PEGylation, an approach for improving the pulmonary delivery of biopharmaceuticals

Exploiting inhalable microparticles incorporating hybrid polymer-lipid nanoparticles loaded with Iloprost manages lung hyper-inflammation

This study focuses on developing of a novel inhalation therapy for managing lung hyper-inflammation, producing hybrid polymer-lipid nanoparticles loaded with Iloprost (Ilo). These nanoparticles showed a size of approximately 100 nm with a core-shell structure and provided prolonged drug release, reaching 28 wt% after 6 h of incubation. The phospholipid composition and quantity (64 wt% on the total sample weight) result in minimal interaction with mucin and a significant effect on the rheology of a cystic fibrosis mucus model, in terms of reducing complex viscosity. To obtain an inhalable microparticulate matrix suitable for incorporating Ilo@PEG-LPHNPs, the qualitative and quantitative composition of the feed fluid for the spray drying (SD) process was optimized. The selected composition (10 % wt/vol of mannitol and 10 % wt of ammonium bicarbonate relative to the weight of mannitol) was used to produce Nano-into Microparticles (NiM). The characterization of NiM revealed excellent aerodynamic properties, with a Mass Median Aerodynamic Diameter (MMAD) of 4.34 μm and a Fine Particle Fraction (FPF) of approximately 57 %. Biological characterization revealed that the particles are non-toxic to 16-HBE cells and can effectively evade macrophage uptake, likely due to the presence of PEG in their composition. Moreover, the delivered Iloprost significantly downregulates the production of the pro-inflammatory cytokine IL-6, showing the therapeutic potential of this drug delivery system.

Microfluidic post-insertion of polyethylene glycol lipids and KK or RGD high functionality and quality lipids in milk-derived extracellular vesicles

To achieve the desired delivery effect, extracellular vesicles (EVs) must bypass rapid clearance from circulation and exhibit affinity for target cells; however, it is difficult to simultaneously incorporate two materials into EVs. Post-insertion is a general modification method that can be performed by simply mixing different solutions. Previously, we have developed a microfluidic post-insertion method that supported fast and upscaled modification of EVs using KK-modified high-functionality and -quality (HFQ) lipids. Here, we used microfluidic post-insertion to achieve simultaneous incorporation of polyethylene glycol (PEG) lipids and KK or RGD-modified HFQ lipids into milk-derived EVs to avoid uptake from the reticuloendothelial system and increase the uptake into target cells. PEG lipid and HFQ lipids were formulated to produce micelles and subsequently mixed with EV solution using a microfluidic device. Compared to bulk mixing, microfluidic post-insertion showed higher cellular association. Altered cellular association capacities and endocytic pathways indicated simultaneous incorporation. The cellular association of modified EVs can be adjusted by altering the ratio of (EK)4-KK in micelles with slight changes in physicochemical properties. Furthermore, microfluidic post-insertion is also suitable for (SG)5-RGD, which is insoluble in phosphate-buffered saline (PBS). Our results may be valuable for the development and manufacture of functional EVs as drug delivery systems for clinical applications.

An organometallic swap strategy for bottlebrush polymer-protein conjugate synthesis

Polymer-protein bioconjugation offers a powerful strategy to alter the physical properties of proteins, and various synthetic polymer compositions and architectures have been investigated for this purpose. Nevertheless, conjugation of molecular bottlebrush polymers (BPs) to proteins remains an unsolved challenge due to the large size of BPs and a general lack of methods to transform the chain ends of BPs into functional groups suitable for bioconjugation. Here, we present a strategy to address this challenge in the context of BPs prepared by "graft-through" ring-opening metathesis polymerization (ROMP), one of the most powerful methods for BP synthesis. Quenching ROMP of PEGylated norbornene macromonomers with an activated enyne terminator facilitates the transformation of the BP Ru alkylidene chain ends into Pd oxidative addition complexes (OACs) for facile bioconjugation. This strategy is shown to be effective for the synthesis of two BP-protein conjugates (albumin and ERG), setting the stage for a new class of BP-protein conjugates for future therapeutic and imaging applications.

Research progress on the PEGylation of therapeutic proteins and peptides (TPPs)

With the rapid advancement of genetic and protein engineering, proteins and peptides have emerged as promising drug molecules for therapeutic applications. Consequently, there has been a growing interest in the field of chemical modification technology to address challenges associated with their clinical use, including rapid clearance from circulation, immunogenicity, physical and chemical instabilities (such as aggregation, adsorption, deamination, clipping, oxidation, etc.), and enzymatic degradation. Polyethylene glycol (PEG) modification offers an effective solution to these issues due to its favorable properties. This review presents recent progress in the development and application of PEGylated therapeutic proteins and peptides (TPPs). For this purpose, firstly, the physical and chemical properties as well as classification of PEG and its derivatives are described. Subsequently, a detailed summary is provided on the main sites of PEGylated TPPs and the factors that influence their PEGylation. Furthermore, notable instances of PEG-modified TPPs (including antimicrobial peptides (AMPs), interferon, asparaginase and antibodies) are highlighted. Finally, we propose the chemical modification of TPPs with PEG, followed by an analysis of the current development status and future prospects of PEGylated TPPs. This work provides a comprehensive literature review in this promising field while facilitating researchers in utilizing PEG polymers to modify TPPs for disease treatment.

Design of Pectin-Based Hydrogel Microspheres for Targeted Pulmonary Delivery

Pulmonary drug delivery via microspheres has gained growing interest as a noninvasive method for therapy. However, drug delivery through the lungs via inhalation faces great challenges due to the natural defense mechanisms of the respiratory tract, such as the removal or deactivation of drugs. This study aims to develop a natural polymer-based microsphere system with a diameter of around 3 μm for encapsulating pulmonary drugs and facilitating their delivery to the deep lungs. Pectin was chosen as the foundational material due to its biocompatibility and degradability in physiological environments. Electrospray was used to produce the pectin-based hydrogel microspheres, and Design-Expert software was used to optimize the production process for microsphere size and uniformity. The optimized conditions were determined to be as follows: pectin/PEO ratio of 3:1, voltage of 14.4 kV, distance of 18.2 cm, and flow rate of 0.95 mL/h. The stability and responsiveness of the pectin-based hydrogel microspheres can be altered through coatings such as gelatin. Furthermore, the potential of the microspheres for pulmonary drug delivery (i.e., their responsiveness to the deep lung environment) was investigated. Successfully coated microspheres with 0.75% gelatin in 0.3 M mannitol exhibited improved stability while retaining high responsiveness in the simulated lung fluid (Gamble's solution). A gelatin-coated pectin-based microsphere system was developed, which could potentially be used for targeted drug delivery to reach the deep lungs and rapid release of the drug.

A new hope? Possibilities of therapeutic IgA antibodies in the treatment of inflammatory lung diseases

Inflammatory lung diseases represent a persistent burden for patients and the global healthcare system. The combination of high morbidity, (partially) high mortality and limited innovations in the last decades, have resulted in a great demand for new therapeutics. Are therapeutic IgA antibodies possibly a new hope in the treatment of inflammatory lung diseases? Current research increasingly unravels the elementary functions of IgA as protector against infections and as modulator of overwhelming inflammation. With a focus on IgA, this review describes the pathological alterations in mucosal immunity and how they contribute to chronic inflammation in the most common inflammatory lung diseases. The current knowledge of IgA functions in the circulation, and particularly in the respiratory mucosa, are summarized. The interplay between neutrophils and IgA seems to be key in control of inflammation. In addition, the hurdles and benefits of therapeutic IgA antibodies, as well as the currently known clinically used IgA preparations are described. The data highlighted here, together with upcoming research strategies aiming at circumventing the current pitfalls in IgA research may pave the way for this promising antibody class in the application of inflammatory lung diseases.

Colistin-loaded aerosolizable particles for the treatment of bacterial respiratory infections

Compared to parenteral administration of colistin, its direct pulmonary administration can maximize lung drug deposition while reducing systemic adverse side effects and derived nephrotoxicity. Current pulmonary administration of colistin is carried out by the aerosolization of a prodrug, colistin methanesulfonate (CMS), which must be hydrolized to colistin in the lung to produce its bactericidal effect. However, this conversion is slow relative to the rate of absorption of CMS, and thus only 1.4 % (w/w) of the CMS dose is converted to colistin in the lungs of patients receiving inhaled CMS. We synthesized several aerosolizable nanoparticle carriers loaded with colistin using different techniques and selected particles with sufficient drug loading and adequate aerodynamic behavior to efficiently deliver colistin to the entire lung. Specifically, we carried out (i) the encapsulation of colistin by single emulsion-solvent evaporation with immiscible solvents using polylactic-co-glycolic (PLGA) nanoparticles; (ii) its encapsulation using nanoprecipitation with miscible solvents using poly(lactide-co-glycolide)-block-poly(ethylene glycol) as encapsulating matrix; (iii) colistin nanoprecipitation using the antisolvent precipitation method and its subsequent encapsulation within PLGA nanoparticles; and (iv) colistin encapsulation within PLGA-based microparticles using electrospraying. Nanoprecipitation of pure colistin using antisolvent precipitation showed the highest drug loading (55.0 ± 4.8 wt%) and spontaneously formed aggregates with adequate aerodynamic diameter (between 3 and 5 μm) to potentially reach the entire lung. These nanoparticles were able to completely eradicate Pseudomonas aeruginosa in an in vitro lung biofilm model at 10 µg/mL (MBC). This formulation could be a promising alternative for the treatment of pulmonary infections improving lung deposition and, therefore, the efficacy of aerosolized antibiotics.

An Update on Advancements and Challenges in Inhalational Drug Delivery for Pulmonary Arterial Hypertension

A lethal condition at the arterial–alveolar juncture caused the exhaustive remodeling of pulmonary arterioles and persistent vasoconstriction, followed by a cumulative augmentation of resistance at the pulmonary vascular and, consequently, right-heart collapse. The selective dilation of the pulmonary endothelium and remodeled vasculature can be achieved by using targeted drug delivery in PAH. Although 12 therapeutics were approved by the FDA for PAH, because of traditional non-specific targeting, they suffered from inconsistent drug release. Despite available inhalation delivery platforms, drug particle deposition into the microenvironment of the pulmonary vasculature and the consequent efficacy of molecules are influenced by pathophysiological conditions, the characteristics of aerosolized mist, and formulations. Uncertainty exists in peripheral hemodynamics outside the pulmonary vasculature and extra-pulmonary side effects, which may be further exacerbated by underlying disease states. The speedy improvement of arterial pressure is possible via the inhalation route because it has direct access to pulmonary arterioles. Additionally, closed particle deposition and accumulation in diseased tissues benefit the restoration of remolded arterioles by reducing fallacious drug deposition in other organs. This review is designed to decipher the pathological changes that should be taken into account when targeting the underlying pulmonary endothelial vasculature, especially with regard to inhaled particle deposition in the alveolar vasculature and characteristic formulations.

Inhaled antibodies: Quality and performance considerations

The use of antibodies in the treatment of lung diseases is of increasing interest especially as the search for COVID-19 therapies has unfolded. Historically, the use of antibody therapy was based on multiple targets including receptors involved in local hyper-reactivity in asthma, viruses and micro-organisms involved in a variety of pulmonary infectious disease. Generally, protein therapeutics pose challenges with respect to formulation and delivery to retain activity and assure therapy. The specificity of antibodies amplifies the need for attention to molecular integrity not only in formulation but also during aerosol delivery for pulmonary administration. Drug product development can be viewed from considerations of route of administration, dosage form, quality, and performance measures. Nebulizers and dry powder inhalers have been used to deliver protein therapeutics and each has its advantages that should be matched to the needs of the drug and the disease. This review offers insight into quality and performance barriers and the opportunities that arise from meeting them effectively.

pH-Responsive Nanoparticles for Delivery of Paclitaxel to the Injury Site for Inhibiting Vascular Restenosis

A high incidence of restenosis has been reported at the site of inflammation following angioplasty and stent implantation. The anti-proliferative drug paclitaxel (PTX) could help to reduce inflammation and restenosis; however, it has poor water solubility and serious adverse side effects at high doses. Given the presence of metabolic acidosis at the site of inflammation, we hypothesized that nanoparticles that are responsive to low pH could precisely release the loaded drug at the target site. We successfully constructed pH-responsive poly(D, L-lactic-co-glycolic acid) (PLGA) nanoparticles loaded with PTX and NaHCO3 as a pH-sensitive therapeutic agent (PTX-NaHCO3-PLGA NPs). The NPs exhibited remarkable pH sensitivity and a good safety profile both in vitro in rat vascular smooth muscle cells and in vivo in Sprague Dawley rats after tail vein injection. In the rat model, the PTX-NaHCO3-PLGA NPs treatment group showed suppressed intimal proliferation following balloon-induced carotid artery injury compared with that of the saline-treated control. Overall, these results demonstrate that our newly developed pH-responsive nanodrug delivery platform has the potential to effectively inhibit restenosis.

Monoclonal Antibodies Carried in Drug Delivery Nanosystems as a Strategy for Cancer Treatment

Monoclonal antibodies carried in nanosystems have been extensively studied and reported as a promising tool for the treatment of various types of cancers. Monoclonal antibodies have great advantages for the treatment of cancer because their protein structure can bind to the target tissue; however, it has some challenges such as denaturation following heat exposure and extreme values of pH, temperature and solvents, the ability to undergo hydrolysis, oxidation and deamination and the formation of non-native aggregates, which compromise drug stability to a large extent. In addition to these characteristics, they suffer rapid elimination when in the blood, which results in a short half-life and the production of neutralizing antibodies, rendering the doses ineffective. These challenges are overcome with encapsulation in nanosystems (liposomes, polymer nanoparticles, cyclodextrins, solid lipid nanoparticles, nanostructured lipid carriers, dendrimers and micelles) due to the characteristics of improving solubility, permeability, and selectivity only with tumor tissue; with that, there is a decrease in side effects beyond controlled release, which is critical to improving the therapeutic efficacy of cancer treatment. The article was divided into different types of nanosystems, with a description of their definitions and applications in various types of cancers. Therefore, this review summarizes the use of monoclonal antibodies encapsulated in nanosystems and the description of clinical studies with biosimilars. Biosimilars are defined as products that are similar to monoclonal antibodies which are produced when the patent for the monoclonal antibodies expires.

PEGylation of recombinant human deoxyribonuclease I decreases its transport across lung epithelial cells and uptake by macrophages

Conjugation to high molecular weight (MW ≥ 20 kDa) polyethylene glycol (PEG) was previously shown to largely prolong the lung residence time of recombinant human deoxyribonuclease I (rhDNase) and improve its therapeutic efficacy following pulmonary delivery in mice. In this paper, we investigated the mechanisms promoting the extended lung retention of PEG-rhDNase conjugates using cell culture models and lung biological media. Uptake by alveolar macrophages was also assessed in vivo. Transport experiments showed that PEGylation reduced the uptake and transport of rhDNase across monolayers of Calu-3 cells cultured at an air-liquid interface. PEGylation also decreased the uptake of rhDNase by macrophages in vitro whatever the PEG size as well as in vivo 4 h following intratracheal instillation in mice. However, the reverse was observed in vivo at 24 h due to the higher availability of PEGylated rhDNase in lung airways at 24 h compared with rhDNase, which is cleared faster. The uptake of rhDNase by macrophages was dependent on energy, time, and concentration and occurred at rates indicative of adsorptive endocytosis. The diffusion of PEGylated rhDNase in porcine tracheal mucus and cystic fibrosis sputa was slower compared with that of rhDNase. Nevertheless, no significant binding of PEGylated rhDNase to both media was observed. In conclusion, decreased transport across lung epithelial cells and uptake by macrophages appear to contribute to the longer retention of PEGylated rhDNase in the lungs.

Developing inhaled protein therapeutics for lung diseases

Biologic therapeutics such as protein/polypeptide drugs are conventionally administered systemically via intravenous injection for the treatment of diseases including lung diseases, although this approach leads to low target site accumulation and the potential risk for systemic side effects. In comparison, topical delivery of protein drugs to the lung via inhalation is deemed to be a more effective approach for lung diseases, as proteins would directly reach the target in the lung while exhibiting poor diffusion into the systemic circulation, leading to higher lung drug retention and efficacy while minimising toxicity to other organs. This review examines the important considerations and challenges in designing an inhaled protein therapeutics for local lung delivery: the choice of inhalation device, structural changes affecting drug deposition in diseased lungs, clearance mechanisms affecting an inhaled protein drug’s lung accumulation, protein stability, and immunogenicity. Possible approaches to overcoming these issues will also be discussed.

Pulmonary Delivery of Biological Drugs

In the last decade, biological drugs have rapidly proliferated and have now become an important therapeutic modality. This is because of their high potency, high specificity and desirable safety profile. The majority of biological drugs are peptide- and protein-based therapeutics with poor oral bioavailability. They are normally administered by parenteral injection (with a very few exceptions). Pulmonary delivery is an attractive non-invasive alternative route of administration for local and systemic delivery of biologics with immense potential to treat various diseases, including diabetes, cystic fibrosis, respiratory viral infection and asthma, etc. The massive surface area and extensive vascularisation in the lungs enable rapid absorption and fast onset of action. Despite the benefits of pulmonary delivery, development of inhalable biological drug is a challenging task. There are various anatomical, physiological and immunological barriers that affect the therapeutic efficacy of inhaled formulations. This review assesses the characteristics of biological drugs and the barriers to pulmonary drug delivery. The main challenges in the formulation and inhalation devices are discussed, together with the possible strategies that can be applied to address these challenges. Current clinical developments in inhaled biological drugs for both local and systemic applications are also discussed to provide an insight for further research.

Biodistribution and elimination pathways of PEGylated recombinant human deoxyribonuclease I after pulmonary delivery in mice

Conjugation of recombinant human deoxyribonuclease I (rhDNase) to polyethylene glycol (PEG) of 20 to 40 kDa was previously shown to prolong the residence time of rhDNase in the lungs of mice after pulmonary delivery while preserving its full enzymatic activity. This work aimed to study the fate of native and PEGylated rhDNase in the lungs and to elucidate their biodistribution and elimination pathways after intratracheal instillation in mice. In vivo fluorescence imaging revealed that PEG30 kDa-conjugated rhDNase (PEG30-rhDNase) was retained in mouse lungs for a significantly longer period of time than native rhDNase (12 days vs 5 days). Confocal microscopy confirmed the presence of PEGylated rhDNase in lung airspaces for at least 7 days. In contrast, the unconjugated rhDNase was cleared from the lung lumina within 24 h and was only found in lung parenchyma and alveolar macrophages thereafter. Systemic absorption of intact rhDNase and PEG30-rhDNase was observed. However, this was significantly lower for the latter. Catabolism, primarily in the lungs and secondarily systemically followed by renal excretion of byproducts were the predominant elimination pathways for both native and PEGylated rhDNase. Catabolism was nevertheless more extensive for the native protein. On the other hand, mucociliary clearance appeared to play a less prominent role in the clearance of those proteins after pulmonary delivery. The prolonged presence of PEGylated rhDNase in lung airspaces appears ideal for its mucolytic action in patients with cystic fibrosis.

Scope and limitations on aerosol drug delivery for the treatment of infectious respiratory diseases

The rise of antimicrobial resistance has created an urgent need for the development of new methods for antibiotics delivery to patients with pulmonary infections in order to mainly increase the effectiveness of the drugs administration, to minimize the risk of emergence of resistant strains, and to prevent patients reinfection. Since bacterial resistance is often related to antibiotic concentration, their pulmonary administration could eradicate strains resistant to the same drug at the concentration achieved through the systemic circulation. Pulmonary administration offers several advantages; it directly targets the site of the infection which allows the inhaled dose of the drug to be reduced compared to that administered orally or parenterally while keeping the same local effect. The review article is made with an objective to compile information about various existing modern technologies developed to provide greater patient compliance and reduce the undesirable side effect of the drugs. In conclusion, aerosol antibiotic delivery appears as one of the best technologies for the treatment of pulmonary infectious diseases and able to limit the systemic adverse effects related to the high drug dose and to make life easier for the patients.

Stimuli-sensitive fatty acid-based microparticles for the treatment of lung cancer

Despite recent advancements in medicine, lung cancer still lacks an effective therapy. In the present study we have decided to combine superparamagnetic iron oxide nanoparticles (SPION) with solid lipid microparticles to develop novel, stimuli-sensitive drug carriers that increase the bioavailability of the anticancer drug (paclitaxel - PAX) through guided accumulation directly at the tumour site and controlled drug delivery. SPION and PAX-loaded microparticles (MPs) were fabricated from lauric acid (LAU) and a mixture of myristic and palmitic acids (MYR/PAL) using hot oil-in-water emulsification method. MP size, surface properties, melting temperature and magnetic mobility were evaluated along with their in vitro efficacy against malignant lung epithelial cells (A549). MPs were spherical in shape with the average particle size between 2 and 3.5 μm and responded to external magnetic field up to the distance of 15 mm. MPs were effectively internalised by the cells. Unloaded or NP-loaded MPs were cytocompatible with A549 cells, while NP + PAX-loaded MPs significantly decreased cell viability and effectively suppressed colony formation. The developed stimuli-sensitive, inhalable MPs have shown promising results as PAX carriers for controlled pulmonary delivery for the treatment of lung cancer.

Assessment of Polyethylene Glycol Hydrogel Spacer and Its Effect on Rectal Radiation Dose in Prostate Cancer Patients Receiving Proton Beam Radiation Therapy

Purpose

To assess the efficacy of placing a polyethylene glycol (PEG) spacing hydrogel in patients undergoing proton beam radiation therapy for prostate cancer. This study also aims to assess the effect on rectal radiation dose of prostate-rectum separation in various anatomic planes.

Methods and Materials

Seventy-two consecutive prostate cancer patients undergoing conventionally fractionated pencil beam scanning proton radiation therapy with and without hydrogel placement were compared. Magnetic resonance images taken after hydrogel placement measured prostate-rectum separation and were correlated to rectal dosing and rectal toxicity. Univariate analysis of clinical variables and radiation dosing was conducted using nonparametric Wilcoxon rank-sum test with continuity correction between groups (hydrogel spacer vs controls). Spearman's rank correlation coefficient assessed relationships between the various anatomic dimensions of perirectal space and rectal radiation dosing.

Results

Fifty-one patients had hydrogel placement before therapy and 21 did not. There was a 42.2% reduction in rectal dosing (mL³ rectum) in hydrogel patients (P < .001). Increasing midline sagittal lift resulted in a greater mitigation of total rectal dose (P = .031). The degree of prostate surface area coverage on coronal plane did not correlate with further reductions in rectal radiation dose (P = .673). Patients who had PEG hydrogels placed reported more rectal side effects during treatment compared with those patients who did not (35.3% vs 9.5%, P = .061). At median 9.5-month follow-up, there was no difference in reporting of grade ≤2 rectal toxicity between the 2 groups (7.7% vs 7.1%, P = .145).

Conclusions

Polyethylene glycol hydrogel placement before pencil proton beam radiation therapy for prostate cancer reduced rectal radiation dose. The most important factor reducing total rectal dose was the degree of sagittal midline separation created by the PEG hydrogel. This is the largest study with the longest follow-up to investigate hydrogel placement in the proton beam radiation setting.

Impact of PEGylation on the mucolytic activity of recombinant human deoxyribonuclease I in cystic fibrosis sputum

Highly viscous mucus and its impaired clearance characterize the lungs of patients with cystic fibrosis (CF). Pulmonary secretions of patients with CF display increased concentrations of high molecular weight components such as DNA and actin. Recombinant human deoxyribonuclease I (rhDNase) delivered by inhalation cleaves DNA filaments contained in respiratory secretions and thins them. However, rapid clearance of rhDNase from the lungs implies a daily administration and thereby a high therapy burden and a reduced patient compliance. A PEGylated version of rhDNase could sustain the presence of the protein within the lungs and reduce its administration frequency. Here, we evaluated the enzymatic activity of rhDNase conjugated to a two-arm 40 kDa polyethylene glycol (PEG40) in CF sputa. Rheology data indicated that both rhDNase and PEG40-rhDNase presented similar mucolytic activity in CF sputa, independently of the purulence of the sputum samples as well as of their DNA, actin and ions contents. The macroscopic appearance of the samples correlated with the DNA content of the sputa: the more purulent the sample, the higher the DNA concentration. Finally, quantification of the enzymes in CF sputa following rheology measurement suggests that PEGylation largely increases the stability of rhDNase in CF respiratory secretions, since 24-fold more PEG40-rhDNase than rhDNase was recovered from the samples. The present results are considered positive and provide support to the continuation of the research on a long acting version of rhDNase to treat CF lung disease.

Fate of PEGylated antibody fragments following delivery to the lungs: Influence of delivery site, PEG size and lung inflammation

Pulmonary administration of anti-cytokine antibodies offers a targeted therapy in asthma. However, the rapid elimination of proteins from the lungs limits the efficacy of inhaled medications. PEGylation has been shown to increase the residence time of anti-interleukin (IL)-17A and anti-IL-13 antibody fragments in the lungs and to improve their therapeutic efficacy. Yet, little is known about the factors that affect the residence time of PEGylated antibody fragments in the lungs following pulmonary delivery. In this study, we showed that the molecular weight of polyethylene glycol (PEG), 20kDa or 40kDa, had a moderate effect on the residence time of an anti-IL-17A Fab' fragment in the lungs of mice. By contrast, the site of delivery of the anti-IL-17A and anti-IL-13 Fab' fragments within the lungs had a major impact on their residence time, with the deeper the delivery, the more prolonged the residence time. The nature of the Fab' fragment had an influence on its residence time as well and the anti-IL-17A Fab' benefited more from PEGylation than the anti-IL-13 Fab' did. Acute lung inflammation slightly shortened the residence time of the anti-IL-17A and anti-IL-13 Fab' fragments in the lungs but PEGylation was able to prolong their presence in both the healthy and inflamed lungs. Antibody fragments were predominately located within the airway lumen rather than the lung parenchyma. Transport experiments on monolayers of Calu-3 cells and studies of fluorescence recovery after photobleaching in respiratory mucus showed that mechanisms involved in the prolonged presence of PEGylated Fab' in the airway lumen might include binding to the mucus, reduced uptake by respiratory cells and reduced transport across lung epithelia. Finally, using I¹²⁵-labeled anti-IL-17A Fab', we showed that the protein fragment hardly penetrated into the lungs following subcutaneous injection, as opposed to pulmonary delivery.