Natural Nanoparticles with Pharmaceutical Potential

Every cell in the human body releases extracellular vesicles (EVs). These membrane-bound particles, ranging from roughly 30 nanometres to several micrometres in size, carry proteins, lipids, nucleic acids, and metabolites between cells. They are natural intercellular communication vehicles, evolved to transfer biological cargo across biological barriers.

The pharmaceutical interest in EVs is obvious. A delivery system that is intrinsically biocompatible, that crosses biological barriers efficiently, that can be loaded with therapeutic cargo, and that does not trigger the immune activation associated with synthetic nanoparticles sounds like exactly what drug delivery scientists have been trying to engineer for decades.

The development challenges are equally obvious. You cannot manufacture EVs the way you manufacture LNPs. They are produced by living cells, isolated from complex biological matrices, and extraordinarily heterogeneous. Controlling their composition, their cargo loading efficiency, and their biological activity from batch to batch is a hard problem that has not yet been fully solved.

EV Subclasses and Their Relevance to Drug Delivery

EV Subclass	Size Range	Biogenesis	Therapeutic Interest
Exosomes	30-150 nm	Formed within multivesicular endosomes; released when MVE fuses with cell membrane	Natural intercellular communication; potential for loading with nucleic acids or small molecules; low immunogenicity
Microvesicles	100-1000 nm	Direct budding from plasma membrane	Larger cargo capacity; surface proteins reflect parent cell; less well characterised than exosomes
Apoptotic bodies	500-5000 nm	Released by cells undergoing programmed cell death	Less clinical interest for drug delivery; relevant to clearance and inflammation biology
Engineered EVs (synthetic biology)	Variable	Cells engineered to overexpress targeting or therapeutic proteins on EV surface	Most therapeutically relevant near term; allows systematic engineering of surface and cargo

The Manufacturing Problem

Natural EVs are produced in tiny quantities. A litre of cell culture medium yields micrograms of EVs after isolation. Scaling that to the quantities needed for clinical trials requires either enormous bioreactor volumes or manufacturing platforms that produce engineered EVs at higher yields than natural cell secretion.

Isolation adds further complexity. The standard methods, ultracentrifugation, size exclusion chromatography, and tangential flow filtration, each have different selectivity for different EV populations. There is no universal isolation method, and different methods produce products with different purity, yield, and biological activity. This makes batch-to-batch comparability extremely challenging when the isolation process is not tightly controlled.

The Characterisation Gap

Characterising EVs to the standard required for a regulatory filing is harder than characterising LNPs. Particle size by DLS gives an ensemble average that poorly represents a heterogeneous population. Single-particle tracking methods like NTA are more informative but harder to standardise. Protein cargo is highly variable depending on the source cell and culture conditions. The ISEV Society’s minimal information for studies of extracellular vesicles (MISEV) guidelines provide a framework for EV characterisation in research, but translating those standards to a GMP context remains an open challenge for the field.

Where the Clinical Evidence Stands

Several EV-based products have reached clinical trials. MSC-derived exosomes have been investigated for graft-versus-host disease and COVID-19 acute respiratory distress syndrome. Tumour-derived EVs have been explored as cancer vaccines. Plant-derived EVs are being investigated as oral drug delivery vehicles.

Results have been mixed. The field has not yet produced the definitive clinical proof-of-concept that would drive widespread investment, and the manufacturing and characterisation challenges mean that many programmes have struggled to produce consistent clinical-grade material. But the pace of basic science, engineered EVs with defined surface proteins, cell-free EV production systems, improved isolation methods, is accelerating.

How Ardena Is Positioned for EV Programme Support

Ardena’s nanomedicine team at Oss monitors the EV therapeutics field closely and is developing the analytical and formulation capabilities needed to support early-stage EV programmes as the field matures. The physicochemical characterisation infrastructure at Oss, including DLS, NTA, and TEM, is applicable to EV characterisation, and the team can advise on the analytical strategy and formulation challenges facing EV development programmes at the current stage of the technology.

The Hardest Drugs to Make

Oncology is consistently the largest therapeutic area in pharmaceutical development pipelines, and it is consistently the most technically demanding. The molecules tend to be highly potent. The patient populations are often defined by specific biomarkers, requiring precise clinical supply and diagnostic coordination. The tolerability window is narrow, making dose accuracy and product consistency critically important. And the speed imperative is real: patients with advanced cancers cannot afford the delays that are merely inconvenient in other therapeutic areas.

A CDMO that works well for a standard oral solid in cardiovascular disease may not be equipped for an oncology programme. The containment requirements, the analytical sensitivity demands, the clinical supply complexity, and the regulatory scrutiny are all substantially higher.

The Technical Demands of Oncology Drug Development

High-Potency Handling

Most small molecule oncology drugs are cytotoxic or have high pharmacological potency. Occupational exposure limits in the nanogram per cubic metre range require engineering controls, dedicated manufacturing suites, and validated decontamination procedures that are a significant capital and operational investment. Not all CDMOs have them.

Bioavailability Challenges

Many kinase inhibitors, PARP inhibitors, and other targeted oncology agents are BCS Class II or IV molecules with poor aqueous solubility. Getting adequate bioavailability to support efficacious plasma exposures often requires amorphous solid dispersion technology, nanosuspension, or lipid-based formulation. The CDMO must have these capabilities in-house, and they must be compatible with HPAPI handling if the API requires it.

Bioanalytical Complexity

Oncology clinical trials require sophisticated bioanalytical programmes. PK characterisation across a wide dose range. Pharmacodynamic biomarkers that demonstrate target engagement. Immunogenicity testing for biologic oncology agents. Cell-based assays for cell therapy programmes. A CDMO with integrated bioanalysis can manage all of these as a coherent programme; a CDMO without bioanalysis capability requires the sponsor to manage a separate vendor relationship.

What Oncology Programmes Need from a CDMO Partner

Requirement	Why It Matters in Oncology	Ardena Capability
HPAPI manufacturing at OEB 4-5	Cytotoxic small molecules and ADC payloads require strict containment	Pamplona: OEB 3-5 containment; isolators; validated decontamination
ASD formulation for BCS Class II/IV	Many targeted oncology agents have poor oral bioavailability	Somerset and Pamplona: spray drying and HME
Aseptic fill-finish for cytotoxic injectables	IV oncology formulations require sterile manufacturing with HPAPI controls	Ghent: aseptic fill-finish; HPAPI-compatible sterile suite
ADC bioanalysis (total Ab, conjugated Ab, free payload)	ADCs require multi-analyte PK characterisation	Assen: LBA and LC-MS/MS for full ADC PK panel
Biomarker and flow cytometry assays	Companion diagnostics and PD biomarkers are central to oncology trial design	Assen: MSD multiplex; multi-parametric flow cytometry
CMC regulatory expertise for oncology	Oncology programmes often use accelerated pathways with higher CMC scrutiny	Multi-site regulatory team; experience with Breakthrough Therapy and PRIME designations
Small-batch GMP for rare tumour subtypes	Patient populations in oncology trials can be very small	All sites: clinical batch capability without minimum batch size constraints that force waste

Speed Without Shortcuts

Oncology drug development operates under genuine time pressure. Patients with limited treatment options are waiting. But the speed imperative does not justify cutting corners that create problems later. A poorly characterised solid form that requires reformulation at Phase II. A stability programme that does not cover the clinical trial duration. A CMC package that triggers a regulatory hold.

The fastest programmes are not the ones that skip steps. They are the ones that identify the critical path clearly, run parallel workstreams where the science allows, and avoid the rework that comes from doing development in the wrong order. That requires a partner with enough experience in oncology to know which steps can be accelerated and which cannot.

How Ardena Serves Oncology Programmes

Ardena’s network covers the full oncology development and manufacturing chain. HPAPI capability at Pamplona, ASD formulation at Somerset and Pamplona, sterile manufacturing at Ghent, and integrated bioanalysis at Assen give oncology sponsors a single partner across the technical domains their programmes require. The project management model, with a single project manager coordinating work across sites, means the sponsor is not left to manage four separate CDMO relationships.

Formulating Oligonucleotide Therapies: siRNA, ASO, and Beyond

A Pipeline That Has Finally Arrived

Oligonucleotide therapies have been in development for decades. The science was compelling from the start: target any gene in the human genome with exquisite specificity by designing a short nucleotide sequence that binds the corresponding mRNA. Switch off disease-causing genes. Restore lost protein expression. Correct splicing errors.

The delivery problem kept most of it on the bench. Oligonucleotides are large, negatively charged, enzymatically unstable molecules that do not cross cell membranes easily. They are rapidly degraded by serum nucleases and cleared by the kidney before they reach their target.

Two decades of formulation innovation have changed that. Lipid nanoparticles, GalNAc conjugation, and chemical modification strategies have collectively unlocked systemic and local delivery of oligonucleotides to a growing range of tissues. The pipeline has followed.

The Three Main Classes and Their Delivery Needs

Class	Mechanism	Primary Delivery Challenge	Current Delivery Solutions
siRNA (small interfering RNA)	Triggers RISC-mediated degradation of complementary mRNA; gene silencing	Negative charge; nuclease degradation; endosomal escape; off-target effects	LNP (ionisable lipid); GalNAc conjugation for hepatic delivery; chemical modifications (2-OMe, PS backbone)
Antisense oligonucleotide (ASO)	Binds pre-mRNA or mRNA; blocks translation or triggers RNase H cleavage	Nuclease degradation; tissue distribution; nuclear access for splice-switching ASOs	Naked delivery with chemical modifications (PS backbone; LNA/BNA); GalNAc for liver; local delivery to CNS or lung
Aptamer	Folds into 3D structure that binds target protein; blocks or modulates protein function	Rapid renal clearance; short half-life; large-scale synthesis	PEGylation; conjugation to larger carriers; chemical modifications
saRNA (self-amplifying RNA)	Encodes an RNA polymerase that amplifies the therapeutic RNA in the cell	Larger molecule than mRNA; requires same endosomal escape strategy; immunogenicity	LNP; same platform as mRNA but larger payload size requires formulation optimisation
miRNA mimic or inhibitor	Modulates endogenous miRNA activity; broad gene regulatory effect	Same as siRNA/ASO depending on class; off-target effects from broad miRNA activity	LNP; conjugate delivery; chemical modifications

GalNAc Conjugation: The Hepatic Delivery Revolution

For oligonucleotides targeting the liver, GalNAc (N-acetylgalactosamine) conjugation has transformed the field. GalNAc is a sugar that binds with high affinity and specificity to the asialoglycoprotein receptor (ASGPR) expressed at high levels on hepatocytes. Conjugating a GalNAc moiety to an ASO or siRNA drives receptor-mediated uptake specifically into liver cells, achieving therapeutic silencing at doses that would be ineffective for the naked oligonucleotide.

GalNAc-conjugated siRNAs (GalNAc-siRNA) are administered as subcutaneous injections, often once monthly or less frequently, with no nanoparticle carrier required. The simplicity of the delivery system relative to LNPs, no lipid formulation, no cold chain, simple subcutaneous administration, has made GalNAc the dominant delivery platform for hepatic oligonucleotide therapies.

The limitation is obvious: it only works for liver targets. For any other tissue, GalNAc does not help.

Chemical Modifications: Stability Before Delivery

Before any delivery system can work, the oligonucleotide must survive long enough to reach the target. Naked, unmodified RNA is degraded by serum nucleases within seconds. Chemical modifications slow that degradation and, in many cases, improve the potency and duration of action of the drug.

The phosphorothioate (PS) backbone modification, where a non-bridging oxygen in the phosphodiester linkage is replaced by sulphur, was the first widely used modification and remains standard in most clinical ASOs. It significantly improves nuclease resistance and increases protein binding in plasma, which extends circulation half-life but also contributes to off-target effects at high doses.

Locked nucleic acid (LNA) modifications constrain the ribose ring in a fixed conformation that increases binding affinity and nuclease resistance. 2-O-methyl and 2-O-methoxyethyl modifications are also widely used. Modern clinical oligonucleotides typically carry a combination of several modification types, optimised for the specific target and delivery context.

Formulation Development for Oligonucleotides

For LNP-delivered siRNAs, the formulation development process is closely analogous to mRNA LNP development: ionisable lipid selection, N:P ratio optimisation, microfluidics manufacture, and physicochemical characterisation of particle size, PDI, encapsulation efficiency, and zeta potential. The key difference is that siRNA is significantly smaller than mRNA, which affects the optimal lipid composition and the encapsulation efficiency assay (Ribogreen versus strand-specific hybridisation assays for siRNA quantification).

For subcutaneous GalNAc-conjugate delivery, the formulation is simpler: the conjugate is dissolved in a compatible aqueous buffer at the target concentration, filtered, and filled into prefilled syringes or vials. The formulation challenges are primarily related to concentration (high concentration formulations can form gels) and stability of the conjugate bond under storage conditions.

Ardena’s Oligonucleotide Platform at Oss

Ardena’s nanomedicine team at Oss has formulation development and GMP manufacturing capability for LNP-delivered oligonucleotides, including siRNA and saRNA payloads. The site’s encapsulation efficiency assays have been adapted for siRNA quantification, and the team has experience optimising LNP formulations for small nucleic acid payloads where the optimal composition differs from mRNA LNP formulations.

The Problem with Crushing Adult Tablets

A remarkable proportion of medicines given to children are unlicensed for paediatric use. Nurses crush adult tablets, pharmacists compound extemporaneous liquids, and parents split scored tablets into fractions. None of these workarounds are ideal. All of them introduce dose uncertainty. Some destroy formulation features, like modified release coatings, that were essential to the drug’s performance.

The push towards age-appropriate paediatric formulations is a regulatory priority. The EMA’s Paediatric Investigation Plan requirement and the FDA’s Paediatric Study Plan mandate that sponsors plan paediatric development early, not as an afterthought once adult registration is secured.

Dose Flexibility: The Core Paediatric Formulation Challenge

Adults generally all receive the same dose. Paediatric patients are dosed by weight, which means the same drug needs to be deliverable across a ten-fold or more dose range. A tablet that comes in two strengths cannot achieve that. The formulation must be inherently flexible.

This is why oral liquids, oral dispersible tablets, and multiparticulate systems (granules, mini-tablets, pellets) dominate paediatric formulation science. Each allows dose adjustment without tablet splitting, compounding, or approximation.

Age-Appropriate Formulation Options by Patient Group

Age Group	Preferred Formulation Types	Key Formulation Considerations
Neonates (0-28 days)	Oral liquids; orodispersible films	Extremely small doses; swallowing reflex not developed; strict excipient restrictions; benzyl alcohol contraindicated
Infants (1-23 months)	Oral liquids; orodispersible granules mixed with food	Palatability critical; volumes below 5 ml preferred; no capsules or standard tablets
Young children (2-5 years)	Chewable tablets; orodispersible tablets; oral liquids	Palatability essential; age-appropriate flavours; tablet size below 6 mm for swallowability
Older children (6-11 years)	Film-coated tablets; mini-tablets; oral liquids	Swallowability improving; tablet size up to 8 mm generally acceptable; can begin to consider capsules
Adolescents (12-17 years)	Adult-equivalent formulations generally acceptable	Consider adult formulation with paediatric dosing; review excipient limits for age

Age-group classifications follow EMA ICH E11(R1) and WHO definitions. Formulation acceptability within each group varies by patient and clinical context.

Excipients: Not Everything That Is Safe in Adults Is Safe in Children

Paediatric patients metabolise and excrete differently from adults. Enzyme systems are immature in neonates and infants. Renal function is proportionally different. Excipients that are routinely used in adult formulations can be hazardous in young children.

Benzyl alcohol, used as a preservative in many injectable products, has been associated with gasping syndrome and death in premature neonates. Propylene glycol, a common solubiliser, can accumulate in infants with immature metabolic pathways. Sorbitol at high doses causes osmotic diarrhoea and dehydration in young children.

The EMA’s guideline on excipients in the label and package leaflet and the EMA’s reflection paper on the use of excipients in paediatric formulations are required reading for any team developing a paediatric formulation. The acceptable daily intake thresholds for excipients in children are often significantly lower than the amounts present in adult formulations.

Palatability: The Formulation Variable That Determines Adherence

A paediatric formulation that children refuse to take is not a medicine; it is a negotiation. Palatability, covering taste, smell, texture, and mouthfeel, is a genuine development objective, not a cosmetic one.

Taste masking is one of the most technically challenging aspects of paediatric oral formulation. Bitter APIs are the norm in pharmaceutical development. Options include polymer coating of drug particles, complexation with ion exchange resins, microencapsulation, and flavouring. Each approach has limits, and the most effective strategy depends on the API’s physicochemical properties and the target formulation.

Formal paediatric acceptability testing using age-appropriate assessment tools, such as hedonic scales adapted for young children, is increasingly expected as part of the development programme and is recognised in EMA guidance as a component of the pharmaceutical development evidence package.

Ardena’s Paediatric Formulation Experience

Ardena’s formulation teams have experience developing paediatric oral formulations including orodispersible tablets, oral liquids, and multiparticulate systems across its European sites. The team is familiar with the EMA’s paediatric regulatory requirements and with the practical challenges of excipient selection, taste masking, and dose flexibility that make paediatric development distinct from adult work.

Inorganic Nanoparticles in Pharmaceutical Development

The pharmaceutical nanoparticle landscape extends well beyond lipid and polymer systems. Metal and metal oxide nanoparticles, particularly gold nanoparticles and iron oxide nanoparticles, have physical properties that make them uniquely useful in diagnostic imaging, thermal therapy, and the emerging field of theranostics, where a single agent combines diagnostic and therapeutic functions.

Interest in these materials has grown steadily alongside advances in nanomedicine formulation science, and several iron oxide nanoparticle products are already approved for clinical use as MRI contrast agents. The broader field of metal nanoparticle applications in pharmaceuticals is advancing through clinical development, with programmes in cancer imaging, hyperthermia therapy, and targeted drug delivery among those in active investigation.

Iron Oxide Nanoparticles: MRI Contrast and Beyond

How Iron Oxide Nanoparticles Enhance MRI Contrast

Superparamagnetic iron oxide nanoparticles (SPIONs) enhance the contrast of magnetic resonance imaging by shortening the T2 and T2* relaxation times of water protons in tissues where the particles accumulate. This produces a signal reduction (darkening) in T2-weighted images, allowing tissues with SPION accumulation to be distinguished from surrounding tissue. The degree of contrast enhancement depends on the size, surface coating, and magnetic properties of the particles.

Approved SPION-based MRI contrast agents including ferumoxytol are used clinically for imaging of the lymphatic system, the liver, and the vasculature. The EMA’s reflection paper on non-clinical studies for generic nanoparticle medicinal products provides guidance relevant to the development of SPION-based imaging agents and new nanoparticle therapeutics.

Emerging Applications: Hyperthermia and Drug Delivery

Beyond MRI contrast, iron oxide nanoparticles can generate heat when exposed to an alternating magnetic field, a phenomenon known as magnetic hyperthermia. Localised heat generation in tumour tissue can directly kill cancer cells or sensitise them to concurrent chemotherapy or radiotherapy. Magnetic hyperthermia using iron oxide nanoparticles has been investigated in clinical trials for glioblastoma and prostate cancer.

Surface-functionalised iron oxide nanoparticles can also act as drug carriers, with the magnetic core providing imaging capability and the surface providing a platform for drug loading and targeting ligand attachment. This combination of imaging and therapeutic function in a single particle is the theranostic concept at its most direct.

Gold Nanoparticles: Optical Properties and Biomedical Applications

Surface Plasmon Resonance

Gold nanoparticles exhibit a phenomenon known as surface plasmon resonance: the conduction electrons on the gold surface oscillate in resonance with incident light at specific wavelengths, producing intense absorption and scattering at those wavelengths. The resonance wavelength depends on the size and shape of the particle and can be tuned from the visible to the near-infrared range by controlling particle geometry during synthesis.

This optical tunability makes gold nanoparticles attractive for photothermal therapy, where near-infrared light penetrates tissue and is absorbed by gold nanoparticles localised in the tumour, generating heat that destroys tumour cells. Near-infrared light causes minimal damage to surrounding tissue, making this a highly targeted thermal ablation approach.

Surface Functionalisation for Drug Delivery

The surface of gold nanoparticles can be functionalised with a wide range of chemical groups, including thiol-linked molecules, antibodies, oligonucleotides, and polymer coatings. This versatility makes gold nanoparticles a flexible platform for targeted drug delivery, where the gold core provides photothermal or imaging capability and the surface carries therapeutic cargo and targeting ligands.

Characterisation Requirements for Inorganic Nanoparticles

Property	Measurement Technique	Regulatory Relevance
Core size and size distribution	Transmission electron microscopy (TEM); X-ray diffraction	Core size affects magnetic and optical properties; must be defined and controlled
Hydrodynamic diameter and PDI	Dynamic light scattering (DLS)	Reflects particle size in biological media including protein corona formation
Surface chemistry and coating	X-ray photoelectron spectroscopy (XPS); FTIR; NMR	Surface coating determines colloidal stability, protein adsorption, and biological fate
Zeta potential	Electrophoretic light scattering	Colloidal stability indicator; relevant to aggregation and non-specific interactions
Metal content and purity	ICP-MS or ICP-OES	Precise metal quantification for dose control; impurity profiling required for regulatory filing
Endotoxin and sterility	LAL assay; sterility testing	Critical for injectable products; inorganic nanoparticles can interfere with standard LAL assays

Characterisation requirements for metal nanoparticle pharmaceuticals are evolving. Regulatory expectations should be confirmed with the relevant agency for each specific application and development stage.

Ardena’s Metal and Metal Oxide Nanoparticle Platform

Ardena’s nanomedicine team at Oss has experience with metal and metal oxide nanoparticle systems, including formulation development, physicochemical characterisation, and GMP manufacturing support for inorganic nanoparticle products. The analytical capabilities at Oss include DLS, zeta potential measurement, and the infrastructure for handling metal-containing pharmaceutical materials under GMP conditions.

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.

A Platform Proven at Unprecedented Scale

The COVID-19 pandemic accelerated the clinical and regulatory validation of mRNA LNP technology at a pace that would otherwise have taken a decade. Within two years of the initial sequencing of the SARS-CoV-2 spike protein, billions of doses of mRNA vaccine had been manufactured, distributed globally, administered under emergency authorisation, and then fully approved by the FDA and EMA. The safety, immunogenicity, and manufacturing scalability of the mRNA LNP platform were demonstrated at a scale that no preclinical model could have predicted.

The scientific and industrial community that built the COVID-19 vaccine supply chain did not then stand still. The formulation scientists, manufacturing engineers, regulatory professionals, and clinical researchers who learned their trade on vaccine programmes are now applying the same platform to a new generation of therapeutic applications, each of which presents its own formulation challenges and clinical expectations.

Personalised Cancer Vaccines: mRNA as Precision Medicine

The most scientifically compelling near-term application of therapeutic mRNA beyond infectious disease is personalised cancer vaccination. Tumour cells accumulate somatic mutations that produce altered proteins called neoantigens, which are not present in normal tissue and are therefore visible to the immune system as foreign. A personalised cancer vaccine encodes the patient’s own tumour neoantigens in an mRNA construct, delivers it via LNP to antigen-presenting cells, and stimulates a T cell response targeted specifically at the tumour.

The clinical results from early trials of personalised mRNA cancer vaccines, including data from Moderna and Merck’s mRNA-4157/V940 programme in melanoma, have shown meaningful improvements in recurrence-free survival in combination with checkpoint inhibitor therapy. BioNTech’s BNT111 programme for melanoma and several other solid tumour programmes are advancing through Phase II, establishing the clinical evidence base for what could become a standard of care in tumour-specific adjuvant therapy.

Rare Genetic Diseases: Protein Replacement by mRNA

For rare genetic diseases caused by loss-of-function mutations that result in absent or non-functional proteins, mRNA therapeutics offer a route to protein replacement that is fundamentally different from enzyme replacement therapy (ERT) or gene therapy. Rather than administering the protein directly (ERT) or permanently correcting the gene (gene therapy), mRNA therapy temporarily restores protein expression by delivering the instructions for the normal protein to the patient’s own cells.

The transient nature of mRNA expression, typically lasting days to weeks depending on the mRNA design and the tissue target, is both a limitation and a safety feature. The treatment must be repeated at regular intervals, but the absence of permanent genomic modification eliminates the risk of insertional mutagenesis associated with viral gene therapy vectors. For diseases like methylmalonic acidemia, propionic acidemia, and other inborn errors of metabolism affecting the liver, mRNA LNP therapy delivered intravenously to hepatocytes is an active area of clinical investigation.

The Formulation Challenges That Remain Unsolved

Challenge	Clinical Implication	Active Research Direction
Extra-hepatic delivery	Most LNP platforms accumulate in the liver after IV administration; reaching lung, muscle, or tumour tissue requires active targeting or alternative routes	Selective organ targeting (SORT) lipids; receptor-targeted LNPs; inhaled LNP delivery for respiratory targets
Repeated dosing immunogenicity	PEG-specific IgM responses can cause accelerated blood clearance after repeat doses; some ionisable lipids generate innate immune responses	PEG-alternatives (PEGylation-free LNPs); optimised immunisation schedules; stealth LNP designs
mRNA half-life in vivo	Unmodified mRNA is rapidly degraded; modified nucleosides improve stability but add manufacturing complexity	Circular mRNA; self-amplifying mRNA for lower doses; codon and UTR optimisation for enhanced expression
Cold chain dependency	Current approved mRNA products require storage at minus 20 or minus 80 degrees C, limiting access in resource-limited settings	Thermostable formulations; lyophilised mRNA LNP products; room-temperature stable excipient systems
Manufacturing cost at personalised scale	Personalised cancer vaccines require individual mRNA synthesis per patient; current GMP cost is high	Automated mRNA synthesis platforms; modular GMP; point-of-care manufacturing concepts

What the Expanding mRNA Pipeline Demands from CDMOs

The breadth of the mRNA therapeutic pipeline, from infectious disease vaccines to oncology, rare disease, and cardiac applications, creates a formulation and manufacturing demand that is qualitatively different from the vaccine manufacturing experience. Cancer vaccine programmes require patient-specific mRNA synthesis and formulation under GMP conditions. Rare disease programmes require precision dosing, specialised patient populations, and regulatory packages adapted to small-batch GMP. Cardiac and pulmonary programmes may require inhaled or locally administered formulations that are outside the IV delivery paradigm of the COVID-19 vaccines.

CDMOs that can support this breadth of application need more than a microfluidics machine and a vial filler. They need formulation scientists who understand the relationship between LNP composition and delivery to specific tissue targets, analytical teams capable of characterising mRNA integrity and potency in complex formulation environments, and regulatory expertise in the evolving framework for mRNA therapeutics beyond the emergency authorisation pathway.

Ardena’s Role in the mRNA Therapeutic Pipeline

Ardena’s nanomedicine facility at Oss is positioned to support mRNA therapeutic development beyond the vaccine applications that established the platform. The formulation team has expertise in ionisable lipid-based LNP systems, and the analytical team at Oss and Assen provides the mRNA integrity, potency, and physicochemical characterisation capabilities needed for regulatory-grade data packages across vaccine and therapeutic applications.