The synthesis and characterization of Hno1pa2py, a new tacn-based ligand, is reported. The complexation process with Cu(2+) was proved to be very fast even in acidic medium. Potentiometric titrations allowed us to establish that Hno1pa2py exhibits an overall low basicity as well as a high selectivity for Cu(2+) over Zn(2+) cations. The copper(II) complex was synthesized and characterized using UV-vis and EPR spectroscopies and density functional theory (DFT) calculations. The studies clearly showed that the [Cu(no1pa2py)](+) complex is present in solution as a mixture of two isomers in which the ligand is coordinated to the metal center using a N5O donor set with the metal center in a distorted octahedral geometry. The very high kinetic inertness of the [Cu(no1pa2py)](+) complex was demonstrated by using acid-assisted dissociation assays as well as cyclic voltammetry. Preliminary investigations of (64)Cu complexation were performed to validate the potential use of such chelating agent for further application in nuclear medicine. The X-ray crystal structures of copper(II) complexes of L1, the ester derivative of Hno1pa2py, have been determined.

Mapping tumor hypoxia is a great challenge in positron emission tomography (PET) imaging as the precise functional information of the biological processes is needed for many effective therapeutic strategies. Tumor hypoxia has been widely reported as a poor prognostic indicator and is often associated with tumor aggressiveness, chemo- and radio-resistance. An accurate diagnosis of hypoxia is a challenge and is crucial for providing accurate treatment for patients’ survival benefits. This challenge has led to the emergence of new and novel PET tracers for the functional and metabolic characterization of tumor hypoxia non-invasively. Among these tracers, copper semicarbazone compound [64Cu]-diacetyl-bis(N4-methylthiosemicarbazone) (=64Cu-ATSM) has been developed as a tracer for hypoxia imaging. This review focuses on 64Cu-ATSM PET imaging and the concept is presented in two sections. The first section describes its in vitro development and pre-clinical testing and particularly its affinity in different cell lines. The second section describes the controversial reports on its specificity for hypoxia imaging. The review concludes that 64Cu-ATSM – more than a hypoxic tracer, exhibits tracer accumulation in tumor, which is linked to the redox potential and reactive oxygen species. The authors concluded that 64Cu-ATSNM is a marker of over-reduced cell state and thus an indirect marker for hypoxia imaging. The affinity of 64Cu-ATSM for over-reduced cells was observed to be a complex phenomenon. And to provide a definitive and convincing mechanism, more in vivo studies are needed to prove the diagnostic utility of 64Cu-ATSM.

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te1pa conjugated to an F6 antibody was confirmed to be an interesting alternative to dota for64Cuin vivoPET imaging.

Azamacrocyclic bifunctional chelating agents (BCAs) are essential for the development of radiopharmaceuticals in nuclear medicine and we wish to prove that their bioconjugation by a function present on a carbon atom of the macrocyclic skeleton is a solution of choice to maintain their in vivo inertness. Based on our very recent methodology using a bisaminal template and selective N-alkylation approach, a new synthesis of conjugable C-functionalised teta, te2a and cb-te2a has been developed. These chelators have indeed a growing interest in nuclear medicine for positron emission tomography (PET) and radioimmunotherapy (RIT) where they show in several cases better complexation properties than dota or dota-like macrocycles, especially with (64)Cu or (67)Cu radioisotopes. Chelators are bearing an isothiocyanate grafting function introduced by C-alkylation to avoid as much as possible a critical decrease of their chelating properties. The synthesis is very efficient and yields the targeted ligands, teta-Ph-NCS, te2a-Ph-NCS and cb-te2a-Ph-NCS without fastidious work-up and could be easily extended to other cyclam based-BCAs. The newly synthetised te2a-Ph-NCS has been conjugated to an anti mCD138 monoclonal antibody (mAb) to evaluate its in vivo behavior and potentiality as BCA and to explore a first attempt of PET-phenotypic imaging in multiple myeloma (MM). Mass spectrometry analysis of the immunoconjugate showed that up to 4 chelates were conjugated per 9E7.4 mAb. The radiolabeling yield and specific activity post-purification of the bioconjugate 9E7.4-CSN-Ph-te2a were 95 ± 2.8% and 188 ± 27 MBq mg(-1) respectively and the immunoreactivity of (64)Cu-9E7.4-CSN-Ph-te2a was 81 ± 7%. Animal experiments were carried out on 5T33-Luc(+) tumor bearing mice, either in subcutaneous or orthotopic. To achieve PET imaging, mice were injected with (64)Cu-9E7.4-CNS-Ph-te2a and acquisitions were conducted 2 and 20 h post-injection (PI). A millimetric bone uptake was localised in a sacroiliac of a MM orthotopic tumor. Nonspecific uptakes were observed at 2 h PI but, unlike for the tumor, a significant decrease was observed at 20 h PI which improves the contrast of the images.

Radioimmunoconjugates have been used for 30 years to diagnose and treat cancer. For many years, the use of these therapeutic tools has been limited to haematological disorders, such as non-Hodgkin's lymphoma, given that they have only had a moderate effect on solid tumours. Areas covered: Recently, several strategies have revived the potential therapeutic application for radioimmunoconjugates. In this review, the authors review the advances in immunological engineering to develop new tools like monoclonal antibodies and their derivatives. Then, the authors summarize the development of radionuclides, the use of recombinant antibodies, pretargeting approaches, and dose fractionation techniques, providing opportunities for both therapeutic and diagnostic applications. Expert opinion: Radioimmunoconjugates used in nuclear medicine have entered a new era of development. These advances give rise to a variety of opportunities in the management of various cancers, where the radiolabelled antibodies may be particularly useful in immuno-specific phenotypic imaging e.g. companion diagnostics. Concerning therapeutic applications, radioimmunoconjugates have demonstrated their efficacy in the treatment of both haematological malignancies and solid tumours. Recent procedural developments are of great interest in optimising oncological targeted therapies. In the field of cancer theranostics, we believe that radioimmunoconjugated compounds are likely to play a large part in near future.

Background In this prospective study (NCT03443609), we investigated the impact of 68Ga‐PSMA‐11 PET‐CT on the treatment plan and therapeutic response obtained for patients with prostate cancer (PCa) presenting a recurrence with a low rising PSA. Methods One hundred thirty hormone‐naive (PSA < 1.5 ng/mL) patients were enrolled. All patients received radical treatment. PET images were recorded 1 and 2  hours after injection of tracer and interpreted by two independent nuclear physicians. Six months after treatment ended, a PSA assay was requested to evaluate the therapeutic efficacy of the treatment based on PSMA results. Results Data analysis for the first 52 included patients has been completed. 68Ga‐PSMA‐11–positive lesions were detected in 38/52 (73.1%) patients. Ninety‐four lesions were detected as follows, 53/94 in lymph nodes (56.4%), 25/94 in bone (26.6%), and 12/94 into the prostate bed (12.7%). Detection rates were 58%, 81%, and 82% for serum PSA levels lower than 0.25 ng/mL, between 0.25 to ≤ 0.69  ng/mL and 0.70  ng/mL, respectively. As a result of the PSMA PET‐CT, therapeutic management changed in 38/52 patients (73.1%). Patients had undetectable serum PSA levels after treatment guided by 68Ga‐PSMA‐11 PET‐CT results in 10/52 (19.2%) cases and with a PSA decrease of over 60% in 18/52 (34.6%) patients. Conclusion Whilst our patient population presented a very low PSA level, preliminary results of the 68Ga‐PSMA PET‐CT study showed recurrence localization in more than half of the patients and this had a major clinical impact, as it resulted in treatment change in more than half of the patients and a significant decrease in PSA levels in a third of patients.

Background In this retrospective study, we investigated the impact of 68Ga‐PSMA‐11 PET‐CT (PSMA PET‐CT) upon the treatment plan and therapeutic response obtained for Prostate Cancer (PCa) patients presenting an occult biochemical recurrence. Methods Forty‐two patients with previously negative or doubtful 18F‐Choline (FCH) were enrolled. PET images were recorded 1 h after injection of tracer. Only a few months after treatment ended, a PSA assay was requested to evaluate the therapeutic efficacy of the treatment based on PSMA results. Results PSMA—positive lesions were detected in 34/42 (80.9%) patients. Detection rates were 85.7% and 89.3% for serum PSA levels lower than 2 ng/mL, and >2 ng/mL, respectively. One hundred seventy‐three lesions were detected: 132/173 in lymph nodes (76.3%), 22/173 as metastatic sites (bone or lung) (12.7%), and 19/173 in the prostate bed (10.9%). As a result of the PSMA PET‐CT, therapeutic management changed in 31/42 patients (73.8%). With a follow‐up of 4.9 ± 2.27 months, 32/42 (76.2%) PSA assays after treatment guided by PSMA PET‐CT were collected. For 37.5% (12/32) of patients, the serum PSA level was lower than 0.2 ng/mL and a PSA decrease of over 50% in 8 (25.0%) other patients were obtained. Conclusion Performing a PSMA PET‐CT when FCH PET‐CT was doubtful or negative allows the recurrence localization in more 80% of patients and this had a major clinical impact, as it resulted in treatment change in more than 70% of patients as well as a significant decrease in PSA levels in more than 60% of them.