This study is a multicenter, open-label trial to evaluate the safety and pharmacokinetics of weekly intravenous (IV) infusions of 60 mg/kg of the investigational drug in participants with alpha1-antitrypsin deficiency (AATD). The trial will be conducted at approximately 5 medical institutions in Japan, aiming to enroll a minimum of 3 adult participants or more. The trial will consist of a screening period scheduled within 3 weeks before trial entry, an open-label treatment period for 8 weeks, and a pharmacokinetic (PK) evaluation period for 1 week. At the Week 9 visit when the PK evaluation period is completed, participant will be asked whether they would like to participate in an extension trial (GTI1401-OLE). For participants not intending to participate in the extension trial, the date of follow-up/study completion visit (30 days \[4 weeks\] after the last dose of the investigational drug) will be arranged. Participants will participate in this trial for approximately 14 weeks from the start of the screening period through the completion of the trial.
At the screening visit (scheduled within 3 weeks before trial entry), after providing informed consent (agreement based on adequate explanation and understanding of the treatment plan), participants will be evaluated for eligibility for participation during the screening period. Participants considered eligible will enter the 8-week treatment period to receive a total of 8 weekly IV infusions of 60 mg/kg of Alpha-1 MP. The initial IV infusion will be given at the Week 1 (baseline) visit. During the treatment period, participants will receive weekly IV infusions of Alpha-1 MP at the Weeks 1 (baseline), 2, 3, 4, 5, 6, 7, and 8 visits. After the last IV infusion of Alpha-1 MP at the Week 8 visit, participants will enter the 1-week PK evaluation period. During this PK evaluation period, participants will visit the study center to undergo blood sampling for PK evaluation at the PK1 visit (the next day of the Week 8 visit), the PK2 visit (2 days after the Week 8 visit), the PK5 visit (5 days after the Week 8 visit), and at the Week 9 visit. At 30 days after the last dose (Week 8), participants will visit the study center for follow-up/study completion (Week 12). All participants will undergo blood sampling for the measurement of alpha1-PI trough concentrations at the Weeks 1 (baseline), 7, and 8 visits (blood samples will be collected before dosing) as well as at the Week 9 visit.
Blood samples for the evaluation of PK parameters will be collected from Week 8 to Week 9. The blood sample collected before the infusion of Alpha-1 MP at the Week 8 visit and the blood sample for PK evaluation collected at the Week 9 visit (7 days after the infusion at the Week 8 visit) will be also used for the measurement of alpha1-PI trough concentrations for Weeks 8 and 9.
At the Week 9 visit, participants will be asked whether they would like to participate in the extension trial (GTI1401-OLE). Participants intending to participate in the extension trial will be able to continue the treatment with IV infusions of 60 mg/kg of Alpha-1 MP for at least another year (participants will be further asked whether they would like to continue the treatment at yearly intervals) for the purpose of evaluation of the safety of long-term Alpha-1 MP treatment. Participants not intending to enter the extension trial will visit the study center for follow-up/study completion at 30 days (4 weeks) after the last dose of Alpha-1 MP (Week 12).
