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1.
J Med Chem ; 63(5): 2358-2371, 2020 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-31589041

RESUMO

G-protein-coupled receptors like the human Y1 receptor (hY1R) are promising targets in cancer therapy due to their high overexpression on cancer cells and their ability to internalize together with the bound ligand. This mechanism was exploited to shuttle boron atoms into cancer cells for the application of boron neutron capture therapy (BNCT), a noninvasive approach to eliminate cancer cells. A maximized number of carboranes was introduced to the hY1R-preferring ligand [F7,P34]-NPY by solid phase peptide synthesis. Branched conjugates loaded with up to 80 boron atoms per peptide molecule exhibited a maintained receptor activation profile, and the selective uptake into hY1R-expressing cells was demonstrated by internalization studies. In order to ensure appropriate solubility in aqueous solution, we proved the need for eight hydroxyl groups per carborane. Thus, we suggest the utilization of bis-deoxygalactosyl-carborane building blocks in solid phase peptide synthesis to produce selective boron delivery agents for BNCT.

2.
J Org Chem ; 85(3): 1446-1457, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31813224

RESUMO

Boron neutron capture therapy (BNCT) allows the selective elimination of malignant tumor cells without affecting healthy tissue. Although this binary radiotherapy approach has been known for decades, BNCT failed to reach the daily clinics to date. One of the reasons is the lack of selective boron delivery agents. Using boron loaded peptide conjugates, which address G protein-coupled receptors overexpressed on tumor cells allow the intracellular accumulation of boron. The gastrin-releasing peptide receptor (GRPR) is a well-known target in cancer diagnosis and can potentially be used for BNCT. Here, we present the successful introduction of multiple bis-deoxygalactosyl-carborane building blocks to the GRPR-selective ligand [d-Phe6, ß-Ala11, Ala13, Nle14]Bn(6-14) (sBB2L) generating peptide conjugates with up to 80 boron atoms per molecule. Receptor activation was retained, metabolic stability was increased, and uptake into PC3 cells was proven without showing any intrinsic cytotoxicity. Furthermore, undesired uptake into liver cells was suppressed by using l-deoxygalactosyl modified carborane building blocks. Due to its high boron loading and excellent GRPR selectivity, this conjugate can be considered as a promising boron delivery agent for BNCT.

3.
J Pept Sci ; 24(10): e3119, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30168238

RESUMO

Boron neutron capture therapy (BNCT) is a binary cancer therapy, which combines the biochemical targeting of a boron-containing drug with the regional localization of radiation treatment. Although the concept of BNCT has been known for decades, the selective delivery of boron into tumor cells remains challenging. G protein-coupled receptors that are overexpressed on cancer cells in combination with peptidic ligands can be potentially used as shuttle system for a tumor-directed boron uptake. In this study, we present the generation of short, boron-rich peptide conjugates that target the ghrelin receptor. Expression of the ghrelin receptor on various cancer cells makes it a viable target for BNCT. We designed a novel hexapeptide super-agonist that was modified with different specifically synthesized carborane monoclusters and tested for ghrelin receptor activation. A meta-carborane building block with a mercaptoacetic acid linker was found to be optimal for peptide modification, owing to its chemical stability and a suitable activation efficacy of the conjugate. The versatility of this carborane for the development of peptidic boron delivery agents was further demonstrated by the generation of highly potent, boron-loaded conjugates using the backbone of the known ghrelin receptor ligands growth hormone releasing peptide 6 and Ipamorelin.


Assuntos
Boro/farmacologia , Peptídeos/síntese química , Receptores de Grelina/agonistas , Boro/química , Terapia por Captura de Nêutron de Boro , Portadores de Fármacos , Células HEK293 , Humanos , Oligopeptídeos/química , Peptídeos/química
4.
Chem Sci ; 7(6): 3569-3573, 2016 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29997849

RESUMO

The impact of remote substituents on the affinity of cucurbit[n]urils (CB[n]) towards a homologous series of guests, which differ from one another only by a single substituent, and adopt the same geometry within the cavity of the macrocycle, is presented for the first time, and is used to decipher the competition between water and the carbonylated portal of CB[7] for the stabilization of positively charged guests. Binding affinities of CB[7] towards substituted N-benzyl-trimethylsilylmethylammonium cations relative to the unsubstituted member (X = H) range from 0.9 (X = CH3) to 3.1 (X = SO2CF3), and correlate very precisely with a linear combination of Swain-Lupton field/inductive (F; 67%) and resonance (R; 33%) parameters tabulated for each substituent. We show that this subtle sensitivity results exclusively from the balance between two competing mechanisms, on which the substituents exert an approximately 11 times greater impact: (1) the solvation of the ammonium unit and its immediate surroundings by water in the free guests, and (2) the coulombic attraction between the ammonium unit and the rim of CB[7] in the complexes.

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