Aerosolized KL4 surfactant improves short-term survival and gas exchange in spontaneously breathing newborn pigs with hydrochloric acid-induced acute lung injury

Development of a New Dry Powder Aerosol Synthetic Lung Surfactant Product for Neonatal Respiratory Distress Syndrome (RDS) - Part I: In Vitro Testing and Characterization

PURPOSE

Improving the deep lung delivery of aerosol surfactant therapy (AST) with a dry powder formulation may enable significant reductions in dose while providing improved efficacy. The objective of Part I of this two-part study was to present the development of a new dry powder aerosol synthetic lung surfactant (SLS) product and to characterize performance based on aerosol formation and realistic in vitro airway testing leading to aerosol delivery recommendations for subsequent in vivo animal model experiments.

METHODS

A new micrometer-sized SLS excipient enhanced growth (EEG) dry powder formulation was produced via spray drying and aerosolized using a positive-pressure air-jet dry powder inhaler (DPI) intended for aerosol delivery directly to intubated infants with respiratory distress syndrome (RDS) or infant-size test animals.

RESULTS

The best-case design (D2) of the air-jet DPI was capable of high emitted dose (> 80% of loaded) and formed a < 2 µm mass median aerodynamic diameter (MMAD) aerosol, but was limited to ≤ 20 mg mass loadings. Testing with a realistic in vitro rabbit model indicated that over half of the loaded dose could penetrate into the lower lung regions. Using the characterization data, a dose delivery protocol was designed in which a 60 mg total loaded dose would be administered and deliver an approximate lung dose of 14.7-17.7 mg phospholipids/kg with a total aerosol delivery period < 5 min.

CONCLUSIONS

A high-efficiency aerosol SLS product was designed and tested that may enable an order of magnitude reduction in administered phospholipid dose, and provide rapid aerosol administration to infants with RDS.

Trial of aerosolised surfactant for preterm infants with respiratory distress syndrome

OBJECTIVE

To evaluate the safety of an aerosolised surfactant, SF-RI 1, administered via nasal continuous positive airway pressure (nCPAP) and a prototype breath synchronisation device (AeroFact), to preterm infants with respiratory distress syndrome (RDS).

DESIGN

Multicentre, open-label, dose-escalation study with historical controls.

SETTING

Newborn intensive care units at Mater Mothers' Hospital, Brisbane, and Royal Hospital for Women, Sydney, Australia.

PATIENTS

Infants 26 weeks through 30 weeks gestation who required nCPAP 6-8 cmH₂O and fraction of inspired oxygen (FiO₂) <0.30 at <2 hours of age.

INTERVENTIONS

In part 1, infants received a single dose of 216 mg/kg of aerosolised surfactant. In part 2, infants could receive up to four doses of aerosolised surfactant. Three historical control infants were matched for each enrolled infant.

MAIN OUTCOME MEASURES

Treatment failure was defined as Respiratory Severity Score (FiO₂×cmH₂O nCPAP) >2.4, nCPAP >8 cmH₂O, arterial carbon dioxide >65 mm Hg, pH <7.20 or three severe apnoeas within 6 hours during the first 72 hours of life. Other outcomes included tolerance of the AeroFact treatment and complications of prematurity.

RESULTS

10 infants were enrolled in part 1 and 21 in part 2 and were compared with 93 historical controls. No safety issues were identified. In part 2, 6 of 21 (29%) AeroFact-treated infants compared with 30 of 63 (48%) control infants met failure criteria. Kaplan-Meier analysis of patients in part 2 showed a trend towards decreased rate of study failure in the AeroFact-treated infants compared with historical controls (p=0.10).

CONCLUSION

The AeroFact system can safely deliver aerosolised surfactant to preterm infants with RDS who are on nCPAP.

TRIAL REGISTRATION NUMBER

ACTRN12617001458325.

Aerosolized Surfactant for Preterm Infants with Respiratory Distress Syndrome

Currently, the administration of surfactant to preterm infants with respiratory distress syndrome (RDS) mainly relies on intratracheal instillation; however, there is increasing evidence of aerosolized surfactant being an effective non-invasive strategy. We present a historical narrative spanning sixty years of development of aerosolization systems. We also offer an overview of the pertinent mechanisms needed to create and manage the ideal aerosolization system, with a focus on delivery, distribution, deposition, and dispersion in the context of the human lung. More studies are needed to optimize treatment with aerosolized surfactants, including determination of ideal dosages, nebulizer types, non-invasive interfaces, and breath synchronization. However, the field is rapidly evolving, and widespread clinical use may be achieved in the near future.

Nebulized Poractant Alfa Reduces the Risk of Respiratory Failure at 72 Hours in Spontaneously Breathing Surfactant-Deficient Newborn Piglets

Supplemental Digital Content is available in the text.

We have setup for the first time a long-term (72 hr) respiratory distress syndrome model in spontaneously breathing surfactant-deficient newborn piglets to investigate the continuous positive airway pressure failure rate with nebulized poractant alfa compared with that with the intubation surfactant extubation technique or continuous positive airway pressure only.

Aerosol drug delivery to spontaneously-breathing preterm neonates: lessons learned

Delivery of medications to preterm neonates receiving non-invasive ventilation (NIV) represents one of the most challenging scenarios for aerosol medicine. This challenge is highlighted by the undersized anatomy and the complex (patho)physiological characteristics of the lungs in such infants. Key physiological restraints include low lung volumes, low compliance, and irregular respiratory rates, which significantly reduce lung deposition. Such factors are inherent to premature birth and thus can be regarded to as the intrinsic factors that affect lung deposition. However, there are a number of extrinsic factors that also impact lung deposition: such factors include the choice of aerosol generator and its configuration within the ventilation circuit, the drug formulation, the aerosol particle size distribution, the choice of NIV type, and the patient interface between the delivery system and the patient. Together, these extrinsic factors provide an opportunity to optimize the lung deposition of therapeutic aerosols and, ultimately, the efficacy of the therapy.In this review, we first provide a comprehensive characterization of both the intrinsic and extrinsic factors affecting lung deposition in premature infants, followed by a revision of the clinical attempts to deliver therapeutic aerosols to premature neonates during NIV, which are almost exclusively related to the non-invasive delivery of surfactant aerosols. In this review, we provide clues to the interpretation of existing experimental and clinical data on neonatal aerosol delivery and we also describe a frame of measurable variables and available tools, including in vitro and in vivo models, that should be considered when developing a drug for inhalation in this important but under-served patient population.

Breath-Synchronized Nebulized Surfactant in a Porcine Model of Acute Respiratory Distress Syndrome

Objectives

Effective treatment options for surfactant therapy in acute respiratory distress syndrome and coronavirus disease 2019 have not been established. To conduct preclinical studies in vitro and in vivo to evaluate efficiency, particle size, dosing, safety, and efficacy of inhaled surfactant using a breath-synchronized, nebulized delivery system in an established acute respiratory distress syndrome model.

Design

Preclinical study.

Setting

Research laboratory.

Subjects

Anesthetized pigs.

Intervention

In vitro analysis included particle size distribution and inhaled dose during simulated ventilation using a novel breath-synchronized nebulizer. Physiologic effects of inhaled aerosolized surfactant (treatment) were compared with aerosolized normal saline (control) in an adult porcine model (weight of 34.3 ± 0.6 kg) of severe acute respiratory distress syndrome (Pao₂/Fio₂ <100) with lung lavages and ventilator-induced lung injury during invasive ventilation.

Measurements and Main Results

Mass median aerosol diameter was 2.8 µm. In vitro dose delivered distal to the endotracheal tube during mechanical ventilation was 85% ± 5%. Nebulizers were functional up to 20 doses of 108 mg of surfactant. Surfactant-treated animals (n = 4) exhibited rapid improvement in oxygenation with nearly full recovery of Pao₂/Fio₂ (~300) and end-expiratory lung volumes with nominal dose less than 30 mg/kg of surfactant, whereas control subjects (n = 3) maintained Pao₂/Fio₂ less than 100 over 4.5 hours with reduced end-expiratory lung volume. There was notably greater surfactant phospholipid content and lower indicators of lung inflammation and pathologic lung injury in surfactant-treated pigs than controls. There were no peridosing complications associated with nebulized surfactant, but surfactant-treated animals had progressively higher airway resistance post treatment than controls with no differences in ventilation effects between the two groups.

Conclusions

Breath-synchronized, nebulized bovine surfactant appears to be a safe and feasible treatment option for use in coronavirus disease 2019 and other severe forms of acute respiratory distress syndrome.

Fusion Expression and Fibrinolytic Activity of rPA/SP-B

BACKGROUND

Pulmonary surfactant dysfunction is an important pathological factor in acute respiratory distress syndrome (ARDS) and pulmonary fibrosis (PF).

OBJECTIVE

In this study, the characteristics of recombinant mature surfactant protein B (SP-B) and reteplase (rPA) fusion protein maintaining good pulmonary surface activity and rPA fibrinolytic activity in acute lung injury cell model were studied.

METHODS

We studied the characteristics of SP-B fusion expression, cloned rPA gene and N-terminal rPA/C-terminal SP-B co-expression gene, and constructed them into eukaryotic expression vector pEZ-M03 to obtain recombinant plasmids pEZ-rPA and pEZ-rPA/SP-B. The recombinant plasmids was transfected into Chinese hamster ovary (CHO) K1 cells and the expression products were analyzed by Western Blot. Lipopolysaccharide (LPS) was used to induce CCL149 (an alveolar epithelial cell line) cell injury model. Fluorescence staining of rPA and rPA/SP-B was carried out with the enhanced green fluorescent protein (eGFP) that comes with pEZ-M03; the cell Raman spectroscopy technique was used to analyze the interaction between rPA/SP-B fusion protein and the phospholipid structure of cell membrane in CCL149 cells. The enzyme activity of rPA in the fusion protein was determined by fibrin-agarose plate method.

RESULTS

The rPA/SP-B fusion protein was successfully expressed. In the CCL149 cell model of acute lung injury (ALI), the green fluorescence of rPA/SP-B is mainly distributed on the CCL149 cell membrane. The rPA/SP-B fusion protein can reduce the disorder of phospholipid molecules and reduce cell membrane damage. The enzyme activity of rPA/SP-B fusion protein was 3.42, and the fusion protein still had good enzyme activity.

CONCLUSION

The recombinant eukaryotic plasmid pEZ-rPA/SP-B is constructed and can be expressed in the eukaryotic system. Studies have shown that rPA/SP-B fusion protein maintains good SP-B lung surface activity and rPA enzyme activity in acute lung injury cell model.

Dose-Response Study on Surfactant Nebulization Therapy During Nasal Continuous Positive Airway Pressure Ventilation in Spontaneously Breathing Surfactant-Deficient Newborn Piglets

OBJECTIVES

The current clinical treatment of neonates with respiratory distress syndrome includes endotracheal intubation and intratracheal instillation of exogenous surfactant. Nebulization of surfactant offers an attractive alternative. The aims of this study were to test nebulization as a noninvasive method of administering surfactant and determine the optimal dose for the treatment of respiratory distress syndrome-associated pathophysiology of the neonatal lungs.

DESIGN

Prospective, randomized, animal model study.

SETTING

An experimental laboratory.

SUBJECTS

Thirty-six newborn piglets.

INTERVENTIONS

Different doses (100, 200, 400, and 600 mg/kg) of poractant alfa were administered via a vibrating membrane nebulizer (eFlow-Neos; Pari Pharma GmbH, Starnberg, Germany) or a bolus administration using the intubation-surfactant-extubation (Insure) technique (200 mg/kg) to spontaneously breathing newborn piglets (n = 6/group) with bronchoalveolar lavage-induced respiratory distress syndrome during nasal continuous positive airway pressure (180 min).

MEASUREMENTS AND MAIN RESULTS

Pulmonary, hemodynamic, and cerebral effects were assessed. Histologic analysis of lung and brain tissue was also performed. After repeated bronchoalveolar lavage, newborn piglets developed severe respiratory distress syndrome. Rapid improvement in pulmonary status was observed in the Insure group, whereas a dose-response effect was observed in nebulized surfactant groups. Nebulized poractant alfa was more effective at doses higher than 100 mg/kg and was associated with similar pulmonary, hemodynamic, and cerebral behavior to that in the Insure group, but improved lung injury scores.

CONCLUSIONS

In newborn piglets with severe bronchoalveolar lavage-induced respiratory distress syndrome, our results demonstrate that the administration of nebulized poractant alfa using an investigational customized eFlow-Neos nebulizer is an effective and safe noninvasive surfactant administration technique.

Devices for Improved Delivery of Nebulized Pharmaceutical Aerosols to the Lungs

Nebulizers have a number of advantages for the delivery of inhaled pharmaceutical aerosols, including the use of aqueous formulations and the ability to deliver process-sensitive proteins, peptides, and biological medications. A frequent disadvantage of nebulized aerosols is poor lung delivery efficiency, which wastes valuable medications, increases delivery times, and may increase side effects of the medication. A focus of previous development efforts and previous nebulizer reviews, has been an improvement of the underlying nebulization technology controlling the breakup of a liquid into droplets. However, for a given nebulization technology, a wide range of secondary devices and strategies can be implemented to significantly improve lung delivery efficiency of the aerosol. This review focuses on secondary devices and technologies that can be implemented to improve the lung delivery efficiency of nebulized aerosols and potentially target the region of drug delivery within the lungs. These secondary devices may (1) modify the aerosol size distribution, (2) synchronize aerosol delivery with inhalation, (3) reduce system depositional losses at connection points, (4) improve the patient interface, or (5) guide patient inhalation. The development of these devices and technologies is also discussed, which often includes the use of computational fluid dynamic simulations, three-dimensional printing and rapid prototype device and airway model construction, realistic in vitro experiments, and in vivo analysis. Of the devices reviewed, the implementation of streamlined components may be the most direct and lowest cost approach to enhance aerosol delivery efficiency within nonambulatory nebulizer systems. For applications involving high-dose medications or precise dose administration, the inclusion of active devices to control aerosol size, guide inhalation, and synchronize delivery with inhalation hold considerable promise.

The Future of Bronchopulmonary Dysplasia: Emerging Pathophysiological Concepts and Potential New Avenues of Treatment

Yearly more than 15 million babies are born premature (<37 weeks gestational age), accounting for more than 1 in 10 births worldwide. Lung injury caused by maternal chorioamnionitis or preeclampsia, postnatal ventilation, hyperoxia, or inflammation can lead to the development of bronchopulmonary dysplasia (BPD), one of the most common adverse outcomes in these preterm neonates. BPD patients have an arrest in alveolar and microvascular development and more frequently develop asthma and early-onset emphysema as they age. Understanding how the alveoli develop, and repair, and regenerate after injury is critical for the development of therapies, as unfortunately there is still no cure for BPD. In this review, we aim to provide an overview of emerging new concepts in the understanding of perinatal lung development and injury from a molecular and cellular point of view and how this is paving the way for new therapeutic options to prevent or treat BPD, as well as a reflection on current treatment procedures.

Restoring pulmonary surfactant membranes and films at the respiratory surface

Pulmonary surfactant is a complex of lipids and proteins assembled and secreted by the alveolar epithelium into the thin layer of fluid coating the respiratory surface of lungs. There, surfactant forms interfacial films at the air-water interface, reducing dramatically surface tension and thus stabilizing the air-exposed interface to prevent alveolar collapse along respiratory mechanics. The absence or deficiency of surfactant produces severe lung pathologies. This review describes some of the most important surfactant-related pathologies, which are a cause of high morbidity and mortality in neonates and adults. The review also updates current therapeutic approaches pursuing restoration of surfactant operative films in diseased lungs, mainly through supplementation with exogenous clinical surfactant preparations. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Physiological, Biochemical, and Biophysical Characterization of the Lung-Lavaged Spontaneously-Breathing Rabbit as a Model for Respiratory Distress Syndrome

Nasal continuous positive airway pressure (nCPAP) is a widely accepted technique of non-invasive respiratory support in spontaneously-breathing premature infants with respiratory distress syndrome (RDS). Surfactant administration techniques compatible with nCPAP ventilation strategy are actively investigated. Our aim is to set up and validate a respiratory distress animal model that can be managed on nCPAP suitable for surfactant administration techniques studies. Surfactant depletion was induced by bronchoalveolar lavages (BALs) on 18 adult rabbits. Full depletion was assessed by surfactant component analysis on the BALs samples. Animals were randomized into two groups: Control group (nCPAP only) and InSurE group, consisting of a bolus of surfactant (Poractant alfa, 200 mg/kg) followed by nCPAP. Arterial blood gases were monitored until animal sacrifice, 3 hours post treatment. Lung mechanics were evaluated just before and after BALs, at the time of treatment, and at the end of the procedure. Surfactant phospholipids and protein analysis as well as surface tension measurements on sequential BALs confirmed the efficacy of the surfactant depletion procedure. The InSurE group showed a significant improvement of blood oxygenation and lung mechanics. On the contrary, no signs of recovery were appreciated in animals treated with just nCPAP. The surfactant-depleted adult rabbit RDS model proved to be a valuable and efficient preclinical tool for mimicking the clinical scenario of preterm infants affected by mild/moderate RDS who spontaneously breathe and do not require mechanical ventilation. This population is of particular interest as potential target for the non-invasive administration of surfactant.

Nebulization of Poractant alfa via a vibrating membrane nebulizer in spontaneously breathing preterm lambs with binasal continuous positive pressure ventilation

BACKGROUND

Surfactant replacement therapy is the gold standard treatment of neonatal respiratory distress (RDS). Nebulization is a noninvasive mode of surfactant administration. We administered Poractant alfa (Curosurf) via a vibrating perforated membrane nebulizer (eFlow Neonatal Nebulizer) to spontaneously breathing preterm lambs during binasal continuous positive pressure ventilation (CPAP).

METHODS

Sixteen preterm lambs were operatively delivered at a gestational age of 133 ± 1 d (term ~150 d), and connected to CPAP applied via customized nasal prongs. Nebulization was performed (i) with saline or (ii) with surfactant for 3 h in humidified or (iii) nonhumidified air, and with surfactant (iv) for 60 min or (v) for 30 min. We measured arterial oxygenation, lung gas volumes and surfactant pool size and deposition.

RESULTS

Nebulization of surfactant in humidified air for 3 h improved oxygenation and lung function, and surfactant was preferentially distributed to the lower lung lobes. Shorter nebulization times and 3 h nebulization in dry air did not show these effects. Nebulized surfactant reached all lung lobes, however the increase of surfactant pool size missed statistical significance.

CONCLUSION

Positive effects of surfactant nebulization to spontaneously breathing preterm lambs depend on treatment duration, surfactant dose, air humidity, and surfactant distribution within the lung.

Aerosol delivery of synthetic lung surfactant

Background. Nasal continuous positive airway pressure (nCPAP) is a widely accepted technique of non-invasive respiratory support in premature infants with respiratory distress syndrome due to lack of lung surfactant. If this approach fails, the next step is often intubation, mechanical ventilation (MV) and intratracheal instillation of clinical lung surfactant.

Objective. To investigate whether aerosol delivery of advanced synthetic lung surfactant, consisting of peptide mimics of surfactant proteins B and C (SP-B and SP-C) and synthetic lipids, during nCPAP improves lung function in surfactant-deficient rabbits.

Methods. Experimental synthetic lung surfactants were produced by formulating 3% Super Mini-B peptide (SMB surfactant), a highly surface active SP-B mimic, and a combination of 1.5% SMB and 1.5% of the SP-C mimic SP-Css ion-lock 1 (BC surfactant), with a synthetic lipid mixture. After testing aerosol generation using a vibrating membrane nebulizer and aerosol conditioning (particle size, surfactant composition and surface activity), we investigated the effects of aerosol delivery of synthetic SMB and BC surfactant preparations on oxygenation and lung compliance in saline-lavaged, surfactant-deficient rabbits, supported with either nCPAP or MV.

Results. Particle size distribution of the surfactant aerosols was within the 1–3 µm distribution range and surfactant activity was not affected by aerosolization. At a dose equivalent to clinical surfactant therapy in premature infants (100 mg/kg), aerosol delivery of both synthetic surfactant preparations led to a quick and clinically relevant improvement in oxygenation and lung compliance in the rabbits. Lung function recovered to a greater extent in rabbits supported with MV than with nCPAP. BC surfactant outperformed SMB surfactant in improving lung function and was associated with higher phospholipid values in bronchoalveolar lavage fluid; these findings were irrespective of the type of ventilatory support (nCPAP or MV) used.

Conclusions. Aerosol delivery of synthetic lung surfactant with a combination of highly active second generation SP-B and SP-C mimics was effective as a therapeutic approach towards relieving surfactant deficiency in spontaneously breathing rabbits supported with nCPAP. To obtain similar results with nCPAP as with intratracheal instillation, higher dosage of synthetic surfactant and reduction of its retention by the delivery circuit will be needed to increase the lung dose.

Synthetic surfactant containing SP-B and SP-C mimics is superior to single-peptide formulations in rabbits with chemical acute lung injury

Background. Chemical spills are on the rise and inhalation of toxic chemicals may induce chemical acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Although the pathophysiology of ALI/ARDS is well understood, the absence of specific antidotes has limited the effectiveness of therapeutic interventions.

Objectives. Surfactant inactivation and formation of free radicals are important pathways in (chemical) ALI. We tested the potential of lipid mixtures with advanced surfactant protein B and C (SP-B and C) mimics to improve oxygenation and lung compliance in rabbits with lavage- and chemical-induced ALI/ARDS.

Methods. Ventilated young adult rabbits underwent repeated saline lung lavages or underwent intratracheal instillation of hydrochloric acid to induce ALI/ARDS. After establishment of respiratory failure rabbits were treated with a single intratracheal dose of 100 mg/kg of synthetic surfactant composed of 3% Super Mini-B (S-MB), a SP-B mimic, and/or SP-C33 UCLA, a SP-C mimic, in a lipid mixture (DPPC:POPC:POPG 5:3:2 by weight), the clinical surfactant Infasurf^®, a bovine lung lavage extract with SP-B and C, or synthetic lipids alone. End-points consisted of arterial oxygenation, dynamic lung compliance, and protein and lipid content in bronchoalveolar lavage fluid. Potential mechanism of surfactant action for S-MB and SP-C33 UCLA were investigated with captive bubble surfactometry (CBS) assays.

Results. All three surfactant peptide/lipid mixtures and Infasurf equally lowered the minimum surface tension on CBS, and also improved oxygenation and lung compliance. In both animal models, the two-peptide synthetic surfactant with S-MB and SP-C33 UCLA led to better arterial oxygenation and lung compliance than single peptide synthetic surfactants and Infasurf. Synthetic surfactants and Infasurf improved lung function further in lavage- than in chemical-induced respiratory failure, with the difference probably due to greater capillary-alveolar protein leakage and surfactant dysfunction after HCl instillation than following lung lavage. At the end of the duration of the experiments, synthetic surfactants provided more clinical stability in ALI/ARDS than Infasurf, and the protein content of bronchoalveolar lavage fluid was lowest for the two-peptide synthetic surfactant with S-MB and SP-C33 UCLA.

Conclusion. Advanced synthetic surfactant with robust SP-B and SP-C mimics is better equipped to tackle surfactant inactivation in chemical ALI than synthetic surfactant with only a single surfactant peptide or animal-derived surfactant.