The aim of this study is to draw blood from patients with well-defined atopic asthma that will be subsequently used in invitro experiments to investigate the activation potency of Prostaglandin D2 metabolites to the DP2 receptor in comparison to Prostaglandin D2. The inhibitory activity of a potent DP2 receptor antagonist, Fevipripant, shall be determined.

The inhibitory activity of a potent DP2 receptor antagonist shall be determined. For these experiments eosinophil granulocytes and ILC2 cells will be isolated from the collected blood samples and used in specific assays in respect to their functional reactivity against the DP2 receptor antagonist Fevipiprant after respective stimulation using Prostaglandin D2 metabolites or Prostaglandin D2. Major rationale is to show and determine the EC70 of the effectivity of Fevipiprant against Prostaglandin D2 metabolite triggered activation of eosinophil granulocytes and ILC2 innate lymphoid cells.

Inclusion Criteria:

• Women will be considered for inclusion if they are:

Not pregnant, as confirmed by pregnancy test (see flow chart), and not nursing. Of non-child bearing potential (i.e. physiologically incapable of becoming pregnant, including any female who is pre-menarchial or post-menopausal, with documented proof of hysterectomy or tubal ligation, or meets clinical criteria for menopause and has been amenorrhoeic for more than 1 year prior to the screening visit).

Of childbearing potential and using a highly effective method of contraception during the entire study (vasectomised partner, sexual abstinence - the lifestyle of the female should be such that there is complete abstinence from intercourse from two weeks prior to the first dose of study medication until at least 72 hours after treatment -, implants, injectables, combined oral contraceptives, hormonal IUDs or double-barrier methods, i.e. any double combination of IUD, condom with spermicidal gel, diaphragm, sponge, and cervical cap).

• Body weight ≥ 50 kg and BMI within the range 19-32 kg/m²
• History of allergic asthma since at least 12 months
• A concentration of at least 0,15 x 106/mL eosinophils in peripheral blood

Exclusion Criteria:

• History of an acute infection two weeks prior to the screening visit.
• Intake of oral steroids within 4 weeks prior to screening
• Past or present disease, which as judged by the investigator, may affect the outcome of this study. These diseases include, but are not limited to, cardiovascular disease, malignancy, hepatic disease, renal disease, hematological disease, neurological disease, endocrine disease or pulmonary disease (including but not confined to chronic bronchitis, emphysema, tuberculosis, bronchiectasis or cystic fibrosis).
• Participation in another clinical trial 30 days prior to enrollment.
• Donation of more than 100 ml of blood in the preceding 2 months before the screening visit.