ADC and XDC Drug Development: What CDMOs Need to Deliver

The Complexity Behind the Acronym

Antibody-drug conjugates (ADCs) are a class of targeted oncology therapeutics that combine the selectivity of a monoclonal antibody with the potency of a cytotoxic small molecule payload. The concept is elegant: deliver a chemotherapy agent directly to the tumour cell, spare normal tissue, and improve the therapeutic index over conventional chemotherapy. The execution is considerably more demanding.

The next generation of conjugated therapeutics, often grouped under the XDC umbrella, extends the conjugation concept beyond antibodies to include peptides, nanobodies, small molecules, and even oligonucleotides as targeting vehicles. Each variation introduces new chemistry, new stability considerations, and new analytical challenges. For a CDMO to credibly support an ADC or XDC programme, it needs capabilities that span formulation science, high-potency manufacturing, linker and conjugation chemistry, and a bioanalytical function capable of characterising every component of the molecule.

The End-to-End Requirements of an ADC Development Programme

Development Stage	Key Activity	Technical Requirement	Ardena Capability
Drug substance development	API synthesis and characterisation of cytotoxic payload	HPAPI synthesis or handling at OEB 4-5; analytical characterisation of warhead	Pamplona: HPAPI containment; analytical characterisation
Linker-payload synthesis	Assembly of linker-payload intermediate or final conjugate	Controlled synthesis of reactive intermediates; high-sensitivity analytical monitoring	Specialist chemistry capability; MS-based characterisation
Formulation development	Stabilisation of the ADC in solution or lyophilised form	Buffer optimisation; excipient compatibility; physical stability of the antibody-drug conjugate	Ghent: injectable and lyophilisation formulation expertise
Analytical characterisation	DAR determination, aggregation, charge variant analysis	HIC, SEC-HPLC, icIEF, LC-MS for intact mass and peptide mapping	Assen: analytical platform for complex biologic characterisation
GMP manufacturing	Aseptic fill-finish of the final conjugated product	Sterile manufacturing with HPAPI handling capability	Ghent: aseptic fill-finish; HPAPI containment
Bioanalysis	PK characterisation of total antibody, conjugated antibody, free payload, and ADA	LBA and LC-MS/MS validated methods; ICH M10 compliance	Assen: integrated ADC bioanalytical programme

The Linker Is Not Just a Chemical Spacer

A common misconception in early ADC development is that the linker is a simple chemical bridge between the antibody and the payload, and that its design is secondary to the choice of antibody and warhead. In reality, the linker determines where and when the payload is released, how stable the conjugate is in systemic circulation, and how quickly it degrades after uptake into the tumour cell.

Cleavable linkers, which release the payload in response to conditions found in the tumour microenvironment such as low pH, elevated protease activity, or reductive conditions, offer the advantage of targeted payload release but must be stable enough in circulation to avoid premature release and off-target toxicity. Non-cleavable linkers, which release the payload only after complete lysosomal degradation of the antibody, are more stable in circulation but release a metabolite of the payload rather than the payload itself, which may have different potency and pharmacokinetic properties.

The FDA’s guidance on ADC development addresses the characterisation requirements for the linker-payload component and the stability testing needed to demonstrate adequate linker stability under physiologically relevant conditions.

HPAPI Handling: The Non-Negotiable Safety Requirement

The cytotoxic payloads used in ADCs are among the most potent compounds handled in pharmaceutical manufacturing. Maytansinoids, auristatins, calicheamicins, and pyrrolobenzodiazepines are typically active at picomolar concentrations and have occupational exposure limits in the nanogram per cubic metre range. Manufacturing with these payloads requires engineering controls, closed systems, and operator monitoring programmes that go well beyond standard pharmaceutical handling practices.

Occupational exposure banding (OEB) is the framework used to classify the hazard of a compound and define the engineering controls required for its manufacture. Most ADC payloads fall into OEB 4 or OEB 5, requiring isolator or dedicated closed-system manufacturing environments. Ardena’s Pamplona facility provides OEB 4 and 5 containment capability for HPAPI handling, offering the safety infrastructure needed for ADC payload work without the need to build or operate dedicated in-house HPAPI facilities.

Why ADC Programmes Need an Integrated Partner

The multi-component nature of an ADC programme is precisely why integration matters. The formulation decisions made for the drug product affect the linker stability, which affects the bioanalytical characterisation required, which affects the PK data interpretation, which informs the dose selection for Phase I. When each of these activities sits with a different vendor, data flows between organisations with inevitable delays and potential for misinterpretation.Ardena’s ability to handle HPAPI synthesis at Pamplona, aseptic fill-finish and lyophilisation at Ghent, and bioanalytical characterisation at Assen within a single project management framework gives ADC programmes the integration that their complexity requires.

Inside Ardena Pamplona: High Potency, Oral Solids, and Controlled Substances

The Site Built for Difficult Molecules

Not every pharmaceutical development programme involves a straightforward API in a standard formulation. Some molecules are highly cytotoxic. Some are scheduled narcotics. Some are biologically active at doses measured in micrograms. These are not unusual compounds at the edges of drug development. They are increasingly common in oncology, neurology, and rare disease pipelines.

Ardena’s Pamplona facility, which operates under the Idifarma brand within the Ardena network, is the site in the group best equipped to handle them. OEB 4 and 5 containment, controlled substance manufacturing licences, and a formulation team experienced in the specific challenges of high-potency and low-solubility molecules make Pamplona the natural home for programmes that other sites cannot take on.

HPAPI Manufacturing and Containment

Pamplona’s HPAPI infrastructure includes containment isolators for handling at OEB 4 and 5, dedicated manufacturing suites with independent HVAC systems, and validated decontamination procedures using hydrogen peroxide vapour. The site’s environmental monitoring programme covers HPAPI air monitoring in work areas using validated analytical methods capable of detecting compounds at the nanogram per cubic metre level.

The containment capability supports both drug substance handling (weighing, dispensing, and transfer of HPAPI starting materials and intermediates) and drug product manufacture (blending, granulation, and tabletting of HPAPI oral solid drug products). Yield accountability and mass balance documentation are maintained throughout, meeting the strict record-keeping requirements associated with potent compound manufacturing.

Controlled Substance Manufacturing

Pamplona holds manufacturing authorisations for narcotic and psychotropic substances under Spanish and European regulatory requirements. This enables the site to manufacture clinical batches of scheduled compounds including opioids, cannabinoids, and emerging psychedelic-derived therapeutics within a GMP framework that meets both EU GMP and the specific national requirements of the Spanish competent authority (AEMPS).

The site has experience managing the import and export licence requirements associated with controlled substance clinical supply, and can coordinate with regulatory authorities in importing countries to ensure that cross-border shipments are compliant.

Oral Solid Formulation for Challenging Molecules

Pamplona’s formulation team specialises in molecules that present both potency and solubility challenges simultaneously. The site operates hot melt extrusion and wet milling capability for bioavailability enhancement, alongside standard granulation and tabletting for more conventional formulations. High-sensitivity LC-MS/MS analytical methods are used for content uniformity and dissolution testing of HPAPI drug products where standard HPLC-UV methods lack sufficient sensitivity.

What Pamplona Is Best Suited For

Programme Type	Why Pamplona Is a Good Fit
Oncology HPAPI oral solid	OEB 4-5 containment; formulation development; GMP clinical batch; high-sensitivity analytical methods
ADC payload synthesis or handling	HPAPI containment for cytotoxic warheads; controlled transfer to conjugation chemistry steps
Controlled substance development	AEMPS manufacturing licence; experience with import/export documentation; GMP batch supply for scheduled compounds
Psychedelic-assisted therapy programmes	Schedule 1 and 2 handling capability; experience with regulatory requirements for novel controlled substance clinical programmes
BCS Class II HPAPI formulation	HME and wet milling with containment; simultaneous management of solubility challenge and exposure risk
Low-dose solid dosage forms	Experience with microgram-level content uniformity; validated LC-MS/MS release methods

Integration with the Ardena Network

For ADC programmes, Pamplona’s HPAPI capabilities connect with the formulation and fill-finish work at Ghent and the bioanalytical programme at Assen. For programmes involving solid state uncertainty, Pamplona’s formulation work draws on the solid state research expertise at Ghent. For programmes requiring simultaneous EU and US GMP compliance, Pamplona’s EU GMP certification and the US cGMP status of the Somerset facility together provide the geographic footprint needed for dual submissions.

Inside Ardena Assen: Bioanalysis, Clinical Supply, and Patient Kits

Where the Clinical Trial Meets the Laboratory

Ardena’s Assen facility sits at the intersection of two things that are normally separated: the bioanalytical laboratory that measures what is happening in patients and the clinical supply operation that gets the drug to them. Bringing these capabilities together under one roof is not just operationally convenient. It means the people designing the patient kit are the same people who will receive the blood samples it generates, and the lessons from one directly improve the other.

Bioanalytical Services at Assen

Small Molecule PK by LC-MS/MS

The analytical chemistry team at Assen provides fully validated LC-MS/MS methods for quantification of small molecule drugs and their metabolites in plasma, serum, urine, and other biological matrices. Studies run under GLP or GCP conditions as required, with ICH M10-compliant validation packages and ISR programmes as standard.

Large Molecule and Immunogenicity Assays

The ligand-binding assay platform at Assen covers PK quantification for biologics including monoclonal antibodies, ADCs, and fusion proteins, alongside the complete tiered immunogenicity testing programme for anti-drug antibody detection and characterisation. MSD electrochemiluminescence and ELISA platforms are both operated, with assay development experience across a wide range of therapeutic targets.

Biomarker and Flow Cytometry

The biomarker team provides fit-for-purpose assay development and validation for pharmacodynamic, safety, and predictive biomarkers using MSD multiplex platforms, single-plex ELISA, and qPCR. The flow cytometry laboratory runs multi-parametric immunophenotyping panels for T cell subset analysis, B cell characterisation, NK cell phenotyping, and MRD assessment in haematological programmes.

Clinical Supply and Patient Kit Services

The clinical supply team at Assen assembles and quality-checks patient kits for clinical trials, including pre-labelled sample collection tubes, visit-specific configurations, cool pack integration, and laminated step-by-step processing instructions designed to minimise site errors. Kits are assembled to programme-specific designs, with barcode labelling, personalisation to patient ID where required, and IATA-compliant packaging for temperature-controlled international shipment.

Sample logistics are managed end to end: kits ship out to investigator sites, samples arrive back at Assen, chain of custody is logged from receipt, and storage conditions are verified against validated stability data before analysis proceeds. The same team that designed the kit handles the incoming samples, which means any recurring collection errors are identified and fed back to sites quickly.

The Scope of What Assen Handles

Service Area	Capability	Regulatory Standard
Small molecule bioanalysis	LC-MS/MS in plasma, serum, urine, CSF, tissue	GLP / GCP; ICH M10 compliant
Large molecule bioanalysis	LBA (MSD, ELISA) for mAbs, ADCs, bispecifics, fusion proteins	GLP / GCP; ICH M10 compliant
Immunogenicity	Tiered ADA screening, confirmation, titration, neutralisation	FDA and EMA guideline compliant
Biomarker assays	MSD multiplex, ELISA, qPCR; fit-for-purpose validation	FFP approach; scope defined by intended use
Flow cytometry	Multi-parametric panels; up to 15+ parameters; immunophenotyping and MRD	Fit-for-purpose; EuroFlow-aligned panel design
Patient kit assembly	Visit-specific kits, barcode labelling, cool pack integration, IATA packaging	Quality-controlled assembly; batch records
Clinical sample logistics	Receipt, chain of custody, condition verification, storage management	GCP-compliant sample handling
Global clinical distribution	IMP storage and distribution to EU and international sites; customs coordination	GDP-compliant distribution; temperature-monitored

Connecting Assen to the Rest of the Ardena Network

Bioanalytical data from Assen is interpreted alongside PK, PD, and safety data generated across the wider clinical programme. For nanomedicine programmes, the nanoparticle payload bioanalysis at Assen connects directly with the formulation and CQA data from Oss. For ADC programmes, the ADC PK and immunogenicity assays at Assen are coordinated with the HPAPI manufacturing at Pamplona. The integration is structural, not just aspirational.

Inside Ardena Oss: The Nanomedicine Manufacturing Centre

A Site Built Around Nanoparticles

Ardena’s facility in Oss, the Netherlands, is not a general pharmaceutical site that also does nanomedicines. It is a site designed from the ground up for nanoparticle development and manufacturing. The equipment, the analytical infrastructure, the technical expertise, and the quality systems are all configured around the specific demands of LNPs, polymeric nanoparticles, liposomes, and related complex nanotechnology-based products.

That focus matters. The difference between a general injectable site that can manufacture an LNP and a dedicated nanomedicine site is the same as the difference between a GP and a specialist. The specialist has seen the edge cases, solved the unexpected problems, and built the institutional knowledge that makes the process more reliable.

What Oss Offers

LNP Development and GMP Manufacturing

The formulation team at Oss develops LNP products from initial lipid screening through to GMP clinical batch manufacture. Microfluidics and nanoparticle extrusion platforms are available at development and GMP scale, with integrated tangential flow filtration (TFF) capability for buffer exchange and concentration. The site has experience with mRNA, siRNA, and small molecule LNP products across a range of ionisable lipid systems.

Polymeric and Other Nanoparticle Systems

Beyond LNPs, the Oss team has formulation capabilities for PLGA and other biodegradable polymer nanoparticles, nanosuspensions prepared by wet milling, and lipid-polymer hybrid systems. The common thread is that the site is equipped for the characterisation-intensive development work that nanoparticle products require, with DLS, NTA, RiboGreen encapsulation efficiency assays, and in vitro release testing all available in-house.

Analytical Characterisation

The analytical team at Oss provides the full suite of physicochemical characterisation required for LNP and nanoparticle drug product development, including particle size and PDI by DLS, zeta potential, encapsulation efficiency by RiboGreen or equivalent, lipid composition by HPLC, and mRNA integrity by gel electrophoresis. The team develops the analytical methods needed for GMP batch release and regulatory filing alongside the formulation programme.

The Programmes Oss Is Best Suited to Support

Programme Type	Why Oss Is a Good Fit
mRNA LNP therapeutics	Dedicated microfluidics and TFF equipment; mRNA integrity and potency testing; GMP clinical batch capability
siRNA or ASO LNP	Nucleic acid encapsulation experience; encapsulation efficiency optimisation; GMP manufacturing at clinical scale
Polymeric nanoparticle sustained release	PLGA and polymer nanoparticle development; in vitro release testing; GMP scale-up
Nanosuspension for BCS Class II	Wet milling with particle size characterisation; downstream processing to solid dosage form
LNP regulatory filing support	Integrated regulatory team; experience with Module 3 CMC for LNP products; familiarity with FDA and EMA expectations
Scale-up from development to GMP	Same facility and team at both scales; no formal tech transfer; process parameters maintained consistently

Connection to the Broader Ardena Network

Oss does not work in isolation. For ADC programmes where the payload requires HPAPI containment, the formulation work at Oss connects with the Pamplona facility’s containment manufacturing capability. For bioanalysis of nanoparticle payloads, Oss works alongside the bioanalytical team at Assen. For aseptic fill-finish of finished nanoparticle drug products, Oss programmes can connect to the sterile manufacturing infrastructure at Ghent.

IMPD vs. IND: Navigating Dual Regulatory Submissions

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.

Inside Ardena Ghent: Oral Solids, Sterile Manufacturing, and Solid State Research

The Site That Does the Most

Of all Ardena’s European sites, Ghent carries the broadest scope. It is where solid state research happens. It is where oral solid development and manufacturing runs. It is also where sterile injectables, lyophilised products, and complex parenteral formulations are developed and manufactured under GMP. For a programme that spans multiple dosage forms or that needs solid state characterisation feeding directly into drug product development, Ghent is where those conversations happen in one building.

Solid State Research

The solid state research group in Ghent is dedicated to pre-formulation work: polymorph screening, salt and co-crystal screening, hydrate and solvate assessment, and the characterisation of physical and chemical properties that determine how a molecule will behave in a formulation. The team works with XRPD, DSC, TGA, DVS, and Raman spectroscopy as its core analytical toolkit.

What makes the Ghent setup particularly effective is the direct connection between solid state research and drug product development. The scientist who identifies the optimal salt form is part of the same organisation as the scientist who will formulate the tablet. Decisions made in pre-formulation are informed by what the downstream process can accommodate, rather than handed over in a report and interpreted by someone else months later.

Oral Solid Development and Manufacturing

Ghent’s oral solid development team covers the full formulation development pathway for tablets and capsules: pre-formulation, formulation screening, process development, and scale-up to GMP clinical batch manufacture. The site operates batch and continuous manufacturing capability for tabletting, granulation (wet and dry), film coating, and capsule filling.

PAT tools including near-infrared spectroscopy are integrated into the manufacturing environment, supporting blend uniformity monitoring and granulation endpoint determination. The team has experience with immediate release, modified release, and enteric-coated dosage forms, and with challenging APIs including poorly soluble compounds that require bioavailability enhancement strategies.

Sterile Manufacturing and Lyophilisation

The sterile manufacturing suite at Ghent provides aseptic fill-finish for vials and ampoules under Grade A conditions within a RABS environment. Lyophilisation capacity supports both conventional small molecule injectables and biologics requiring freeze-drying for stability.

The sterile manufacturing team has experience with complex injectable formulations including liposomal products and nanoparticle drug products requiring the specific process controls and in-process monitoring discussed in the broader nanomedicine fill-finish programme. Environmental monitoring and media fill qualification are maintained to EU GMP Annex 1 standards.

Analytical and Regulatory Support

Ghent’s analytical teams provide method development and validation for both oral solid and injectable products. The regulatory team in Ghent contributes to CMC dossier preparation for IND and IMPD submissions, with particular expertise in the solid state and oral solid sections of Module 3.

What Ghent Is Particularly Well Suited For

Programme Type	Why Ghent Is a Good Fit
Early-phase oral solid with solid state uncertainty	Solid state research and formulation development in the same site; findings translate directly into formulation decisions
Poorly soluble oral API	HME, wet milling, and lipid formulation capabilities alongside solid state analytics
Sterile injectable for Phase I	Aseptic fill-finish under EU GMP; lyophilisation available; experienced with small clinical batches
Liposomal or nanoparticle injectable	Specialist experience in nanoparticle fill-finish process development; particle size monitoring during filling
Programme needing dual IMPD/IND filing	EU GMP certified site; regulatory team experienced in both jurisdictions
Continuous manufacturing evaluation	Batch and continuous manufacturing capability; PAT tools in place; team experienced in Q13 requirements

Working with the Ghent Team

Projects based primarily at Ghent are managed by dedicated project managers who coordinate work across the solid state, formulation, analytical, and manufacturing teams within the site. For multi-site programmes, the Ghent project manager integrates with counterparts at Oss, Assen, Pamplona, and Somerset to ensure that the work is coordinated and that data flows between teams without friction.

Continuous Manufacturing in Oral Solids: Is Your Product a Candidate?

Beyond the Batch Paradigm

Pharmaceutical tablet manufacturing has been batch-based for most of its history. Raw materials in, process step by step, finished product out, test and release. The batch is a defined, auditable unit of production with a clear beginning and end.

Continuous manufacturing challenges that model. Materials flow through an integrated process train without stopping: blending, granulation, drying, tabletting, and coating happen in sequence, in real time, monitored by inline sensors that provide a continuous stream of data on the product being made. There is no batch in the traditional sense. There is a time-defined unit of production, characterised by the process data collected during its manufacture.

The FDA has actively encouraged this transition. Its 2019 guidance on pharmaceutical quality for continuous manufacturing and the ICH Q13 guideline both provide frameworks that make continuous manufacturing a viable regulatory pathway for new products.

The Real Advantages of Continuous Over Batch

Smaller Footprint, Faster Output

A continuous manufacturing line produces tablets at a defined throughput rate, typically measured in kilograms per hour. To increase output, you run the line for longer, not build a bigger facility. For clinical supply, this means small campaigns can be run efficiently without the scale-up losses inherent in batch tabletting. For commercial supply, it means flexible throughput without capital investment in larger equipment.

Better Process Understanding

Because continuous manufacturing relies on real-time sensors, the process data generated per batch equivalent is orders of magnitude richer than in conventional manufacturing. Blend uniformity, particle size, tablet hardness, and dissolution are all monitored continuously rather than sampled at fixed intervals. This data density enables faster identification of process drift and more rapid root-cause analysis when deviations occur.

Reduced Scale-Up Risk

In batch manufacturing, scaling from a development batch to a commercial batch means different equipment, different shear forces, different mixing dynamics. In continuous manufacturing, the same equipment runs at the same process parameters regardless of the total batch size. Scale-up is a matter of runtime, not equipment change. That removes one of the most unpredictable phases of pharmaceutical development.

Is Your Product a Candidate? A Practical Checklist

Factor	Favourable for Continuous Manufacturing	Less Favourable
API flow properties	Good to moderate flowability; amenable to loss-in-weight feeding	Very poor flow; tendency to bridge or rat-hole in feeders
Blend sensitivity	Blend uniformity maintained under continuous mixing conditions	Very segregation-prone blends; sticky or cohesive powders
Granulation requirement	Direct compression or dry granulation preferred; wet granulation possible on integrated lines	Products requiring aqueous wet granulation with long drying times
Dose and tablet size	Mid-range doses; standard tablet geometries	Very low dose (microgram range) where blend uniformity at feeder level is challenging
Development stage	New development with flexibility to design process for continuous manufacturing from the start	Established batch process with significant existing clinical data package
Regulatory timeline	Sufficient time to generate continuous manufacturing process data for CMC filing	Accelerated timeline where batch process is faster to validate

The Regulatory Pathway for Continuous Manufacturing

ICH Q13, finalised in 2022, provides the harmonised guidance for continuous manufacturing of drug substances and drug products. It addresses the definition of batch, the control strategy for continuous processes, the use of PAT tools for real-time release, and the stability data requirements. The FDA’s own guidance on continuous manufacturing complements Q13 with US-specific expectations on process validation and real-time release testing.

For sponsors considering continuous manufacturing for a new programme, engaging with the regulatory agency early, through a Type B meeting with the FDA or a scientific advice procedure with the EMA, is the most reliable way to confirm that the proposed control strategy and batch definition approach will be accepted before significant development investment is made.

Ardena’s Oral Solid Manufacturing Capabilities at Ghent

Ardena’s oral solid manufacturing team at Ghent has both batch and continuous manufacturing capability, with experience developing control strategies and CMC packages that meet the regulatory expectations for both approaches. The team can advise on whether a specific product profile is suited to continuous manufacturing and help design a development programme that builds the process understanding needed for a regulatory filing.

Process Analytical Technology (PAT) in Tablet Manufacturing

The Problem with Testing at the End

Traditional pharmaceutical manufacturing is built around the idea of testing finished product. You make a batch, you sample it, you test it, and you decide whether it passes. The problem is that by the time you know a batch is out of specification, you have already used the time, materials, and manufacturing capacity to make it. Rejection at the end of the process is expensive. For complex drug products, it can be catastrophic.

Process analytical technology (PAT) flips that model. Instead of testing the finished product, you monitor the process in real time and make adjustments before problems develop. The batch still gets tested for release, but the data generated during manufacture gives you confidence before you even run the final tests.

The Core PAT Tools in Oral Solid Manufacturing

Near-Infrared Spectroscopy (NIR)

NIR is the most widely implemented PAT tool in tablet manufacturing. It works by shining near-infrared light onto a powder or granule blend and measuring the wavelengths absorbed. Because different chemical bonds absorb at characteristic wavelengths, the resulting spectrum is a fingerprint of the material’s chemical composition. With appropriate calibration models, NIR can measure blend uniformity in real time during mixing, detect the endpoint of a granulation process, and confirm coating uniformity during film coating.

NIR does not require sample preparation or consumables, and it can be implemented as a non-contact measurement that does not disturb the process. Those properties make it well suited to continuous monitoring applications in blending and coating.

Raman Spectroscopy

Raman provides complementary chemical information to NIR and is particularly useful for monitoring polymorphic form in real time. Because different polymorphs of the same API have distinct Raman spectra, a probe positioned in a dryer or granulator can detect whether the solid form is changing during the process. For APIs that are prone to polymorphic conversion under the heat and humidity conditions of wet granulation, real-time Raman monitoring provides a direct safety net.

Particle Size Analysers

Focused beam reflectance measurement (FBRM) uses a scanning laser to measure the chord length distribution of particles in suspension or slurry in real time. In wet granulation, it provides continuous data on how granule size is evolving during the granulation process, allowing the endpoint to be determined from the particle size profile rather than from a fixed time or a grab sample.

PAT in the Regulatory Framework

Regulatory Document	Relevance to PAT
ICH Q8(R2) Pharmaceutical Development	Introduces design space and Quality by Design concepts that PAT supports; encourages understanding of process-property relationships
ICH Q10 Pharmaceutical Quality System	Promotes continual improvement; PAT data feeds directly into process monitoring and improvement programmes
FDA PAT Guidance (2004)	Established the FDA’s position that PAT is encouraged and that real-time release testing can replace end-product testing where appropriate
EMA Reflection Paper on PAT	Aligns with FDA position; supports use of NIR and other inline tools in EU GMP environments
ICH Q13 Continuous Manufacturing	PAT is foundational to continuous manufacturing; real-time monitoring required for process control in continuous processes

Real-Time Release Testing: The Regulatory Endgame

The ultimate application of PAT in pharmaceutical manufacturing is real-time release testing (RTRT): replacing traditional end-product testing with a combination of inline process data and reduced end-product testing that together provide equivalent or greater assurance of product quality. ICH Q8(R2) explicitly supports RTRT as an outcome of Quality by Design development. For blend uniformity in particular, the FDA has accepted NIR-based RTRT as a replacement for conventional powder sampling and HPLC analysis in several approved products.

Implementing RTRT requires robust calibration models, validated PAT methods, and a clearly defined control strategy that specifies how real-time data is used in batch disposition decisions. It is not a shortcut, but it produces better process understanding and more robust manufacturing than conventional end-point testing alone.

PAT Capability at Ardena Ghent

Ardena’s oral solid manufacturing team at Ghent uses PAT tools including NIR spectroscopy and particle size analysis as part of its development and manufacturing programmes. The team has experience developing NIR calibration models for blend uniformity and granulation endpoint determination, and integrating PAT data into the process understanding and control strategy documentation required for CMC regulatory filings.

Encapsulating Challenging APIs: High Potency and Low Solubility

The Double Problem

The molecules that generate the most clinical excitement are often the ones that cause the most formulation headaches. Modern oncology APIs, for example, tend to be both highly potent (small doses, strict containment requirements) and poorly soluble (BCS Class II or IV, significant bioavailability challenges). Solving one problem in isolation is hard enough. Solving both simultaneously requires a formulation strategy that navigates containment requirements and bioavailability enhancement at the same time.

This article looks at how those two challenges interact and how development teams can avoid designing a solution for one that undermines the other.

Where the Challenges Collide

Spray Drying with HPAPIs

Spray drying is one of the most effective routes to an amorphous solid dispersion for a poorly soluble API. For a high-potency compound, it also generates an aerosol of fine particles during atomisation, exactly the exposure route that makes HPAPIs dangerous. The spray drying chamber needs engineering controls appropriate to the OEB classification of the API, and the secondary drying step, which typically involves fluid bed processing, must also be conducted within a contained environment.

This is not insurmountable, but it requires a facility where spray drying equipment is integrated with HPAPI containment infrastructure. A site that has spray drying and a site that has HPAPI containment are not the same thing as a site that has both in the same building.

Wet Milling with HPAPIs

Wet milling for nanosuspension manufacture is lower-risk from a containment perspective because the API is suspended in liquid throughout the milling process, reducing the risk of airborne exposure. However, the downstream steps, particularly spray drying or fluid bed granulation of the milled suspension, reintroduce aerosol risk. Closed transfer systems and contained fluid bed processing are standard mitigations.

HME with HPAPIs

Hot melt extrusion produces a solid extrudate rather than an aerosol, which gives it an inherent containment advantage over spray drying. The milling of the cooled extrudate to a usable particle size does generate dust, which requires containment. For many HPAPIs, HME followed by contained milling is a more practical manufacturing route than spray drying, provided the API is thermally stable at processing temperatures.

Formulation Technology Options for High Potency, Low Solubility APIs

Technology	Bioavailability Benefit	HPAPI Containment Considerations	Best Suited For
Hot melt extrusion (HME)	ASD formation; 2-10 fold AUC improvement	Contained milling of extrudate required; lower aerosol risk than spray drying	Thermally stable HPAPIs; OEB 3-4
Spray dried dispersion	ASD formation; similar bioavailability benefit to HME	Contained spray dryer and secondary drying required; aerosol generation in chamber	Thermally labile HPAPIs where HME is not feasible; requires dedicated HPAPI spray drying facility
Nanosuspension (wet milling)	2-5 fold dissolution rate improvement; crystalline API retained	Closed milling system; contained downstream processing	HPAPIs where crystalline form is required; OEB 3-4
Lipid-based formulation (SMEDDS)	Enhanced solubilisation via self-emulsification	Liquid handling; lower aerosol risk; containment simpler	Lipophilic HPAPIs; fill-in-capsule formulations
Cyclodextrin complexation	Solubility improvement via inclusion complex	Aqueous processing; low aerosol risk	Moderate potency; HPAPIs with suitable cavity fit for cyclodextrin complexation

Dose Accuracy: The Third Challenge

For HPAPIs dosed at microgram or sub-milligram levels, the analytical challenge of confirming content uniformity is significant. Standard HPLC-UV methods may lack the sensitivity needed at the concentrations involved. LC-MS/MS methods with lower limits of detection in the nanogram range are often required for content uniformity and dissolution testing of HPAPI drug products.

This analytical requirement must be built into the development plan early. A formulation team that spends six months developing an ASD strategy, then discovers the release method cannot measure the drug at the target dose, has a problem that is expensive to solve retrospectively.

Ardena’s HPAPI Formulation Capabilities at Pamplona

Ardena’s Pamplona (Idifarma) facility combines OEB 3, 4, and 5 containment capability with formulation development infrastructure for poorly soluble APIs, including HME, wet milling, and lipid-based formulation platforms. The analytical team at Pamplona develops high-sensitivity LC-MS/MS methods for content uniformity and dissolution testing of HPAPI drug products as an integrated part of the formulation development programme.

Bioanalytical Characterisation of Nanoparticle Payloads

The Question Nobody Asks Early Enough

When you are developing a nanoparticle drug product, the bioanalytical question you need to answer is not simply ‘how much drug is in the blood?’ It is ‘which form of the drug are you measuring, and what does that tell you about what is actually happening in the patient?’

For a conventional small molecule, total plasma drug concentration is a reliable surrogate for the concentration available to interact with the target. For a nanoparticle product, the drug in the plasma exists in at least two distinct populations: drug encapsulated within intact nanoparticles (not directly bioavailable until the particle releases it), and free drug (the fraction that has been released and is available for cellular uptake or systemic distribution). These two fractions have different pharmacokinetic profiles, different safety implications, and different relationships to efficacy. Measuring only the total gives you a misleading picture of both.

The Three Fractions and What They Tell You

Analyte Fraction	What It Represents	Clinical Relevance	Measurement Approach
Total drug (encapsulated + free)	Everything in the sample, regardless of form	Overall systemic exposure; comparison to free drug PK for benefit of encapsulation	Extract with detergent or organic solvent before analysis; LC-MS/MS or validated immunoassay
Free (unencapsulated) drug	Drug released from the particle in circulation	Off-target toxicity risk; available for direct cellular uptake; clearance profile	Separate free fraction by ultrafiltration or SEC before extraction; subtract from total
Encapsulated drug	Drug retained within intact nanoparticles	Depot of drug still in delivery system; circulation half-life of the carrier	Calculated as total minus free; or direct measurement after nanoparticle enrichment

How to Separate the Fractions

Ultrafiltration

Centrifugal ultrafiltration is the most commonly used approach for separating free drug from encapsulated drug. The sample is centrifuged through a membrane with a molecular weight cut-off appropriate to retain the nanoparticles while allowing free drug to pass into the filtrate. The free drug is then quantified in the filtrate, and total drug is measured in a separately extracted aliquot of the unprocessed sample.

The main limitation of ultrafiltration is the potential for non-specific binding of the drug to the membrane, which can lead to underestimation of the free fraction. Membrane compatibility must be assessed during method development using spiked samples at relevant concentrations.

Size Exclusion Chromatography

Size exclusion chromatography (SEC) physically separates nanoparticles from free drug based on size. Nanoparticles elute in the void volume; free drug elutes later. Fractions can be collected and analysed separately. SEC is gentler than ultrafiltration for fragile nanoparticle formulations and avoids membrane binding artefacts, but is lower throughput and requires careful method development to ensure complete separation.

Matrix-Specific Challenges for Nanoparticle PK Assays

Nanoparticle products interact with blood components in ways that complicate sample handling. Plasma proteins adsorb to nanoparticle surfaces to form a protein corona within seconds of contact with blood, changing the particle’s surface properties and, in some assays, interfering with the detection of the encapsulated payload. Lipid nanoparticles can fuse with endogenous lipoproteins in plasma, causing transfer of lipid payload and apparent changes in the free-to-encapsulated ratio that are artefacts of the in vitro processing rather than the in vivo behaviour.

These matrix interactions must be characterised during method development and controlled by standardised sample collection and processing procedures. Samples for nanoparticle PK analysis should be processed promptly after collection, and freeze-thaw stability of the sample before the separation step must be validated to confirm that particle integrity is maintained under study storage conditions.

Regulatory Expectations for Nanoparticle PK Bioanalysis

The FDA and EMA have not yet published dedicated guidance specifically on bioanalytical methods for nanoparticle drug products, but the general principles of ICH M10 apply. Sponsors developing nanoparticle products are expected to define the analyte clearly in the validation protocol, to justify the choice of measurement (total versus free versus encapsulated), and to demonstrate that the sample preparation procedure does not introduce systematic bias through nanoparticle disruption or membrane binding. FDA review comments on approved nanoparticle products provide useful precedent for the level of characterisation expected.

Ardena’s Nanoparticle Payload Bioanalysis at Assen

Ardena’s bioanalytical team in Assen develops and validates methods for nanoparticle payload quantification using ultrafiltration and SEC-based fractionation combined with LC-MS/MS detection. The team has experience with liposomal, LNP, and polymeric nanoparticle products, and can advise on bioanalytical strategy design to ensure the PK data package supports both dose selection decisions and the regulatory filing.