Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare disorder of progressive surfactant accumulation and resulting hypoxemic respiratory failure caused by disruption of granulocyte/macrophage-colony stimulating factor (GM-CSF) signaling, which alveolar macrophages require to remove pulmonary surfactant.
The current therapy of aPAP, whole lung lavage (WLL), is a procedure requiring general anesthesia, endotracheal intubation to isolate each lung, and mechanical ventilation of the untreated lung while the treated lung repeatedly filled with saline and drained while percussing the chest to loosen and emulsify the surfactant and saline to physically remove the excess surfactant.
Inhaled GM-CSF is a promising pharmacotherapeutic approach shown in case reports, small series, moderate open-label studies, and two randomized, double-blinded, placebo-controlled trials to be safe and improve the clinical, physiological, radiological, and biochemical disease manifestations in patients with mild-moderate aPAP. In contrast to the present study, prior studies were too short in duration to permit an evaluation on the requirement for WLL, which aPAP patients require a mean of every 15 months. The present study addressed the effects on WLL by studying patients with moderate-severe aPAP and by utilizing a long-term follow up period.
The study design included a screening visit (month -3) to establish eligibility, an observation period (-3 to 0 months) to establish the presence of progressive/unremitting aPAP and establish disease severity, a pre-WLL visit (-1 month), a baseline visit (month 0) during which all patients received a scheduled, baseline, bilateral WLL, a 10-month, open-label treatment period, and a 20-month follow-up period. Study visits were scheduled at months -3, -1, 0, 1, 3, 6, 10, 18, and 30 months. Patients were randomized by the statistician to the GM-CSF Group (n=9) or the Control Group (n=9). Investigators were blinded to group assignment until after the participant's baseline visit.
Patients randomized to the GM-CSF group (n=9) received inhaled GM-CSF (sargramostim (Leukine®), 250 mcg daily every other week for 12 weeks beginning 1 week after the baseline WLL - termed GM-CSF induction therapy period, followed by a 4-week washout period during which no GM-CSF was administered), and then received inhaled GM-CSF (sargramostim, 250 mcg/day on days 1 and 3 of every 14-day period for 6 months - termed GM-CSF maintenance therapy period). Inhaled GM-CSF (Leukine®) was administered using AKITA2 APIXNEB nebulizer system (Activaero, Vectura GmbH, Germany). Patients randomized to the Control Group (n=9) received no further scheduled treatment. Any patient in either group experiencing with disease progression resulting in respiratory failure (defined as peripheral artery oxygen concentration (PaO2) \<60 mmHg at rest or PaO2 \>60 mmHg at rest AND a peripheral blood oxygen saturation (SpO2) \< 90% OR a decline in SpO2 of 5% or more during exercise), received (unscheduled) rescue WLL and were considered to have failed their assigned intervention (GM-CSF or Control).
The primary outcome measure was time, in months, between the scheduled baseline WLL and first administration of unscheduled 'rescue' WLL (termed 'time to rescue WLL'). Key secondary outcome measures included the response in peripheral arterial oxygen concentration (PaO2), alveolar-arterial difference in oxygen concentration (A-aDO2), diffusing capacity of the lungs for carbon monoxide (DLco), vital capacity, ground glass opacification (GGO) of the lungs measured by visual scoring of chest computed tomography (CT) scans, and serum biomarkers of PAP (carcinoembryonic antigen, Krebs von-Lungren antigen, Cyfra-21.1). Other outcome measures included the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), serum GM-CSF autoantibody concentration, the peripheral white blood cell and platelet counts.
The occurrence and timing of rescue WLL administration in each group was evaluated using Kaplan-Meyer analysis. The primary end point was analyzed as the difference in median time to rescue WLL between the GM-CSF group and the Control group. Categorical outcomes were compared using Fisher's exact test. Key secondary end points were evaluated using repeated measures analysis of variance (RM-ANOVA) after adjustment for baseline values, gender, age, and the number of patients at risk at each time point. Secondary outcome measures were also evaluated by comparing the between-group mean (or median) values at each visit using Student's t-test (or Mann-Whitney test) after imputation of missing data using a last observation carried forward approach to reduce selection-type bias by comparing the corresponding group means or medians. All reported p values are two-sided and have not been adjusted for multiple testing. P values of less than 0.05 were considered to indicate statistical significance. Analysis of the primary and key secondary outcomes was performed with the use of Stata software version 14.2. Analyses of secondary outcome measures were performed with the use of Prism for Mac OS software, version 9.51.
Anticipated results were intended to compare the effects of inhaled GM-CSF following baseline WLL to those of baseline WLL alone in patients with moderate to severe aPAP.
