At the nanometric scale, all dreams can be achieved. Even those of Paul Ehrlich, who imagined 'magic bullets' at the beginning of the 20th Century: drugs that target infectious agents and spare host cells. Nanomedicine is rising to the challenge, and has been a source of great hope over the past 20 years, with new techniques for diagnosis, therapy and patient monitoring. Now that several products are on the market and a level of maturity has been reached with increasingly complex objects in the laboratories, this revolution now requires additional guarantees of safety and quality, which industry, regulators and metrologists are gradually deploying.
Although nanomedicines have long been unknown to the general public, they came to the forefront in 2020 with the development of messenger RNA vaccines to control Covid-19. Nanoparticles are at the heart of this vaccine technology: mRNA is encapsulated in lipid nanoparticles (tiny fat droplets), which protect it from destruction once in the body and can fuse with the cell membrane for safe and effective delivery. This then allows the cells to produce the antigens and their immune response.
This is the whole principle of nanomedicine. It involves most of the time combining an active ingredient with a nanoscale vehicle, called a 'carrier'. The challenge is to transport the molecule directly to the infected area, to treat it without damaging the healthy cells around it. In other words, to increase the therapeutic effectiveness and reduce the toxicity of treatments. The nanometric size (10-9 m) is indeed the scale of many biological mechanisms in the human body. Nanoparticles and nanomaterials can cross natural barriers and access new drug delivery sites, interact with DNA or small proteins at different levels, whether in the blood or inside organs, tissues and cells.
However, nanomedicine can no longer be seen as a simple drug delivery system, as the nanomaterials themselves can become the active therapeutic principle. The use of a new class of radiation-enhancing nanoparticles, for example, could be a revolutionary approach to the local treatment of solid tumours treated with radiotherapy. Finally, nanotechnology is also of interest in medical imaging. Some nanoparticles with a luminescent core and specific recognition agents can, for example, detect and 'illuminate' cancerous tumours.
Three generations of nanovectors have been developed (1) :
Until ten years ago, nanomedicine was considered mainly in research laboratories. As explained by the ETPN, it has now already made a concrete difference at the clinical level in the treatment of cancer and other diseases and has reached a new level of maturity (1). Various formulations are already approved by regulators for cancer treatment, iron replacement therapies, anaesthetics, fungal treatments, macular degeneration and rare genetic diseases. In the last three years alone, the European Medicines Agency (EMA) has approved three new solutions, accelerating the ongoing revolution:
Meanwhile, there are now more than 400 clinical trials around the world focusing on therapy and diagnostics, a sign of the sector's dynamism.
However, the LEEM (French Pharmaceutical Companies Association) stresses certain obstacles that need to be overcome, in particular through the creation of a network with qualified methods to answer the quality and safety issues raised by the use of nanotechnologies in medicines.
For their part, researchers feel the need for reliable methods to characterise the physicochemical properties (physical quality attributes) that influence the safety and efficacy of nanotechnology-based medical products. As one of the pioneers of nanomedicine, Patrick Couvreur (Institut Galien Paris-Saclay), explained: (4) : « We recently discovered that the shape of nanovectors modifies the distribution of the drug in the body. ».
As for the European Medicines Agency (EMA), it expresses its reservations in the strategy document EMA Regulatory Science to 2025 (5) : « The pace of innovation in the field of nanomedicine has accelerated dramatically in recent years and regulators must be prepared to support the development of increasingly complex medicines. [There is a need to] develop and standardise new test methods to assess the quality and safety of nanomedicines. »
To be placed on the market, a nanodrug must meet the same criteria for safety, efficacy and pharmaceutical quality as any other drug. But because of its structural complexity, its evaluation poses substantial analytical challenges, compared to molecular or biological drugs. The EMA and the Food and Drug Administration (FDA/USA) have defined a list of quality attributes considered relevant (6): particle size, particle size distribution and polydispersity, surface charge and properties, drug charge and release profile, and complex chemical and physical core-shell structure. However, validated and standardised characterisation methods are needed to measure these accurately and in a comparable way. Only comparable data of high metrological quality can facilitate the regulatory process and the clinical translation to practitioners and patients. praticiens et patients.
To identify which characterisation methods should be developed and standardised, the REFINE European project, funded under the Horizon 2020 programme, compared the information required for nanotechnology-based health products with existing methods and regulatory needs. This work, the results of which were published in 2021 (6), will help guide standardisation efforts in response to methodological gaps identified in five main areas:
Various R&D projects have already led to recommendations for the characterisation of extracellular vesicles (EVs). These are promising for regenerative medicine, because of their ability to cross biological barriers (particularly blood-brain barriers) and to deliver molecules to certain cells to modify their activity. They also have the advantage of low immunogenicity (which avoids an immune response that neutralises the therapeutic activity) and high engineering potential (addition of targeting agents, etc.).
At the end of 2021, the Extracellular Vesicle translatiOn to clinicaL perspectiVEs group - EVOLVE France, thus published a summary document (7) on the development of EV-based nanomedicines, with recommendations for manufacturing, quality control, analysis, non-clinical development and clinical trials, in accordance with current European legislation. In particular, it makes recommendations on :
For their part, the European METVES (2012 - 2015) and METVES II (2019 - 2022) projects, financed under the EMPIR programme organised by EURAMET, have provided initial metrological responses. METVES II, to which LNE is contributing, focuses more specifically on the pre-standardisation of EV concentration measurements, by developing reference materials containing stable particles whose concentrations, fluorescence, refractive indices and sizes are close to those of EVs.
As part of the new European Partnership on Metrology (EPM), which is taking over from EMPIR, LNE is coordinating in 2022 a new project proposal entitled “Metrology for Nanotherapeutics” (8) under the "Metrology for Health" call.
This project aims to develop and validate different analytical approaches related to the methodological gaps identified by the REFINE project (size, surface properties, drug loading and release, kinetic properties in complex biological media) in the case of metal oxide nanoparticles and lipid nanoparticles.
A second call on "Metrology for Health" is planned for 2026, and pre-normative calls are organised every year to support the development of testing standards.
In parallel with these R&D initiatives, characterisation infrastructures make it possible to create bridges between regulators, metrologists and standardisation bodies. The result is harmonised and validated test methods to support industry in meeting regulatory requirements and innovation challenges.
In the United States, the National Cancer Institute's Nanotechnology Characterization Laboratory (NCI-NCL) was the first infrastructure of its kind in 2004, set up in collaboration with the FDA and the NIST (US National Metrology Institute). Europe followed in 2015, with the creation of the European Nanomedicine Characterisation Laboratory (EUNCL), which however did not survive the end of the project that set it up. In addition to providing expertise in nanodrug characterisation, these structures develop numerous Standardised Operational Procedures (SOPs) available to stakeholders.
LNE's advanced characterisation infrastructures (metrological AFM, CARMEN, MONA and NAEL platforms) and the metrology expertise of its teams enable nanomaterials used in nanomedicine to be detected, characterised and quantified. Whether in drug formulations, biological matrices, cells or tissues.
More recently, in 2021, in order to support dialogue between scientists from industry, regulatory and research backgrounds, the NPL (UK National Metrology Institute) organised a workshop entitled "Advancing Measurement Technologies and Standards for Nanomedicine" (9), in collaboration with NIST, JRC (EU) and AstraZeneca, on recent advances and practical challenges on these characterisation issues. This enabled the identification and prioritisation of specific methods and standards needed to move forward in light of new emerging priorities. Lipid-based delivery systems were identified as a priority for standardisation and development of reference materials. These systems play a key role in Covid-19 vaccines and cancer treatment. cancer.
Supported by LNE, the NanoMesureFrance Centre will be operational by the end of 2022. In response to the French national desire to structure an industrial sector for nanomaterials, it will bring together in a single Hub a network of stakeholders with complementary skills: producers and users of nanomaterials, characterisation instruments manufacturers, service providers, academic platforms and research institutes. The aim is to create conditions conducive to the development of applications based on nanomaterials for multiple fields, including nanomedicine, by working on information sharing and the establishment of collaboration to make progress on the development, validation and harmonisation of characterisation and testing methods according to the priorities defined by the national and European regulatory authorities.
Today, standardisation is already progressing, even if at the European level, the European Committee for Standardization (CEN) has not yet launched anything on nanomedicine. It has however expressed the will to initiate activities through the TC 352 Nanotechnologies, while the European Pharmacopoeia (10) also considers the subject to be central. This is not the case at the international level where multiple activities are already underway.
For example, ASTM/E56 Nanotechnologies is working to produce several documents on the analysis of Liposomal Drug Formulations using Multidetector Asymmetrical-Flow Field-Flow Fractionation (WK68060) or the characterisation of Encapsulation, Extraction, and Analysis of RNA in Lipid Nanoparticle Formulations (WK75607). Or it has developed three standards - recently approved - on the quantification of lipids by liquid chromatography coupled to mass spectrometry, evaporative light-scattering or charged aerosol detector.
For its parts, ISO/TC 229 Nanotechnologies is developing a standard on liposome terminology (ISO/AWI TS 4958), and another on RNA-containing nanoemulsions.
Finally, within the VAMAS (Versailles Programme on Advanced Materials and Standards), an international initiative active in the field of pre-standardisation for advanced materials in which LNE represents France on the Steering Committee, the TWA40 Working Group is interested in the physico-chemical profiling of viral-like particles as reference materials for vaccine development and viral particle diagnostics.
As a participant in the work carried out within ISO/TC 229 and ASTM/E56, as well as in discussions at European Pharmacopoeia level (10), LNE contributes to standardisation efforts and guidance documents on liposomes and lipid-based formulations. To be continued.