Novel and emerging medical radionuclides

This 3D graphic shows the SINQ that aids in the manufacture of radionuclides for medical purposes. Photo credit: Mahir Dzambegovic

Nuclear therapy and molecular imaging are widely used in hospitals for new promising medical procedures. They can drastically improve the outcome of many diseases and, in particular, enable the treatment of disseminated cancer. However, their effective development has long been limited by the difficult access to radionuclides, which are not yet commercially available. This should change with PRISMAP – the European program for medical radionuclides. The Paul Scherrer Institute PSI, which belongs to PRISMAP, is one of the suppliers of radionuclides.

In nuclear medicine, a radioactive substance is introduced into a patient and finds its way to certain biological targets in the body. Depending on the radioactive properties of the radionuclide, it can emit radiation that can be detected with external detectors in order to make the distribution of the nuclide in question visible (SPECT, PET imaging); alternatively, it can emit charged particles such as α- or β-particles, which use their energy locally (in the range from micrometers to a few millimeters, e.g. for the treatment of cancer with targeted radionuclide therapy (TRNT).

Of the more than 3,000 different radionuclides that scientists have synthesized in the laboratory, only a handful are regularly used for medical procedures, mostly for imaging, although interest in TRNT has increased in recent years. One of the main limits to the development of novel radiomedical products is access to radionuclides during the development and early biomedical research phase. Within the framework of PRISMAP – the European program for medical radionuclides, this development phase can be made possible by giving medical researchers access to novel radionuclides of high purity.

Production of radionuclides

The radioactive elements used in nuclear medicine are of course not available and must be synthesized in the laboratory. There are two main routes: neutron irradiation in a nuclear research reactor and proton, deuteron or alpha irradiation with a particle accelerator. The size and energy of the particle accelerator determine which radionuclide can be produced: In many hospitals there are small, compact machines that enable access to the radionuclides used today. To produce new types of radionuclides, however, more energy-rich machines are required that are currently not available.

Purification of radionuclides

PRISMAP consortium specifically highlighting the facilities providing access to radionuclides and biomedical research facilities in development to expand the network’s capabilities in the near future. Photo credit: SCIPROM 2021

New challenges arise in the production of these novel radionuclides: One is the co-production of undesired radioactivity, which affects the quality of the drug, has undesirable effects on the patient and can make waste disposal in a hospital environment seriously difficult. New cleaning techniques are required to address this. Within PRISMAP, techniques based on physical mass separation and radiochemistry are being developed in order to achieve high-purity radionuclide production that is suitable for pharmaceuticals.

Access and Translational Research

To support ongoing research across Europe and beyond, PRISMAP will provide immediate access to novel radionuclides. A single-access platform was set up via their website, on which the production and support options are presented.

A network of world-leading European institutions, including nuclear reactors, medium and high energy accelerators and radiochemical laboratories, has been established to offer the most comprehensive catalog of radionuclides for medical research. Mass separation is available at CERN MEDICIS to enable the physical separation of isotopes of an element. This is complemented by a network of biomedical research institutions that can take on external researchers to carry out their research in the vicinity of the production site if the radionuclides are not suitable for a long transport to their facility or if the European approval for novel radionuclides has not yet been obtained.

Access to radionuclides and associated facilities is granted on the basis of a selection of excellence by applying for access to radionuclides and, if applicable, to the complementary biomedical facilities via the PRISMAP online access platform. A selection committee consisting of experts from the fields of radionuclide production, molecular imaging and radionuclide therapy selects the best projects from the applicants. The first call for proposals will be published before the end of 2021 for applications in the first quarter of 2022. It is open to anyone interested.

Look to the future

Novel and emerging medical radionuclides Paul Scherrer Institute, Injector 2 cyclotron with separated sectors (left) and SINQ neutron irradiation system (right). Photo credit: Paul Scherrer Institute

In the rapidly developing landscape surrounding nuclear medicine, PRISMAP is also geared towards the future. The European Commission is committed to tackling the societal impact of cancer through the European Plan to Fight Cancer and in particular the SAMIRA Action Plan presented earlier this year, including the establishment of a European Radioisotopental Initiative. The PRISMAP consortium of 23 academic and research institutions across Europe is investigating the development towards upscaling the production of these novel radionuclides in the form of novel production technologies, new cleaning methods and feasibility studies that show the development of new treatments from test beds to patient care that are directly in incorporate this Europe-wide plan.

As a consortium serving an incipient research community, PRISMAP aims to become a more established community and welcome new facilities to expand the capabilities of the program. New plants are in sight, such as the Jules Horowitz reactor in CEA Cadarache (France), the ISOL (at) MYRRHA mass separator plant at SCK CEN (Belgium), the new SPES accelerator complex in the Legnaro National Laboratories of the INFN (Italy), the European Spallation Source in Lund (Sweden) and, finally, both the new SPIRAL2 facility in GANIL (France), which recently accelerated its first jets, and the FAIR facility in GSI (Germany), the construction of which is proceeding. These new facilities will directly benefit from PRISMAP’s insights to increase production capacity across Europe.

The collaboration between research hospitals and metrology institutes generates and compiles new data so that the novel radionuclides can be used immediately and smoothly in medical environments. Any new knowledge will be used to create new teaching material for professionals in the different areas of this multidisciplinary field, to train the next generation of professionals and to advise the European Commission on these emerging radionuclides.

The Paul Scherrer Institute (PSI) is one of the main partners of the PRISMAP consortium. With their large research facilities SINQ (Swiss Spallation Neutron Source) and Injector 2 as well as the irradiation station IP2, researchers produce radionuclides for medical purposes. Radionuclides are coupled to a molecular complex, selectively dock on tumor cells in the body and can destroy them with their particle radiation. The Center for Radiopharmaceutical Sciences is one of the few research organizations in Switzerland that is able to develop radiopharmaceuticals not only for research purposes but also for clinical studies. The registration process for clinical studies with the promising therapeutic radionuclide terbium-161 is currently ongoing. In addition, as part of the new Swiss Infrastructures (BFI) project IMPACT (Isotope and Myon Production with Advanced Cyclotron and Target Technology), the High Intensity Proton Accelerator Facility (HIPA) is to be upgraded for the period 2024 to. planned for 2028 to enable the production of new radionuclides for diagnostics and therapy

Nuclear medicine research is a truly multidisciplinary approach, and to move forward, bridges must be built between physicists, engineers, radiochemists, inorganic chemists, structural biologists, clinicians, medical physicists, dosimetricians, pharmacologists and oncologists. PRISMAP – The European program for medical radionuclides will certainly support the implementation of a multidisciplinary working concept in practice.

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