SMALL MOLECULE IMAGING AGENT FOR MUTANT KRAS G12C

Multiple potent covalent inhibitors targeting mutant KRAS G12C have been developed, with some currently undergoing clinical trials. These small molecule inhibitors offer the potential for companion imaging probe development, thereby enriching the chemical biology toolkit for studying mutant KRAS biology. In this study, we synthesized and evaluated a series of fluorescent companion imaging drugs (CIDs) for KRAS G12C, using two scaffolds: ARS-1323 and AMG-510. Eight fluorescent derivatives were created by conjugating BODIPY dyes, yielding four derivatives per scaffold.

Our findings revealed that two ARS-1323 derivatives, labeled with BODIPY FL and BODIPY TMR, successfully bound mutant KRAS and could be utilized in biochemical binding assays. However, these derivatives were unsuitable for direct cellular imaging due to non-specific membrane labeling. To address this limitation, we implemented a two-step labeling strategy in cancer cells. This approach involved target binding with an ARS-1323 alkyne derivative, followed by fluorescence imaging via in situ click chemistry with picolyl azide Alexa Fluor 647. Using this method, we demonstrated the ability to image mutant KRAS G12C directly in cells.

Given the current unavailability of specific antibodies for mutant KRAS G12C, these reagents offer a valuable tool for fluorescence imaging with enhanced specificity.