A Trifunctional, Rare-Earth Theranostic Chelator Platform to Enable Diagnostic Nuclear Imaging, Surgical Resection, and Radiotherapy

Here, we establish a single-molecule, trifunctional platform compatible with diagnostic positron emission tomography (PET), optical imaging-assisted intrasurgical resection, and chelation of radiotherapeutic rare-earth nuclides. Building on previous pyridylalkynylaryl (PEPA) antenna scaffolds, mono- and bisantenna analogs incorporating either PEPA or methoxy-substituted MEPA chromophores were prepared to assess the role of pyridylalkynylaryl number and polyethylene glycol (PEG) substitution on photophysical and biological performance. Photophysical characterization with Eu(III) revealed that antenna truncation had minimal impact on quantum yields and Cerenkov radiation energy transfer (CRET) imaging while substantially improving water solubility. Biodistribution studies with Y-86-labeled analogs identified [⁸⁶Y]Y-pepa-pic₂ as the lead scaffold, showing rapid renal clearance, minimal nontarget retention, and high in vivo stability. This platform was functionalized with the peptide sequence C-Hex-KuE targeting prostate-specific membrane antigen. PET imaging with the corresponding ⁸⁶Y-based probe showed selective tumor uptake and rapid renal clearance, affirming that the pepa-pic₂ chelator produced a favorable in vivo profile. Intratumoral administration of Eu-pepa-pic₂-C-Hex-KuE, paired with the systemically injected [⁶⁸Ga]Ga-PSMA-617 tracer as the intermolecular CRET photon source, produces selective enhancement of the optical signal in the target tissue. Finally, in vivo studies with [¹⁷⁷Lu]Lu-pepa-pic₂-C-Hex-KuE and [¹⁶¹Tb]Tb-pepa-pic₂-C-Hex-KuE evidence efficient tumor uptake of β⁻ radiotherapeutics. Together, these results establish a versatile, single chelator platform for targeted rare-earth-metal optical imaging and theranostic nuclear medicine.