An overview of in vitro and in vivo techniques for characterization of intranasal protein and peptide formulations for brain targeting.

The surge in neurological disorders necessitates innovative strategies for delivering active pharmaceutical ingredients to the brain. The non-invasive intranasal route has emerged as a promising approach to optimize drug delivery to the central nervous system by circumventing the blood-brain barrier. While the intranasal approach offers numerous advantages, the lack of a standardized protocol for drug testing poses challenges to both in vitro and in vivo studies, limiting the accurate interpretation of nasal drug delivery and pharmacokinetic data. This review explores the in vitro experimental assays employed by the pharmaceutical industry to test intranasal formulation. The focus lies on understanding the diverse techniques used to characterize the intranasal delivery of drugs targeting the brain. Parameters such as drug release, droplet size measurement, plume geometry, deposition in the nasal cavity, aerodynamic performance and mucoadhesiveness are scrutinized for their role in evaluating the performance of nasal drug products. The review further discusses the methodology for in vivo characterization in detail, which is essential in evaluating and refining drug efficacy through the nose-to-brain pathway. Animal models are indispensable for pre-clinical drug testing, offering valuable insights into absorption efficacy and potential variables affecting formulation safety. The insights presented aim to guide future research in intranasal drug delivery for neurological disorders, ensuring more accurate predictions of therapeutic efficacy in clinical contexts.

Intranasal delivery of thin-film freeze-dried monoclonal antibodies using a powder nasal spray system.

Monoclonal antibodies (mAbs) administered intranasally as dry powders can be potentially applied for the treatment or pre-exposure prevention of viral infections in the upper respiratory tract. However, a method to transform the mAbs from liquid to dry powders suitable for intranasal administration and a device that can spray the dry powders to the desired region of the nasal cavity are needed to fully realize the potentials of the mAbs. Herein, we report that thin-film freeze-dried mAb powders can be sprayed into the posterior nasal cavity using Aptar Pharma's Unidose (UDS) Powder Nasal Spray System. AUG-3387, a human-derived mAb that neutralizes the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was used in the present study. First, we prepared thin-film freeze-dried AUG-3387 powders (i.e., TFF AUG-3387 powders) from liquid formulations containing different levels of mAbs. The TFF AUG-3387 powder with the highest solid content (i.e., TFF AUG-3387C) was then chosen for further characterization, including the evaluation of the plume geometry, spray pattern, and particle size distribution after the powder was sprayed using the UDS Powder Nasal Spray. Finally, the deposition patterns of the TFF AUG-3387C powder sprayed using the UDS Powder delivery system were studied using 3D-printed nasal replica casts based on the CT scans of an adult and a child. It is concluded that it is feasible to intranasally deliver mAbs as dry powders by transforming the mAbs into dry powders using thin-film freeze-drying and then spraying the powder using a powder nasal spray system.

Laboratory Performance Testing of Aqueous Nasal Inhalation Products for Droplet/Particle Size Distribution: an Assessment from the International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS).

Although nasal inhalation products are becoming more and more important for the delivery of medicines, characterization of these products for quality control and assessment of bioequivalence is complicated. Most of the problems encountered are associated with the assessment of aerodynamic droplet/particle size distribution (APSD). The droplets produced by the various nasal devices are large, and for suspension products, individual droplets may contain multiple drug particles or none at all. Assessment of suspension products is further complicated by the presence of solid excipient particles. These complications make it imperative that the limitations of the instruments used for characterization as well as the underlying assumptions that govern the interpretation of data produced by these instruments are understood. In this paper, we describe various methodologies used to assess APSD for nasal inhalation products and discuss proper use, limitations, and new methodologies on the horizon.

Feasibility of intranasal delivery of thin-film freeze-dried, mucoadhesive vaccine powders.

Intranasal vaccination by directly applying a vaccine dry powder is appealing. However, a method that can be used to transform a vaccine from a liquid to a dry powder and a device that can be used to administer the powder to the desired region(s) of the nasal cavity are critical for successful intranasal vaccination. In the present study, using a model vaccine that contains liposomal monophosphoryl lipid A and QS-21 adjuvant (AdjLMQ) and ovalbumin (OVA) as a model antigen, it was shown that thin-film freeze-drying can be applied to convert the liquid vaccine containing sucrose at a sucrose to lipid ratio of 15:1 (w/w) into dry powders, in the presence or absence of carboxymethyl cellulose sodium salt (CMC) as a mucoadhesive agent. Ultimately, the thin-film freeze-dried AdjLMQ/OVA vaccine powder containing 1.9% (w/w) of CMC (i.e., TFF AdjLMQ/OVA/CMC1.9% powder) was selected for additional evaluation because the TFF AdjLMQ/OVA/CMC1.9% powder was mucoadhesive and maintained the integrity of the antigen and the physical properties of the vaccine. Compared to the TFF AdjLMQ/OVA powder that did not contain CMC, the TFF AdjLMQ/OVA/CMC1.9% powder had a lower moisture content and a higher glass transition temperature. In addition, the TFF AdjLMQ/OVA/CMC1.9% thin films were relatively thicker than the TFF AdjLMQ/OVA thin films without CMC. When sprayed with Aptar Pharma's Unidose Powder Nasal Spray System (UDSP), the TFF AdjLMQ/OVA powder and the TFF AdjLMQ/OVA/CMC1.9% powder generated similar particle size distribution curves, spray patterns, and plume geometries. Importantly, after the TFF AdjLMQ/OVA/CMC1.9% powder was sprayed with the UDSP nasal device, the integrity of the OVA antigen and the AdjLMQ liposomes did not change. Finally, a Taguchi L4 orthogonal array was applied to identify the optimal parameters for using the UDSP device to deliver the TFF AdjLMQ/OVA/CMC1.9% powder to the middle and lower turbinate and the nasopharynx regions in both adult and child nasal replica casts. Results from this study showed that it is feasible to apply the thin-film freeze-drying technology to transform a nasal vaccine candidate from liquid to a dry powder and then use the UDSP nasal device to deliver the vaccine powder to the desired regions in the nasal cavity for intranasal vaccination.

In Vitro Anatomical Models for Nasal Drug Delivery.

Nasal drug delivery has been utilized for locally acting diseases for decades. The nose is also a portal to the systemic circulation and central nervous system (CNS). In the age of SARS-CoV2, the development of nasal sprays for vaccination and prophylaxis of respiratory diseases is increasing. As the number of nasal drug delivery applications continue to grow, the role of targeted regional deposition in the nose has become a factor is nasal drug development. In vitro tools such as nasal casts help facilitate formulation and product development. Nasal deposition has been shown to be linked to pharmacokinetic outcomes. Developing an understanding of the complex nasal anatomy and intersubject variability can lead to a better understanding of where the drug will deposit. Nasal casts, which are replicas of the human nasal cavity, have evolved from models made from cadavers to complex 3D printed replicas. They can be segmented into regions of interest for quantification of deposition and different techniques have been utilized to quantify deposition. Incorporating a nasal cast program into development can help differentiate formulations or physical forms such as nasal powder versus a liquid. Nasal casts can also help develop instructions for patient use to ensure deposition in the target deposition site. However, regardless of the technique used, this in vitro tool should be validated to ensure the results reflect the in vivo situation. In silico, CFD simulation or other new developments may in future, with suitable validation, present additional approaches to current modelling, although the complexity and wide degree of variability in nasal anatomy will remain a challenge. Nonetheless, nasal anatomical models will serve as effective tools for improving the understanding of nasal drug delivery.

Spray Pattern and Plume Geometry Testing and Methodology: An IPAC-RS Working Group Overview.

Plume characterization for orally inhaled and nasal drug products (OINDP) provides valuable information during OINDP development. Spray pattern and plume geometry techniques, methods, and technology have evolved over the past 20 years since the publication of the original 1998 FDA MDI DPI draft guidance. The International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) discusses the historical context and background to plume geometry and spray pattern characterization studies; provides an analysis of the current regulatory context; addresses results from its industry surveys on application and value of such testing; and presents case studies and best practices-seeking to provide insights to regulatory bodies and other stakeholders. Assessment and consideration of published studies and industry experience note the value of plume geometry and spray pattern in development, and that further data is needed regarding their use in assessing formulation characteristics. Continued dialogue between industry and regulatory bodies is needed to establish the optimum use of these techniques.

Current understanding of nasal morphology and physiology as a drug delivery target.

The nasal cavity is both a target for locally and systemically acting medications. An adequate treatment for rhinosinusitis continues to be an unmet need. With the recent approval of intranasal medications for the treatment of pain, the nasal cavity continues to be a viable route for rapid uptake into the systemic circulation. Despite the opportunities, there is still a void in the knowledge of how therapeutic entities interact with the nasal epithelium. In addition, new opportunities in mucosal immunity via nasal vaccination as well as the elusive nose to brain uptake continue to drive innovation. To facilitate understanding of the issues involved that facilitate drug delivery in the nose, a review of nasal morphology and physiology is presented.

Demonstrating Bioequivalence of Locally Acting Orally Inhaled Drug Products (OIPs): Workshop Summary Report.

This March 2009 Workshop Summary Report was sponsored by Product Quality Research Institute (PQRI) based on a proposal by the Inhalation and Nasal Technology Focus Group (INTFG) of the American Association of Pharmaceutical Scientists (AAPS). Participants from the pharmaceutical industry, academia and regulatory bodies from the United States, Europe, India, and Brazil attended the workshop with the objective of presenting, reviewing, and discussing recommendations for demonstrating bioequivalence (BE) that may be considered in the development of orally inhaled drug products and regulatory guidances for new drug applications (NDAs), abbreviated NDAs (ANDAs), and postapproval changes. The workshop addressed areas related to in vitro approaches to demonstrating BE, biomarker strategies, imaging techniques, in vivo approaches to establishing local delivery equivalence and device design similarity. The workshop presented material that provided a baseline for the current understanding of orally inhaled drug products (OIPs) and identified gaps in knowledge and consensus that, if answered, might allow the design of a robust, streamlined method for the BE assessment of locally acting inhalation drugs. These included the following: (1) cascade impactor (CI) studies are not a good 2 predictor of the pulmonary dose; more detailed studies on in vitro/in vivo correlations (e.g., suitability of CI studies for assessing differences in the regional deposition) are needed; (2) there is a lack of consensus on the appropriate statistical methods for assessing in vitro results; (3) fully validated and standardized imaging methods, while capable of providing information on pulmonary dose and regional deposition, might not be applicable to the BE of inhaled products mainly due to the problems of having access to radiolabeled innovator product; (4) if alternatives to current methods for establishing local delivery BE of OIPs cannot be established, biomarkers (pharmacodynamic or clinical endpoints) with a sufficiently steep dose-response need to be identified and validated for all relevant drug classes; and (5) the utility of pharmacokinetic studies for evaluating "local pulmonary delivery" equivalence deserves more attention. A summary of action items for seminars and working groups to address these topics in the future is also presented.

Characterization of stability and nasal delivery systems for immunization with nanoemulsion-based vaccines.

BACKGROUND: Many infectious diseases that cause significant morbidity and mortality, especially in the developing world, could be preventable through vaccination. The effort to produce safe, thermally stable, and needle-free mucosal vaccines has become increasingly important for global health considerations. We have previously demonstrated that a thermally stable nanoemulsion, a mucosal adjuvant for needle-free nasal immunization, is safe and induces protective immunity with a variety of antigens, including recombinant protein. The successful use of nanoemulsion-based vaccines, however, poses numerous challenges. Among the challenges is optimization of the formulation to maintain thermal stability and potency and another is accuracy and efficiency of dispensing the vaccines to the nasal mucosa in the anterior and turbinate region of the nasal cavity or potentially to the nasopharynx-associated lymphoid tissue. METHODS: We have examined the effects of different diluents [phosphate-buffered saline (PBS) and 0.9% NaCl] on the stability and potency of nanoemulsion-based vaccines. In addition, we have determined the efficiency of delivering them using commercially available nasal spray devices (Pfeiffer SAP-62602 multidose pump and the BD Hypak SCF 0.5 ml unit dose Accuspray(TM)). RESULTS: We report the stability and potency of PBS-diluted ovalbumin-nanomeulsion mixtures for up to 8 months and NaCl-diluted mixtures up to 6 months when stored at room temperature. Significant differences in spray characteristics including droplet size, spray angle, plume width, and ovality ratios were observed between the two pumps. Further, we have demonstrated that the nanoemulsion-based vaccines are not physically or chemically altered and retain potency following actuation with nasal spray devices. Using either device, the measured spray characteristics suggest deposition of nanoemulsion-based vaccines in inductive tissues located in the anterior region of the nasal cavity. CONCLUSIONS: The results of this study suggest that nanoemulsion-based vaccines do not require specially engineered delivery devices and support their potential use as nasopharyngeal vaccine adjuvants.

Validity of in vitro tests on aqueous spray pumps as surrogates for nasal deposition, absorption, and biologic response.

This research investigated the impact of the full range of in vitro spray characterization tests described in the FDA Draft Bioequivalence Guidance on nasal deposition pattern, pharmacokinetics, and biological response to nicotine administered by two aqueous nasal spray pumps in human volunteers. Nicotine was selected as a model drug (even though it is not locally acting) based on its ability to alter cardiac function and available plasma assay. Significant differences in pump performance-including mean volume diameters, spray angle, spray width, and ovality ratios-were observed between the two pumps. There were no significant differences in deposition pattern, or pharmacokinetic or pharmacodynamic response to the nasally administered nicotine. Although there were statistical differences in the in vitro tests between the two pumps, these differences did not result in significant alterations in the site of droplet deposition within the nose, the rate and extent of nicotine absorption, or the physiologic response it induced. These results suggest that current measures of in vitro performance, particularly spray angle and spray pattern (ovality), may not be clinically relevant. Additional research is needed to define what spray pump characteristics are likely to produce differences in deposition pattern and drug response.

Inhalation therapy: technological milestones in asthma treatment.

The humble origins of the propellant driven metered dose inhaler, as a response to a child's enquiry, initiated an industry which supplies approximately a half billion inhalers globally for the treatment of asthma. These inhalers fall into three major groups: nebulizers; propellant driven metered dose inhalers and dry powder inhalers. Each requires drug formulation, metering and device technology to be successful. In recent years there have been several new developments in the field including auxiliary systems to improve drug delivery from the device to the patient and new categories of device, notably single breath aqueous systems. As device technology improves and our understanding of the disease leads to new drugs the only barrier to therapy is the patient. Patient training and compliance will continue to be important factors in the success, or failure, of inhaled therapy and the role of health care professionals will depend on who sponsors their intervention.

Nasal drug delivery.

The Nasal Drug Delivery Conference was held at the Institute of Directors in London, England. The meeting was organised by the Management Forum Ltd and chaired by P Seeney (PA Consulting, UK) and Professor F Merkus (Leiden University, The Netherlands; Innoscience Technology, Belgium). The conference covered a wide range of topics including aspects of nasal physiology, formulation, new nasal products, nasal vaccines, nose to brain transport and pain management via nasal sprays.

Validity of in vitro tests on aqueous spray pumps as surrogates for nasal deposition.

PURPOSE: To determine whether deposition pattern is related to in vitro measurements of droplet size, plume geometry, and spray pattern between two different nasal spray pumps believed to have different performance characteristics. METHODS: Ten healthy volunteers inhaled radiolabeled saline from two different spray pumps (pump A and pump B). Deposition pattern was quantified from lateral views of the nose by gamma scintigraphy, expressed as the ratio of anterior to posterior (I:O) and superior to inferior (U:L) deposition. Droplet size was determined by Malvern Mastersizer S. Spray patterns were determined at 2.5 and 5 cm from the tip of the spray nozzle. Two-dimensional images of the emitted plume were captured by high-speed still photography. RESULTS: There were no significant differences in I:O or U:L ratios for pump A compared to pump B, indicating no significant differences in deposition pattern. The volume diameters, Dv10 and Dv50, were not statistically different for pump A compared to pump B. There was a significant difference in Dv90 between pump A and pump B, (86.9 +/- 5.8 microm and 77.4 +/- 2.4 microm. respectively; P < 0.001). The ratio of the longest to shortest diameter for the spray pattern with pump A was 1.26 +/- 0.06 at 2.5 cm and 1.44 +/- 0.08 at 5 cm. The ratio for pump B was 1.13 +/- 0.03 at 2.5 cm and 1.19 +/- 0.05 at 5 cm. Ratios at both heights were statistically different for pump A compared to pump B (P < 0.00002 and P < 0.000001, respectively) Plume geometry analysis indicated statistical differences in both the width (17.0 +/- 0.97 vs. 18.5 +/- 0.56 cm, respectively: p<0.001) and the maximum length of the plumes (46.0 +/- 1.83 vs. 53.1 +/- 4.88 cm, respectively; p < .002). The differences in velocity of the plume and spray angle between the two pumps were not statistically different. CONCLUSIONS. Certain in vitro tests detected performance differences between the two pumps. However, these differences did not translate into different deposition patterns in vivo.