Abstract
Prostate specific membrane antigen (PSMA) targeted microbubbles (MBs) were developed using bioorthogonal chemistry. Streptavidin-labeled MBs were treated with a biotinylated tetrazine (MBTz) and targeted to PSMA expressing cells using trans-cyclooctene (TCO)-functionalized anti-PSMA antibodies (TCO-anti-PSMA). The extent of MB binding to PSMA positive cells for two different targeting strategies was determined using an in vitro flow chamber. The initial approach involved pretargeting, where TCO-anti-PSMA was first incubated with PSMA expressing cells and followed by MBTz, which subsequently showed a 2.8 fold increase in the number of bound MBs compared to experiments performed in the absence of TCO-anti-PSMA. Using direct targeting, where TCO-anti-PSMA was linked to MBTz prior to initiation of the assay, a 5-fold increase in binding compared to controls was observed. The direct targeting approach was subsequently evaluated in vivo using a human xenograft tumor model and two different PSMA-targeting antibodies. The US signal enhancements observed were 1.6- and 5.9-fold greater than that for non-targeted MBs. The lead construct was also evaluated in a head-to-head study using mice bearing both PSMA positive or negative tumors in separate limbs. The human PSMA expressing tumors exhibited a 2-fold higher US signal compared to those tumors deficient in human PSMA. The results demonstrate both the feasibility of preparing PSMA-targeted MBs and the benefits of using bioorthogonal chemistry to create targeted US probes.
Highlights
Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men [1]
J591 was chosen from among several anti-Prostate specific membrane antigen (PSMA) monoclonal antibody (mAb) that have been investigated for targeted imaging and targeted radiotherapy [47,48,49,50,51,52]
J591 has the advantages of being a humanized mAb used in clinical studies [28] and it binds to the extracellular domain of PSMA present on the surface of viable tumor cells [38], rather than targeting the intracellular domain that is accessible only within necrotic regions [53]
Summary
Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men [1]. Agents for visualizing PSMA with nuclear imaging methods such as positron emission tomography (PET) include both radiolabeled small molecules and antibodies, which have been used clinically in patients with both primary and metastatic disease [20,21,22,23,24,25,26,27,28,29,30] Results from these studies support the use of PSMA as a PCa biomarker. The second is a pretargeting strategy, in which the TCO-labeled antibody is administered first, to allow binding to sites of target antigen overexpression and clearance from non-target organs This is followed by injection of MBTz that will selectively react with target-bound TCO-anti-PSMA in vivo. We report here the development and evaluation of both approaches and demonstrate US imaging of PSMA-expressing tumors in vivo
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have