- AAT deficient patients who are either naïve (not receiving IV augmentation therapy) or AAT deficient patients (receiving IV augmentation therapy), if they have been stable on regular therapy for at least 3 months prior to the screening visit and are willing to continue the same regime throughout this trial. Note that only sites in Germany can recruit patients who are currently being treated with IV AAT.Patients who stopped IV augmentation treatment 6 months prior to screening date and will not re-start this treatment for the course of the study will be considered Naïve.