A Study to Evaluate Safety, Tolerability and Pharmacokinetics of Two Different Doses of Alpha1-Proteinase Inhibitor Subcutaneous (Human) 15% in Participants With Alpha1-Antitrypsin Deficiency

Inclusion Criteria: * Have a diagnosis of congenital Alpha1-antitrypsin deficiency (AATD) with an allelic combination of ZZ, SZ, Z(null), (null)(null), S(null), or "at-risk" alleles (subjects with "at-risk" alleles must be individually evaluated for eligibility by the Medical Monitor). * Have a documented pre-Alpha1-Proteinase Inhibitor (PI) augmentation therapy serum alpha-1 antitrypsin (AAT) level \<11 micrometer (μM) (80 milligrams per decilitre (mg/dL) if measured by radial immunodiffusion or 50 mg/dL if measured by nephelometry). * Subjects may be naïve to Alpha1-PI augmentation therapy or may be currently receiving Alpha1-PI augmentation therapy or received Alpha1-PI augmentation therapy within the past. If the subject is currently receiving Alpha1-PI augmentation therapy of any kind, he/she must be willing to discontinue that treatment for at least 25 days prior to the Week 1 (Baseline) Visit and remain off any kind of Alpha1-PI treatment, other than the IPs for this study, while participating in the study. * At the Screening Visit, have a post-bronchodilator forced expiratory volume (FEV1) ≥30% and \<80% of predicted and FEV1/forced vital capacity (FVC) \<70% (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage II or III). Exclusion Criteria: * Have had a moderate or severe Chronic obstructive pulmonary disease (COPD) exacerbation during the 4 weeks before the Week 1 (Baseline) Visit. * Have history of lung or liver transplant. * Have any lung surgery during the past 2 years (excluding lung biopsy). * Have severe concomitant disease (example, congestive heart failure, clinically significant pulmonary fibrosis, malignant disease \[except for skin cancers other than melanoma\], history of acute hypersensitivity pneumonitis reaction, or current chronic hypersensitivity pneumonitis). * Females who are pregnant, breastfeeding or, if of child-bearing potential, unwilling to practice a highly effective method of contraception (oral, injectable, or implanted hormonal methods of contraception, placement of an intrauterine device (IUD) or intrauterine system (IUS), condom or occlusive cap with spermicidal foam/gel/film/cream/suppository, male sterilization, or true abstinence) throughout the study. * Have smoked during the past 6 months or a positive urine cotinine test at the Screening Visit that is due to smoking. * Participate in another Investigational product (IP) study within one month prior to the Week 1 (Baseline) Visit. * Have history of anaphylaxis or severe systemic response to any plasma-derived Alpha1-PI preparation or other blood product(s). * Use systemic steroids above a stable dose equivalent to 5 mg/day prednisone (i.e., 10 mg every 2 days) within the 4 weeks prior to the Week 1 (Baseline) Visit. It is recommended to maintain the same dose throughout the study. * Use systemic or aerosolized antibiotics for a chronic COPD exacerbation within the 4 weeks prior to the Week 1 (Baseline) Visit. * Have known selective or severe Immunoglobulin A (IgA) deficiency.