The cellular adhesion receptor αvβ6-integrin is highly expressed in many cancers, e.g., pancreatic, lung, head-and-neck, cervical, bladder, and esophageal carcinoma. Multimerization of αvβ6-integrin-specific RGD peptides increases the target affinity and retention but affects biodistribution and pharmacokinetics. Amide formation of the terminal carboxylic acid moieties of the square-symmetrical bifunctional chelator DOTPI with 3-azidopropylamine yields derivatives with 4, 3, and 2 terminal azides and zero, 1, and 2 remaining carboxylic acids, respectively, whereby formation of the 2-cis-isomer is preferred according to NMR investigation of the Eu(III)-complexes. Cu(II)-catalyzed alkyne-azide cycloaddition (CuAAC) of the alkyne-functionalized αvβ6-integrin binding peptide cyclo[YRGDLAYp(NMe)K(pent-4-ynoic amide)] (Tyr2) yields the respective di-, tri-, and tetrameric conjugates for Lu-177-labeling. In mice bearing αvβ6-integrin-expressing xenografts of H2009 (human lung adenocarcinoma) cells, the Lu-177-labeled trimer's tumor-to-blood ratio of 112 exceeds that of the tetramer (10.4) and the dimer (54). Co-infusion of gelofusine (succinylated gelatin) reduces the renal uptake of the trimer by 89%, resulting in a 10-fold better tumor-to-kidney ratio, while no improvement of that ratio is observed with arginine/lysine, para-aminohippuric acid (PAH), and hydroxyethyl starch (HES) coinfusions. Since the Lu-177-labeled Tyr2-trimer outperforms the dimer and the tetramer, such trimers are considered the best lead structures for the ongoing development of αvβ6-integrin targeted anticancer theranostics.
- MeSH
- antigeny nádorové * metabolismus MeSH
- chelátory * chemie MeSH
- integriny * metabolismus MeSH
- lidé MeSH
- lutecium * chemie MeSH
- myši nahé MeSH
- myši MeSH
- nádorové buněčné linie MeSH
- nádory farmakoterapie MeSH
- oligopeptidy * chemie farmakokinetika MeSH
- radiofarmaka farmakokinetika chemie terapeutické užití MeSH
- radionuklidy * chemie MeSH
- syntetická chemie okamžité shody MeSH
- teranostická nanomedicína metody MeSH
- tkáňová distribuce MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: The recently growing interest in targeted alpha-therapy (TAT) calls for improvement of the labelling chemistry of the corresponding radionuclides. 213BiIII is a short-lived alpha emitter which emits only one alpha particle in its decay chain. Hence, it might be safer in application than other respective nuclides, such as 223Ra or 225Ac, because no alpha-emitting daughters are released upon recoil. We investigated cyclen derivatives with phosphorus-containing pendant arms regarding their suitability for 213Bi labelling. RESULTS: The concentration dependency of 213Bi labelling at 25 °C and 95 °C was determined for DOTP, DOTPH, DOTPEt, and DOTPI, as well as for DOTA and CHX-A"-DTPA for comparison. The labelling efficiency of the phosphorus-containing ligands was at least comparable to CHX-A"-DTPA and exceeded that of DOTA. DOTP was most efficient, requiring chelator concentrations for labelling which were approx. two orders of magnitude lower than those required for CHX-A"-DTPA, both at 25 °C and 95 °C. The 213Bi complexes of phosphorus ligands furthermore showed a higher stability against demetallation (> 96% of intact complex after 120-min incubation in plasma were found for DOTP, DOTPH, and DOTPEt, compared to 85% for DOTA and 76% for CHX-A"-DTPA). CONCLUSION: Cyclen derivatives bearing four N-methylenephosphonic or -phosphinic acid substituents, e.g., DOTP, are capable of complexing the alpha-emitting radionuclide 213BiIII with higher efficiency and in-vitro stability than the current gold standards DOTA and CHX-A"-DTPA.
- Publikační typ
- časopisecké články MeSH
In order to compare the coordination properties of 1,4,7-triazacyclononane (tacn) derivatives bearing varying numbers of phosphinic/carboxylic acid pendant groups towards 68Ga, 1,4,7-triazacyclononane-7-acetic-1,4-bis(methylenephosphinic) acid (NOPA) and 1,4,7- triazacyclononane-4,7-diacetic-1-[methylene(2-carboxyethyl)phosphinic] acid (NO2AP) were synthesized using Mannich reactions with trivalent or pentavalent forms of H-phosphinic acids as phosphorus components. Stepwise protonation constants logK1-3 12.06, 3.90 and 1.95, and stability constants with GaIII and CuII, logKGaL 24.01 and logKCuL 16.66, were potentiometrically determined for NOPA. Both ligands were labelled with 68Ga and compared with NOTA (tacn-N,N',N″-triacetic acid) and NOPO, a TRAP-type [tacn-N,N',N″- tris(methylenephosphinic acid)] chelator. At pH 3, NOPO and NOPA showed higher labelling efficiency (binding with lower ligand excess) at both room temperature and 95 °C, compared to NO2AP and NOTA. Labelling efficiency at pH = 0-3 correlated with a number of phosphinic acid pendants: NOPO > NOPA > NO2AP > NOTA; however, it was more apparent at 95 °C than at room temperature. By contrast, NOTA was found to be labelled more efficiently at pH > 4 compared to the ligands with phosphinic acids. Overall, replacement of a single phosphinate donor with a carboxylate does not challenge 68Ga labelling of TRAP-type chelators. However, the presence of carboxylates facilitates labelling at neutral or weakly acidic pH.
