Evaluation of Intranasal Vaccine Delivery Using Anatomical Replicas of Infant Nasal Airways

Scale-up of a low-temperature spray-drying process for a tuberculosis vaccine candidate using lab-scale equipment

Laboratory-scale spray drying can be a useful tool in developing new dry powder formulations for the delivery of biologics such as therapeutic proteins or vaccines. Low-temperature drying is often used in these processes to prevent the exposure of biologics to harsh conditions that could potentially lead to degradation or instability of the final product. However, low-temperature drying on small-scale equipment can result in very low production rates that may not be practical for generating sufficient material for studies requiring larger sample quantities, such as key preclinical or toxicology studies. This study demonstrates a scale-up effort for a spray dried adjuvanted protein tuberculosis (TB) vaccine candidate using a custom lab-scale spray dryer. To achieve higher throughput without compromising the stability of the powder and biologic material, a process model for the spray dryer was used to determine optimal processing parameters and establish general vaccine powder manufacturing guidelines, such as minimizing exposure to high temperatures and relative humidity during drying. Maximizing dryer throughput and increasing overall feed concentration resulted in a tenfold increase in production rate using lab-scale equipment, such that 97.6 g of powder (the equivalent of about 5,000 human doses) could be produced using a lab-scale spray dryer in a single 6-hour spray drying run.

Development of a predictive model for pediatric intranasal drug delivery with nasal sprays: Leveraging intersubject variability in anatomical dimensions, administration-related parameters, and airway patency

In this study, we examined the correlation between anatomical dimensions, spray administration parameters, pressure drop across 40 pediatric nasal cavities, and in vitro posterior drug delivery (PDD) using Nasacort ALLERGY 24HR and FLONASE SENSIMIST nasal suspensions sprays, with different nozzle and actuation designs. The importance of each parameter and their interaction in the outcome (PDD) was evaluated. To do so, initially we measured anatomical and administration-related parameters, and the pressure drop of each cavity. Afterwards, a stepwise regression method was used to find a combination of parameters that can effectively predict the outcome. Two strong correlations, r2 = 0.802 and 0.895, were found between a combination of three explored parameters and the PDD of Nasacort and Flonase Sensimist, respectively. While, based on the p-values, the insertion depth was found to be the most influential parameter for determining the PDD with Nasacort, and the administration coronal angle was found to be the most important one for Flonase Sensimist, anatomical parameters, or an interaction between anatomical and administration parameters were among the five most important parameters for both sprays. Furthermore, variable importance assessment, based on the variance of the response, demonstrated the tip-to-INV distance as the most important parameter for Nasacort and coronal angle for Flonase Sensimist, while cross sectional area at the end of the anterior piece was the only parameter that found to be in the three most important parameters for both sprays. Having this in mind, as well as the wide range of PDD within the pediatric population, it can be concluded that the performance of targeted intranasal drug delivery, even when using a set of patient-specific administration parameters, is strongly influenced by the anatomical features of the subject. Additionally, comparing the key factors in predicting PDD in pediatric and adult population for Flonase Sensimist demonstrate no similarity between the influential parameters on PDD in the two age groups, which further emphasizes the importance of airway anatomy.

Anatomically-detailed segmented representative adult and pediatric nasal models for assessing regional drug delivery and bioequivalence with suspension nasal sprays

In vitro nasal models can potentially facilitate development and approval of nasal drug products. This study aims to evaluate the potential for using regional deposition measurements from in vitro nasal models to evaluate nasal spray performance across several products. To accomplish this, the posterior regions of six anatomically realistic nasal airway models of adult and pediatric subjects, representing Low (L), Mean (M) and High (H) posterior drug deposition (PD) for each of the two age groups, were segmented with high anatomical precision into five regions of interest. These models were previously developed with the goal of quantifying the range of intersubject variability of PD following administration of inhaled corticosteroids. The in vitro regional drug deposition values were measured for the reference listed drug (RLD) product for triamcinolone acetonide and two corresponding generic (test) nasal spray products, as well as an RLD product for fluticasone furoate nasal spray. In general, the pediatric models mostly demonstrated higher PD compared to the adult models. The majority (>85 %) of PD was confined to the front and the inferior meatus regions. Subsequent population bioequivalence (PBE) analyses of the regional nasal deposition suggested that the anatomical differences among subjects may impact the nasal spray performance across different nasal products.

Characterizing regional drug delivery within the nasal airways

INTRODUCTION

The nose has been receiving increased attention as a route for drug delivery. As the site of deposition constitutes the first point of contact of the body with the drug, characterization of the regional deposition of intranasally delivered droplets or particles is paramount to formulation and device design of new products.

AREAS COVERED

This review article summarizes the recent literature on intranasal regional drug deposition evaluated in vivo, in vitro and in silico, with the aim of correlating parameters measured in vitro with formulation and device performance. We also highlight the relevance of regional deposition to two emerging applications: nose-to-brain drug delivery and intranasal vaccines.

EXPERT OPINION

As in vivo studies of deposition can be costly and time-consuming, researchers have often turned to predictive in vitro and in silico models. Variability in deposition is high due in part to individual differences in nasal geometry, and a complete predictive model of deposition based on spray characteristics remains elusive. Carefully selected or idealized geometries capturing population average deposition can be useful surrogates to in vivo measurements. Continued development of in vitro and in silico models may pave the way for development of less variable and more effective intranasal drug products.

Numerical and experimental evaluation of nasopharyngeal aerosol administration methods in children with adenoid hypertrophy

Administering aerosol drugs through the nasal pathway is a common early treatment for children with adenoid hypertrophy (AH). To enhance therapeutic efficacy, a deeper understanding of nasal drug delivery in the nasopharynx is essential. This study uses an integrated experimental, numerical modelling approach to investigate the delivery process of both the aerosol mask delivery system (MDS) and the bi-directional delivery system (BDS) in the pediatric nasal airway with AH. The combined effect of respiratory flow rates and particle size on delivery efficiency was systematically analyzed. The results showed that the nasopharyngeal peak deposition efficiency (DE) for BDS was approximately 2.25-3.73 times higher than that for MDS under low-flow, resting and high-flow respiratory conditions. Overall nasopharyngeal DEs for MDS were at a low level of below 16 %. For each respiratory flow rate, the BDS tended to achieve higher peak DEs (36.36 % vs 9.74 %, 37.80 % vs 14.01 %, 34.58 % vs 15.35 %) at smaller particle sizes (15 µm vs 17 µm, 10 µm vs 14 µm, 6 µm vs 9 µm). An optimal particle size exists for each respiratory flow rate, maximizing the drug delivery efficiency to the nasopharynx. The BDS is more effective in delivering drug aerosols to the nasal cavity and nasopharynx, which is crucial for early intervention in children with AH.

Repurposing mucosal delivery devices for live attenuated tuberculosis vaccines

Tuberculosis (TB) remains one of the most lethal infectious diseases globally. The only TB vaccine approved by the World Health Organization, Bacille Calmette-Guérin (BCG), protects children against severe and disseminated TB but provides limited protection against pulmonary TB in adults. Although several vaccine candidates have been developed to prevent TB and are undergoing preclinical and clinical testing, BCG remains the gold standard. Currently, BCG is administered as an intradermal injection, particularly in TB endemic countries. However, mounting evidence from experimental animal and human studies indicates that delivering BCG directly into the lungs provides enhanced immune responses and greater protection against TB. Inhalation therapy using handheld delivery devices is used for some diseases and allows the delivery of drugs or vaccines directly into the human respiratory tract. Whether this mode of delivery could also be applicable for live attenuated bacterial vaccines such as BCG or other TB vaccine candidates remains unknown. Here we discuss how two existing inhalation devices, the mucosal atomization device (MAD) syringe, used for influenza vaccines, and the Respimat® Soft Mist™ inhaler, used for chronic obstructive pulmonary disease (COPD) therapy, could be repurposed for mucosal delivery of live attenuated TB vaccines. We also outline the challenges and outstanding research questions that will require further investigations to ensure usefulness of respiratory delivery devices that are cost-effective and accessible to lower- and middle-income TB endemic countries.

In Vitro Comparison of Local Nasal Vaccine Delivery and Correlation with Device Spray Performance

PURPOSE

This study is the first vaccine candidate in vitro investigation with a focus on finding a correlation between the spray characteristics and the delivery efficiency of the local deposition in the nasal airways of infants under 24 months using various intranasal devices.

METHODS

In vitro tests were developed to measure the spray characteristics of four intranasal delivery devices and how they regionally deliver a candidate vaccine formulation matrix in five nasal airway replicas (3 to 24 months). The correlation between the spray performance, geometric parameters, and delivery efficiency were assessed.

RESULTS

All four devices performed consistently in terms of spray characteristics and were capable of delivering a high percentage of the candidate vaccine to the target areas, with a minimum delivery efficiency of 80%. Moreover, the delivery efficiency was affected by either the spray droplet size distribution or the distance between the nozzle tip and the internal nasal valve. Correlations between the spray performance and the in vitro local dose deposition were established.

CONCLUSION

The infant nasal model tests can be complementary to device spray performance evaluation. In the absence of in vivo correlations, they can also facilitate the process of new product development by estimating delivery a priori.

Intranasal delivery of a synthetic Entamoeba histolytica vaccine containing adjuvant (LecA + GLA-3M-052 liposomes): in vitro characterization

Amebiasis, a disease caused by the parasite Entamoeba histolytica, is estimated to cause millions of infections and at least 55,000 deaths globally each year. With no vaccine currently available, there is an urgent need for an accessible means of stimulating protective mucosal immunity. The objective of this study was to characterize the nasal spray of a novel amebiasis vaccine candidate from a syringe-based liquid atomization device, the Teleflex MAD Nasal™, in both adult and infant nasal airways. Human ergonomic testing was completed to determine realistic actuation parameters. Spray pattern, plume geometry, and droplet size distribution were measured to evaluate reproducibility of free plume characteristics. The Alberta Idealized Nasal Inlet (AINI) and three realistic infant nasal airways were used to determine the in vitro deposition profile in adult and infant airways, respectively. Collectively, in vitro results demonstrated the feasibility of delivering the vaccine candidate to target sites within the nasal airways. Penetration through the nasal airways that could lead to deposition in the lungs was below the limit of quantification for both adult and infant geometries, indicating a low likelihood of adverse events due to lung exposure. These results support continued investigation of intranasal delivery of the synthetic Entamoeba histolytica vaccine.

Validation and Sensitivity analysis for a nasal spray deposition computational model

Validating numerical models against experimental models of nasal spray deposition is challenging since many aspects must be considered. That being said, it is a critical step in the product development process of nasal spray devices. This work presents the validation process of a nasal deposition model, which demonstrates a high degree of consistency of the numerical model with experimental data when the nasal cavity is segmented into two regions but not into three. Furthermore, by modelling the flow as stationary, the computational cost is drastically reduced while maintaining quality of particle deposition results. Thanks to this reduction, a sensitivity analysis of the numerical model could be performed, consisting of 96 simulations. The objective was to quantify the impact of four inputs: the spray half cone angle, mean spray exit velocity, breakup length from the nozzle exit and the diameter of the nozzle spray device, on the three quantities of interest: the percentage of the accumulated number of particles deposited on the anterior, middle and posterior sections of the nasal cavity. The results of the sensitivity analysis demonstrated that the deposition on anterior and middle sections are sensitive to injection angle and breakup length, and the deposition on posterior section is only, but highly, sensitive to the injection velocity.

The Communication between Ocular Surface and Nasal Epithelia in 3D Cell Culture Technology for Translational Research: A Narrative Review

There is a lack of knowledge regarding the connection between the ocular and nasal epithelia. This narrative review focuses on conjunctival, corneal, ultrastructural corneal stroma, and nasal epithelia as well as an introduction into their interconnections. We describe in detail the morphology and physiology of the ocular surface, the nasolacrimal ducts, and the nasal cavity. This knowledge provides a basis for functional studies and the development of relevant cell culture models that can be used to investigate the pathogenesis of diseases related to these complex structures. Moreover, we also provide a state-of-the-art overview regarding the development of 3D culture models, which allow for addressing research questions in models resembling the in vivo situation. In particular, we give an overview of the current developments of corneal 3D and organoid models, as well as 3D cell culture models of epithelia with goblet cells (conjunctiva and nasal cavity). The benefits and shortcomings of these cell culture models are discussed. As examples for pathogens related to ocular and nasal epithelia, we discuss infections caused by adenovirus and measles virus. In addition to pathogens, also external triggers such as allergens can cause rhinoconjunctivitis. These diseases exemplify the interconnections between the ocular surface and nasal epithelia in a molecular and clinical context. With a final translational section on optical coherence tomography (OCT), we provide an overview about the applicability of this technique in basic research and clinical ophthalmology. The techniques presented herein will be instrumental in further elucidating the functional interrelations and crosstalk between ocular and nasal epithelia.

In Vitro Evaluation of Nasal Aerosol Depositions: An Insight for Direct Nose to Brain Drug Delivery

The nasal cavity is an attractive route for both local and systemic drug delivery and holds great potential for access to the brain via the olfactory region, an area where the blood–brain barrier (BBB) is effectively absent. However, the olfactory region is located at the roof of the nasal cavity and only represents ~5–7% of the epithelial surface area, presenting significant challenges for the deposition of drug molecules for nose to brain drug delivery (NTBDD). Aerosolized particles have the potential to be directed to the olfactory region, but their specific deposition within this area is confounded by a complex combination of factors, which include the properties of the formulation, the delivery device and how it is used, and differences in inter-patient physiology. In this review, an in-depth examination of these different factors is provided in relation to both in vitro and in vivo studies and how advances in the fabrication of nasal cast models and analysis of aerosol deposition can be utilized to predict in vivo outcomes more accurately. The challenges faced in assessing the nasal deposition of aerosolized particles within the paediatric population are specifically considered, representing an unmet need for nasal and NTBDD to treat CNS disorders.