Noninvasive in vivo mapping of intracellular signaling proteins using a pairing of targeted and untargeted fluorescently labeled small molecule kinase inhibitors

摘要

Small molecule kinase inhibitors (SMKIs) drugs have the potential to offer exquisite specificity in controllingaberrant intracellular signaling pathways in cancer and other disease states. However, while nearly 50 SMKIshave been FDA-approved, patient responses have been variable, and sensitive populations not easy toidentify. For instance, in non-small-cell lung cancer, only 30% of patients respond to the epidermal growthfactor receptor (EGFR) targeted SMKI, erlotinib, yet the level of erlotinib uptake is a poor indicator oftreatment efficacy. The development of fluorescently-labeled SMKIs that maintain their viability as drugshas facilitated the use of paired-agent molecular imaging protocols that are able to discriminate, in vivo,between imaging agent uptake and binding. Here we present a mathematical framework of SMKI transportand binding, in vivo, and derive a kinetic model for extracting SMKI binding potential (BP) from kineticfluorescent-SMKI imaging data—proposed as a more effective indicator of potential therapeutic responsethan SMKI uptake alone. The accuracy and precision of the SMKI BP kinetic model was demonstrated insimulation studies and in an in ovo xenograft experiment. In simulation, the SMKI BP estimates were within20 5% of expected values over a large range of physiologically relevant blood flow, vascular permeabilityand cell permeability; and over a range of SMKI affinity, cell membrane permeability, and blood plasmapharmacokinetics. The in ovo experiment bolstered the simulation findings, demonstrating a statisticallysignificant spatial correlation (r > 0.9, p < 0.01) between EGFR concentration measured by a validatedextracellular approach and the SMKI BP approach.