Specific Immunotherapy With Mannan-Conjugated Allergoids for HDM-Allergic Rhinitis/Rhinoconjunctivitis. MM09-SIT-063.

The goal of this clinical trial is to learn whether EP-088\_MM09 works to treat house dust mite allergy. It will also assess the treatment\'s safety. EP-088\_MM09 contains modified house dust mite allergens called mannan-conjugated allergoids. The study plans to include 250 participants aged 12 to 65 years. They will have persistent, moderate to severe nasal allergy symptoms, with or without eye symptoms. Participants may also have mild or moderate allergic asthma, provided it is controlled. The main questions are: * Does the treatment lower allergy symptoms and the need for symptom-relief medicines compared with a placebo? * What medical problems or reactions occur during treatment? Researchers will assess how well the treatment works using a score combining symptoms and medication use. The main assessment will cover four weeks after the treatment course. Participants will be assigned by chance to receive either EP-088\_MM09 or a placebo. They will have an equal chance of receiving either treatment. The placebo looks like EP-088\_MM09 but contains no active ingredients. Neither participants nor study doctors will know which treatment each participant receives. Each participant will be in the study for approximately 14 to 21 months. Participants will: * Attend one or two visits before starting treatment to check whether they can take part. * Attend 12 treatment visits, approximately once a month, to receive injections under the skin. They will receive two injections at the first treatment visit and one at each later visit. * Stay at the clinic for at least 30 minutes after each injection. * Record symptoms and medication use daily during specified periods. * Complete questionnaires about their symptoms and quality of life, and provide blood samples. * Attend a final visit about one month after the last treatment visit. Participants who are also sensitive to pollen may need a second visit before starting treatment. This is needed if their first visit falls during the relevant pollen season or within one month before or after it.