Potency of HDM Sublingual AIT Tablets in Assuring the Persistency of Asthma Control in HDM Allergic Patients With Severe Asthma, Treated With Tezepelumab

The TEZEPAIT study is a prospective, multicentre, 2-parallel-arms, placebo-controlled, double-blind, randomized (1:1) trial. PHASE 1: Patients will be included in the study after verification of eligibility criteria and signing of informed consent. All patients will be treated with Tezepelumab for 3-6 months and randomized in two groups: * Group A: Tezepelumab + Acarizax® * Group B: Tezepelumab + Placebo If patients are not controlled (ACT ≥ 20/25) after 3 months of Tezepelumab, they will be re-assessed monthly, for 3 consecutive months, until asthma symptoms are controlled or they will be excluded from the rest of the study. If they are not controlled after 6 months, they will be excluded from the study. PHASE 2: After the phase 1, if asthma symptoms are controlled (Asthma Control Test, ACT ≥20/25), patients in Group A will start Acarizax®, in addition to Tezepelumab, while patients in Group B will continue Tezepelumab plus a placebo. Patients will all receive a 6-month treatment of Acarizax® or placebo, before stopping Tezepelumab (M6), to assure an optimal effect of AIT, as shown in Phase 3 trials. Patients will all receive an additional 6 months of Tezepelumab starting at D0 (Start of Acarizax®/placebo), before stopping it. PHASE 3: After stopping Tezepelumab, patients will receive an additional 12-month treatment of Acarizax® or placebo. Patients will receive an 18-month course of Acarizax® or placebo. For safety and ethical reasons, between M6 and M18 (Tezepelumab treatment will be suspended), in case of reappearance of uncontrolled severe asthma, Tezepelumab will be re-prescribed to patients. At the end of the study, patients on placebo, if their asthma is controlled, will be offered Acarizax® treatment (as a regular prescription and paid / reimbursed as proposed by the National French HealthCare system) and patients on Acarizax® treatment and controlled will be able to continue it as routine care.