because asthma affects adults across a wide age range, all participants aged >=18 years will be included.

• (Persistent use subgroup only) Persistent to the index biologic agent for at least 6 months following biologic initiation

>=1 diagnosis for cystic fibrosis, lung cancer, interstitial lung disease, or alpha-1 antitrypsin deficiency during the baseline period or on the index date

• >=1 medical or pharmacy claim for mepolizumab, omalizumab, reslizumab, benralizumab, dupilumab, or tezepelumab any time prior to the index date
• >=1 diagnosis for eosinophilic granulomatosis with polyangiitis (EGPA), hypereosinophilic syndrome (HES), chronic rhinosinusitis with nasal polyps (CRSwNP), chronic spontaneous urticaria (CSU), or pulmonary eosinophilia during the baseline period or on the index date
• Participants with EGPA, HES, CSU, and CRSwNP will be excluded as these represent non-asthma indications that may drive biologic initiation independent of asthma severity. In addition, participants with pulmonary eosinophilia will be excluded, as this condition reflects eosinophilic lung disease that may influence selection of anti-interleukin (IL)-5 or IL-5 receptor therapies independent of asthma-related factors. This approach aims to minimize confounding by treatment indication while preserving generalizability to the broader severe asthma population