Design, synthesis and in vitro evaluation of heterobivalent peptidic radioligands targeting both GRP- and VPAC1-Receptors concomitantly overexpressed on various malignancies - Is the concept feasible?

Radiolabeled heterobivalent peptidic ligands (HBPLs), being able to address different receptors, are highly interesting tumor imaging agents as they can offer multiple advantages over monovalent peptide receptor ligands. However, few examples of radiolabeled HBPLs have been described so far. One promising approach is the combination of gastrin-releasing peptide receptor (GRPR)- and vasoactive intestinal peptide receptor subtype 1 (VPAC1R)-targeting peptides into one single radioligand since gastrinomas, prostate and breast cancer have been shown to concomitantly or complementarily overexpress both receptors. Here we report the design and synthesis of different HBPLs, comprising a GRPR-binding (BBN7-14) and a VPAC1R-targeting (PACAP-27) peptide. The heterodimers were varied with regard to the distance between the peptide binders and the steric rigidity of the systems. We radiolabeled the HBPLs 19-23 as well as their monomeric reference standards 26 and 27 with 68Ga, achieving radiochemical yields and purities of 95-99% and non-optimized molar activities of 25-61 GBq/µmol. We tested the stability of the radioligands and further evaluated them in vitro regarding their uptake in different prostate carcinoma cell lines (PC-3, DU-145 and VCaP cells). We found that the heterobivalent substances [68Ga]19 - [68Ga]23 showed comparable uptakes into the tumor cells to those of the respective monomers [68Ga]26 and [68Ga]27, indicating that both peptides are still able to address their target receptors. Furthermore, the obtained results indicate that in case of overall low receptor densities, heterobivalent peptides surpass peptide monomers in tumor cell uptake. Most importantly, it could be shown by blocking studies that both peptide parts of the HBPL [68Ga]19 contributed to tumor cell uptake in VCaP cells, expressing both receptor types. Thus, we describe here the first examples of HBPLs being able to address the GRPR as well as the VPAC1R and have the potential to - by several mechanisms - improve tumor targeting for several malignancies compared to monospecific peptides.

Fully Automated Production and Characterization of 64 Cu and Proof-of-Principle Small-Animal PET Imaging Using 64 Cu-Labelled CA XII Targeting 6A10 Fab.

64 Cu is a cyclotron-produced radionuclide which offers, thanks to its characteristic decay scheme, the possibility of combining positron emission tomography (PET) investigations with radiotherapy. We evaluated the Alceo system from Comecer SpA to automatically produce 64 Cu for radiolabelling purposes. We established a 64 Cu production routine with high yields and radionuclide purity in combination with excellent operator radiation protection. The carbonic anhydrase XII targeting 6A10 antibody Fab fragment was successfully radiolabelled with the produced 64 Cu, and proof-of-principle small-animal PET experiments on mice bearing glioma xenografts were performed. We obtained a high tumor-to-contralateral muscle ratio, which encourages further in vivo investigations of the radioconjugate regarding a possible application in diagnostic tumor imaging.

Associations to pain and analgesics in Indian pain patients and health workers.

AIM: This study explores the attitudes toward analgesic therapy among persistent pain patients and health workers in palliative care in India. METHODS: Free word association was used and quantitative content analysis was performed. RESULTS: A total of 59 patients and 28 health workers participated. In total, 41% of the patients had <5/10 points on a pain scale. A total of 3733 associations were recovered. Personal associations were majorly coming from patients having negative connotation. Morphine produced few associations, especially among patients. Most of them were about pain relief and for patients about negative emotions. CONCLUSION: Two types of knowledge were detectable, differing in quality and quantity. One was based on lived experience among patients; the other arose from scientific foundation among health workers.