Respreeza (higher dose) is a medication made from a purified human protein called alpha‑1 proteinase inhibitor. It comes as a powder that is mixed with a liquid right before it is given. In the study, participants receive the medication through an IV (intravenous) infusion, which means it is delivered directly into a vein. The purpose of this higher‑dose version is to see if giving more of the protein can better protect the lungs of people with alpha‑1 antitrypsin deficiency, a condition that can cause emphysema.

Respreeza (lower dose) contains the same human alpha‑1 proteinase inhibitor as the higher‑dose product, but it is prepared in a smaller amount of powder that is also mixed with a liquid for IV infusion. This lower‑dose version is tested to determine whether a smaller amount of the protein is still effective at slowing lung damage in participants with the same genetic deficiency. By comparing the two doses, researchers hope to find the optimal amount that balances benefit and safety.

Respreeza (standard marketed dose) is the version of the medication that is already approved and commonly used for long‑term maintenance in adults with alpha‑1 antitrypsin deficiency–related emphysema. It is also given as an IV infusion of the human alpha‑1 proteinase inhibitor. In the trial, this standard dose serves as the reference point, allowing investigators to compare the new higher and lower doses against the established treatment to see if they provide any additional advantage.

Alpha-1 proteinase inhibitor deficiency – It is a genetic condition where the body makes too little of a protein that protects the lungs from damage. As the deficiency continues, small airway inflammation can develop and the lung tissue may become less elastic. Over time, the reduced protection can lead to a gradual loss of lung capacity. The condition is often identified early in life but its effects become more noticeable as the person ages. The disease may coexist with other lung problems.
Alpha-1 antitrypsin deficiency – This inherited disorder results in low levels of antitrypsin, a protein that safeguards lung tissue from harmful enzymes. Without enough antitrypsin, the enzymes can damage the walls of the airways, causing them to become stiff and less functional. The damage progresses slowly, leading to a steady decline in breathing efficiency. Symptoms often appear in adulthood and can worsen with exposure to smoke or pollutants. The disease primarily affects the respiratory system.
Emphysema – Emphysema is a chronic lung disease characterized by the destruction of the tiny air sacs that help oxygen enter the blood. The loss of these sacs reduces the surface area for gas exchange, making breathing more difficult. Over time, the lungs become over‑inflated and the airways lose their shape. This results in a gradual decrease in lung capacity and endurance. The condition typically develops slowly and worsens with continued exposure to irritants.