Abstract Introduction Pulmonary alveolar proteinosis (PAP) is a rare lung syndrome characterized by the accumulation of surfactant in the alveoli. Using a longitudinal claims database, we compared measures of clinical and economic burden between a sample of diagnosed PAP patients and non-PAP matched controls. Methods PAP patients were identified leveraging IPM.ai’s longitudinal U.S. claims database spanning January 1, 2009, through May 1, 2022. PAP patients were selected based on the presence of ICD-10: J84.01 or ICD-9: 516.0 in their claims history and were indexed for observation. An age, gender, and geographically matched control cohort was created (ratio of 1:4) for comparison. A third cohort, consisting of likely undiagnosed PAP patients, was identified using a machine learning model. The PAP and control cohorts were tracked longitudinally, depending on individual index dates, from January 1, 2018, through May 1, 2023. Inclusion criteria required evidence of continual claims activity 12 months prior to and after the index date, which reduced the total number of diagnosed PAP and control patients in the analysis. Demographics, comorbidities, procedures, medication use, annual healthcare resource utilization (HCRU), and costs were calculated for eligible PAP and control patients and were compared 12 months prior to, and 12 months after each patient’s index date. Results After inclusion criteria were applied, 2312 confirmed PAP patients and 9247 matched controls were included in the analysis. Compared with matched controls, PAP patients had significantly higher rates of diagnosed conditions at baseline as defined by the Charlson Comorbidity Index (CCI). During the follow-up period, PAP patients had higher rates of diagnosed conditions, procedures, medication use, and cost-of-care compared with controls. PAP patients also had higher rates of emergency room visits (35% vs. 14%; P < 0.001), outpatient visits (87% vs. 56%; P < 0.001), inpatient visits (20% vs. 5%; P < 0.001) and had longer lengths of stay for inpatient hospitalizations (2.8 days vs. 0.56 days; P < 0.001), respectively. Conclusion This study represents the largest dataset of PAP patients and matched controls to be analyzed to date. Findings indicate that PAP patients have higher rates of diagnosed conditions, procedures, medication use, HCRU, and costs compared with non-PAP patients.
COVID-19 is a clinical syndrome ranging from mild symptoms to severe pneumonia that often leads to respiratory failure, need for mechanical ventilation, and death. Most of the lung damage is driven by a surge in inflammatory cytokines [interleukin-6, interferon-γ, and granulocyte-monocyte stimulating factor (GM-CSF)]. Blunting this hyperinflammation with immunomodulation may lead to clinical improvement. GM-CSF is produced by many cells, including macrophages and T-cells. GM-CSF-derived signals are involved in differentiation of macrophages, including alveolar macrophages (AMs). In animal models of respiratory infections, the intranasal administration of GM-CSF increased the proliferation of AMs and improved outcomes. Increased levels of GM-CSF have been recently described in patients with COVID-19 compared to healthy controls. While GM-CSF might be beneficial in some circumstances as an appropriate response, in this case the inflammatory response is maladaptive by virtue of being later and disproportionate. The inhibition of GM-CSF signaling may be beneficial in improving the hyperinflammation-related lung damage in the most severe cases of COVID-19. This blockade can be achieved through antagonism of the GM-CSF receptor or the direct binding of circulating GM-CSF. Initial findings from patients with COVID-19 treated with a single intravenous dose of mavrilimumab, a monoclonal antibody binding GM-CSF receptor α, showed oxygenation improvement and shorter hospitalization. Prospective, randomized, placebo-controlled trials are ongoing. Anti-GM-CSF monoclonal antibodies, TJ003234 and gimsilumab, will be tested in clinical trials in patients with COVID-19, while lenzilumab received FDA approval for compassionate use. These trials will help inform whether blunting the inflammatory signaling provided by the GM-CSF axis in COVID-19 is beneficial.
Abstract Pulmonary alveolar proteinosis (PAP) is a life-threatening rare lung syndrome characterized by the accumulation of surfactant and lipid-loaded macrophages within the alveoli for which there is no cure and no approved therapies. The clinical diagnosis of PAP, often made by invasive lung biopsies and/or cytology of bronchoalveolar lavage fluid does not identify the underlying cause of disease. In addition, no biomarkers exist to inform prognosis or therapeutic options in PAP. We now report on the use of comprehensive mass spectrometry to profile and define the lipid signature of alveolar macrophages obtained from PAP patients. In addition, we quantify how these macrophage-associated lipids change during clinical treatment. Our studies demonstrate that clinical improvement in treated PAP patients is associated with a decrease in total lipid content, indicating that levels of these macrophage-associated lipids correlate with the severity of the disease.
Pulmonary alveolar proteinosis (PAP) is a syndrome of reduced GM-CSF-dependent, macrophage-mediated surfactant clearance, dysfunctional foamy alveolar macrophages, alveolar surfactant accumulation, and hypoxemic respiratory failure for which the pathogenetic mechanism is unknown. Here, we examine the lipids accumulating in alveolar macrophages and surfactant to define the pathogenesis of PAP and evaluate a novel pharmacotherapeutic approach. In PAP patients, alveolar macrophages have a marked increase in cholesterol but only a minor increase in phospholipids, and pulmonary surfactant has an increase in the ratio of cholesterol to phospholipids. Oral statin therapy is associated with clinical, physiological, and radiological improvement in autoimmune PAP patients, and ex vivo statin treatment reduces cholesterol levels in explanted alveolar macrophages. In Csf2rb-/- mice, statin therapy reduces cholesterol accumulation in alveolar macrophages and ameliorates PAP, and ex vivo statin treatment increases cholesterol efflux from macrophages. These results support the feasibility of statin as a novel pathogenesis-based pharmacotherapy of PAP.
Autoantibodies to multiple cytokines have been identified and some, including antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), have been associated with increased susceptibility to infection. High levels of GM-CSF autoantibodies that neutralize signaling cause autoimmune pulmonary alveolar proteinosis (aPAP), an ultrarare autoimmune disease characterized by accumulation of excess surfactant in the alveoli, leading to pulmonary insufficiency. Defective GM-CSF signaling leads to functional deficits in multiple cell types, including macrophages and neutrophils, with impaired phagocytosis and host immune responses against pulmonary and systemic infections. In this article, we review the role of GM-CSF in aPAP pathogenesis and pulmonary homeostasis along with the increased incidence of infections (particularly opportunistic infections). Therefore, recombinant human GM-CSF products may have potential for treatment of aPAP and possibly other infectious and pulmonary diseases due to its pleotropic immunomodulatory actions.
