The purpose of this study is to investigate the safety of different doses of sublingual tablets of house dust mite allergen extracts in adults with house dust mite-associated allergic asthma.

Inclusion Criteria:

• Written informed consent.
• Male or female patient from 18 to 50 years.
• Diagnosed asthma with medical history consistent with HDM-induced allergic asthma.
• Positive SPT to House Dust Mites(HDM)and HDM-specific IgE serum value ≥ 0.7 kU/L.
• Stable asthma treatments.
• Spirometry with best FEV1 > 70% of the predicted value.
• Spirometry with reversibility of FEV1 of ≥ 12% and ≥ 200 mL.
• Asthma Control Test™ (ACT) score ≥ 20.

Exclusion Criteria:

• Current smoker or former smoker with > 10 pack/year history.
• Co-sensitisation to any allergen possibly leading to clinically relevant respiratory allergy likely to significantly change the symptoms of the patient throughout the treatment period.
• Patient with a past or current disease, which as judged by the Investigator, may affect the patient's participation in or the outcome of this study.
• Patient with any oral condition that could confound the safety assessments or planning to have a dental extraction during the study.
• Female patient pregnant or breast-feeding/lactating.
• Female patient of childbearing potential not using a medically accepted contraceptive method.
• Patient treated with beta-blockers, tricyclic antidepressants or monoamine oxidase inhibitors (MAOIs).
• Patient who received allergen immunotherapy for HDM in the last 10 years.
• Ongoing treatment by immunotherapy with another allergen.