GB119

GB119 is a quenched activity-based fluorescent imaging probe (qABP) designed for the rapid, real-time detection of cancer margins during surgical resections. It consists of an acyloxymethylketone (AOMK) electrophilic warhead that covalently and irreversibly binds to the active site of cysteine cathepsins, particularly cathepsin L, which are highly overexpressed in the tumor microenvironment. Upon covalent binding, the quenching group is released, resulting in a robust near-infrared fluorescent signal (via a Cy5 fluorophore) that highlights tumor margins and infiltrating cancer cells. GB119 is typically applied topically to excised surgical specimens, such as breast lumpectomies or non-melanoma skin cancer excisions, to differentiate malignant tissue from healthy surrounding tissue within minutes.