Chronic rhinosinusitis (CRS) has a prevalence of more than 10% in the United States and Europe and is associated with several co-morbidities including asthma, acute infection, and obstructive sleep apnea. There are principally two forms of CRS namely with and without nasal polyps. CRS with nasal polyps (CRSwNP) in particular can be a severe and debilitating disease resulting in significant morbidity, complete anosmia, headaches, missed work, and hospitalizations. Not uncommonly, patients require chronic oral corticosteroids, multiple courses of antibiotics, and repeated surgical polypectomies to control participants' disease. Total health care expenditure for CRS (which includes both with and without polyps) is more than $60 billion annually in the United States accounting for as much as 5% of the total US health care budget. Annual direct and indirect costs to treat CRS in Europe is estimated to be similar to this amount but data is limited.

For CRSwNP patients suffering with severe and recurrent nasal polyps there are few treatment options. High dose topical nasal steroids and repeated surgical procedures do not halt progression in many patients. Allergen immunotherapy is often non-curative in this population. Similarly, due to the fact that CRSwNP is not exclusively an Immunoglobulin E (IgE) driven process, omalizumab was shown to have mixed benefit in this population. Likewise, omalizumab resulted in no reduction in polyp size among patients with Aspirin Exacerbated Respiratory Disease (AERD).

More typically chronic nasal polyp disease is an eosinophil mediated process. Patients with demonstrated elevations in serum and mucosal eosinophils tend to have more severe disease and higher nasal polyp recurrence rates. Clinical researchers have begun to recognize this connection. A recent Phase II study in Europe showed a reduction in polyp burden using mepolizumab anti-Interleukin (IL) 5 monoclonal antibody. Benralizumab which targets IL-5 receptor signaling has been shown to have powerful apoptotic effects on eosinophils and may likely prove to be even more efficacious. Because of its unique mechanism of action, benralizumab may have a profound impact on reducing mucosal eosinophils resulting in great benefit to patients suffering with severe nasal polyps refractory to standard treatment.

Benralizumab has been shown to be efficacious treating severe asthmatics with eosinophilia. The unique mechanism of action of benralizumab targets the IL-5 receptor leading to degradation of signaling and apoptosis. This direct effect on eosinophils leads to reduction of proinflammatory processes in the asthmatic airways among those with elevated eosinophil counts. While many subjects with allergic asthma do indeed have concomitant local and systemic elevations in eosinophils, the primary driver of inflammation in allergic asthmatics is IgE and IL-4. Allergen immunotherapy and anti-IgE therapy (omalizumab) has long been known to be effective in these atopic individuals. However, a significant portion of non-asthmatics respond poorly to these IgE targeted therapies.

In a similar manner, chronic rhinosinusitis with nasal polyps (CRSwNP) is a disease often associated with atopy and propagated by IgE/IL-4 mediated inflammation. However, more than 50% of patients with CRSwNP have no evidence of allergen sensitivity. Nasal and sinus inflammation in these non-atopic individuals is often characterized by IL-5 upregulation, eosinophilia, leukotrienes, and more severe polyps. These individuals tend to have more aggressive disease requiring frequent surgeries, high dose intranasal budesonide irrigation, and oral steroids yet the polyps more often than not are persistent and may return post surgery. In a subset of patients, concomitant aspirin sensitivity can be managed with aspirin desensitization, however this approach is not always effective and can also be cumbersome. A more universal and potentially more efficient approach to treating severe polyps is to target eosinophils directly using a monoclonal antibody. Previous reports have shown some benefit targeting IL-5 ligand itself with mepolizumab but the potential benefit of directly eliminating eosinophils by shutting down cellular signaling with benralizumab would be expected to have a more dramatic effect and needs to be investigated.