Preclinical Investigations Toward Gd-free Molecularly Targeted Dual-Modal, MRI Dynamic (DCE-MRI)/Optical Imaging Contrast Agent for Cardiac Angiosarcoma.

AIMS

Cardiac tumors are aggressive and asymptomatic in early stages, causing late diagnosis and locoregional metastasis. Currently, the standard of care uses gadolinium-based contrast agents for MRI, and the associated hypersensitivity reactions are a significant concern, such as gadolinium deposition disease. In addition, the proximity of cardiac lesions closer to vital structures complicates surgical interventions. We envisage the development of a scalable, Gd-free, multimodal contrast agent based on EDTA bisamide with pyridine-based fluorophore (L1). The diagnostic arm should have manganese (Mn)-enhanced high relaxivity for MRI and high sensitivity for PET and/or optical imaging (eg, fluorescence lifetime imaging), with comparable/higher than commercial diagnostic agents, along with the multikinase targeted anticancer activity and strong affinity for human serum albumin.

MATERIAL AND METHODS

Mn complex of EDTA bisamide of 4-(aminomethyl)pyridine (L1), MnL1, was reproduced in high yield (77%) and purity (98%), characterized by liquid chromatography-mass spectrometry (LC-MS). The solubility in water and stability in sodium acetate buffer were evaluated. T1 mapping followed by static and dynamic contrast-enhanced MRI (DCE_MRI) image acquisition, post-tail vein injection of healthy C57BL/6 mice through I.V. with 1mM of MnL1/PBS was carried out by 3T-MRI (BioSpec, Bruker), wherein standard gadobutrol was used as control. Optical properties of L1 dissolved in solvent mixtures of dimethyl sulfoxide were optimized using PhotonIMAGER RT OPTIMA by Biospace Lab with AlexaFluor750 as the positive control. Docking studies with FAP and EGFR kinases were conducted by AutoDock Vina, followed by MD simulation (My Presto).

RESULTS

LC-MS: The highest UV absorption peak was correlated to more than 80% relative abundance of the highest molecular ion peak in mass spectra (cal: 525.18234; found 525.750), indicating strong chelation of L1 to Mn (II). 3T-MRI data of MnL1 revealed comparable performance with a standard gadobutrol. L1 exhibited multiple excitation wavelengths and NIR1 emission. DCE-MRI revealed contrasting dynamics with strong uptake in the kidney, liver, and heart. Docking studies revealed inhibition of FAP (allosteric) and EGFR (-7.0 and 6.7 Kcal/mol), validated by their respective cocrystallized ligands and commercial standards and by MD simulation, reflecting constant gyration ratios and strong hydrogen bonding.

CONCLUSION

Preclinical MRI imaging justified the efficacy of Mn(II)L1. L1 validated as a promising visible and NIR1dye along with its ability to bind and inhibit pan-cancer targets, FAP (allosteric) and EGFR kinases. Previously validated features of lifetime sensing/high stokes shift and Cu (II) quenching are also noteworthy. Dual-echo acquisitions for quantitative DCE-MRI as a standalone (with T2* corrections) or in combination with PET/MRI of 64Cu-L1(separately studied) or as 52MnL1 by single injection envisaged. T1 mapping for therapy response monitoring based on the reduction of native tumor T1 upon binding of MnL1 to the kinase is hereby envisaged for the future.