Measurement of (A-a)DO2 was done by blood gas analysis. An arterial blood sample was collected in the supine position, after resting for at least 10 minutes (or longer if required to achieve stable oxygen saturation). The sample was analyzed for arterial oxygen tension (PaO2) and partial pressure of carbon dioxide (PaCO2). The calculation of (A-a)DO2 was done centrally by using a formula described in the protocol.

Full analysis set (FAS): all randomized participants, analyzed according to randomized treatment. Not all participants in the FAS had blood gas analysis done at Week 24, therefore the overall number of participants analyzed is less than the total number of randomized participants.

The 6MWD was assessed by the use of 6-minute walking test (6MWT). The 6MWT was performed in accordance with the 2014 ATS/ERS guideline "field walking tests in chronic respiratory disease" (Holland et al. 2014) by technicians with documented training and experience.

Where possible, the test was conducted with the participant breathing ambient atmospheric air. If the participant required oxygen supplementation at rest, a titration procedure was carried out as part of the 6MWT at screening in order to determine the oxygen flow rate required for the participant to complete the test. This flow rate was to be used during subsequent tests, if possible.

FAS. Not all participants in the FAS had 6MWT done at Week 24, therefore the overall number of participants analyzed is less than the total number of randomized participants.

The SGRQ is designed to measure health impairment in patients with asthma and chronic obstructive pulmonary disease (COPD). It consists of two parts, where Part 1 covers the participants' recollection of their symptoms over the preceding period (1 month recall used in this trial, Symptoms component) and Part 2 addresses the participants' current state in terms of disturbances to their daily physical activity (Activity component) and a wide range of disturbances of psycho-social function (Impact component). A total score as well as individual component scores were calculated. Scores (total and component) range from 0 to 100, with higher scores indicating more limitations.

FAS. Not all participants in the FAS had SGRQ assessed at Week 24, therefore the overall number of participants analyzed is less than the total number of randomized participants.

In all versions of the protocol (no participants were recruited under version 1.0), whole lung lavage (single lung or both lungs) was applied as rescue therapy. In protocol version 2.0, the criterion for performing whole lung lavage was an increase in (A-a)DO2 by more than 10 mmHg/1.33 kilopascal compared to baseline. In protocol version 3.0 onwards, the criterion for performing whole lung lavage was clinical worsening of aPAP based on symptoms, reduced exercise capacity and/or findings of hypoxemia or desaturation according to the investigator's judgement.

In protocol versions 2.0 and 3.0, participants undergoing whole lung lavage during the double-blind period were to discontinue double-blind treatment, encouraged to continue to follow the same visit schedule and, if required, receive further whole lung lavage at the investigator's discretion. In protocol version 4.0 and 5.0, participants undergoing whole lung lavage were to continue double-blind treatment.

FAS.

Treatment-emergent adverse events (AEs) were assessed on or after the first dose of trial drug to 28 days after last dose.

Information about AEs was collected by the investigator by a non-leading question such as "have you experienced any new health problems or worsening of existing conditions" and by reporting events directly observed or spontaneously volunteered by participants (e.g., in the Subject Diary Card, where subjects were asked to record any AEs and answer questions regarding lung toxicity and known systemic effects). Participants were also encouraged to contact the clinic in between visits if they experienced AEs or had any concerns.

All AEs were assessed by the investigator for severity (mild, moderate, severe), outcome (recovered, not recovered, recovered with sequelae, fatal, unknown) and causality (unlikely, possible, probable, not applicable) according to current regulatory standards.

Safety analysis set: all randomized participants who received at least one dose of the trial drug, analyzed according to actual treatment.

SAEs are defined as any untoward medicinal occurrence or effect that at any dose:

• Results in death
• Is life-threatening
• Requires hospitalisation or prolongation of existing hospitalisation
• Results in persistent or significant disability or incapacity
• Is a congenital anomaly or birth defect
• May jeopardise the subject or may require intervention to prevent one or more of the other outcomes listed above (Important Medical Events)

Safety analysis set

All AEs judged by either the reporting investigator or the sponsor as having a reasonable causal relationship to a medicinal product qualify as ADRs. The expression reasonable causal relationship means that a causal relationship between a medicinal product and an AE is at least a reasonable possibility i.e. the relationship cannot be ruled out.

Safety analysis set

All AEs were assessed by the investigator for severity (mild, moderate, severe) according to current regulatory standards:

• Mild: The AE is easily tolerated and does not interfere with daily activity.
• Moderate: The AE interferes with daily activity, but the subject is still able to function. Medical intervention may be considered.
• Severe: The AE is incapacitating and requires medical intervention.

Safety analysis set

Participants could be discontinued from treatment and assessments at any time, if deemed necessary by the investigator. Potential reasons for discontinuation of treatment included e.g. unacceptable AE.

Safety analysis set