14C Radiolabelled Microtracers

AMS can be used analytically in any investigation that employs a 14C radiolabel. 14C microtracers refer to a low level administration of [14C] in combination with a full therapeutic, pharmacologically active dose of drug. We then employ the exquisite sensitivity of AMS as the analytical platform. Typically, the upper limit of radioactivity dosed is ~1 µCi per subject. At this level in human, dosimetry data is not required.

How does a microtracer differ from a microdose?

By definition (ICH M3 R2 Section 7.1), a microdose is a limit on mass dose of drug administered equivalent to ≤100 µg or ≤1/100th of the pharmacological active dose (whichever the lower). Therefore, microdose studies are conducted at a sub-therapeutic dose of the candidate drug(s) in development and can either be labelled with 13C employing LC-MS/MS analysis or with 14C employing AMS analysis.

Microtracers, conversely are a low tracer dose of radioactivity and a low mass dose of 14C-API combined with the “cold” API with the normal therapeutic dose. AMS-enabled 14C microtracer studies are therefore conducted at a full pharmacological dose of the candidate drug(s) in development.

Disposition of Radiolabelled Biologics
3H and 14C Radiolabels (RadioTag)
Microdosing Phase 0


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