PROJECT SUMMARY The low chemical sensitivity of magnetic resonance imaging (MRI) has been a persistent obstacle for the development of molecular imaging agents that can be visualized using clinical scanners. These agents were often designed “one-to-one”, wherein one targeting molecule was attached to one signal-generating molecule, often with a linker. This monomeric design requires molecules that can generate strong MR signals; however, signal-generating molecules with these attributes are too toxic or immunogenic at detectable doses. To overcome this challenge, polymers recently have been incorporated into the design of molecular MRI agents. The repeated chemical groups of polymers can provide multiple attachment sites for the signal-generating molecule, enabling the number of less toxic and less immunogenic MRI signal-generating molecules to be increased to detectable levels. Previously, we demonstrated the proof-of-concept of polymeric molecular MRI agents with two formulations that could detect prostate-specific membrane antigen (PSMA) using the chemical exchange saturation transfer (CEST) MRI method. Still, the translation and widespread clinical use of polymeric molecular MRI agents will require improvements to their sensitivity and specificity. Physiochemical properties (i.e. charge, hydrophobicity) have been shown to influence the in vitro and in vivo specificity of molecular imaging agents. Research Plan: We propose to optimize polymeric CEST MRI agents by varying the charge and hydrophilicity of the signal-generating molecule. These molecular MRI agents will target CD154, an inflammatory marker that can detect benign prostate hyperplasia, a condition that that can mimic prostate cancer in PSMA images. Aim 1: We will synthesize and characterize CEST MRI agents of varying charge and hydrophilicity by adjusting the type and number of signal-generating molecules on the agent, as well as the length of its polymer. We will measure their uptake and internalization in CD154+ (BPH-1) and CD154-(LNCaP) cells. Aim 2: We will measure the uptake of two molecular MRI agent formulations in vivo in prostate models with varying levels of CD154 expression (BPH-1 > LNCaP). We will also measure the uptake of PSMA PET agent 18F-DCFPyL in these same mice (LNCaP > BPH-1). We will validate in vivo images using fluorescent microscopy.

NARRATIVE The development of magnetic resonance imaging (MRI) agents can expand and complement the imaging biomarkers currently available to provide more individualized patient care (precision medicine), but current approaches to their design lack the sensitivity to detect molecular targets of interest. This project will use polymers to enhance their sensitivity on MRI scanners and validate them in prostate models. This MRI agent is readily translatable and will provide information on CD154, a marker which will ultimately be used to improve the detection and diagnosis of inflammatory conditions and events.