We generated 18F-labeled antibody fragments for positron emission tomography (PET) imaging using a sortase-mediated reaction to install a trans-cyclooctene-functionalized short peptide onto proteins of interest, followed by reaction with a tetrazine-labeled-18F-2-deoxyfluoroglucose (FDG). The method is rapid, robust, and site-specific (radiochemical yields > 25%, not decay corrected). The availability of 18F-2-deoxyfluoroglucose avoids the need for more complicated chemistries used to generate carbon–fluorine bonds. We demonstrate the utility of the method by detecting heterotopic pancreatic tumors in mice by PET, using anti-Class II MHC single domain antibodies. We correlate macroscopic PET images with microscopic two-photon visualization of the tumor. Our approach provides easy access to 18F-labeled antibodies and their fragments at a level of molecular specificity that complements conventional 18F-FDG imaging.

Antibodies are currently the fastest-growing class of therapeutics. Although naked antibodies have proven valuable as pharmaceutical agents, they have some limitations, such as low tissue penetration and a long circulatory half-life. They have been conjugated to toxic payloads, PEGs, or radio-isotopes to increase and optimize their therapeutic efficacy. Although nonspecific conjugation is suitable for most in vitro applications, it has become evident that site specifically modified antibodies may have advantages for in vivo applications. Herein we describe a novel approach in which the antibody fragment is tagged with two handles: one for the introduction of a fluorophore or 18F isotope, and the second for further modification of the fragment with a PEG moiety or a second antibody fragment to tune its circulatory half-life or its avidity. Such constructs, which recognize Class II MHC products and CD11b, showed high avidity and specificity. They were used to image cancers and could detect small tumors.

Natural products form attractive leads for the development of chemical probes and drugs. The antibacterial lipopeptide Brabantamide A contains an unusual enol cyclocarbamate and we used this scaffold as inspiration for the synthesis of a panel of enol cyclocarbamate containing compounds. By equipping the scaffold with different groups, we identified structural features that are essential for antibacterial activity. Some of the derivatives block incorporation of hydroxycoumarin carboxylic acid-amino d-alanine into the newly synthesized peptidoglycan. Activity-based protein-profiling experiments revealed that the enol carbamates inhibit a specific subset of penicillin-binding proteins in B. subtilis and S. pneumoniae.

Antibodies are currently the fastest-growing class of therapeutics. Author Manuscript penetration and a long circulatory half-life. They have been conjugated to toxic payloads, PEGs, or radio-isotopes to increase and optimize their therapeutic efficacy. Although nonspecific conjugation is suitable for most in vitro applications, it has become evident that site specifically modified antibodies may have advantages for in vivo applications. Herein we describe a novel approach in which the antibody fragment is tagged with two handles: one for the introduction of a fluorophore or 18 F isotope, and the second for further modification of the fragment with a PEG moiety or a second antibody fragment to tune its circulatory half-life or its avidity. Such constructs, which recognize Class II MHC products and CD11b, showed high avidity and specificity. They were used to image cancers and could detect small tumors. HHS Public Access

Casestudy: Phosphaturic mesenchymal tumor (PMT) is a rare, benign neoplasm. It is associated with oncogenic osteomalacia, a paraneoplastic condition caused by secretion of a peptide hormone-like substance, fibroblast growth factor 23, which increases renal clearance of phosphate and increased mobilization of calcium and phosphate from bone. PMT is difficult to diagnose as a primary etiology because patients usually experience non- specific symptoms associated with hypophosphatemia like bone pain, muscular weakness, and pathologic fractures. Because PMT is a benign neoplasm, surgical excision is curative and rapid resolution of symptoms typically ensues. Discussed here is a case of PMT arising in the soft tissue of the medial thigh of a 65 year old man with a five year history of osteomalacia with pathologic fractures and complicated healing. Lab studies revealed hypophosphatemia, hyperphosphaturia, hypercalcemia, and elevated serum fibroblast growth factor 23 during workup for fracture. A small superficial soft tissue mass was discovered in the proximal thigh via octreotide scan which was subsequently excised. On histologic examination it was composed of an encapsulated proliferation of spindle cells in a chondromyxoid background with distinctive areas of flocculent calcification and osteoclast-like giant cells. A diagnosis of PMT was rendered. The patient’s symptoms resolved rapidly after surgery. Despite the benign characteristics and behavior of this rare neoplasm; delayed or mis-diagnosis can have severe implications for patient’s health. Interdisciplinary communication, shrewd clinical index of suspicion, and awareness of the causes of, and the tests available to diagnose oncogenic osteomalacia can speed accurate diagnosis leading to better outcomes for patients.