Table 1.

Contrasting how molecular imaging is applied in different stages of drug development. In early stage studies, methods can be highly complex and established at a single centre. In later-phase studies, techniques must be simplified to enable standardized implementation across many study centres.

	molecular imaging for early phase drug development	molecular imaging for late phase drug development
applications	bio-distribution, target engagement, markers of pharmacology, patient stratification	patient stratification; response/progression evaluation
availability	complexity is acceptable, bespoke single centre study or if necessary standardized scanning across a small number of centres	a distribution network needs to be in place to access the tracer for the study in the required geographies. May need to be available in tens to hundreds of centres
image acquisition	can be highly specialized, e.g. dynamic scanning, blood sampling	close to clinical routine but standardization is important
cost	cost of the method development (e.g. radiolabelling) can be far higher than the total scanning cost	costs include scanning, standardization and central analysis efforts. When multiplied by the number of subjects and time points this can represent a significant percentage of the total trial cost
analysis	highly specialized analysis/modelling can be conducted	site-based assessments or images transferred for central, standard analysis
examples	radiolabelled drug, target engagement	18F-FDG-PET supplementing structural response criteria in assessment of solid tumours; amyloid PET
impediments to broader use	cost and complexity of method development	availability of the method across clinical trial centres; evidence that a given method has clinical relevance