This study is designed to evaluate a new therapy formulation for Alpha-1 Antitrypsin Deficiency (AATD). AATD is an inherited condition in which a person has low blood levels of a protein known as alpha-1 protease inhibitor (called Alpha1-PI). AATD causes an increased risk of chronic obstructive pulmonary disease (COPD) in the form of emphysema (long term lung disease) and, less frequently, other diseases.

This study is being conducted to evaluate the safety and tolerability of 2 different doses of Alpha-1 drugs (Alpha-1 15% and Liquid Alpha1-PI) in participants with AATD. Participants will be placed into one of two groups. Each group will receive both drugs, but different doses of each, at different points in the treatment period (8 Weekly IV infusions of Liquid Alpha1-PI 60 mg/kg followed by 8 Weekly SC (subcutaneous) infusions Alpha1-PI 90 mg/kg OR 8 Weekly IV infusions of Liquid Alpha1-PI 120 mg/kg followed by 8 Weekly SC (subcutaneous) infusions Alpha1-PI 180 mg/kg).

This is an "open label" study, meaning participants and the study staff know which dose of study drug participants receive. The study will last up to 161 days (23 weeks). Many visits are able to be conducted through home health care, lessening the need to come into the clinic.

Alpha-1 15% is an investigational product, meaning it is not approved by the U.S. Food and Drug Administration (FDA). The other drug in this study is Liquid Alpha1-PI (licensed as Prolastin®-C Liquid) and is an FDA approved treatment for adults with emphysema due to AATD. However, it is only approved for the recommended dose of 60 mg/kg. This study includes both the FDA approved 60mg/kg of Liquid Alpha1-PI and an experimental dose of 120 mg/kg that is not FDA approved. Alpha-1 15% is given as an injection under the skin and Liquid Alpha1-PI is given as an infusion into the veins.