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

Inclusion Criteria:

• Written informed consent.
• Male or female from 18 to 50 years of age.
• Diagnosed asthma and rhinitis with medical history consistent with HDM-induced allergic asthma and rhinitis.
• Positive SPT to HDM and and HDM-specific IgE serum value ≥ 0.7 kU/L.
• Stable asthma therapies.
• Spirometry (pre-bronchodilator) with best FEV1 ≥ 70% of the predicted value.
• Spirometry with reversibility in FEV1 of ≥ 12% and ≥ 200 mL.
• Asthma Control Test™ (ACT) score ≤ 19.

Exclusion Criteria:

• Former smoker with > 10 pack year history or current smoker.
• Patient with a urine level of cotinine ≥ 500 ng/mL.
• Co-sensitisation to any allergen possibly leading to clinically relevant symptoms likely to significantly change the asthma symptoms of the subject during the study.
• Patient who received allergen immunotherapy for HDM within the past 10 years.
• Ongoing immunotherapy for an aeroallergen other than house dust mite.
• Patient with any oral condition that could confound the safety assessments or planning to have a dental extraction during the study.
• Patient treated with beta-blockers, tricyclic antidepressants or monoamine oxidase inhibitors (MAOIs).
• Pregnant women or breast-feeding/lactating.
• Women with childbearing potential who are not using a medically accepted birth control method.
• 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.