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Following the successful synthesis of a C-functionalized version of the TE1PA ligand, a monopicolinate cyclam, we looked to demonstrate its in vivo properties versus DOTA and NOTA, after conjugation on the 9E7.4 rat antibody, an IgG2a against CD138 murine, which has relevant properties for multiple myeloma targeting. For each ligand, different conjugation approaches had been considered to select the most appropriate for the comparative study. The p-SCN-Bn-TE1PA, NHS-DOTA, and p-SCN-Bn-NOTA were finally chosen for conjugation and radiolabeling tests. For in vivo comparison, we used a model of subcutaneous grafted mice with 5T33 tumor cells. In vitro tests and immuno-PET study highlighted 64Cu-9E7.4-p-SCN-Bn-NOTA as the least attractive. Further competitive biodistribution and hepatic metabolic studies at 2, 24, and 48 h post-injection (100 μg radiolabeled with 10 MBq of 64Cu) were then performed with the 64Cu-9E7.4-p-SCN-Bn-TE1PA and 64Cu-9E7.4-NHS-DOTA. Results show a better in vivo resistance of 64Cu-9E7.4-p-SCN-Bn-TE1PA to transchelation compared to 64Cu-9E7.4-NHS-DOTA, especially at later times. This was confirmed with 64Cu-9E7.4-p-SCN-Bn-NOTA at 48 h PI. 64Cu-9E7.4-p-SCN-Bn-TE1PA also demonstrated an excellent hepatic clearance. 64Cu-9E7.4-p-SCN-Bn-TE1PA displayed an overall superiority compared to 64Cu-9E7.4-NHS-DOTA and 64Cu-9E7.4-p-SCN-Bn-NOTA in terms of in vivo stability, reinforcing the usefulness of the p-SCN-Bn-TE1PA ligand for 64Cu immuno-PET imaging.

IntroductionThe objective was to evaluate whether hybrid imaging combining single photon emission tomography with computed tomography (SPECT/CT) provides additional clinical value for dectection of sentinel lymph nodes (SLNs) compared with intraoperative combined mapping in uterine and cervical malignancies.MethodsThis was a retrospective study of prospectively collected data from patients with stages IA–IB2 cervical cancer (International Federation of Gynecology and Obstetrics (FIGO) 2018) or stage I endometrial cancer, who underwent preoperative SPECT/CT for SLN detection. All included patients had dual injection of technetium-99m (99mTc) with patent blue or indocyanine green.ResultsA total of 171 patients were included with 468 SLNs detected during surgery: 146/171 patients (85.4%) had both radiotracer and blue injection whereas 25/171 patients (14.6%) had radiotracer and indocyanine green injected. The overall detection rate was 95.3%. The detection rate of SLN mapping was 74.9% for SPECT/CT, 90.6% for99mTc, 91.8% for blue dye, and 100% for indocyanine green. Bilateral drainage was found in 140 patients (81.9%), detected by99mTc in 105 patients (61.4%), by blue in 99 patients (67.3%), by indocyanine green in 23 patients (92%), and by SPECT/CT in 62 patients (36.4%). Atypical SLN locations were identified by SPECT/CT in 64 patients (37.4%), by 99mTc in 28 patients (16.4%), by blue in 17 patients (9.9%), and by indocyanine green in 8 patients (4.7%). Sensitivity and negative predictive value of SLN biopsy to detect lymph node metastasis using dual injection of different intraoperative combined techniques were 88.9% and 97.5%, respectively.ConclusionSPECT/CT enhanced topographic delineation of SLN and more accurately identified drainage to atypical locations. Fluorescent SLN mapping using indocyanine green offered the highest SLN detection rate. When indocyanine green was used, SPECT/CT did not increase SLN detection, and did not add further information to improve lymph node localization and removal.

International audience; In view of the excellent copper(ii) and 64-copper(ii) complexation of a TE1PA ligand, a monopicolinate cyclam, in both aqueous medium and in vivo, we looked for a way to make it bifunctional, while maintaining its chelating properties. Overcoming the already known drawback of grafting via its carboxyl group, which is essential to the overall properties of the ligand, a TE1PA bifunctional derivative bearing an additional isothiocyanate coupling function on a carbon atom of the macrocyclic ring was synthesized. This led to an architecture that is comparable to that of other commercially available bifunctional copper(ii) chelators such as p-SCN-Bn-DOTA already used in clinical trials for 64Cu-immuno-PET imaging. The C-functionalization of TE1PA on one carbon atom in the β-N position of the cyclam backbone was successfully achieved by adapting our patented methodology to the huge challenge, allowing the regiospecific mono-N-functionalization of the unsymmetrical ligand. The obtained ligand p-SCN-Bn-TE1PA was coupled to a 9E7.4 murine antibody (mAb), an IgG2a anti CD-138 for multiple myeloma (MM) targeting. The conjugation efficiency was assessed by looking at the 64Cu radiolabeling and the radiopharmaceutical 64Cu-9E7.4-p-SCN-Bn-TE1PA immunoreactivity, and in particular by comparing with 9E7.4-p-SCN-Bn-NOTA and 9E7.4-p-SCN-Bn-DOTA obtained from commercial and presumably highly efficient chelators NOTA and DOTA, respectively. The results are quite clear, showing that p-SCN-Bn-TE1PA has a coupling rate 5 times higher and an immunoreactivity 1.5 to 2 times greater than those of its two competitors. p-SCN-Bn-TE1PA also outperforms TE1PA conjugated via its carboxylic function on the same antibody. The first 64Cu-immuno-PET preclinical study in a syngeneic model of MM was performed, confirming the good in vivo properties of 64Cu-9E7.4-p-SCN-Bn-TE1PA for PET imaging, considering the high clearance even after 24 h and the particularly important tumor-to-liver ratio that was increasing at 48 h.