This study is designed to learn about the safety and effectiveness of a new gene therapy called KB408 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.
KB408 delivers copies of the genes that produce AAT to the lungs and is given by inhaling a mist (called nebulization). The genes are carried and delivered by a modified herpes simplex virus type 1 (HSV-1). This virus is not harmful and simply acts as a vehicle to deliver the genes to the lungs. The genes that are delivered by KB408 do not change a person's own DNA. This is an open-label study, meaning that the participants, the study doctor, and the sponsor all know that the participants are receiving KB408. KB408 is an investigational product, meaning it is not approved for commercial use by the FDA.
Eligible participants will receive one of three doses of KB408. Participants will have a screening visit first to make sure that they are able to participate in the study. After the screening visit, participants will need to return to the study center 6 more times over 2 months. At the second visit, participants will receive the study drug. Each visit will take between 2 and 6 hours to complete. Study procedures include medical history collection, vitals, physical exam, ECG, spirometry and DLCO, urine cotinine test, blood work, cheek swab, sputum sample, and bronchoscopy (only for participants in cohorts 3a and 3b).
Possible side effects of KB408 include temporary increases in certain cell types in the lungs and temporary increases in the breathing rate after dosing. Since this is the first time that KB408 has been given to humans, it is possible that participants may have an immune reaction to the study drug. There is also a risk with genetic testing and a risk to confidentiality. Participants may not receive any personal benefit from being in this study. There is no guarantee that the Study Drug will help. The information that is collected from the study may help other people in the future.

The purpose of this research study is to help us understand patients' experiences with alpha-1 antitrypsin deficiency – lung disease. 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 and other lung diseases.
During screening, participants will be asked questions to assess their eligibility to take part in this study. To be considered for enrollment into the study, participants must: be between 18 to 80 years old, have a diagnosis of severe AATD, meet the additional relevant inclusion criteria, understand the study instructions, and be willing and able to follow the study instructions. Participants will participate in a one-time, 120-minute, telephone or web-based interview. At the end of the interview, participants will complete a brief questionnaire. There is a risk of discomfort answering the questions during the interview and a risk of loss of confidentiality. There is no direct benefit from participation in the study.