In a chronic cigarette smoker, the alveolar walls are damaged and the alveoli coalesced due to which they become larger but fewer. Which of the following can be used in his treatment?

Alpha 1 - antitrypsin, a human protein is used treat emphysema. 
Emphysema is a chronic disorder in which alveolar walls are damaged and their walls coalesce due  to which respiratory surface area of exchange of gases is decreased. The lungs shows larger but fewer alveoli and more fibrous and less elastic.