Over the past decade, theranostic imaging has emerged as a powerful clinical tool in oncology for identifying patients likely to respond to targeted therapies and for monitoring the response of patients to treatment. Herein, we report a theranostic approach to pretargeted radioimmunotherapy (PRIT) based on a pair of radioisotopes of copper: positron-emitting copper-64 (64Cu, t1/2 = 12.7 h) and beta particle-emitting copper-67 (67Cu, t1/2 = 61.8 h). This strategy is predicated on the in vivo ligation between a trans-cyclooctene (TCO)-bearing antibody and a tetrazine (Tz)-based radioligand via the rapid and bioorthogonal inverse electron-demand Diels–Alder reaction. Longitudinal therapy studies were conducted in a murine model of human colorectal carcinoma using an immunoconjugate of the huA33 antibody modified with TCO (huA33-TCO) and a 67Cu-labeled Tz radioligand ([67Cu]Cu-MeCOSar-Tz). The injection of huA33-TCO followed 72 h later by the administration of 18.5, 37.0, or 55.5 MBq of [67Cu]Cu-MeCOSar-Tz produced a dose-dependent therapeutic response, with the median survival time increasing from 68 d for the lowest dose to >200 d for the highest. Furthermore, we observed that mice that received the highest dose of [67Cu]Cu-MeCOSar-Tz in a fractionated manner exhibited improved hematological values without sacrificing therapeutic efficacy. Dual radionuclide experiments in which a single administration of huA33-TCO was followed by separate injections of [64Cu]Cu-MeCOSar-Tz and [67Cu]Cu-MeCOSar-Tz revealed that the positron emission tomography images produced by the former accurately predicted the efficacy of the latter. In these experiments, a correlation was observed between the tumoral uptake of [64Cu]Cu-MeCOSar-Tz and the subsequent therapeutic response to [67Cu]Cu-MeCOSar-Tz.

Molecules containing lysine-ureido-glutamate functional groups bind to the active site of prostate specific membrane antigen, which is overexpressed in prostate cancer. To prepare copper radiopharmaceuticals for the diagnosis and therapyofprostate cancer,macrobicyclic sarcophagine ligands tethered to either one or two lysine-ureido-glutamate functional groups through an appropriate linker have been prepared. Sarcophagine ligands can be readily radiolabeled with positron-emitting copper-64 at room temperature.T he bivalent agent, in which two targeting groups are tethered to as ingle copper complex, dramatically outperforms the monomeric agent with respect to tumor uptake and retention. The high tumor uptake,l ow background, and prolonged tumor retention, even at 24 hours post injection, suggest the bivalent agent is apromising diagnostic for prostate cancer and could be used for prospective dosimetry for therapywith acopper-67 variant.

The application of small molecules targeting prostate-specific membrane antigen (PSMA) has emerged as a highly promising clinical strategy for visualization and treatment of prostate cancer. Ligands that integrate the ability to both quantify the distribution of radioactivity and treat disease through the use of a matched pair of radionuclides have particular value in clinical and regulatory settings. In this study, we describe the development and preclinical evaluation of RPS-085, a ligand that binds PSMA and serum albumin and exploits the 64/67 Cu radionuclide pair for prostate cancer theranostics. RPS-085 was synthesized by conjugation of a PSMA-targeting moiety, an N ε -(2-(4iodophenyl)acetyl)lysine albumin binding group, and a bifunctionalized MeCOSar chelator. The IC 50 of the metal-free RPS-085 was determined in a competitive binding assay. The affinity for human serum albumin of the radiolabeled compound was determined by high-performance affinity chromatography. Radiolabeling was performed in NH 4 OAc buffer at 25 °C. The stability of the radiolabeled compounds was assessed in vitro and in vivo. The biodistribution of [ 64/67 Cu]Cu-RPS-085 was determined following intravenous administration to male BALB/c mice bearing LNCaP tumor xenografts. The radiochemical yields of [ 64/67 Cu]Cu-RPS-085 were nearly quantitative after 20 min. The metal-free complex is a potent inhibitor of PSMA (IC 50 = 29 ± 2 nM), and the radiolabeled compound has moderate affinity for human serum albumin (K d = 9.9 ± 1.7 μM). Accumulation of the tracer in mice was primarily evident in tumor and kidneys. Activity in all other tissues, including blood, was negligible, and the radiolabeled compounds demonstrated high stability in vitro and in vivo. Tumor activity reached a maximum at 4 h post injection (p.i.) and cleared gradually over a period of 96 h. By contrast, activity in the kidney cleared rapidly from 4 to 24 h p.i. As a consequence, by 24 h p.i., the tumor-to-kidney ratio exceeds 2, and the predicted dose to tumors is significantly greater than the dose to kidneys. [ 64 Cu]Cu-RPS-085 combines rapid tissue distribution and clearance with prolonged retention in LNCaP tumor xenografts. The pharmacokinetics should enable radioligand therapy using [ 67 Cu]Cu-RPS-085. By virtue of its rapid kidney clearance, the therapeutic index of [ 67 Cu]Cu-RPS-085 likely compares favorably to its parent structure, [ 177 Lu]Lu-RPS-063, a highly avid PSMA-targeting compound. On this basis, [ 64/67 Cu]Cu-RPS-085 show great promise as PSMA-targeting theranostic ligands for prostate cancer imaging and therapy.

Disclosure E. M. van Dam and M. J. Harris are employed by Clarity Pharmaceuticals, the licensee of relevant intellectual property. P. S. Donnelly and N. A. Zia are inventors of intellectual property, licensed from the University of Melbourne to Clarity. P. S. Donnelly serves on the Scientific Advisory Board of Clarity and has a financial interest. Unrelated to this project, Prof. Hicks has shares in Telix Radiopharmaceuticals with proceeds donated to his institution. No other potential conflict of interest relevant to this article was reported.

This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record.

3557 Background: This is a first in human in-vivo biodistribution of ex-vivo labelled CAR T cells assessed in a cohort of patients. Cells were labelled with novel Cu-64 labelled superparamagnetic iron oxide nanoparticles (SPION) and infused IV into patients with solid tumors & tracked using clinical dual PET-MR. The study validates the clinical translation of CAR T cell in-vivo tracking in real time. Methods: Cu-64 radioisotope was bound to silica coated SPION using electrolysis plating with tin & palladium seeding. Cellular uptake of Cu-64 SPION was facilitated with a transfecting agent. Functional assays including 51Chromium release, cytometric bead array demonstrated that labelling process did not affect cytotoxicity & cytokine secretion (TNFα & IFN-g). T cells were transduced with retroviral vector constructs encoding for second-generation chimeric T-cell receptor specific for carbohydrate Lewis Y antigen. Modified T-cells were expanded ex-vivo & were labelled with Cu-64 (~300 MBq) prior to re-infusion (3 x108 labelled cells). Scanning is performed with Siemens 3T dual PET-MR scanner. Results: In this first in human in-vivo study (HREC/16/PMCC/30) a cohort of patients received ex-vivo labelled CAR T cells to determine how many labelled cells distribute to solid tumor sites within 3-5 days. Our results demonstrate that cells can be efficiently labelled (≤60%) with high cell viability (≥85%) at a sensitivity sufficient to detect labelled cells at tumor site for up to 5 days. An observed trend in SUVmean & SUVmax provided insight into efficacy & individual response to therapy. Early time points showed moderate uptake of labelled cells in lungs posterior basal segments without increased activity over next few days, suggesting a transient process. Mild, diffuse bone marrow & relatively intense uptake of labelled cells in liver & spleen suggests margination of cells to reticulo-endothelial system. Distinct PET signal at some of the tumor sites at 24 h suggests antigen specific localization & time taken to reach these sites. Excretion via hepatobiliary indicated reabsorption from GI tract & re-circulation of labelled cells. Minimal uptake in brain & heart supported safety profile of labeling agent. Conclusions: This is first in human in-vivo study to provide highly valuable visual and dynamic data in real time and provides insight into individual responses to therapy. CAR T cell functionality largely remain unchanged due to labeling process. The findings indicate that labelled cells traffic to tumor sites at later time points & remain persistent for extended period of time.

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Otera's distannoxane catalyst was found to promote the cleavage of carbamate groups from N-protected aziridines. This method enables the chemoselective cleavage of an aziridinyl N-carbobenzyloxy (Cbz) group in the presence of other N-Cbz groups. The selectivity is due to the longer, weaker N-C bond of aziridinyl carbamates, as inferred through IR and crystallographic analyses.