cGMP-Compatible preparative scale synthesis of near-infrared fluorophores

Image-guided surgery using optical imaging requires the availability of large quantities of clinical-grade fluorophores. We describe the cGMP-compatible synthesis of the zwitterionic heptamethine indocyanine near-infrared fluorophore ZW800-1 at the 10 g scale (~1000 patient doses) using facile and efficient solvent purification, and without the need for column chromatography. ZW800-1 has >90% yield at the final step and >99% purity as measured by fluorescence and evaporative light scatter detection. We describe an analytical framework for qualifying impurities, as well as a detailed analysis of counterion identities. Finally, we report the unique in vivo properties of ZW800-1 in large animals approaching the size of humans, thus laying the foundation for rapid clinical translation of these methods.