How Drug Delivery Choices Shape Regulatory Review Risk

Key Takeaways

Drug delivery decisions now influence regulatory review outcomes, not just patient experience, as usability, packaging, and performance deficiencies appear repeatedly in complete response letters.
Increased FDA transparency has exposed delivery-related failure modes that were previously obscured, making them visible to regulators, sponsors, and investors alike.
Human factors, extractables and leachables, and dose-delivery performance are no longer secondary considerations but explicit review risks that can delay or block approval.
Delivery complexity is increasingly interpreted as execution risk unless it is proactively characterized and justified through credible development planning.
Early engagement with CDMOs enables anticipatory identification and mitigation of delivery-linked risks, strengthening both regulatory positioning and capital confidence.

Drug Delivery Is No Longer a Neutral Design Choice

Drug delivery decisions have long been presented as downstream optimizations: important for patient convenience and adherence but secondary to the core scientific questions of safety and efficacy. That view no longer holds. In today’s regulatory and capital environment, delivery choices increasingly shape how development programs are scrutinized, influencing not only how a therapy is used but how it is judged during review.

This shift is partly a function of visibility. As regulatory transparency has increased, the reasons therapies fail to secure approval have become clearer and more accessible. Delivery-related deficiencies, once buried in confidential correspondence, now appear openly in regulatory records, revealing how issues tied to usability, packaging, and performance can delay or derail otherwise promising programs. What was once treated as a solvable technical detail has emerged as a visible contributor to non-approval.

At the same time, delivery systems themselves have grown more complex. Combination products, novel devices, and highly engineered formulations introduce additional interfaces between product, patient, and process. In that context, complexity is no longer interpreted as neutral. Absent a clear rationale and credible controls, it is increasingly read as execution risk.

These forces have reframed the role of drug delivery in development strategy. Delivery choices now influence how regulators and investors assess whether a program is buildable, not just biologically sound. In an environment defined by heightened scrutiny and constrained capital, delivery is no longer an afterthought but an early signal of how well a sponsor understands the path from molecule to market.

Regulatory Transparency Changed the Stakes

The regulatory context in which drug delivery decisions are evaluated has shifted materially over the past several years. As part of a broader transparency initiative, the U.S. Food and Drug Administration (FDA) now publishes complete response letters (CRLs), making public the agency’s detailed reasoning when applications fail to meet approval standards.¹ These documents provide direct insight into the specific deficiencies identified during review, including issues related to manufacturing, controls, and delivery systems.

Importantly, these letters are no longer isolated disclosures. CRLs are now accessible through a centralized openFDA data set that aggregates regulatory actions and allows systematic examination of failure modes across applications and time periods.² This shift has transformed CRLs from a legacy of anecdotes into a searchable body of evidence, enabling sponsors, investors, and advisors to identify recurring patterns rather than relying on informal accounts or selective disclosures.

This increased visibility has real consequences for drug delivery. Deficiencies related to usability, packaging, extractables and leachables, and dose-delivery performance — areas that historically received limited public attention — are now explicitly documented and easily discoverable within the regulatory record.¹ As a result, delivery-related risks that were once obscured or minimized have become pattern-recognizable components of regulatory outcomes.

In this environment, narrative explanations are no longer sufficient. Sponsors and investors cannot rely solely on high-level statements about regulatory setbacks when the underlying documentation is accessible and detailed. The regulatory record itself now serves as a primary source of truth, revealing how delivery choices contribute to approval risk alongside clinical and safety considerations.²

The heightened scrutiny of drug delivery is not driven by isolated anecdotes but by patterns that emerge when recent regulatory outcomes are examined systematically. Independent analyses of CRLs issued between 2020 and 2024 consistently report that quality and manufacturing deficiencies appear in a substantial majority of cases, on the order of roughly three-quarters of all letters reviewed.^3,4 While these analyses group multiple technical issues under the chemistry, manufacturing, and controls (CMC) umbrella, they underscore how frequently manufacturing-related concerns shape regulatory decisions.

Within that broad category, deficiencies often extend beyond core process controls to encompass formulation robustness and delivery system performance. Reviews of the CRL corpus describe cases in which questions about how a product is delivered (e.g., its reliability, consistency, and interface with the patient) are intertwined with broader manufacturing concerns rather than treated as peripheral issues.³ This overlap reinforces the idea that delivery performance is increasingly evaluated as part of overall execution risk.

More granular quantitative reviews further clarify how delivery-specific issues surface within CMC. Analyses that code individual CRLs by deficiency type identify meaningful subsets that include device-related deficiencies, human factors or usability validation failures, and inadequate extractables and leachables (E&L) assessment.⁵ These categories recur across the data set, indicating that delivery-linked concerns are not rare cases but recognizable review themes that appear with regularity.

These findings help explain why delivery risk now attracts early attention. Even when delivery is not the sole reason for non-approval, it often contributes to regulatory uncertainty that compounds other issues. In a review environment shaped by cumulative risk assessment, delivery-related deficiencies can amplify concerns about a program’s overall readiness, making them difficult to dismiss as secondary or easily remediated late in development.

Human Factors and Usability: When the Device Becomes the Liability

Expectations around usability in drug–device combination products are no longer implicit or discretionary. FDA guidance explicitly rquires human factors engineering (HFE) for combination products, with sponsors expected to demonstrate that products can be used safely and effectively by the intended users under anticipated conditions of use.^6,7 Within this framework, usability validation is not treated as a design preference or a late-stage refinement but as a core element of safety and effectiveness that must be substantiated with evidence.

This posture has direct implications for regulatory review outcomes. Quantitative analyses of CRLs issued between 2020 and 2024 show that human factors validation failures appear in a non-trivial fraction of recent letters, often grouped within broader device-related deficiencies.⁵ These failures commonly relate to user interface complexity, use-related risk that was not adequately mitigated, or validation studies that did not sufficiently represent real-world use scenarios. In such cases, the device itself becomes a source of regulatory concern, even when the underlying drug substance or formulation is otherwise acceptable.

The recurrence of these issues in the CRL record has shifted how usability risk is perceived. Rather than being viewed as unforeseeable late surprises, shortcomings in HFE are increasingly treated as predictable failure modes when delivery systems are complex or insufficiently characterized. As regulatory transparency has made these patterns visible, usability has moved from the margins of development planning to the center of how combination products are evaluated during review.

Extractables, Leachables, and Packaging: The Quiet Review Risk

Packaging and materials choices have traditionally been treated as supporting technical details: important for stability and shelf life but rarely central to regulatory decision-making. That assumption is increasingly outdated. FDA guidance on container-closure systems and the agency’s draft Q3E E&L guidance underscore that materials of construction can pose direct risks to patient safety and product quality and therefore warrant systematic, risk-based evaluation.^8,9 These expectations apply across both small molecule drugs and biologics, reflecting a unified regulatory view that E&L risk is route-, dose-, and duration-dependent rather than modality-specific.

The regulatory consequences of this formalization are visible in the CRL record. Quantitative reviews identify inadequate E&L assessment as a recurring, explicitly named deficiency category, appearing with meaningful frequency alongside other CMC concerns.⁵ In these cases, questions about the suitability of packaging materials, data gaps in E&L characterization, or insufficient toxicological justification have contributed to regulatory delays.

Notably, some CRLs indicate that deficiencies tied primarily to container-closure systems and materials — independent of clinical or formulation shortcomings — were sufficient to prevent approval until remedied.⁵ This highlights how packaging decisions can become gating issues when E&L risks are not anticipated and addressed early in development.

Materials and container-closure choices now carry regulatory consequences that extend well beyond stability testing, influencing whether a product is viewed as safe, controllable, and approvable. In an environment shaped by regulatory transparency, E&L risk has become a quiet but consequential determinant of review outcomes rather than a secondary technical consideration.

Dose Accuracy and Delivery Performance: Precision as a Review Criterion

Regulatory scrutiny of drug delivery increasingly extends beyond whether a dose can be administered to whether it can be delivered accurately, reproducibly, and under appropriate controls. FDA review actions have explicitly cited deficiencies in dose-delivery performance data, signaling that performance characterization itself can be a gating factor in approval decisions.¹⁰ In these cases, concerns are not limited to extreme failures but include variability in delivered dose, insufficient in vitro performance characterization, or weak linkages between performance testing and proposed specifications.

The regulatory record shows that delivery performance issues are often framed as CMC deficiencies rather than device anomalies. When performance data do not adequately demonstrate consistency across lots, conditions, or use scenarios, regulators may conclude that the product’s quality cannot be assured at scale, triggering non-approval until additional data or controls are provided.¹⁰ This reinforces the idea that dose accuracy is treated as a quality attribute with direct implications for safety and effectiveness.

These expectations have great impact for modern delivery systems. As devices become more complex (e.g., incorporating higher viscosities, novel actuation mechanisms, or integrated electronics) the tolerance for poorly characterized performance narrows. Regulators increasingly expect clear alignment between formulation properties, device mechanics, and performance data, supported by test methods that are sensitive to the ways delivery systems may fail or drift over time.³

In this context, delivery performance is no longer assumed based on design intent or precedent. It must be demonstrated with the same rigor applied to other CMC elements, including defined acceptance criteria, validated methods, and a clear understanding of how performance will be maintained through scale-up and commercial manufacture. Where that evidence is incomplete or misaligned, delivery systems themselves can become a source of regulatory risk rather than an enabling feature of the product.

Anticipatory Design vs. Reactive Remediation

A recurring theme across delivery-related CRLs is not novelty but timing. Many of the deficiencies cited — whether related to usability validation, extractables and leachables, or dose-delivery performance — reflect issues that, in retrospect, could have been identified earlier through more integrated delivery and CMC planning.⁵ Their appearance late in review suggests less a failure of innovation than a failure to surface delivery-linked risks at a stage when they were still manageable.

Once a CRL has been issued, remediation becomes inherently reactive. Addressing delivery deficiencies after non-approval often requires redesign, additional studies, or expanded testing programs that are costly and time-consuming and that may disrupt development timelines in ways that are difficult to conceal from investors or partners.³ In a capital-constrained environment, these delays are not viewed in isolation; they compound broader concerns about execution discipline and development predictability.

By contrast, anticipatory design approaches delivery as a source of foreseeable risk rather than a downstream detail. This mindset emphasizes early identification of usability, materials, and performance vulnerabilities before they harden into regulatory objections that must be unwound under pressure. The goal is not to eliminate delivery risk entirely, but to confront it at a point where design choices, test strategies, and controls can still be adjusted with minimal disruption.

Seen through this lens, the strategic inflection point is not whether delivery risk exists (it almost always does!) but when it is confronted. Programs that surface and address delivery-linked uncertainties early signal a more credible path through review than those that defer these questions until regulators force the issue.

Where CDMOs Change the Equation

As delivery systems grow more complex, the technical work required to make them regulatory-credible increasingly spans multiple domains at once. Contract development and manufacturing organizations (CDMOs) sit at the intersection of formulation, filling, packaging, and device integration, giving them a systems-level view of how delivery choices translate into manufacturability and review risk. That vantage point allows CDMOs to surface delivery-linked vulnerabilities early, before they appear as fragmented deficiencies late in regulatory review.

This integrative role is particularly relevant given how delivery issues emerge in the regulatory record. Usability validation failures, E&L gaps, and dose-delivery performance concerns often reflect misalignment across disciplines rather than isolated technical errors.5 Since CDMOs routinely work across these interfaces, they are positioned to identify where assumptions about devices, materials, or performance may not hold under scale, real-world use, or regulatory scrutiny.

Early CDMO engagement can therefore support design choices with a higher degree of regulatory credibility. By aligning delivery systems with human factors expectations, E&L risk frameworks, and performance characterization strategies from the outset, sponsors can reduce the likelihood that delivery becomes a late-stage liability requiring reactive remediation.^6,9 This alignment does not require perfection at early stages, but it does require coherent planning that acknowledges how delivery risks will be evaluated over time.

In this way, CDMOs increasingly function as more than execution partners. They act as risk translators and early validators, providing tangible evidence that delivery risk has been recognized, interrogated, and managed rather than deferred. In a review environment shaped by transparency and cumulative risk assessment, that evidence can meaningfully influence how a program is perceived long before final approval decisions are made.

What This Means for Sponsors

For sponsors navigating development and capital formation in parallel, the implications of this shift are increasingly concrete. Delivery uncertainty is no longer treated as a neutral placeholder to be resolved later; it is more often interpreted as a signal of execution risk. As regulatory records make delivery-related deficiencies visible and pattern-recognizable, gaps in delivery strategy can amplify concerns about overall readiness, even when clinical data are compelling.^3,5

This reframing also clarifies the purpose of early delivery planning. The objective is not premature optimization or over-engineering at early stages but credibility. Sponsors that articulate a coherent delivery strategy that acknowledges usability, materials, and performance risks and outlines how those risks will be addressed over time signal foresight and discipline rather than unnecessary complexity.^6,9 In a regulatory environment shaped by cumulative risk assessment, that clarity can matter as much as the underlying technical choices themselves.

As a result, engagement with CDMOs is increasingly intertwined with both regulatory and capital strategy. CDMO relationships now serve not only to execute development plans but to demonstrate that delivery risks have been identified and integrated into those plans in a way that aligns with regulatory expectations. For sponsors, this means that delivery decisions (and the partners involved in executing them) are becoming part of how programs are evaluated well before late-stage review, shaping perceptions of risk, credibility, and ultimately value.

Conclusion: Delivery Choices Shape Review Outcomes

The regulatory record now makes clear that drug delivery choices play a material role in review outcomes. Increased transparency has revealed delivery-related deficiencies that were formerly once difficult to observe from the outside as recurring contributors to non-approval, documented openly in complete response letters and accessible for systematic analysis. What was previously treated as a downstream technical matter has become a visible element of regulatory risk.

Within that record, specific delivery-linked issues recur with enough frequency to shape expectations. Human factors and usability shortcomings, gaps in E&L assessment, and weaknesses in dose-delivery performance characterization now function as recognizable review risks rather than idiosyncratic exceptions. Their presence in non-approval decisions reinforces the idea that delivery performance, materials, and interfaces are integral to how quality, safety, and effectiveness are judged.

In this environment, the strategic distinction is no longer whether delivery risk exists, but how and when it is addressed. Innovators and CDMOs that confront delivery-linked risks anticipatorily — integrating usability, packaging, and performance considerations into development planning — are better positioned to navigate regulatory review without disruptive remediation and to withstand the parallel scrutiny of capital markets. Delivery choices, once peripheral, have become part of the evidentiary basis on which programs are evaluated, making early, credible engagement with these risks a defining feature of execution discipline in modern drug development.