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TRIUMF Submits Plans for Medical Isotope Alternatives

17 September 2009

With the continued uncertainty in the supply of medical isotopes, especially Technetium-99m (99mTc: the most widely used radioisotope for diagnosing diseased organs), clinical and biomedical research communities have begun to look for alternative ways to produce the 99mTc needed for vital clinical procedures and also to explore the potential of alternative medical isotopes to replace 99mTc as the radiopharmaceutical label in clinical practice.

In order to promote this development, the Canadian Institutes of Health Research (CIHR) and the Natural Sciences and Engineering Research Council (NSERC) established a funding opportunity ($6million total) in the form of an operating grant for alternative radiopharmaceuticals for medical imaging. Tuesday, September 15, 2009, marked the deadline for proposal submissions, two of which have been put forward by TRIUMF: one for cyclotron-based production of Tc-radioisotopes and the second to prepare and evaluate three classes of Gallium (Ga) compounds for use as radiopharmaceuticals as alternatives to existing Tc-radiopharmaceuticals.

The first proposal, submitted by 10 applicants with François Bénard (BC Cancer Agency) and Tom Ruth (TRIUMF) as Co-Principal Investigators, proposes an alternative way to produce 99mTc using conventional medical cyclotrons--a means of production, the authors argue, which has long been neglected, due to the widespread availability of 99mTc generators available from fission production of Molybdenum-99 (99Mo).  A benefit of this alternative is that it would allow continued use of all existing radiopharmaceuticals designed for 99mTc in nuclear medicine.

In addition, the production of 94mTc (a positron emitter with a 53 minute half-life)  is proposed so that in combination the two Tc-radioisotopes can make use of the existing Tc-based radiopharmaceuticals for PET as well as SPECT imaging , and assess the suitability of these Tc isotopes for eventual human use. The proposal represents 5 institutions across Canada: TRIUMF and BCCA (Vancouver, BC); Cross Cancer Research Institute (Edmonton, AB); Lawson Health Research Institute and St. Joseph's Hospital (London, ON); and Université de Sherbrooke (Sherbrooke, PQ).

The second application proposes to synthesize Gallium-68 (68Ga) and Gallium-67 (67Ga) radiopharmaceuticals as alternatives to the 99mTc radiopharmaceuticals currently in use. The group intends to produce three classes of compounds: hydrolytic colloids, functionalizable bidentate, and multifunctional polydentate Gallium complexes for use as radiopharmaceuticals. The project will focus on applications in lymphatic mapping, red blood cell labeling, renal imaging, and infection, lung, and cerebrospinal fluid studies.

A benefit of this alternative is that 67Ga will allow users the option of imaging using single photon emission computed tomography (SPECT) while 68Ga provides a generator produced positron emission tomography (PET) isotope that enables access to these agents in facilities without cyclotrons. This project will be a multi-centre study involving the UBC Chemistry Department, TRIUMF, and the BC Cancer Research Centre and its Advanced Therapeutics Department. 67,68Ga will be supplied to the project by TRIUMF's long-standing research and development partner, MDS-Nordion, a leading global provider of medical isotopes and radiopharmaceuticals in molecular medicine.

As one of Canada's premier centres of excellence for nuclear medicine, TRIUMF is poised to continue its contribution to the advancement of existing radiopharmaceuticals and play its role in alleviating the current shortage of medical isotopes to improve the care of patients in Canada and worldwide. The total amount available for this CIHR initiative is $6 million, with $3 million coming from CIHR and $3 million from NSERC. Grants will be awarded for a period of up to 2 years, with funding starting October 31, 2009, after the successful applicants have been announced on October 25, 2009.


-- Meghan Magee, Communications Assistant