Our project is to describe retrospectively and prospectively CF patients treated with biotherapy in French CF centers.

Main objective: To describe the clinical and paraclinical course of CF patients before and after treatment with anti-IL5 and other biotherapies since 2019.

Secondary objective: To describe adverse events potentially related to the biotherapies.

•Background: ABPA and asthma associated with cystic fibrosis impact the CF course with a more rapid decline in lung function.

Corticosteroid therapy can be harmful and must be avoid in CF to prevent diabetes, osteoporomalacia or mycobacterium infections.

Monoclonal antibodies have the marketing authorization for severe uncontrolled asthma and, up to now, some CF patients with ABPA or severe asthma and high plasma IgE levels benefit from omalizumab.

Anti-Il5 agents are available since February 2019 and have demonstrated their efficacy in severe and hypereosinophilic asthma control (plasma eos.>300mmol/L).

Some patients with CF who have severe asthma or ABPA are still poorly controlled despite Omalizumab with other treatments (steroids and/or azoles). Some of them have persistent hypereosinophilia suggesting a possibility to treat with antiIL5 antibodies.

About 5% of patients have biotherapy treatment criteria, some have already received it, others are elective to such treatment and will receive in the future.

Methods:

Our project is to describe retrospectively and prospectively the clinical history of CF patients eligible for biotherapy in French CF centers.

Main objective: To describe the clinical and paraclinical course of CF patients before and after treatment with anti-IL5 and other biotherapies since 2019.

Secondary objective: To describe any adverse events potentially related to the biotherapies.

Inclusion criteria:

• Cystic fibrosis (2 known variants)
• Age ≥ 6 years
• Plasma hypereosinophilia ≥ 300/µl
• Uncontrolled ABPA or uncontrolled asthma, or failure of other biotherapy (intolerance, ineffectiveness)

Exclusion criteria

- Refusal to participate in this research

CF patients (2 known variants) with hypereosinophilia ≥ 300/µl and uncontrolled ABPA or uncontrolled asthma, or failure of other biotherapy (intolerance, ineffectiveness)

NC