The Signatories to this ‘Memorandum of Understanding’, declaring their common intention to participate in the concerted Action referred to above and described in the ‘Technical Annex to the Memorandum’, have reached the following understanding:

1. The Action will be carried out in accordance with the provisions of document COST 299/06 ‘Rules and Procedures for Implementing COST Actions’, or in any new document amending or replacing it, the contents of which the Signatories are fully aware of.
2. The main objective of the Action is to improve the potential of cancer therapy through the development and application of innovative vectors labelled with therapeutic radionuclides for ‘targeted radionuclide therapy’ of disseminated cancer.
3. The economic dimension of the activities carried out under the Action has been estimated, on the basis of information available during the planning of the Action, at approximately 60 million EUR in 2006 prices.
4. The Memorandum of Understanding will take effect on being signed by at least five Signatories.
5. The Memorandum of Understanding will remain in force for a period of four years, calculated from the date of the first meeting of the Management Committee, unless the duration of the Action is modified according to the provisions of the document referred to in Point 1 above.

COST ACTION BM0607
Targeted Radionuclide Therapy (TRNT)

A. ABSTRACT AND KEYWORDS

Molecular targeted radionuclide cancer therapy is becoming of increasing importance, especially for disseminated diseases. Systemic chemotherapies often lack selectivity; targeted radionuclide therapy has important advantages as the radioactive cytotoxic unit of the targeting vector is specifically directed to the cancer, sparing normal tissues. The basis of this COST Action is the great potential of targeted radionuclide therapy using a variety of vectors and radionuclides. This Action brings together the different disciplines involved and provide a reliable and rapid means for developing new (fundamental) knowledge, method standardization and products while promoting transfer of technologies.
This Action on cancer therapy using innovative targeting nanomedicines is highly multidisciplinary: nuclear medicine physicians, clinical oncologists, surgeons, physicists, radiobiologists, (in)organic chemists, radiochemists, radiopharmacists, pathologists and scientists from biomics participate in it. They define innovative new targets for cancer therapy, develop lead compounds and new radiolabelled ligands as vectors, perform molecular imaging and biologic testing, develop improved software and protocols for dosimetric calculations and select new vectors for early human use.
The Action facilitates the cooperation of more than 100 scientists from 21 countries; the economic dimension amounting to about 400 man years.

Key words: targeted radionuclide therapy, ligand, radiolabelling, target selection, cancer

B. BACKGROUND

Surgery, external beam radiation and chemotherapy have been the mainstays of human cancer treatment. In systemic disease, chemotherapy is usually the only therapeutic option. However, because of its very low tumour selectivity, systemic chemotherapy is often limited by serious side effects to normal tissues. A consequence is the use of suboptimal doses that often results in therapeutic failure and the development of drug resistance. Tumour-targeting therapeutics have therefore gained momentum. In the last 10 to 15 years the understanding of many diseases has seen enormous advances as a result of important developments in molecular biology, genomics, proteomics, protein engineering, etc. Importantly, a renaissance in the use of monoclonal antibodies as targeting agents for cancer has emerged; an example is Rituximab (Mabthera®), targeted against the CD20 antigen expressed by lymphoma cells. In parallel with Rituximab, a ‘new’ therapeutic approach in which the murine version of Rituximab is linked to the therapeutic radionuclide 90Y was developed. This radiopharmaceutical, Zevalin®, is FDA-approved and registered in the European Union for treatment of patients with chemotherapy refractive B-cell lymphoma (recurrent follicular lymphoma). Zevalin® was the first radiolabelled monoclonal antibody approved for radioimmunotherapy. This approval was swiftly followed by that of the radiopharmaceutical Bexxar®, a 131I-labeled anti-CD20-antibody, which showed similar efficacy in relapsed patients with follicular lymphoma. The high efficacy of these two agents in relapsed patients has subsequently led to clinical trials using radioimmunotherapy for first line treatment. Using Bexxar® in 76 patients with stage III or IV follicular lymphoma as first line treatment, 95% of the patients responded and 75% had a complete response. These excellent results indicate the potential of targeted radionuclide therapy for treating tumours even when these have failed to respond to conventional chemotherapies.
New radiolabelled monoclonal antibodies for the effective treatment of solid tumours along with pretargeting strategies are also being developed.

In continuation of this, new targets are defined, new lead ligands need to be developed and tested in special preclinical models before entering the clinic.

Why a COST Action?

The basis of this COST Action is the great potential of targeted radionuclide therapy using a variety of vectors and radionuclides. This Action brings together the different disciplines involved and provides a reliable and rapid means for developing new (fundamental) knowledge and products while promoting transfer of technologies.

This Action combines skills in different fields. A multidisciplinary effort determines the form of organization; this is reflected in the formation of 4 working groups (see below). The complexity of the different tasks necessary to identify, develop and evaluate new therapeutic radiopharmaceuticals, (animal) therapy models and dosimetry methods makes it impossible for any single group to undertake the complete range of work in a reasonable time-frame. The networking approach of this Action allows each group to focus on tasks where it has expertise and to benefit from the output of the others.

This COST Action creates a unique opportunity to exchange knowledge between these multidisciplinary groups, by supporting meetings, conferences, short term scientific exchanges and outreach activities.

This Action also covers the gap in defining standards for synthesis and testing procedures of the vectors to be developed/applied. Very often these methods are not handled in exactly the same conditions in laboratories. The multidisciplinary aspect of the elements of the Action requires a real collaboration between disciplines. Otherwise, comparison of results or drawing of conclusions is very difficult.

In this Action there is a strong complementarity with ongoing or planned research in the EU Framework Programme. Radiolabelled probes for imaging purposes are being developed and applied in e.g. the 2 Networks of Excellence EMIL and DIMI or in the COST D38 Action . These probes could also be very useful for therapy (the aim of this Action) after radiolabelling with therapeutic radionuclides. Several labs interested in this Action cooperate actively in one of these programmes.

This Action also provides short-term scientific missions to educate junior scientists. These provide support for training in specific skills, also by sharing facilities and equipment, and assist the development of joint research projects. A particular effort is made to imply youngsters at the MC and WG levels, both for scientific as well as managerial activities. The research groups interested in this Action provide the different levels of expertise and the capacity required for these training sessions.

This Action has been received with enthusiasm. Initial discussions with potentially interested research groups showed an overwhelmingly positive response to the idea: more than 50 research groups originating from 21 countries have already indicated interest in participating. This Action deepens cooperation in Europe. The Therapy, the Radiopharmacy and the Dosimetry Committee of the European Association of Nuclear Medicine (EANM) also committed themselves to be an active part of the Action.

C. OBJECTIVES AND BENEFITS

The main objective of this Action is to improve the potential of cancer therapy through the development and application of innovative vectors labelled with therapeutic radionuclides for ‘targeted radionuclide therapy’ of disseminated cancer.

The vectors used may be based on monoclonal antibodies (or derivatives thereof), peptides, peptidomimetics, affibodies, amino acids or small organic molecules with well-defined tumour associated molecular targets.
Besides the therapeutic probes, also imaging probes based on the same vectors are developed/applied in order to allow pre-therapeutic imaging for patient-specific dosimetry and therapy planning as well as for therapy monitoring. Recent advances in proteomics and genomics help to define new target molecules. Innovations are expected in such areas as ligand design, chemical ligation methods, radionuclide production, radionuclide generator design, etc.
Although European laboratories have been responsible for many of the developments in targeted radionuclide therapy (including the discovery of monoclonal antibodies), the only two registered innovations in the field have come from the US. Therefore, it is crucial to develop stronger links amongst European scientists. The early involvement of the pharmaceutical industry/small companies with special expertise is fostered, also to promote implementation of the processes by insuring reliable, safe and standardized (e.g. GLP, GMP) methods.

The Action is highly interdisciplinary and includes nuclear medicine physicians, clinical oncologists, surgeons, physicists, radiobiologists, (in)organic chemists, radiochemists, radiopharmacists, pathologists and scientists from biomics. This combination results in a better insight into all aspects of the field ‘Targeted Radionuclide Therapy’. The Action puts specific emphasis on the translation of preclinical research (i.e. new targets, radionuclides and compounds,dosimetric models and cellular/animal models) into the clinical practice of targeted radionuclide therapy.
The techniques developed have an impact on the design of other ligand-targeted therapies such as ligand-toxin and ligand-chemotherapeutic agent conjugates.

Direct Scientific Objectives:

• To define new targets and new vectors
• To synthesize and radiolabel new vectors
• To evaluate the new vectors in e.g. pharmacokinetic, dosimetric and therapeutic studies and using animal imaging instrumentation
• To advance targeted radionuclide therapy to a high scientific and technical status

Additional Objectives:

• To evaluate, coordinate and disseminate the acquired knowledge
• To support the establishment of new SMEs, new (standardized) methods, new networks, etc
• To contribute to/stimulate training through STSMs, participation of young scientists, etc.

The ultimate goal and benefit of the Action is the improvement of patient care; especially those patients who currently lack any effective therapy options for the treatment of their condition.

D. SCIENTIFIC PROGRAMME

The principle strategy to improve cancer selectivity is to couple therapeutic agents to tumourtargeting vectors. In targeted radionuclide therapy, the cytotoxic portion of the conjugates normally contains a therapeutic radiometal immobilised by a bifunctional chelator.
The Action uses as ligand-targeted therapeutics vectors coupled to Auger-, alpha- and/or betaemitting radionuclides. An advantage of using radiation instead of chemotherapeutics as the cytotoxic agent is the so called ‘crossfire effect’. This allows sterilisation of tumour cells that are not directly targeted due to heterogeneity in target molecule expression or inhomogeneous vector delivery. Before the targeting ligands can be selected, the target molecule on the tumour has to be selected. It should be uniquely expressed, or at least highly overexpressed, on or in the target cells relative to normal tissues. The target should be easily accessible for ligand delivery and should not be shed or down-regulated after ligand binding. An important property of a receptor (or antigen) is its potential to be internalized upon binding of the ligand. This provides an active uptake mechanism and allows the therapeutic agent to be trapped within the tumour cells.

Molecular targets of interest
According to the current experience of the participants with therapeutic agents (peptide and monoclonal antibody derived vectors), the Action starts with those extracellular targets, but considers for further developments also intracellular targets. Extracellular targets are:

Receptors: Optimal targets that are known to several of the interested laboratories are G-protein coupled receptors, overexpressed on many major human tumours. The prototype of these receptors are somatostatin receptors which show very high density in neuroendocrine tumours, but there are many other most interesting receptors to be applied for the aims of the Action. The targeting ligands for these receptors are radiolabelled regulatory peptides and their metabolically stabilised analogues. Some of the laboratories, participating in the new Action, have already successfully collaborated in this field.
Antigen epitopes: Antibodies, as unlabelled biological drugs, are becoming of increasing interest. They exert an antibody-dependent cellular cytotoxicity which leads to lysis of tumour cells. Radiolabelled versions of these (and other) antibodies are being developed worldwide. The disadvantage of the long circulating time of antibodies can be solved by engineering fragments such as diabodies, bivalent single chain variable fragments (scFv), minibodies or by pretargeting approaches.
Transmembrane transporters: Other interesting targets are transporters for radiolabelled amino acids and nutrients. Cancer cells require an increased supply of many such nutrients and obtain these by increased expression of some types of amino-acid transporter. A more detailed analysis of the relationship between amino-acid uptake and transporter expression in normal and malignant cells would be very valuable in identifying the clinical therapeutic potential of this class of tracer.
Extra-cellular matrix: Recently, another relevant class of target antigens has raised interest. Lectins, or carbohydrate binding proteins, recognize specific oligosaccharide structures on glycoproteins and glycolipids. It is well known that protein and lipid glycosylation are consistently altered in cancer cells for the aberrant activity of specific glycosyltransferase and glycosydases. Experimental evidence demonstrated that tumour growth and progression may depend, at least in part, on the presence of altered glycoproteins on the cell surface, which can mediate aberrant receptor-ligand interactions.

Vector synthesis and labelling
Novel ligands based on peptides, affibodies and scFv are developed by phage display techniques (techniques used to display a protein or peptide on the surface of a bacteriophage containing the gene that encodes the displayed peptides or proteins), peptides can also be synthesised by conventional organic synthetic techniques (this may be preferable if good lead ligands exist) and optimised by parallel synthetic approaches or via combinatorial libraries. Subsequently, modification of the ligands for labelling and the development of labelling protocols is the work of organic/inorganic chemists and radiopharmacists.
Multicentre-efforts are necessary to improve the radionuclide availability by either sharing resources for the use and optimization of handling of generators or by transferring radionuclideproduction knowledge. For efficient biochemical targeting the radiochemical labelling strategies have to be optimized. These optimization tasks need a network of laboratories sharing knowledge and resources, since individual non-commercial laboratories cannot develop and compare the multiple possible pathways, which need to be tested against each other. New methods of chemical ligation allowing quick and efficient labelling are also developed. In addition, modern aspects of optimising drug delivery and of utilising gene transfer are considered. Newly developed ligands that enter into clinic studies are prepared in adherence to The rules Governing Medicinal Products in the European Union.
These tasks are performed by WG1 and WG2.

Dosimetry, Radiobiology, Radiation safety
An important issue in using radioactive probes in therapeutic (and diagnostic) procedures is that of safety. Careful dosimetric protocols/calculations of internal emitters are important to understand the relationships between dose, efficacy and toxicity. This requires a close working cooperation with radiation physicists and radiobiologists as well as clinicians.
The availability of radionuclides, especially those with ‘ideal’ radiobiological properties, contribute to the success of targeted radionuclide therapy, but also to the understanding how radiation energy, physical half-life, and particle range influence radiobiological effects (treatment efficacy). Translation of the dosimetric calculations in animal models versus clinical practice is pursued; the feedback of practical experiences is used to amend or modify models where appropriate.
The development and optimisation of radionuclide production, in particular radionuclide generator systems, also forms a part of this research. The work described in this paragraph is performed by physicists, nuclear chemists, radiochemists, radiobiologists and nuclear physicians within WG3.

Pharmacology, Animal Models, Clinical Practice
In vitro assays need to be developed and standardized. Cytotoxicity needs to be evaluated in cell culture models and the therapeutic potential as well as toxicity at the level of the whole organism has to be documented in animal models. Imaging probes based on the therapeutic vectors are needed to determine the phenotype of the respective tumours, in dosimetry, in therapy follow-up, to determine clinical endpoints, and to serve as surrogate markers of efficacy. The probes and their effects may be assessed by non-invasive techniques, e.g. optical imaging, SPECT, PET, CT and MRI. High-quality PET, SPECT, CT and MRI are available for animals (mice, rats, and larger animals), in parallel to their counterparts in the clinic, facilitating the translation of animal results into clinical practice. Relevant animal models are used: syngeneic tumours, orthotopic sites of implantation and models of small size metastases.

One early objective of the consortium is to select a few of these models to run comparative experiments in several institutions. Quantification of the new radiolabelled vectors using these techniques in animal dosimetry and pharmacology is validated against classical invasive methods. The final aim is to bring some of these compounds into the clinic in order to treat patients with either no or limited alternative therapy options. These experiments are performed within WG4.
Physicians have to be involved early on and in every step of development to jointly develop targeting vectors of highest possible relevance.

E. ORGANISATION

This Action combines skills in the different fields of target definition (by pathologists, proteomic researchers, etc) in (radio)chemistry (by organic/inorganic synthetic chemists), radiopharmacy, physics, biology, medicine (nuclear oncology, nuclear medicine, oncology/haematology) and imaging technologies. A coherent collaboration between these disciplines is aimed to lead to real progress in the development and optimisation of new approaches to targeted radionuclide therapy.

The administrative organisation of the Action is based on a Management Committee (MC) with support from the Scientific Secretariat in Brussels. The MC defines the strategy of the Action, supervises the work and re-evaluates the work programme when needed. A Steering Committee (SC) / Core Group within the MC includes the chair, secretary and the Working Groupleaders. They are elected in the kick-off meeting. This Steering Committee organises the STSMs, the annual workshops and communication items.

A multidisciplinary effort determines the form of organization; this is reflected in the formation of 4 working groups (WG). Each WG is led by a coordinator.

A communication structure to be used between these different components of the Action is as follows:

WG1:

Search for New Targets and New Vectors:
Target definition/lead ligand definition
Methods

• Genomis
• Proteomics
• Analysis of tumour section using e.g. autoradiography

WG2:

Ligand Development: amino acids, mAbs (fragments of mAbs, diabodies, etc) peptides, peptidomimetics, pretargeting approaches, labelling protocols

Methods

• Phage display
• Combinatorial methods
• Parallel synthesis
• Organic synthesis
• Coordination chemistry
• Labelling protocols

WG3:

Dosimetry/Radiobiology/Production of Radionuclides and Generators

WG4:

Pharmacology/Cell Biology/Animal Models/Preclinical Studies Using Animal PET, PET/CT; SPECT/CT/Development of Dosimetric Models

Upon approval of this Action, the composition of the MC is established and their first task is to finalise the scope of the research around which the WGs are to be organised. The MC is also responsible for appointing coordinators for each of the WGs and for stimulating a well-balanced participation of research teams in each WG.

The Action organises at least one annual workshop at which both the status and the progress of the Action is to be monitored. A series of regular check points are to be defined against which the progress of research projects of the WGs can be assessed. Whenever possible, this workshop is to be arranged to coincide with larger meetings in the field (for example annual congresses in Nuclear Medicine or Oncology) to increase the visibility of the Action. Links are established with other interested groups such as the Therapy, the Radiopharmacy and the Dosimetry Committee of the European Association of Nuclear Medicine. These workshops include state-of-the-art lectures and educational parts in the main areas of interest to increase the knowledge of all participants, including the junior scientists.
WGs meet independently once or twice a year, when possible in connection with the MC-meeting, and as a pre- or post-congress meeting of one of the larger conferences (eventually with the participation of invited experts). The Action provides short-term scientific missions (STSMs) for junior scientists. The STSMs provide support for training in specific skills and assist the development of joint research projects. Applications for short-term scientific missions are to be assessed by the MC/TC. Furthermore, state-of-the-art lectures and other forms of education at the annual workshop as well as such activities in the WGs are to be organised. Participants produce reports for review by the MC and are encouraged to present results at meetings.
Electronic communication between all participants is also strongly encouraged. The possibility of a dedicated web-site with opportunity for on-line discussions is also to be pursued.

F. TIMETABLE

The duration of the Action is four years. The work plan of the Action can be divided in phases as follows:

Phase 1: (Month 1) MC formation. Inclusion of the most active scientists in the MC.

Phase 2: (Months 2-12) WG formation. The MC reviews the ongoing research in the field and defines the topics and goals of each WG by contacting the respective research groups. The selected WG coordinators prepare a report in which they outline the work plan and the role and expected contribution of the different teams to the research project. Networking the research activities of the WGs is of major importance. This phase involves the set-up of the coordination planning that includes the organisation of STSM, the sharing of technologies among the different platforms, and the exchange of training activities inside the Action. It is important that coordinators and WG members communicate very actively during this period. During the second half of the first year research groups having collaborated before already start working actively together.

Phase 3: (Years 2 and 3) Mid-term Assessment. The MC together with the WG coordinators evaluate the results from the activities of the WGs on the basis of the approved Scientific Programme. Amendments to the work plan of the WGs may be introduced at this stage. The overall assessment and the resulting amendments are to be defined in the annual reports.

Phase 4: (Year 4). Activities leading to the completion of the tasks. On the basis of the continuous monitoring and the feedback from the Mid-term Assessment, the MC together with the WG coordinators are reviewing the initiatives useful for the fulfilment of the tasks of the Action and focus the activities of the working groups in these directions.

The Action ends with a dedicated final conference and the publication of a final report with the results obtained for all groups interested, including the industry.

Overall Timetable

G. ECONOMIC DIMENSION

The following COST countries have actively participated in the preparation of the Action or otherwise indicated their interest: Austria, Belgium, Czech Republic, Denmark, France, Finland, Germany, Greece, Italy, Norway, Poland, Portugal, Romania, Serbia, Slovenia, Spain, Sweden, Switzerland, The Netherlands, Turkey, United Kingdom.
On the basis of national estimates provided by the group leaders of these countries, the economic dimension of the activities to be carried out under the Action has been estimated, in 2006 prices, at approximately 60 million Euro in salary, fellowships, consumables and equipment for the total duration of the Action.
This estimate is valid on the assumption that all the countries mentioned above but no other countries participate in the Action. Any departure from this changes the total costs accordingly.

The complexity of different tasks necessary to identify, develop and evaluate new
radiopharmaceuticals, (animal) therapy models and dosimetry methods makes it impossible for any single group to undertake the complete range of work in a reasonable time-frame. The networking approach of the Action allows each group to focus on tasks where it has expertise and to benefit from the output of the others. A new radiopharmaceutical, dosimetric method or therapy model would be developed most economically and efficiently by collaboration in such a complementary effort. The development of effective new radiopharmaceuticals, dosimetric methods or therapy models would ultimately lead to better treatment strategies for patients with disseminated disease and assist in the development of more effective drugs, with corresponding economic benefits in the prevention of morbid disease or costly treatment. As mentioned above, early involvement of industry is considered with the likelihood of resulting in commercial exploitation of the developments arising from the project.

H. DISSEMINATION PLAN

Members of the MC are expected to take a pro-active role in the dissemination of information about Action events and reports.
All members of the MC are to be linked by e-mail. It is the responsibility of the MC members for each country to maintain and update a list of key laboratories/scientists in that country and ensure that the list is available to other members of the MC. MC members are responsible for ensuring that those interested in the COST Action are aware of activities and reports.
Dissemination of knowledge within the Action is also to be done via the set-up of an Action website and through regular reporting. The website is to be established at the beginning of the COST Action, all activities are to be posted and links are to be established to other related sites. In particular, each WG coordinator summarises the work carried out in the context of the Action every year through a report that is to be assessed by the MC.
The MC ensures close contacts with the European Association of Nuclear Medicine (EANM) and its Therapy Committee by presenting its results at the annual workshop. Representatives of the industry target group are to be contacted personally through the members of the COST-Action and the MC invites representatives of the companies to take part in the annual symposia and as participants and/or invited guest speakers at the WG meetings.
To ensure dissemination of the Action’s results the proceedings of the annual symposia are to be published in peer reviewed journals. Furthermore, papers on relevant results are to be submitted to the respective scientific journals and presented as oral talks and posters on the yearly conferences of EANM and SNM (Society of Nuclear Medicine) and the biannual European Symposium on Radiopharmacy and Radiopharmaceuticals. A list of scientific publications and reviews is to be maintained on the website, with downloadable PDF-files where permitted by copyright restrictions.
This includes both (a) publications of members of the COST Action and (b) publications derived from joint research projects that have developed from the COST Action and include authors from different EU laboratories.
At the end of the Action, the results obtained will be collected in a final report (in a form suitable for publication and wide dissemination) and will be presented in a dedicated Symposium open to scientists interested in the work carried out in the Action.