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In-Human Microdosing

Prof G.M. Van Dam, MD, PhD

TRACER applies, as part of its unique optical and nuclear molecular imaging strategy, the so-called microdosing concept, as defined by the FDA / EMA.

Microdosing, is a defined concept for studying the behaviour of tracers and/or therapeutic compounds (drugs) in humans through the administration of doses so low (“sub-therapeutic”) they are unlikely to produce local or a whole-body therapeutic effects, but high enough to allow the cellular response or binding of the tracer or therapeutic compound to be studied. The labelling of the tracer / drug is either performed by GMP fluorescent or nuclear labelling and provides respectively, real-time in vivo and ex vivo tissue distribution data for image-guided surgery, pathology or endoscopy purposes when it concerns fluorescence, or whole-body pharmacokinetic and biodistribution data when it concerns nuclear labelling.

The particular studies are defined as phase 0 studies and conducted before a clinical Phase I to predict whether a drug is viable for the next phase of testing and thus creating early go/no-go decision-making. Human microdosing aims to reduce the amount of testing done on animals, the resources spent on non-viable drugs, and creating earlier go / no-go decision-making in the early phases of clinical development.

In august 2018, the FDA has released the guidance to assist sponsors of microdose studies and the ICH guidance for industry M3(R2). Read about the FDA fast track guidance.

FDA Report


1: Stenstrom K, Sydoff M, Mattsson S. Microdosing for early biokinetic studies in

humans. Radiat Prot Dosimetry. 2010 Apr-May;139(1-3):348-52. Epub 2010 Feb 18.

2: Rani PU, Naidu MU. Phase 0 – Microdosing strategy in clinical trials. Indian J

Pharmacol. 2008 Nov;40(6):240-2.

3: Lundqvist H, Antoni G, Langstrom B. Genotoxic hazard of radiopharmaceuticals

in humans: chemical and radiation aspects coupled to microdosing. Eur J Clin

Pharmacol. 2007 Jul;63(7):641-5. Epub 2007 Apr 25.

4: Garner RC, Lappin G. The phase 0 microdosing concept. Br J Clin Pharmacol.

2006 Apr;61(4):367-70.




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