New Synthetic Approaches to Small Molecules for Imaging
Emerging imaging applications require probes tailored to the specific demands of each method. Our approach is to define the complex reactivity of the cyanine chromophore and apply these chemistries to enable molecular design and probe discovery efforts. Through our now decade-long experience with these molecules, we have significant insight into their preparation, reactivity, and relationships between chemical structure and physical/biological properties. A major component of our efforts is to create novel synthetic methods, which allows us access to previously unknown molecules. We have developed the chemistry to assemble exceptionally bright, polycyclic pentamethine cyanines that are enabling for a variety of advanced microscopy applications. We have also worked extensively to develop novel heptamethine cyanine dyes. These molecules operate in the near-infrared (NIR) range making them applicable to in vivo live animal imaging applications. We developed a highly modified heptamethine cyanine dye, FNIR-tag, that is uniquely resistant to aggregation and provides exceptionally bright bioconjugates. We are also developing bioconjugatable nonamethine indocyanine dyes with emission beyond 1000 nm. These molecules have extended the range of wavelengths available for targeted multicolor in vivo imaging. Finally, we are developing novel turn-on or “fluorogenic” probe chemistries to enable responsive in vivo imaging applications.
Applying Optical Approaches to the Drug Delivery Problem
Recent progress establishing the clinical utility of ADCs has validated the potential of ligand-targeted small molecule delivery strategies. However, the application of these drugs has encountered significant toxicities that limits the scope of their use. Critically, these toxicities rarely result from the mAb binding to its cognate target, but rather from deleterious effects of the hydrophobic small molecule/linker combination on in vivo targeting. Consequently, the chemical components - the linker and payload - require redesign to realize the promise of these strategies. In prior studies, we developed a cyanine-based light-activated ADC strategy. Building on this work and our efforts to optimize mAb conjugates for FGS applications, we are applying optical imaging to define key criteria that determine the tumor targeting of ADCs. These efforts will identify tumor selective protease-cleavable linkers and payloads with improved physical properties. This approach builds on our expertise in optical imaging and probe design, and benefits from CCR collaborations with experts in mAb and therapeutic development.
Dr. Schnermann attended Colby College and graduated in 2002 with degrees in Chemistry and Physics. At Colby, he worked with Prof. Dasan Thamattoor in the areas of physical organic chemistry and photochemistry. After a year at Pfizer Research and Development (Groton, CT) as an associate in the medicinal chemistry division, he moved to the Scripps Research Institute. During his graduate studies, he performed research on the total synthesis and biological evaluation of anticancer natural products with Prof. Dale Boger and obtained a Ph.D. in 2008. He then completed an NIH-postdoctoral fellowship with Prof. Larry Overman at the University of California, Irvine. At Irvine, he developed light-mediated reactions to enable the synthesis of complex natural products. In addition, working with Prof. Christine Suetterlin, he pursued chemical biology and imaging studies of organelle specific probes. In 2012, Dr. Schnermann joined the Chemical Biology Laboratory at the National Cancer Institute, where his research focuses on the synthesis and development of new small-molecule imaging agents for cancer treatment and diagnosis. In 2018, Dr. Schnermann was promoted to Senior Investigator.
- Nani RR, Gorka AP, Nagaya T, Yamamoto T, Ivanic J, Kobayashi H, Schnermann MJ. In Vivo Activation of Duocarmycin-Antibody Conjugates by Near-Infrared Light. ACS Cent Sci. 2017;3(4):329-337.
- Nani RR, Shaum JB, Gorka AP, Schnermann MJ. Electrophile-integrating Smiles rearrangement provides previously inaccessible C4'-O-alkyl heptamethine cyanine fluorophores. Org Lett. 2015;17(2):302-5.
- Nani RR, Gorka AP, Nagaya T, Kobayashi H, Schnermann MJ. Near-IR Light-Mediated Cleavage of Antibody-Drug Conjugates Using Cyanine Photocages. Angew Chem Int Ed Engl. 2015;54(46):13635-8.
- Nani RR, Kelley JA, Ivanic J, Schnermann MJ. Reactive Species Involved in the Regioselective Photooxidation of Heptamethine Cyanines. Chem Sci. 2015;6(11):6556-6563.
- Gorka AP, Nani RR, Zhu J, Mackem S, Schnermann MJ. A near-IR uncaging strategy based on cyanine photochemistry. J Am Chem Soc. 2014;136(40):14153-9.
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This page was last updated on Friday, March 17, 2023