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Preclinical research - In vivo - Tracer specificity

Q: What is the general idea of blocking studies?

By comparing the tracer uptake in the presence and absence of the blocking compound , researchers can determine the proportion of the tracer's binding that is specific to the target versus non-specific interactions. Als er bij een blocking agent nog steeds veel opname is dan weet je dat de opname niet specifiek is.

4 important questions on Preclinical research - In vivo - Tracer specificity

What is the general idea of blocking studies?

By comparing the tracer uptake in the presence and absence of the blocking compound, researchers can determine the proportion of the tracer's binding that is specific to the target versus non-specific interactions.

Als er bij een blocking agent nog steeds veel opname is dan weet je dat de opname niet specifiek is.

How can you measure in vivo specificity?

Blocking studies.
Blocking studies are conducted to evaluate in vivo specificity

Injecting an increasing amount of competing nonradioactive ligand before, after, or with the radiotracer
Dose of the competing agent should be below the pharmacological effect of the drug to minimize the pharmacological effect (usually in mg/kg)
Significant decrease of in the accumulation of the radiotracer (often 50– 75% less than the positive control)
For small molecule a non structurally related competitor is usually used

What can be used instead of a nonradioactive ligand in blocking studies?
For small molecules;
For peptide tracers;
For antibody radiotracers;

For small molecules; pharmacologically inactive isomer
For peptide tracers; scrambled peptides
For antibody radiotracers; isotype control antibody

What is important in blocking studies?

Important to make assure that both the radiotracer and the blocking agent have similar pharmacokinetic profiles and have been tested in the same tumor models

The question on the page originate from the summary of the following study material:

Medical imaging

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