Navigating Regulatory Bridging Strategies for Nasal Product Development
Nasal drug products are among the most complex combination products to develop—often requiring a careful balance between formulation, device, and clinical performance.
SYNOPSIS
This article explores how regulatory bridging strategies enable more efficient approval of nasal spray products by connecting new data to prior scientific findings. It outlines key FDA pathways—505(b)(2) and ANDA (505(j))—and explains how sponsors can establish scientific bridges between formulations, delivery devices, and prior studies. With insights on bioavailability factors, formulation design, device impact, and bridging methodology, readers will gain a clear framework for navigating nasal product development with greater regulatory confidence and efficiency.
Navigating Regulatory Bridging Strategies for Nasal Product Development
Regulatory bridging strategies are frequently impact how nasal spray products, often complex combinations of drug, biologic, and device components, reach approval. By leveraging relevant data and establishing scientific bridges to previously approved products, sponsors can streamline development, reduce study burden, and ultimately bring innovative treatments to patients faster.
Understanding Regulatory Pathways for Nasal Sprays
Nasal products are regulated as drug/biologic-device combination products, with approval pathways often determined by their similarity or sameness to existing products. Two regulatory strategies enable sponsors to streamline development by leveraging the approval of prior products:
- Abbreviated New Drug Application (ANDA, 505(j)): Requires bioequivalence and sameness to a reference listed drug (RLD).
- 505(b)(2) Hybrid Pathway: Allows reliance on scientific bridging to previously approved drugs.
Abbreviated New Drug Application: Requirements
The ANDA process is reserved for products identical to an approved drug in terms of active ingredients, conditions of use, dosage, route, and labeling (with minor permissible differences). Crucially, ANDA submissions cannot claim unique clinical outcomes or rely on new clinical investigations—approval is anchored in bioequivalence and the FDA’s prior findings about the reference product.
The 505(b)(2) Pathway: Leveraging Prior Data
505(b)(2) applications differ in that they have the same burden of demonstrating safety and effectiveness as a new drug application under 505(b)(1), but this pathway permits sponsors to leverage data that the sponsor does not have right of reference to. Often this allows sponsors to leverage data from studies they have not conducted themselves reducing the overall testing burden for a given product. This pathway requires establishing a scientific bridge to the agency’s safety and effectiveness findings for a Listed Drug (LD), or relevant published literature. The selection of a suitable LD, and/or scientifically credible literature, is central to fully utilizing the 505(b)(2) pathway.
What is Scientific Bridging?
Scientific Bridging refers to demonstrating the scientific relevance of data from previous studies, whether from another product or an earlier phase of development, to support approval for a new combination product. Examples of scientific bridging include:
- Bridging sponsor-owned early-stage clinical data to a final, marketed formulation.
- Establishing a link to a prior LD for FDA reliance (505(b)(2) pathway).
- Device-to-device bridging when transitioning a formulation from one delivery mechanisms/system to another.
Clinical Bridging: FDA Guidance Framework
The FDA has provided a draft Guidance “Bridging for Drug-Device and Biologic-Device Combination Products” to provide a framework to establish a scientific bridge. Per the Guidance, Sponsors should apply a systematic approach to identify potential gaps and devise appropriate bridging strategies:
- Establish Bridging Strategy: Inventory and compare products, clarifying differences.
- Assess Impact: Analyze how those differences affect safety and efficacy.
- Submission Comparison: Ensure information for the new product meets approval requirements.
- Final Gap Analysis: Address remaining gaps, using existing information or proposing new studies.
Common Bridge Methods
Once a gap analysis has been completed, additional data is frequently required to justify any differences between the product in development and the comparator product. Common sources of data to establish a scientific bridge include:
- Comparative PK studies. Key parameters include maximum plasma concentration (Cmax) and area under the curve (AUC).[1]
- Pharmacodynamic assessments
- In vitro-in vivo correlation (IVIVC) data
Tuning Bioavailability: Key Factors
Establishing a scientific bridge for nasal products can be particularly challenging. Unlike parenteral injections, and even some oral products, nasal products are sensitive to a wide variety of variables that can influence bioavailability, making it challenging to establish equivalence between two products. While there are many variables that influence the bioavailability of nasally delivered products, some of the key variables that frequently impact bridging potential include:
- API Characteristics: Size/molecular weight, lipophilicity
- Location of Action: Distribution within nasal cavity can impact absorption; desired profile differs between systemic vs. locally-acting drugs
- Dose and Volume: Accepted ranges for powders (10–50mg) and liquids (20–200μL)
- Delivery Device: Spray administration angle, plume geometry, device usability
- Formulation: Excipients, particle size, viscosity
API Characteristics: Bioavailability Examples
Different products illustrate the impact of molecular characteristics on nasal bioavailability. In general, hydrophilic drugs, though safe, may face lower absorption than hydrophobic drugs due to poor membrane permeation. Similarity, smaller molecules tend to have better absorption compared to larger molecules. However, the unfortunate reality is that other variables frequently override the general trends for API characteristics, making it difficult to predict a given product’s potential bioavailability. The example below shows only minor improvement in bioavailability following nasal delivery of Sumatriptan compared to Zanamivir, despite being smaller and more lipophilic.
Formulation Strategies and Nonclinical Considerations
Improving nasal bioavailability often involves excipient and formulation innovation, such as using chitosan microspheres or absorption promoters. However, given the limited number of approved nasal formulations, oftentimes there is a desire to implement a novel excipient into the formulation to improve bioavailability and match a comparator product. Sponsors must assess new excipients’ safety using appropriate nonclinical testing, following genetic, pharmacological, and repeat-dose toxicology guidelines.
Dose Volume
Formulation and/or stability requirements often result in higher total volumes to deliver the target nominal API dose. This can potentially impact the absorption of the drug and/or lead to safety concerns due to irritation or drainage into the throat. Understanding the deposition of the drug product within the nasal cavity is crucial, especially for higher volume nasal products.
Device Impact and Location of Action:
Device design, such as spray pattern and actuation force, also strongly affects drug deposition in the nasal cavity. For example, targeting delivery specifically to the olfactory region may optimize nose-to-brain delivery, while a more broad spray pattern may increase systemic absorption due to increase surface-area contact. Variations in administration technique can create usability and bridging study challenges depending on the target delivery profile of the nasal product.
Bridging Strategy: Building from the Desired Label
When developing a bridging strategy, Sponsors should “start at the end” by defining which label sections will leverage the LD’s data and which require new substantiation. Strategic principles for LD selection may include flexibility and the ability to use non-nasal products as comparators, as shown in the use of injected Narcan as the LD for nasally administered naloxone.
Proactive alignment with the FDA can streamline clinical development by providing clear guidance and reducing variability. Early meetings are invaluable for validating bridging strategies and minimizing regulatory risks, saving time and cost across nonclinical and clinical program stages.
