The Appeal Is Real. So Are the Traps.

Drug repurposing, taking a compound with an established safety profile and investigating it for a new indication, offers a genuinely shorter path to the clinic. You start with human safety data. You may have existing PK characterisation. You understand the compound’s behaviour in ways that a completely new molecule cannot offer until years of development have passed.

The trap is assuming that the CMC and formulation work will be equally straightforward. It usually is not. The existing formulation was optimised for a different clinical context. The dose range may be very different. The patient population may need a different dosage form. And the CMC regulatory landscape for a repurposed compound often has hidden complexity that surprises teams who assumed the scientific familiarity of the molecule would translate into regulatory simplicity.

When the Existing Formulation Does Not Fit

Different Dose, Different Formulation

An antiviral drug approved at 200 mg twice daily does not automatically have a usable formulation for a repurposing programme that requires 5 mg once daily. A 200 mg tablet cannot simply be divided into forty equal fractions. The dose range change may require a completely new formulation strategy, including potentially a different dosage form, modified release characteristics, or a different route of administration.

Different Patient Population

An adult oral solid formulation is not appropriate for a paediatric repurposing programme. A tablet that is the right size for an adult is too large for a five-year-old. A formulation containing excipients that are acceptable for adults may not be safe in neonates. The paediatric formulation development implications of a repurposing programme are frequently underestimated.

Different Route of Administration

Some repurposing programmes involve a route change. An oral drug being investigated for a local indication may be reformulated as a topical or inhaled product. Each route change is a new formulation development programme, not a straightforward adaptation of the existing one. Bioavailability, formulation stability, and delivery device requirements are all different.

The CMC Regulatory Picture for Repurposing

CMC Scenario	Regulatory Implication	Key Action Required
Same compound, same formulation, new indication	IND amendment or new IND; CMC package can reference the existing approved product or originator dossier if available	Confirm right of reference to existing CMC data; verify stability data covers new intended use
Same compound, new dosage form	New drug application (NDA) or section 505(b)(2) route in US; full CMC required for new formulation	Full formulation development and registration stability; bridging PK study if different bioavailability
Same compound, new dose	May require new strength application or NDA amendment; CMC impact depends on whether existing manufacturing process accommodates new dose	Assess whether existing tablet specifications can support new strength; potentially new dissolution specification
Repurposed compound from academic source (no existing approved product)	Full CMC package as for a new molecular entity; no existing dossier to reference	Full drug substance and drug product development from the beginning; no CMC shortcut
Compound under orphan designation	Orphan drug designation provides CMC flexibility in some cases; EMA and FDA have specific provisions	Engage early with agency on CMC expectations; may qualify for reduced stability dataset at filing

The Drug Substance Question: Who Controls the API?

For many repurposing programmes, particularly those originating in academic research, the drug substance is either a commercial API purchased through a supplier, or a small quantity of material synthesised for research purposes without GMP controls. Neither is suitable for a clinical trial without significant additional work.

A commercial API must be qualified for pharmaceutical use: its specification must be assessed for fitness for purpose, the supplier must be audited or a certificate of GMP compliance obtained, and analytical methods for the API must be transferred and validated. A non-GMP research batch must be replaced entirely with GMP-manufactured material before human dosing.

Establishing GMP supply of the drug substance is often the longest lead-time activity in a repurposing programme. It should be initiated at the earliest stage of the programme planning.

How Ardena Supports Repurposing Programmes

Ardena’s integrated model is well suited to the specific needs of repurposing programmes. The CMC regulatory team can assess the existing data package and identify the gaps. The formulation team can design a fit-for-purpose development strategy for the new indication and patient population. And the GMP manufacturing sites can produce clinical batches without the sponsor needing to establish new vendor relationships for each activity.

Why Your CDMO’s Inspection Record Is Your Problem Too

When a regulatory agency inspects a contract manufacturing organisation, it is not just inspecting the CDMO. It is inspecting the GMP compliance of every product made at that site, including yours.

A Form 483 observation or a warning letter to your CDMO does not automatically stop your programme, but it can. Regulators may place a clinical hold, request additional manufacturing information, or delay the approval of a marketing authorisation application if there are unresolved GMP concerns at a manufacturing site named in the submission. Understanding how inspections work, and what questions to ask your CDMO before one happens, is basic programme risk management.

How Inspections Are Triggered

Routine Surveillance Inspections

The FDA inspects domestic manufacturing sites roughly every two years and foreign sites less frequently, prioritising those associated with products marketed in the US. EU national competent authorities inspect licensed sites on a risk-based schedule, typically every three to five years. These routine inspections are not triggered by any specific concern and are a normal part of operating a GMP facility.

Application-Based Inspections

When a new drug application, biologics licence application, or marketing authorisation application names a manufacturing site, regulators may conduct a pre-approval inspection (PAI) to verify that the site is capable of manufacturing the product as described in the application. A PAI finding that identifies significant GMP deficiencies can delay approval or require a complete response.

For-Cause Inspections

A for-cause inspection is triggered by a specific concern, such as a product recall, a serious adverse event with a potential manufacturing cause, a whistleblower complaint, or unsatisfactory results from a prior inspection. These inspections are more intensive than routine surveillance and carry higher risk of serious regulatory action.

What Inspectors Look For

Inspection Focus Area	What the Inspector Is Assessing	Common Finding
Data integrity	Are records accurate, complete, and attributable? Can the inspector trace every action to a person and a time?	Electronic records without adequate audit trails; backdated entries; deletions without justification
Change control	Are manufacturing changes properly assessed, approved, and reflected in regulated documents?	Changes implemented without formal change control; regulatory filings not updated
Out-of-specification investigations	Are OOS results properly investigated? Are invalidated results justified?	OOS investigations closed prematurely; root cause attributed to human error without adequate evidence
Contamination control	Are cleaning validation, environmental monitoring, and personnel practices adequate?	Environmental monitoring exceedances not investigated; cleaning validation data gaps
Batch record review	Are batch records complete and do they reflect the actual manufacturing process?	Unexplained corrections; missing critical in-process data; batch records not reflecting deviations
CAPA effectiveness	Are corrective actions actually preventing recurrence?	Repeat deviations for the same root cause; CAPA closed before effectiveness verified

Questions Sponsors Should Ask Their CDMO

You have a right to understand the inspection history of any facility manufacturing your product. The following questions are reasonable and professional to ask before engaging a CDMO and at regular intervals during a manufacturing relationship.

• When was the facility last inspected and by which authority?
• Were there any findings (Form 483 observations or Warning Letters from the FDA; critical or major findings from EU inspectors)?
• How were those findings resolved? Can you share the response?
• Is any ongoing regulatory correspondence active relating to GMP compliance at this site?
• How are inspection preparation activities managed, and can the sponsor attend a mock inspection?

How a Well-Prepared CDMO Handles an Inspection

A GMP-mature CDMO treats inspection readiness as a continuous state, not a sprint that happens when an inspection notice arrives. Documentation is current, deviations are closed or actively progressed, and the quality team can answer questions about any product or process without scrambling for information.

When an inspection begins, the CDMO’s quality leadership manages the interaction professionally, provides accurate and complete information, and does not make commitments on behalf of sponsors without appropriate coordination. Sponsors are notified promptly when their product or process is discussed during an inspection.

Ardena’s Inspection Track Record

Ardena’s manufacturing sites are subject to regular inspection by national competent authorities in Belgium, the Netherlands, and Spain, as well as by the US FDA for sites that supply products to the US market. The quality teams at each site maintain inspection-readiness as a core operational discipline, with regular internal audits and a proactive approach to managing open findings.

Why Standard Module 3 Templates Fall Short for Nanomedicines

The Common Technical Document (CTD) Module 3 template was designed for conventional small molecule and biological drug products. For nanomedicine products, including lipid nanoparticles, polymeric nanoparticles, and metal oxide nanoparticle systems, the template provides a useful framework but cannot accommodate the full complexity of the characterisation data required without substantial adaptation.

The fundamental difference is that for a conventional drug product, the drug substance and the drug product are distinct entities that are characterised and controlled separately. For an LNP encapsulating mRNA, the physical properties of the particle, its size, charge, composition, and payload integrity, are not properties of the drug substance alone or the drug product alone: they emerge from the combination and the manufacturing process that brings them together. Regulators expect the CMC package to reflect this complexity.

The Key Additions to Module 3 for Nanomedicine Products

Module 3 Section	Standard Content	Nanomedicine-Specific Additions
3.2.P.1 Description and Composition	Formulation composition and dosage form description	Nanoparticle system description; lipid or polymer composition; molar ratios; N:P ratio for nucleic acid products
3.2.P.2 Pharmaceutical Development	Formulation rationale; manufacturing process development	CQA identification and justification; design space for particle size and encapsulation; lipid selection rationale; process analytical technology (PAT) tools used
3.2.P.3 Manufacture	Manufacturing process description and controls	Microfluidics or extrusion process parameters; critical process parameters with ranges; in-process controls including real-time particle size monitoring
3.2.P.4 Control of Excipients	Excipient specification and source	Novel lipid excipient characterisation; supplier qualification; impurity profile for ionisable lipids
3.2.P.5 Control of Drug Product	Release specification and methods	Nanoparticle-specific release tests: particle size, PDI, EE%, zeta potential, in vitro release; analytical method description and justification
3.2.P.6 Reference Standards	Reference standard description	Reference nanoparticle batch for comparability; reference payload (mRNA or small molecule)
3.2.P.8 Stability	Stability protocol and data	Nanoparticle-specific stability attributes; physical stability monitoring by XRPD or DLS; storage condition justification for frozen products

Physicochemical Characterisation: Going Beyond the Four CQAs

While particle size, PDI, encapsulation efficiency, and zeta potential are the core release CQAs for most nanomedicine products, regulators expect a more comprehensive characterisation package in the pharmaceutical development section that demonstrates a thorough understanding of the product’s critical quality attributes and their relationship to clinical performance.

Morphology

Transmission electron microscopy (TEM) or cryo-TEM provides direct visual confirmation of nanoparticle morphology, including particle shape, internal structure (for core-shell systems), and the absence of gross aggregation. Cryo-TEM is particularly valuable for LNPs because it images the particles in their native hydrated state, avoiding the artefacts introduced by conventional TEM sample preparation.

Lipid Composition and Purity

The identity and purity of each lipid component must be confirmed in every batch. HPLC-UV or HPLC-ELSD methods are used to quantify the intact lipid species, and LC-MS is used to identify and quantify lipid degradation products, including hydrolysis products and oxidation products, particularly for unsaturated lipids. The FDA’s guidance on drug product impurities applies to lipid degradation products, and the acceptance criteria for these impurities must be justified based on safety data.

mRNA Integrity and Potency (for mRNA Products)

For mRNA LNP products, the integrity of the mRNA payload must be confirmed in the final drug product. Agarose gel electrophoresis or capillary gel electrophoresis is used to assess mRNA integrity, detecting degradation as a shift in the size distribution or the appearance of shorter fragments. An in vitro translation assay using cell-free or cell-based expression systems is used to confirm that the mRNA in the final product retains its biological potency.

Comparability and Manufacturing Changes

For nanomedicine products, manufacturing changes that would be considered minor for a conventional solid dosage form can have significant effects on product quality. A change in the microfluidics chip geometry, the process temperature, or the lipid supplier can shift the particle size distribution, alter the encapsulation efficiency, or change the in vivo behaviour of the product. Regulators expect a rigorous comparability exercise for any manufacturing change that could affect the physicochemical properties of the nanoparticle, and the comparability data must include the full suite of CQAs and, where appropriate, in vitro biological activity data.

How Ardena Builds Nanomedicine CMC Packages

Ardena’s regulatory team works alongside the formulation scientists and analytical chemists at Oss to build Module 3 CMC packages for nanomedicine IND and IMPD filings. The team has experience adapting the CTD format for LNP, polymeric nanoparticle, and metal oxide nanoparticle products, and can advise on the current FDA and EMA expectations for characterisation data and analytical method validation for nanoparticle-specific methods.

A Rapidly Maturing Regulatory Framework

The approval of the first mRNA COVID-19 vaccines in late 2020 was a watershed moment for LNP-based medicines and for the regulatory agencies that oversee them. Within the space of two years, both the FDA and EMA moved from limited experience with LNP products to reviewing and approving the most widely administered pharmaceutical products in history. The data generated during that period, on LNP characterisation, stability, immunogenicity, and manufacturing, has fundamentally shaped the expectations that regulators now bring to new LNP development programmes.

The regulatory frameworks for nanomedicines continue to evolve, and developers entering the field in 2026 face a more defined but also more scrutinised path than those who filed the first LNP programmes a decade ago. This article outlines the current regulatory expectations for LNP-based therapeutics at both the FDA and EMA.

Key Regulatory Guidance Documents for LNP Developers

Document	Agency	Relevance to LNP Programmes
Guidance for Industry: Drug Products, Including Biological Products, that Contain Nanomaterials (2022)	FDA	Defines nanomaterial scope; addresses CMC characterisation expectations including particle size, surface properties, and stability
Reflection Paper on Nanotechnology-Based Medicinal Products for Human Use (EMA/CHMP/79769/2006 and updates)	EMA	Foundational guidance on physicochemical characterisation and non-clinical testing expectations for nanomedicine products
ICH Q8(R2) Pharmaceutical Development	ICH	Quality by Design framework applicable to LNP development; design space and control strategy concepts
ICH Q2(R2) Analytical Validation	ICH	Validation requirements for LNP-specific analytical methods including encapsulation assays and particle characterisation
FDA mRNA Product-Specific Guidance	FDA	Product-specific guidance documents for mRNA vaccines and therapeutics addressing CMC and non-clinical requirements
EMA Guideline on Excipients in the Dossier for Application for Marketing Authorisation	EMA	Relevant to novel lipid excipients used in LNP formulations that are not covered by existing compendial monographs

CMC Expectations for an LNP IND or IMPD Filing

Drug Substance: The Nucleic Acid Payload

For mRNA-based LNP products, the mRNA is the drug substance, and the LNP is the drug product formulation system. The mRNA drug substance section of Module 3 must address the mRNA sequence and structure including the 5-prime cap, UTR design, and codon optimisation strategy, the manufacturing process for in vitro transcription, the impurity profile including residual template DNA, truncated transcripts, and dsRNA, and the analytical methods used to characterise sequence integrity, purity, and potency. FDA’s guidance on mRNA drug substance CMC provides the current framework for these requirements.

Drug Product: The LNP Formulation

The drug product section must describe the LNP composition including the identity and grade of each lipid component, the drug-to-lipid ratio, and the buffer system. Novel ionisable lipids that are not described in the current literature or approved products require a more detailed justification of their physical and safety properties. The manufacturing process description must cover the microfluidics or extrusion process, the critical process parameters and their ranges, and the in-process controls applied at each step.

Characterisation: The Critical Quality Attributes

Regulators expect a comprehensive physicochemical characterisation package covering at minimum particle size and PDI, encapsulation efficiency, zeta potential, lipid composition (identity and purity of each lipid component), mRNA integrity, and potency by in vitro translation assay. The method used to measure each CQA must be described, and where the method is not a compendial or established published method, abbreviated validation data supporting fitness for purpose is expected at the IND or IMPD stage.

Stability: Supporting the Clinical Trial Duration

The stability data submitted with an IND or IMPD must cover the duration of the intended clinical trial, including a margin for shipping and site storage. For LNP products stored at minus 20 or minus 80 degrees Celsius, the stability programme must include data at the intended long-term storage condition and, ideally, at an intermediate temperature to demonstrate the impact of inadvertent excursions. Accelerated stability data at minus 20 degrees Celsius for products stored at minus 80 degrees Celsius is increasingly expected by regulators as an indicator of the stability margin.

The Novel Excipient Question

Many of the ionisable lipids used in current LNP programmes are proprietary compounds not described in pharmacopoeial monographs or in the composition of previously approved products. Regulators classify these as novel excipients and require a more comprehensive safety and characterisation package than would be required for an established excipient. For Phase I filings, the FDA and EMA have accepted abbreviated novel excipient packages that focus on physicochemical characterisation and the non-clinical toxicology data generated in the IND-enabling studies. The full novel excipient justification is required at the NDA or MAA stage.

How Ardena Supports LNP Regulatory Filings

Ardena’s regulatory team works alongside its nanomedicine formulation scientists at Oss to build CMC packages for LNP-based IND and IMPD filings. The team has experience preparing Module 3 sections for both mRNA LNP and small molecule LNP products, and can advise on the current FDA and EMA expectations for characterisation data, novel excipient justification, and stability programme design.

Same Data, Two Submissions

If your clinical programme runs trials in both the European Union and the United States, you will submit essentially the same scientific data to two different regulatory agencies in two different formats with two different sets of expectations. The Investigational Medicinal Product Dossier (IMPD) goes to the relevant national competent authority (or centrally via CTIS) for EU clinical trial authorisation. The Investigational New Drug application (IND) goes to the FDA.

Both use the Common Technical Document (CTD) format as their structural framework. Both require a quality section covering drug substance and drug product. Both need non-clinical safety data and a clinical protocol. But the specific expectations within that structure differ in ways that matter when you are assembling the data package.

Key Differences: IMPD vs. IND

Element	IND (FDA)	IMPD (EMA/National CAs)
Submission format	eCTD or non-eCTD electronic format to FDA	eCTD via CTIS for EU trials under CTR; national formats for legacy CTAs
CMC data expectation at Phase I	Fit-for-purpose; FDA responsive to first-cycle deficiencies; informal resolution common	Variable by national CA; some stricter than others; written clock-stop mechanism for major deficiencies
GMP certification requirement	US GMP (21 CFR 210/211) or equivalent; foreign facility inspection may be required	EU GMP certificate from relevant national CA or EMA required for all manufacturing sites
Impurity qualification thresholds	ICH Q3A/B thresholds; FDA may request additional qualification for specific impurities	Same ICH thresholds; EMA tends to be stricter on genotoxic impurity qualification at Phase I
Stability data required at filing	Data to cover duration of clinical study plus a buffer; real-time data preferred but extrapolation accepted	Similar expectations; some national CAs require more data at Phase I than FDA
Paediatric requirements	Paediatric Study Plan (PSP) under PREA for certain indications	Paediatric Investigation Plan (PIP) required earlier; may need agreed PIP before Phase III start
Expedited pathways	Fast Track, Breakthrough Therapy, RMAT for cell/gene therapies	PRIME for priority medicines; ATMP designation for cell/gene therapies

Building One CMC Package That Serves Both

The most efficient approach to dual submissions is to build a single CMC data package that satisfies both agencies without creating parallel document sets. This is achievable because the CTD format was designed with harmonisation in mind. Module 3 content is structurally identical for an IND and an IMPD. The differences lie in the interpretation and the accompanying documents, not in the underlying data.

A CMC regulatory team with experience in both jurisdictions can write Module 3 sections that meet FDA expectations without creating gaps for EU national CAs, and vice versa. The key is knowing in advance where the expectations diverge, such as GMP certificate requirements or genotoxic impurity qualification, and addressing those areas proactively rather than reactively.

GMP Certificates: The Practical Difference That Trips People Up

This is the most common practical obstacle in dual submissions. The EU requires a GMP certificate from the relevant national competent authority for every manufacturing site listed in the IMPD. If your CDMO is based in the United States and does not hold an EU GMP certificate (issued following an EMA or national CA inspection), your IMPD cannot be accepted until that certificate is obtained or a mutual recognition agreement covers the site.

Ardena’s manufacturing facilities are inspected and certified under EU GMP by national competent authorities in Belgium, the Netherlands, and Spain. The US facility at Somerset, New Jersey operates under FDA cGMP. For programmes requiring dual submissions, the site selection decision should factor in the GMP certificate status of each facility before development work begins.

The CTIS Transition and What It Means for EU Submissions

Since January 2023, new clinical trial applications in the EU must be submitted through the Clinical Trials Information System (CTIS) under the EU Clinical Trials Regulation (CTR) 536/2014. CTIS centralises the submission and assessment process across EU member states, replacing the previous system of separate national submissions. The IMPD is submitted as part of the CTIS dossier, and the technical requirements for the quality section remain consistent with CTD Module 3 structure. EMA’s CTIS guidance provides detailed information on the transition.

How Ardena Supports Dual Submission Programmes

Ardena’s regulatory team has experience preparing CMC packages for both IND and IMPD submissions across its multi-site network. The team works with sponsors to identify divergent requirements early, structure the data generation plan to satisfy both agencies efficiently, and draft Module 3 sections that do not require significant rework between jurisdictions.

The Guideline That Harmonised Global Bioanalysis

Before ICH M10, bioanalytical method validation was governed by separate guidance documents from the FDA and EMA that, while broadly aligned, differed in specific requirements for acceptance criteria, validation parameters, and reporting expectations. A study submitted to both agencies might require two slightly different validation packages, creating additional work and potential for inconsistencies. The ICH M10 guideline on bioanalytical method validation and study sample analysis, finalised in 2022, replaced both sets of guidance with a single harmonised global standard that applies to all major regulatory markets.

ICH M10 covers the validation requirements for chromatographic assays (LC-MS/MS, LC-UV, and related methods) and ligand-binding assays (LBAs including ELISA and ECL platforms) used in regulated bioanalysis for pharmacokinetic, toxicokinetic, and biomarker studies. Its adoption has significant practical implications for bioanalytical CROs and for the sponsors who commission regulated studies.

Key Changes and Clarifications Introduced by ICH M10

Topic	Pre-ICH M10 Position	ICH M10 Position
Incurred sample reanalysis (ISR)	Required by FDA and EMA guidance; acceptance criteria broadly similar	Harmonised: 2/3 of reanalysed samples must agree within 20% (chromatographic) or 30% (LBA) of original result
Parallelism for LBAs	Required by EMA; FDA less prescriptive	Required for all regulated LBAs; failure may indicate matrix effects or non-specific binding
Selectivity testing	Test in minimum 6 individual lots of matrix	Minimum 6 lots confirmed; haemolysed and lipaemic matrix testing explicitly addressed
Carryover	Addressed in FDA guidance; less explicit in EMA	Explicit requirement: must demonstrate carryover does not affect accuracy; defined acceptance criteria
Stability of calibration standards	Covered in guidance; variation in specifics	Detailed stability requirements for stock solutions, working solutions, and matrix-based calibrators and QCs
Regulated biomarker assays	Fit-for-purpose concept; less detailed requirements	Separate section on biomarker assays; partial validation acceptable with documented scientific justification
Reference standard characterisation	Required; specifics varied	Explicit requirements for characterisation certificate; purity correction of nominal concentrations

Parallelism: The LBA Requirement That Catches Teams Out

Parallelism is one of the ICH M10 requirements that most frequently requires additional work for teams transitioning from the previous FDA and EMA guidance. Parallelism testing demonstrates that the dose-response curve generated by serially diluting a study sample is parallel to the calibration curve generated from spiked matrix. Non-parallelism indicates that the analyte in study samples is behaving differently from the reference standard used to construct the calibration curve, which may be due to endogenous matrix components interfering with the assay, a different molecular form of the analyte in study samples, or binding of the analyte to carrier proteins.

Parallelism must be demonstrated during method validation using samples from the target population, not just from healthy volunteers, unless the sponsor can provide a scientific justification for why the two populations would not differ. For oncology programmes where the patient population may have elevated levels of endogenous proteins or circulating drug-related metabolites, this requirement can be practically challenging to meet before the first clinical study provides patient samples.

Reference Standard Characterisation and Purity Correction

ICH M10 introduces an explicit requirement to characterise the reference standard used in a validated bioanalytical method and to apply purity correction to the nominal concentrations of calibration standards and quality control samples. This means that if a reference standard is certified at 95% purity, the nominal concentration of a 1 nanogram per millilitre standard should be reported and calculated as 0.95 nanograms per millilitre. This sounds straightforward but has practical implications for the labelling of calibration standards in the laboratory information management system (LIMS) and for the retrospective recalculation of data from studies conducted before purity correction was applied.

Fit-for-Purpose Biomarker Assays Under ICH M10

ICH M10 formally recognises the fit-for-purpose (FFP) validation framework for biomarker assays, providing a tiered structure where the scope of validation experiments is calibrated to the intended use of the data. A biomarker assay used for exploratory characterisation in a Phase I study requires a less comprehensive validation package than the same assay used as a primary efficacy endpoint in a pivotal Phase III trial.

The ICH M10 framework requires that the validation scope for each biomarker assay is justified by the sponsor, with reference to the intended use, the decision-making consequences of the data, and the regulatory context. This justification must be documented and available for regulatory review. The table in the ICH M10 guideline that maps validation parameters to assay categories provides a practical reference for determining which experiments are required for each application.

Ardena’s ICH M10 Compliant Bioanalysis Services

Ardena’s bioanalytical laboratory in Assen operates under ICH M10-compliant method validation procedures for both chromatographic and ligand-binding assays. The standard operating procedures, validation templates, and reporting formats at the Assen facility have been updated to align with the harmonised requirements, and the scientific team is experienced in applying the parallelism, ISR, and reference standard characterisation requirements to both small molecule PK and large molecule LBA programmes.

A Growing Category in Drug Development

Controlled substances have moved from the margins of pharmaceutical development to its centre. Psychedelic-assisted therapy programmes involving psilocybin, MDMA, and ketamine derivatives are advancing through Phase II and Phase III trials. Cannabis-derived medicines, opioid alternatives, and GABA-modulating compounds for neurological conditions all involve scheduled molecules. The renaissance of interest in controlled substances as therapeutic agents has created a category of drug development that requires specialist regulatory, manufacturing, and logistics expertise.

Working with controlled substances in a clinical development programme is not fundamentally different from working with any other class of active pharmaceutical ingredient, but it involves an additional layer of regulatory authorisations and compliance requirements at every stage that can significantly extend timelines if not planned for early.

The Regulatory Framework for Controlled Substances in Drug Development

The international framework for controlled substances is set by the United Nations 1961 Single Convention on Narcotic Drugs and the 1971 Convention on Psychotropic Substances, which classify controlled substances into schedules based on their therapeutic value and abuse potential, and require signatory states to implement national control measures. At the national level, different jurisdictions apply their own scheduling systems and regulatory requirements.

Jurisdiction	Regulatory Authority	Key Requirement for Clinical Use	Scheduling Framework
United States	DEA (Drug Enforcement Administration) + FDA	Schedule I substances require DEA researcher licence; Schedule II-V require DEA registration. FDA IND required for clinical use.	Schedules I-V based on accepted medical use and abuse potential
European Union	National Competent Authorities (e.g. ANSM in France, BfArM in Germany)	Narcotic drug import/export licences required per shipment; CTA required for clinical use	National scheduling aligned broadly with UN conventions; varies by member state
Spain (Pamplona)	Agencia Espanola de Medicamentos y Productos Sanitarios (AEMPS)	Authorisation for manufacture and clinical use; detailed record-keeping requirements	Psicotropos and narcoticos scheduling under national legislation
United Kingdom	Home Office + MHRA	Home Office controlled drug licence required for Schedule 1 substances; Schedule 2-5 under standard conditions	Misuse of Drugs Regulations 2001 schedules

Manufacturing Controlled Substances Under GMP

The manufacturing of controlled substances under GMP requires not only the standard quality systems applicable to any pharmaceutical product but also specific physical security measures, inventory control procedures, and record-keeping requirements mandated by the relevant national authority. Storage areas for Schedule I and II substances must typically be secured in dedicated locked enclosures with access restricted to authorised personnel, and all movements of controlled substance material must be recorded in a balance ledger that is subject to regulatory inspection.

Yield accounting is a critical element of controlled substance manufacturing under GMP. The mass balance for the drug substance and drug product must be demonstrable at each step of the process, and any discrepancies between theoretical and actual yield must be investigated and documented. This requirement adds a layer of process monitoring to controlled substance manufacturing that is less stringent for conventional pharmaceutical products.

Cross-Border Shipment of Controlled Substances

Moving controlled substances between countries for clinical trial purposes, whether from the manufacturer to a clinical supply depot or from a depot to an investigator site, requires import and export licences for each individual shipment in most jurisdictions. These licences are issued by national competent authorities and typically require information about the substance, the quantity, the consignee, and the purpose of the shipment.

The lead times for obtaining import and export licences vary significantly between countries and can range from a few days to several weeks or more. For multi-country clinical trials, coordinating the licence applications across all importing jurisdictions in advance of the planned shipment schedule is a specialist logistics task that must be factored into the programme timeline from the outset.

Planning for Controlled Substance Programmes

Secure Your Manufacturing Licences Early

The licence to manufacture a controlled substance for clinical use must be in place before any GMP manufacturing campaign begins, and obtaining it requires an application to the relevant national authority well in advance. For new substances, or for CDMOs adding a new controlled substance category to their existing licences, the application and inspection process can take several months. Starting this process at the beginning of the development programme, not at the time of the first GMP batch, is essential.

Design Your Stability Programme for Controlled Substance Compliance

Stability samples containing controlled substances must be stored under the same security conditions as the primary drug substance and drug product, and their movements must be subject to the same inventory controls. This affects the design of the stability storage programme and must be factored into the stability facility requirements.

Ardena’s Controlled Substance Capabilities at Pamplona

Ardena’s Pamplona facility in Spain holds authorisations for the manufacture and handling of controlled substances under Spanish and European regulatory requirements. The facility has the physical security infrastructure, inventory management systems, and procedural controls required for GMP manufacturing of scheduled compounds.

Ardena’s regulatory team at Pamplona has experience managing the licence applications and compliance requirements for controlled substance clinical programmes, including coordination with AEMPS and, where required, with the competent authorities of importing countries. For programmes targeting both European and US clinical sites, Ardena can advise on the coordination of European and DEA requirements.

Formulation Change Is Inevitable

It is the rare pharmaceutical development programme that reaches Phase III with exactly the same formulation that entered Phase I. Scale-up changes, stability-driven modifications, bioavailability improvements, and the practical realities of manufacturing optimisation all result in formulation differences between the early clinical and the intended commercial product.

This is not a problem in itself. Regulators understand that development involves iteration. What they need to be confident of is that the clinical data generated with earlier formulations is still relevant to the product being developed, and that any changes have been characterised, controlled, and disclosed appropriately. Bridging studies are the mechanism for providing that confidence.

When a Bridging Study Is Required

The requirement for a bridging study depends on the nature and magnitude of the formulation change, and the stage of development at which it occurs. FDA’s guidance on INDs and EMA’s guidance on clinical trial authorisations both address formulation changes, though the specific triggers and requirements differ between jurisdictions.

Change Type	Likely Bridging Requirement	Bridging Approach
Minor composition change (same formulation concept, adjusted ratio)	Comparative dissolution in multiple pH media	In vitro dissolution comparison; statistical evaluation
Bioavailability-enhancing technology change (e.g. crystalline to ASD)	In vivo pharmacokinetic bridging study	Crossover PK study in healthy volunteers or patients
Dosage form change (e.g. capsule to tablet)	Comparative dissolution; potentially in vivo PK	In vitro first; in vivo if dissolution differences identified
Manufacturing site or scale change	Comparative analytical data; potentially dissolution	Batch analysis comparison; process validation data
Excipient change (novel excipient or significant level change)	Regulatory assessment; potentially safety bridging	Toxicology assessment of new excipient if required

In Vitro Dissolution as a Bridging Tool

For many formulation changes where the mechanism of absorption is not fundamentally altered, comparative dissolution testing in multiple pH media is the first-line bridging tool. Dissolution testing at pH 1.2, 4.5, and 6.8 captures the range of conditions encountered in the gastrointestinal tract and provides evidence that the modified formulation will deliver the drug at a comparable rate and extent.

The statistical approach to comparing dissolution profiles, using the f2 similarity factor or more sophisticated modelling approaches, is addressed in FDA’s dissolution guidance for industry and the EMA’s guideline on dissolution. An f2 value of 50 or greater indicates similarity for most formulation types, though this criterion does not apply to highly variable drugs or drugs with narrow therapeutic windows.

In Vivo PK Bridging Studies

When an in vitro approach is not sufficient to bridge a formulation change, an in vivo pharmacokinetic study in human subjects is required. The design of a PK bridging study depends on the objectives: for a change that may affect rate of absorption but not extent, a crossover study in healthy volunteers measuring Cmax and AUC is typically the most efficient approach. For changes where the effect on bioavailability is expected to be small, a two-period crossover with a 90% confidence interval approach is standard.

Planning PK bridging studies as part of the CMC development strategy, rather than as a reactive response to a regulatory question, avoids the scenario of needing to design and execute a clinical study under time pressure at a critical programme milestone.

Practical Considerations for Formulation Change Management

Document the Scientific Rationale

Every formulation change should be accompanied by a written scientific rationale that explains why the change was made, what data supported the decision, and how the bridging approach was selected. This documentation is both good practice and a regulatory requirement for programmes operating under an active IND or CTA.

Engage Regulators Early

For changes that are likely to require in vivo bridging, early engagement with the relevant regulatory agency, through a Type B meeting request to the FDA or a scientific advice procedure at the EMA, can clarify the bridging expectations before the study is designed. This avoids the risk of executing a study that does not satisfy the agency’s requirements.

Consider the Phase of Development

A formulation change at Phase I is far easier to manage than the same change at Phase III. The earlier a formulation is locked, or a deliberate development path to the intended commercial formulation is established, the less bridging work will ultimately be required.

How Ardena Supports Formulation Change Management

Ardena’s integrated CMC teams manage formulation change programmes across its development and analytical sites. The analytical teams in Ghent and Assen develop and execute comparative dissolution studies and provide the bioanalytical support for in vivo PK bridging studies. The regulatory team advises on jurisdiction-specific requirements and can prepare the CMC change documentation needed for IND amendments or CTA updates.

The Commercial Life of a Drug Molecule

A new drug’s commercial life is bounded by its patent estate. The composition of matter patent, which covers the chemical structure of the active ingredient, is typically the most valuable piece of IP and is usually filed at or near the time of initial synthesis. By the time a drug reaches the market, after a development programme that commonly takes ten to fifteen years, much of the composition of matter patent life has already been consumed.

This is where solid form IP becomes commercially significant. A patent covering a novel crystal polymorph, a pharmaceutically beneficial salt form, or a co-crystal with advantages over existing forms can be filed and prosecuted independently of the composition of matter patent, and can provide exclusivity that extends well beyond it.

What Can Be Patented in Solid Form Work

Novel Polymorphs

A new crystalline form of a known API may be patentable if it is novel, non-obvious, and has utility. Patentability is typically supported by demonstrating that the polymorph has advantages over previously known forms, such as improved chemical stability, more favourable hygroscopicity, better manufacturability, or improved dissolution performance. An XRPD characterisation establishing the uniqueness of the form is a standard element of a polymorph patent application.

Salt Forms

A novel pharmaceutical salt is patentable if it is not described in the prior art and has demonstrated physicochemical advantages. The patent should describe the process for preparing the salt, its analytical characterisation, and the evidence for its advantages. Salt patents have a long history in pharmaceutical IP, and the prior art landscape for common APIs is often dense, making thorough prior art searching an important early step.

Co-Crystals

The patentability of pharmaceutical co-crystals has been established through a series of patent office decisions and court cases in major jurisdictions over the past fifteen years. A novel co-crystal with demonstrable advantages, supported by characterisation data and evidence of the co-crystal nature of the material, is a patentable entity in most jurisdictions. The regulatory status of the coformer, whether it is a GRAS substance or an approved excipient, is relevant to patentability arguments in some cases.

IP Strategy Considerations by Solid Form Type

Form Type	IP Opportunity	Key Evidence Required	Timing Consideration
Polymorph	New crystal form with demonstrated stability or performance advantage	XRPD characterisation; stability comparison to other known forms	File before public disclosure; prior art search essential
Pharmaceutical salt	Novel counterion combination with physicochemical advantages	Characterisation of salt; solubility/stability comparison to free form	Screen broadly; file on most promising forms
Co-crystal	Non-ionic multicomponent crystal with measurable advantage	Crystal structure confirmation; coformer identification; comparative data	Growing patent landscape; freedom to operate analysis important
Amorphous dispersion	Novel polymer-drug combination or process for preparation	Characterisation of dispersion; stability and dissolution data	Process patents may offer longer-term protection than form patents

The Risk of Not Screening Thoroughly

The IP risk of incomplete solid state screening runs in both directions. If your development team works with the first crystal form synthesised and a competitor later patents a more stable polymorph, you may face freedom-to-operate issues when you move to commercial manufacturing. Conversely, if you do not identify and protect novel forms early, you risk a competitor doing so and establishing a blocking position on what you might eventually want to use as your commercial form.

Thorough solid state screening, conducted systematically with a combined scientific and IP lens, is the most effective way to both secure your own IP position and establish freedom to operate in your intended commercial form.

How Ardena Supports Solid Form IP Strategy

Ardena’s solid state research team in Ghent conducts polymorph, salt, and co-crystal screening programmes designed to generate data of the quality and scope needed to support patent applications. The team is experienced in structuring screening work to systematically explore the solid form landscape and in generating the characterisation data, including XRPD, DSC, TGA, and comparative physicochemical data, that patent attorneys need to prosecute a strong application.

Ardena works with clients and their patent counsel to ensure that the timing of screening work, the documentation of findings, and the structure of the characterisation data package all support the IP strategy alongside the development programme.

Related: Solid State Screening: Finding the Optimal Crystal Form | Co-Crystals vs. Salts: Which Is Right for Your API?

Build Your Solid Form IP Strategy with Ardena

If you want to understand the IP landscape for your molecule’s solid forms, or design a screening programme that generates patentable data, our team in Ghent is ready to discuss your programme.

CMC Strategy Is Not a Static Document

There is a common misconception in early drug development that CMC strategy means writing a dossier. It does not. CMC strategy means making deliberate decisions, at every stage of development, about which data to generate, which manufacturing processes to lock, and how to position the product for the regulatory interactions that lie ahead.

The CMC strategy appropriate for an IND or Phase I IMPD filing is structurally different from the strategy needed to support a Phase II submission, and different again from what an NDA or MAA will require. A development team that treats its CMC work as a series of discrete filing exercises, rather than as a continuously evolving strategy, typically creates avoidable work and avoidable risk at each transition.

CMC Requirements at Each Development Stage

Development Stage	Regulatory Filing	CMC Data Expectations	Key Decisions
Preclinical / IND-enabling	IND (US) / IMPD (EU)	Fit-for-purpose; sufficient to support safety of first dose. Process need not be final.	Solid form selection; initial specification setting; stability to cover trial duration
Phase I	IND amendment / IMPD update	Characterisation of development batches; preliminary stability. Process may still evolve.	Scale-up direction; control strategy development; method development roadmap
Phase II	IND amendment / clinical trial authorisation update	More complete characterisation; comparative dissolution if formulation changed; updated stability	Formulation and process lock or defined change control; bridging data if formulation changed
Phase III / NDA/MAA	NDA / MAA Module 3	Full ICH Q6A specification; validated methods; 12 months real-time stability; process validation	Specification finalisation; scale-up and validation; regulatory starting material justification

The Formulation Lock Decision

One of the most consequential CMC decisions in early development is when to lock the formulation. A formulation change between Phase I and Phase II is manageable with appropriate bridging data. A formulation change between Phase II and Phase III is significantly more costly and time-consuming, requiring bioequivalence or pharmacokinetic bridging data to justify the change to regulators.

The FDA’s guidance on comparability protocols and the EMA’s guidance on changes to approved products provide frameworks for managing post-approval changes, but the optimal strategy is to make the major formulation decisions as early as the data allows, so that the Phase II formulation is as close as possible to the one that will go into Phase III and registration.

Regulatory Starting Materials and Their Long-Term Impact

The designation of regulatory starting materials (RSMs) for the drug substance synthesis has long-term implications for the regulatory dossier and for commercial supply chain flexibility. Designating a starting material too early in the synthetic route creates a large regulatory footprint that is difficult to modify later. Designating it too late, at a complex intermediate, may not be accepted by regulators. Getting the RSM designation right at the IND stage, with a view to how the synthetic route will evolve through development and into commercial manufacture, is a decision that benefits from early input from an experienced CMC regulatory team.

Managing Formulation Changes with Bridging Data

It is unusual for the Phase I formulation to be identical to the commercial formulation. Scale-up changes, manufacturing process improvements, and changes driven by stability or bioavailability data all occur during development. Each change creates a potential regulatory question about whether the clinical data generated with the earlier formulation is still representative of the product being developed.

Bridging studies, whether dissolution comparisons, pharmacokinetic crossover studies, or formal bioequivalence studies, provide the evidence base for justifying formulation changes to health authorities. Planning for these studies as part of the CMC strategy, rather than retrospectively, avoids last-minute surprises at the Phase II or III transition.

How Ardena Builds CMC Strategy into Development Programmes

Ardena’s CMC regulatory advisors work alongside the formulation and analytical teams throughout development programmes, not just at filing milestones. This means that the CMC strategy is reviewed and updated as the science evolves, and that decisions with long-term regulatory implications, such as solid form selection, RSM designation, and specification setting, are made with full visibility of their downstream consequences.

For programmes approaching the Phase I to Phase II transition, Ardena can conduct a CMC gap analysis against the requirements for the next regulatory filing and identify the studies needed to close those gaps efficiently.