This study is a pragmatic, real-life, observational study recruiting adult patients with chronic rhinosinusitis with nasal polyposis who are eligible to start biologicals as standard treatment. The aim of this study is to observe the long-term outcomes of biologicals in CRSwNP patients with or without comorbid asthma in 'real life'. Moreover, the investigators will gain insight into the mechanisms of biologicals in the local and systemic immunity of these patients and investigate novel local and systemic biomarkers and predictors of response.

In this project, thanks to intense collaboration between the ENT department and the pulmonary diseases within the Allergy Network UZ Gent, the investigators set up a prospective study and biobank with the following aims:

• To observe and follow-up on clinical characteristics in patients with chronic rhinosinusitis with nasal polyposis (CRSwNP) with or without asthma. Primary outcomes will be the endoscopic total nasal polyp score (NPS) and the nasal symptom scores (SNOT-22, VAS, NCS and UPSIT).
• Identifying key nasal inflammatory biomarkers to predict therapeutic response to biologicals in CRSwNP patients (identification on blood samples, nasal secretions, small tissue biopsies and superficial scrapings before, during and at month 24 of treatment).
• Unravel the effects of biologicals in the local nasal immune regulation.
• Performing additional analyses to search for new biomarkers via complete proteomic analysis.

Using a unique combination of nasal sampling and state of the art biomarker discovery, the investigators believe this research will provide unprecedented insights which will aid the treatment of patients with biologicals.

Inclusion Criteria:

Patients must meet the following criteria to be eligible for the enrolment in the study:

• Signed informed consent form (ICF),
• Age between 18 and 80 years at time of signing ICF,
• Able to comply with the study protocol, in the investigator's judgment,
• In group one: patients with severe allergic and/or eosinophilic asthma, defined by being currently treated with a biological (SoC) OR starting treatment with a biological (SoC).
• In group two: patients with CRSwNP with or without asthma, defined by starting treatment with a biological (SoC) and fulfill the criteria for reimbursement of a biological therapy

Exclusion Criteria:

Patients who do not meet the reimbursement criteria of a biological therapy cannot participate in the study.

Adult patients (between 18 and 80 years old) with severe allergic and/or eosinophilic asthma in group 1 and CRSwNP in group 2 that are receiving or will start to receive a biological as standard of care treatment, and agree on participating (signature of a written informed consent).