Needs and possibilities for tracking therapeutic cells
Needs
Tracking cells after administration should provide information on the distribution of the cells in the body, and how long they survive and stay in the body. During the development of the therapy, this type of information helps, for example, to determine the optimal dosing regimen of the cells. Furthermore, tracking cells throughout the clinical application, i.e., not just in the development phase of the therapy but also post-marketing, may aid in distinguishing responding from non-responding patients and in further personalising the treatment.
From a developers’ perspective, it is important to determine why the imaging agent is needed in the first place, for example, to optimise the dosing regimen, to determine the long-term fate of cells, or to distinguish responding from non-responding patients. Subsequently, this need determines the type of information their imaging agent needs to provide; local vs whole body, short-term vs long-term tracking, quantitative vs qualitative data, etc. Developers also need to know to what extent the imaging agent needs to be compatible with different cell types, what specific equipment is needed, and if the total cost and potential risk outweighs the benefit to the patient or to the therapy in general.
From a regulator’s perspective, any information on the fate of therapeutic cells upon administration is of added value for the marketing authorisation assessment process for a CTP, as currently, this information is often not available to regulators.
At the same time, from an ethical point of view, the potential (extra) risk involved in using an imaging agent to track therapeutic cells needs to be weighed against the benefit for the patient and for cell therapy in general.
Possibilities
Various options for tracking therapeutic cells are available, and each have their own disadvantages and limitations (reviewed by Helfer et al. 2021) (Figure 2)[1]. The ideal tracking method is non-invasive, uses imaging agents that are compatible with and inert to any type of (therapeutic) cells and accommodate multiple imaging techniques. In addition, the imaging agent should ideally be cleared from the body as soon as possible to prevent accumulation in organs and potential long-term adverse effects. In contrast, fast clearance of the imaging agent may not be ideal in case there is a need for long-term tracking of the cells, for example for several weeks. As there is no fit-for-all purposes option, the method of choice depends on a number of factors such as therapeutic cell type, location of the target tissue, duration of tracking needed and availability of the required resources. The selection of the most appropriate imaging agent involves a case-by-case analysis.
Defining the aim at an early stage
We experienced that defining the aim of the nanoparticles should be done at a very early stage of development. Although the nTRACK project aimed at tracking distribution, viability and duration of the cells both during development and clinical application of cell therapies, we faced that these different application purposes may lead to a different final product (nanoparticles versus an ATMP including nanoparticles) and thus a different regulatory roadmap. This implies not only different safety and efficacy studies required, but also different regulatory authorities involved in obtaining marketing authorisation for the final product.
The nTRACK consortium, therefore, decided to define the purpose of the nTRACK nanoparticles more precisely: ‘tracking of cell therapy with labelled stem cells to be used during (non-clinical and clinical) development of new cell therapies’. Initially, the imaging agent would only be used in the development phase of the cell therapy to provide input on the fate and distribution of the cells and to optimize the dosing regimen. A future option may be to develop nanoparticles for use beyond the development phase of the therapy, i.e., as an integral part of the final, marketing-authorised ATMP.
Regulatory classification of nanoparticles
In the European Union (EU), any product with a medical purpose needs to be approved by regulatory authorities before it can enter the market. The regulatory process and the authorities involved depend on the type of product. Medicinal products need to go through an authorisation process at the EMA or at national medicines agencies, while medical devices need to obtain a CE marking from a Notified Body. ATMPs, including CTPs, are subject to a centralised authorisation procedure at the EMA according to Regulation (EC) No 1394/2007[20]. The CE marking for a medical device is a codification mark that implies the product has been assessed to meet high safety, health, and environmental protection requirements in accordance with the Medical Device Regulation (EU) 2017/745 [12].
To determine the regulatory classification of the nTRACK nanoparticles, we considered the EU legal definitions of medicinal product, diagnostic agent, medical device and novel excipient (Table 2) and assessed whether any of them were applicable to nTRACK product.
Table 2 Definitions (EU) of medicinal product, diagnostic agent, medical device and excipient
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Product
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Definition
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Reference
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Medicinal product
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“any substance or combination of substances which may be used in or administered to human beings either with a view to restoring, correcting or modifying physiological functions by exerting a pharmacological, immunological or metabolic action, or to making a medical diagnosis”
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Article 1(2) of Directive 2001/83/EC
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Diagnostic agent
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“Diagnostic agents are medicinal products used for diagnosis or monitoring of a disease. The evaluation of diagnostic agents is governed by the same regulatory rules and principles as for other medicinal products”.
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Guideline on clinical evaluation of diagnostic agents” (CPMP/EWP/1119/98/Rev. 1)
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Medical device
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“any instrument, apparatus, appliance, material or other article, whether used alone or in combination, including the software necessary for its proper application intended by the manufacturer to be used for human beings for the purpose of:
- diagnosis, prevention, monitoring, treatment or alleviation of disease,
- diagnosis, monitoring, treatment, alleviation of or compensation for an injury or handicap,
- investigation, replacement or modification of the anatomy or of a physiological process,
-control of conception, and which does not achieve its principal intended action in or on the human body by pharmacological, immunological or metabolic means, but which may be assisted in its function by such means”.
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Article 2(1) of the new Medical Device Regulation 2017/745/EU (and in the old Article 1(2)a of Directive 93/42/EEC, as amended),
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Excipient
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- “any constituent of a medicinal product other than the active substance and the packaging material.”
- Excipients include e.g., fillers, disintegrants, lubricants, colouring matters, antioxidants, preservatives, adjuvants, stabilisers, thickeners, emulsifiers, solubilisers, permeation enhancers, flavouring and aromatic substances etc. as well as the constituents of the outer covering of the medicinal products, eg. gelatin capsules. A novel excipient is an excipient which is being used for the first time in a drug product, or by a new route of administration (ICH). It may be a new chemical entity or a well-established one which has not yet been used for human administration and/or for a particular human administration pathway in the EU and/or the EU.”
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- Article 1(3b) of Directive 2001/83/EC (consolidated version)
- EMA’s guideline on excipients in the dossier for application for marketing authorisation of a medicinal product (EMA, 2007)
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Medicinal product and Diagnostic agent
The intended purpose of the nTRACK nanoparticles is not to restore, correct or modify physiological functions, nor to make a medical diagnosis. It does not exert its action by pharmacological, immunological or metabolic means, either. Restoring physiological function is the intended action of the therapeutic cell, whether it contains the imaging agent or not.
Diagnostic agents are medicinal products for the diagnosis or monitoring of a disease [27]. However, monitoring or diagnosing a disease is not the intended action of the nTRACK nanoparticles. Although it is intended to be used for monitoring purposes, it monitors the therapeutic cells instead of the disease. We, therefore, considered that the nTRACK nanoparticles do not fit well within the definition of a medicinal product or diagnostic agents and should not be classified as such.
Medical device
As the nTRACK nanoparticles do not exert their action by pharmacological, immunological or metabolic means, a classification as a medical device may be a better fit than classification as a medicinal product. However, as discussed for diagnostic agents, the intended purpose of the nTRACK nanoparticles is not to diagnose or monitor a disease.
Excipient
The nTRACK nanoparticles is always intended to be administrated in combination with therapeutic cells. Therefore, it can be argued that there is no regulatory need to classify the nanoparticles by themselves, but consider them an excipient, i.e., any constituent of a medicinal product other than the active substance and packaging. For excipients, no separate authorisation is required. Instead, details of manufacture, characterisation and controls with cross-references to supporting safety data should be added to the dossier of the final medicinal product when the excipient is novel, according to its dosage form and the route of administration. In the case of using the nTRACK nanoparticles, the medicinal product would be an ATMP used as an investigational medicinal product (IMP) in a clinical trial. However, the nTRACK nanoparticles will only be part of the IMP, but not of the finally marketed ATMP.
Authorities’ point of view
In the EU, there is no authority with the jurisdiction to assign the appropriate regulatory classification to a medical product such as the nTRACK nanoparticles. The respective authorities only determine whether a product market authorization request falls within their own legal scope or not. As a consequence, it is up to the applicants to determine a suitable classification of their product based on the definitions in the various regulatory documents, and submit their application to the relevant authority. However, innovative products or novel applications of a product may not always fit well within the existing definitions of medical products, as demonstrated in the case of the nTRACK nanoparticles. In the EU, the manufacturer should select his own preferred option for classification of his product and justify this to the authority in charge.
In our meetings with regulatory authorities, we learned that the appropriate classification of the nTRACK nanoparticles is unsure and that experts have different preferences for either the classification as medicinal product or medical device. We also became aware that EU Member States might have diverging views on the classification of the nTRACK nanoparticles. Examples of similar products being classified as medical devices and as diagnostic agents reflect the ongoing discussion on which visualisation purposes fall within the term ‘medical diagnosis’.
For the classification of the nTRACK nanoparticles as medical device, it became clear that the interpretation of the term ‘medical purposes’ in the definition of medical device is crucial. For example, the term ‘medical purposes’ currently relate to individual patient benefit and not to medical science in general according to the current German Medical Device Law (§ 3 MPG) and taking this into account, we suppose that nTRACK nanoparticles probably do not qualify as a medical device in the context of current German medical device legislation. However, the interpretation of medical purposes may evolve due to the implementation of the new Medical Device Regulation in the EU.
A representative from a Notified Body who attended our international workshop further argued that the medical device regulation directive is only applicable to products that are placed on the market and used in routine clinical settings and not, as in the case of the nTRACK nanoparticles, for tools used during development (Personal communication). This implies that the particles as such will not need to be assessed and approved by a European NCA as they are neither a medical device nor a medicinal product. However, the nTRACK nanoparticles will be used as part of an IMP according to the EU legislation. Each combination of the nanoparticles and an ATMP would need to be approved as an IMP. The option to consider the nanoparticles as an excipient was brought up during the international workshop. The classification as excipient would be consistent with the opinion of the expert from the Notified Body.
In the USA, a product with a similar purpose to that of the nTRACK nanoparticles was designated a drug by the US-FDA (Personal communication). Furthermore, since the product is intended to be used in combination with cells only, the jurisdiction of reviewing the product was assigned to the US-FDA’s Center for Biologics Evaluation and Research (CBER). The safety and efficacy data supporting the use of the product is largely directed at the impact of the product on the therapeutic cell it is combined with. In other words, while being designated a drug, its review is handled as if it were an excipient.
It is clear that the regulatory classification of the nTRACK nanoparticles for tracking therapeutic cells during (clinical) development is a complex issue that remains to be resolved. Again, it is important to note that the final regulatory classification, process and bodies involved may be entirely different should the nanoparticles be used only during non-clinical development or during clinical use of the therapeutic cell product, as an integral part of this product.
Quality control and preclinical data requirements
Regulatory quality and preclinical information requirements for the nTRACK nanoparticles
Regardless of its regulatory classification, there can be no doubt that the quality, safety and reliability of the nTRACK nanoparticles needs to be assessed extensively before its first use in humans The data required may differ from one regulatory framework to another, although there are large overlaps. Below we discuss the regulatory information requirements for medicinal products and medical devices in the EU.
Directives and guidelines on medicinal products, excipients and diagnostic agents
Directive 2001/83/EC relating to medicinal products for human use in the EU makes no mention of nano-specific considerations. As a consequence, should the nanoparticles be classified as a medicinal product, manufacturers would need to provide the same preclinical data as required for any conventional medicinal product, according to this directive. The required data include information on quality, safety and efficacy which is obtained by following strict technical guidelines. For example, the safety information largely needs to comply to the globally harmonized guidelines laid down by the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH).
Nevertheless, regulating nano-medicinal products as conventional medicinal ones has given rise to concerns. Regional differences in their regulation across the globe are difficult to navigate and lead to a lack of harmonisation [28]. In addition, standardized methodologies used for conventional medicinal products are not always compatible with nano-medicinal products, resulting in uncertainties regarding their quality and safety [29-31]. Due to their particulate nature, nanomaterials tend to interact with the immune system, and it is uncertain whether the current set of preclinical safety studies for conventional medicinal products provides sufficient information for an adequate evaluation of the potential immunotoxicity of nano-medicinal products [32].
Despite the lack of specific regulations for nano-medicinal products, the EMA published a number of reflection papers on safety evaluation of nanomedical products [9, 16-18]. EMA’s paper on general issues for consideration regarding parenteral administration of coated nanomedicine products [9] emphasises the need for a well-defined and controlled manufacturing process supplemented with a suitable control strategy. The paper states that control and assurance of the quality of coated nanomedicine products cannot just be based upon a set of test specifications on the final product. Another paper from EMA discusses the general principles for assessing block copolymer micelle nano-medicinal products, stating that companies are advised to seek product-specific scientific advice on the data requirements due to the complexity of these products [18].
For novel excipients, there is no separate regulatory approval process in the EU, let alone for nano-excipients. The quality and biological safety evaluation is generally done simultaneously with the development of the drug containing the new excipient. In case the nTRACK nanoparticles are considered an excipient, this would mean that mainly its quality and safety are evaluated as part of the ATMP it is combined with. One approach may then be to execute a full-blown stand-alone safety evaluation of the nanoparticles, which may subsequently be used in technical dossiers for multiple ATMPs. However, data will always be needed on the combination of the nanoparticles with the ATMP under evaluation.
Directives and standards for nano-medical devices
The Medical Device Regulation does mention specific requirements for nanomaterials stating that ‘In the design and manufacture of devices, manufacturers should take special care when using nanoparticles for which there is a high or medium potential for internal exposure.’ These devices are classified as class IIa, IIb or III, depending on their potential for internal exposure. If the nTRACK nanoparticles (or similar) are classified as a medical device, they would be classified as class III medical devices because of their high level of internal exposure.
The ISO standard 10993-1:2009, Annex A, provides a framework for an assessment of the biological risks of medical devices and is a part of the international harmonisation of the safe use evaluation of medical devices[13]. This framework is generally applicable to devices that contain, generate or are composed of nanomaterials. Nevertheless, nano-specific considerations apply, as outlined in part 22 of the standard [23]. According to this guidance, nanoparticles would most likely be categorized as ‘nano-object medical device’, and their assessment needs to include characterization of physicochemical properties, toxicokinetics and tissue distribution and a biological evaluation (Table 3).
Table 3 Framework assessment biological risks specific for nanomaterials
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Assessment
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Guideline
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Physicochemical properties
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10993-1:2009 part 22 [23] lists a number of properties to be characterised and refers to ISO/TR 13014 for details on the appropriate methodology [25]. The standard further specifies various nano-specific considerations for biological evaluation, such as storage, stability, characterisation of stock dispersions and dosing solutions, dose metrics, endotoxin analysis and sterilisation.
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Toxicokinetics
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ISO 10993-16 provides a framework for toxicokinetic studies for medical devices [22]. The standard is applicable to nanoparticles but some adjustments might have to be made such as animal model, study duration, dosing strategy and analysing techniques. Manufacturers need to be aware that factors such as physicochemical properties, route of administration, dose, animal species and gender have all been reported to influence the toxicokinetics of nanomaterials in animal models.
Part 22 of the standard also describes the toxicity endpoints that may be of interest for devices that are composed of nanomaterials [23]. These include at least cytotoxicity, genotoxicity, immunotoxicity and systemic toxicity. The intracutaneous reactivity test should be considered to assess the localised reaction of tissue to nanoparticles. Evaluation of haemocompatibility should also be performed, if it is likely that the nanoparticles will come in direct or indirect contact with blood.
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Tissue distribution and a biological evaluation
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Apart from pseudoallergy responses based on complement activation reported for certain nanomedicinal products, it is unknown whether nanomaterials can elicit a sensitising response and currently there is no widely accepted assay available to test for this. An evaluation of the carcinogenic risk should be considered if human exposure is high or chronic. When sufficient and adequate evidence demonstrates that nanoparticles or their metabolites do not reach the reproductive system organs, no reproductive toxicity testing is necessary. This evidence can be based on absorption, distribution, metabolism and excretion (ADME) studies.
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(Lack of) standardised methodologies
It is important to note that for many of the required quality parameters, standardised methods compatible with nanomedicinal products are not yet available [30, 33]. Many methods are available for measuring particle size and size distribution, but large differences exist in terms of their level of standardisation, compatibility with materials, cost, complexity and the type of information they provide [34].
ISO 10993, part 22, describes known pitfalls in toxicity testing of nanomaterials the H2020 project REFINE, (www.refine-nanomed.eu), which aims to advance the regulatory science for nanotechnology-based health products, investigated to what extent standardised methods were available to fulfil the regulatory information needs for nanomedicinal products and nano-medical devices [31]. Analysis indicated that standard test methods did not exist for determining surface properties, kinetic properties in biological media, ADME parameters and interaction with blood and the immune system. For endotoxin determination, methods do exist but need to be adapted for nanomaterials, such as the limulus amebocyte lysate (LAL) based method for endotoxin. The LAL assay interferes with a variety of nanomaterials, potentially resulting in false positive or negative results [35]. ISO 10993, part 22, lists a number of other methods and resources for information on pyrogenicity testing of nanomaterials [23]. For many other information needs, methods still need to be validated or developed, or are at a very early stage of development. For example, the Ames test, a commonly used assay for assessing genotoxicity of soluble medicinal products is considered unreliable for nanomaterials because of their inability to cross bacterial membranes [36].
Extrapolating safety evaluation data from similar products
Developers of nanoparticles may turn to a large number of experimental safety studies with chemically similar nanomaterials (or their parent compounds) to fulfil the biological safety evaluation requirements of their product. While this seems a good approach, the safety profiles of nanomaterials depend on a number of properties other than chemical structure. The regulatory bodies handling medicinal products and medical devices are well aware of this.
EMA published several guidelines for nano-medicinal products, including intravenous liposomal products [17] and intravenous iron-based nano-colloidal products [16] developed with reference to an innovator medicinal product. An important message is that subtle differences in physicochemical properties between the applicant’s product and the innovator product may substantially modify the efficacy/safety of the product, which is not detectable by conventional bioequivalence testing alone.
Similar to nano-medicinal products, ISO 10993 part 22 states that demonstrating equivalence by extrapolating existing data from other similar nanomaterials, or from the corresponding parent compound, is not considered applicable for medical devices [23]. Next to chemical composition, the nanomaterial properties can be influenced by other factors such as size, shape and surface properties of the nanomaterial and/or the source (manufacturer) of these nanomaterials, manufacturing process and storage conditions.
There are quite a few challenges to overcome when extrapolating data from one nanomaterial to another for regulatory purposes [37]. One of them is to elucidate to what extent the various physicochemical properties change the safety profile of nanomaterials, and how these properties can be compared [38]. For these reasons, reliable extrapolation of safety data from studies done with nanomaterials that are not identical to the final product is very limited and will likely not be readily accepted by the authorities.
Lessons learned from discussions with experts
Our two meetings with experts from regulatory authorities (EMA-ITF and National Competent Authorities) were very fruitful for learning which issues may be specifically important during development of nanoparticles for imaging regardless their final classification as a medical device or a medicinal product. In the international workshop, we further discussed the quality control and preclinical data requirements for nanoparticles for imaging with other experts. Based on all expert discussions in different settings, we obtained a clear picture of the main specific regulatory issues for nanoparticles for imaging, which we describe in next section.
First of all, it is important to be aware that the batch of the nanoparticles used in the preclinical studies needs to be representative to the clinical batch. After preclinical testing, changes in the manufacturing process of the nanoparticles could better be avoided.
In addition to general quality, biodistribution and safety studies, it is important to confirm that the nanoparticles do not move between cells, to ensure that the imaging agent is following the therapeutic cells and not, as is the case of the macrophages that clear the nanoparticles from the body. To address this, an option could be to include an extra arm with just the nanoparticles in the preclinical studies with the labelled therapeutic cells, and study the fate and safety of the nanoparticles by themselves compared to when it is administered as part of the therapeutic cell. To see what effect the nanoparticles may have on different cell types, it is essential to include several types of human cells in the preclinical studies.
Furthermore, particle size distribution and data on aggregation behaviour as part of the physical stability characteristics of the nanoparticles are very important. As aggregation of nanoparticles is a concern, the size distribution measurement method has to be able to differentiate between all types of aggregation, reversible and irreversible, during the stability period. For a clinical trial application, morphology, electronic microscopy of the nanoparticles and information on endotoxin levels and sterility will be needed as well.
Apart from the standard studies on ADME, it will also be relevant considering if the exposure to the nanoparticles themselves can affect the patient’s underlying disease, for example, due to a potential anti-angiogenic effect.
With regard to performance, the number of nanoparticles needed to enable imaging has to be quantified and optimised. In the case nanoparticles with a long persistence in the body, the possibility that the materials will interfere with future imaging techniques needs to be considered.
If computer models are used to enhance imaging, it will also be important to validate the underlying algorithms, and to assess the risk for the patient in case of a false output of the model. In general, the individual patient benefit is a critical point in both the medicinal product and the medical device law, and this needs to be addressed in detail.
Depending on the cell type, therapeutic cells may or may not be modulated by the presence of the nanoparticles, in terms of both viability and function. Therefore, for a clinical trial application, extensive quality and preclinical information needs to be provided for the therapeutic cells loaded with the nanoparticles, as will be outlined in the next paragraph.
The EU requires final medicinal products, including ATMPs, to be produced in compliance with Good Manufacturing Practice (GMP) [20]. For medical devices, the accepted standard for production is compliance to ISO standard 13485 Medical devices – Quality management systems – Requirements for regulatory purposes [24].
Although both types of quality systems, GMP and ISO 13485, aim to guarantee the quality and safety of the final product, they have a rather different approach making a comparison complicated. Regardless of the classification of the nanoparticles itself, the final product administered to patients during clinical development contains a medicinal product, i.e. the cell therapy product. Therefore, both the production of the therapeutic cells as well as the labelling of the cells with the nanoparticles need to occur under GMP conditions.
There is no specific regulatory guidance available yet for the particular combination of therapeutic cells loaded with nanoparticles. Our discussions with experts revealed nevertheless several important issues. First of all, it became apparent that it will be crucial to have thorough information on the extent to which the nanoparticles modify the therapeutic cells. Therefore, developers of a nano-imaging agent will have to study in detail, both in vitro and in vivo, where the function and viability of the therapeutic cells containing the nanoparticles is compared to the therapeutic cells without the particles. A study on the functionality of therapeutic cells loaded with the nanoparticles should include the parameters used for release tests of the therapeutic cells as well as other cell function parameters. The ability to distinguish between viable and non-viable therapeutic cells in in vivo studies would also be of great benefit. It is important to demonstrate the stability of the cells after labelling and shipping.
Another important issue is a consistent procedure in labelling the therapeutic cells with the nanoparticles. To know whether the labelling is a consistent process, information on the uptake, excretion and concentration of the nanoparticles in the therapeutic cell has to be obtained, as well as the number of nanoparticles used, and what percentage of the cells have been successfully labelled. The procedure for labelling the therapeutic cell needs to be outlined in detail in a Standard Operating Procedure.
Timing of regulatory steps in the research and development process of a nanoparticles: step-by-step recommendations
The right timing of starting the various steps involved in regulatory approval can save a lot of resources. Preparing a regulatory roadmap early on in the development of nanoparticles for cell tracking purposes has the advantage of being able to anticipate on the regulatory information requirements. However, other steps of the regulatory process, such as executing regulatory required safety studies, should wait until an upscaled manufacturing process has been finalized, and reproducible batches of the material that meet all critical quality criteria can be produced consistently.
The next paragraphs provide a general overview of the regulatory relevant steps in chronological order that can be executed during the development of nanoparticles for tracking therapeutic cells, up until the clinical development (Figure 3). The suggested order is based on experiences from the nTRACK project as well as input during the workshop and meetings held with external experts. The optimal order may change under different circumstances.
Scoping
The first step is to clearly define the scope of the regulatory process. For nTRACK, it was important to decide the intended primary purpose of the nanoparticles, i.e. to identify better which regulatory roadmap to follow.
We recommend deciding on a primary purpose of the product. This will help to identify the best fitting definition of the final product, the most appropriate regulatory process and the authorities involved in the assessment process for bringing the product to the market.
Material selection
The selection of the appropriate source materials to use for nanoparticles depends on their purpose and on the availability of technological expertise to produce the nanoparticles. Each imaging technique has its own benefits and limitations with regard to the information it provides, invasiveness, compatibility with tissues, sensitivity, cost and availability of equipment. Equally important for the material selection is to consider its safety aspects. A quick screening of the literature often provides a first indication of the potential hazards of the materials. The source materials need to be of a quality grade that is suitable for medical purposes.
Lab scale production
Even in a lab-scale production process it is important to obtain reproducible, sterile batches which are well-characterised and free of contaminants in order to avoid interferences and false interpretation of experimental results. An additional factor to take into account when deciding on a production process is that each step of the process is scalable to larger volumes. This will be of great benefit when upscaling the production of the nanoparticles at a later stage of development.
Proof of concept
Once reproducible batches are produced on a lab-scale, some first experimental assays can be done in a number of cell types – therapeutic and non-therapeutic – to study cell uptake, viability and imaging performance. Especially in case the nanomaterials, developers need to be aware of the potential interferences these materials may have with various assays. The nanoparticles need to be fully characterised at this point, and their critical quality criteria need to be well-established.
This could be the right moment to consult experts such as the EMA-ITF to obtain the latest expert input on regulatory classification and information requirements. This information can be used to identify appropriate regulatory standards for material production, quality and safety studies.
Prototype
Next, a standard operating procedure needs to be developed for loading the therapeutic cell with the imaging agent.
Safety/performance screening
Performance and safety studies can be executed, including a thorough investigation of the potential modification of cell therapeutic function by the nanoparticles and performance studies in a small animal model. In the same study, an investigation of the distribution of the nanoparticles administered with and without the therapeutic cells can be used to identify target tissues, the latter representing a scenario where all nanoparticles are released from the therapeutic cell and into the systemic circulation.
Upscaled production
If the nanoparticles prove to be successful in these performance and safety studies, developers can start to design a preliminary protocol for the FiH clinical trial so that an appropriate set of regulatory preclinical studies can be defined. In addition, an upscaled production process that can manufacture a material closely resembling that of the lab-scale product needs to be developed. Especially for nanomaterials, small changes in the production process can alter the material’s properties and affect its performance. It is therefore essential that critical steps in the manufacturing process are identified, appropriate quality controls are in place and stability studies confirm the production of a material with an appropriate shelf-life.
Another essential step in the preclinical development process is that the cell uptake of the nanoparticles needs to be well-characterised and controlled. The optimal concentration of the nanoparticles in the therapeutic cell needs to be established, carefully weighing performance against the potential risk of compromising cell function with increasing concentrations of nanoparticles. The final cell loading process needs to be performed under conditions of Good Manufacturing Practices.
Preclinical development
Both the manufacturing process and the cell loading process need to be finalised before executing the regulatory preclinical safety studies. This is crucial because these studies need to be performed with the exact same product that will be used in a FiH clinical trial. A formal Scientific Advice procedure with the EMA or a national competent authority will help developers to identify what (additional) preclinical studies are needed. The clinical development can start once all required preclinical studies are completed.
