Molecular Imaging in Medicine
- Drug lag and molecular imaging
- Visualizing biodistribution of drug candidate compounds by radionucleotide labeling
- Quantitative evaluation of drug candidate compounds
- Clinical trials of molecular imaging · Application to clinical settings
- Construction of PET / SPECT microdose clinical test systems
Promote Translational Research of drug development
In the field of drug discovery, it takes usually huge amount of time and money until a drug can be developed and reach patients. This problem is called drug lag. Molecular imaging can be used as a drug-discovery process, during which the movement of molecules is visualized and the function of the molecules is evaluated without changing the structure of the drug candidate compounds or derivatives. It is also possible to efficiently evaluate the pharmacokinetics and efficacy of a molecule of interest in a small number of animals or small population of test subjects.
Scintigraphy (SPECT) and positron emission tomography (PET) utilize photons emitted by radionuclides to image molecules of interest in a quantitative manner and at physiological states. For example when bioimaging the distribution of donepezil hydrochloride (Aricept ®), a medication for the treatment of dementia, in rats and comparing it with the distribution in healthy people (Figure 1), it became apparent that the original target organ, the brain, was barely labeled, whereas in a species-specific manner heart and liver were labeled.
For radioactive drugs and their derivatives, it is possible to quantitatively measure tissue distribution using mathematical models by dynamically measuring bio-distribution and dosage. For example during boron neutron capture therapy of refractory malignant tumors, we used B-10 BPA-fructose (fructose) derivative F-18 FBPA as a therapeutic agent to measure the distribution of B-10 in normal organs. We quantitatively measured (Figure 2) and found that the level of damage of normal organs when irradiated with neutrons depends on the time of irradiation. Our data indicated that especially the urinary tract can be damaged during this therapy if not timed properly.