Unlocking drug development: the distinctive roles of PET and SPECT imaging from molecular kinetics to therapeutic...

Drug development is a multifaceted and time-intensive process that spans candidate discovery, formulation, pharmacokinetics (PK), and evaluation of therapeutic efficacy and safety. Nuclear medicine imaging-particularly positron emission tomography (PET) and single-photon emission computed tomography (SPECT)-enables noninvasive, quantitative, and dynamic assessments of drug behavior at the molecular and systemic levels. These modalities visualize real-time biodistribution, tissue PK, target engagement, and treatment response, addressing the limitations of conventional approaches such as plasma sampling and invasive tissue biopsies. This review summarizes the contributions of PET and SPECT across the drug development continuum. Representative case studies illustrate their applications in characterizing molecular kinetics, informing pharmacokinetic and pharmacodynamic (PK/PD) relationships, evaluating target specificity, and detecting early off-target effects. We also discuss how imaging-derived metrics can support earlier go/no-go decisions, enhance preclinical-to-clinical translation through a shared quantitative framework across species and disease models, and inform individualized therapeutic strategies. Overall, PET and SPECT serve as core tools that improve the accuracy, safety, and efficiency of modern drug development for molecularly targeted therapies.