Two square-planar palladium(II) and platinum(II) azido complexes [M(N 3 )(L)] with L = N-phenyl-2-[1-(2-pyridinyl)ethylidene]hydrazine carbothioamide reacted with four different electron-poor alkynes R−CC−R′ with R = R′ = COOCH 3 , COOEt, COOCH 2 CH 2 OCH 3 or R = CF 3 , R′ = COOEt in a [3 + 2] cycloaddition "iClick" reaction. The resulting triazolate complexes [M-(triazolate R,R' )(L)] were isolated by simple precipitation and/or washing in high purity and good yield. Six out of the eight new compounds feature the triazolate ligand coordinated to the metal center via the N2 nitrogen atom, but fortuitous solubility properties allowed isolation of the N1 isomer in two cases from acetone. When the solvent was changed to DMSO, the N1 → N2 isomerization could be studied by NMR spectroscopy and took several days to complete. 19 F NMR studies of the iClick reaction with F 3 C−CC−COOEt led to identification of a putative early linear intermediate in addition to the N1 and N2 isomers, however with the latter as the final product. Rate constants determined by 1 H or 19 F NMR spectroscopy increased in the order Pd > Pt and CF 3 /COOEt > COOR/COOR with R = CH 3 , Et, CH 2 CH 2 OCH 3 . The second-order rate constant k 2 > 3.7 M −1 s −1 determined for the reaction of [Pd(N 3 )(L)] with F 3 C− CC−COOEt is the fastest observed for an iClick reaction so far and compares favorably with that of the most evolved strained alkynes reported for the SPAAC (strain-promoted azide−alkyne cycloaddition) to date. Selected title compounds were evaluated for their anticancer activity on the GaMG human glioblastoma brain cancer cell line and gave EC 50 values in the low micromolar range (2−16 μM). The potency of the Pd(II) complexes increased with the chain length of the substituents in the 4-and 5-positions of the triazolate ligand.

Glioblastoma (GBM) displays a wide range of inter- and intra-tumoral heterogeneity contributing to therapeutic resistance and relapse. Although Tumor Treating Fields (TTFields) are effective for the treatment of GBM, there is a lack of ex vivo models to evaluate effects on patients’ tumor biology or to screen patients for treatment efficacy. Thus, we adapted patient-derived three-dimensional tissue culture models to be compatible with TTFields application to tissue culture. Patient-derived primary cells (PDPC) were seeded onto murine organotypic hippocampal slice cultures (OHSC), and microtumor development with and without TTFields at 200 kHz was observed. In addition, organoids were generated from acute material cultured on OHSC and treated with TTFields. Lastly, the effect of TTFields on expression of the Ki67 proliferation marker was evaluated on cultured GBM slices. Microtumors exhibited increased sensitivity towards TTFields compared to monolayer cell cultures. TTFields affected tumor growth and viability, as the size of microtumors and the percentage of Ki67-positive cells decreased after treatment. Nevertheless, variability in the extent of the response was preserved between different patient samples. Therefore, these pre-clinical GBM models could provide snapshots of the tumor to simulate patient treatment response and to investigate molecular mechanisms of response and resistance.

OBJECTIVE For glioblastoma patients Tumor Treating Fields (TTFields) have been established as adjuvant therapy. The blood brain barrier (BBB) tightly controls the influx of the majority of compounds from blood to brain. Therefore, the BBB may block delivery of drugs for treatment of brain tumors. Here, the influence of TTFields on BBB permeability was assessed in vivo. METHODS Rats were treated with 100 kHz TTFields for 72 h and thereupon i.v. injected with Evan’s Blue (EB) which directly binds to Albumin. To evaluate effects on BBB, EB was extracted after brain homogenization and quantified. In addition, cryosections of rat brains were prepared following TTFields application. The sections were stained for tight junction proteins Claudin-5 and Occludin and for immunoglobulin G (IgG) to assess vessel structure. Furthermore, serial dynamic contrast-enhanced DCE-MRI with Gadolinium contrast agent was performed before and after TTFields application. RESULTS TTFields application significantly increased the EB accumulation in the rat brain. In TTFields-treated rats, the vessel structure became diffuse compared to control cryosections of rat brains; Claudin 5 and Occludin were delocalized and IgG was found throughout the brain tissue. Serial DCE-MRI demonstrated significantly increased accumulation of Gadolinium in the brain, observed directly after 72 h of TTFields application. The effect of TTFields on the BBB disappeared 96 h after end of treatment and no difference in contrast enhancement between controls and TTFields treated animals was detectable. CONCLUSION By altering BBB integrity and permeability, application of TTFields at 100 kHz may have the potential to deliver drugs to the brain, which are unable to cross the BBB. Utilizing TTFields to open the BBB and its subsequent recovery could be a clinical approach of drug delivery for treatment of brain tumors and other diseases of the central nervous system. These results will be further validated in clinical Trials.

Ten thiosemicarbazone ligands obtained by condensation of pyridine-2-carbaldehyde, quinoline-2-carbaldehyde, 2-acetylpyridine, 2-acetylquinoline, or corresponding 2-pyridyl ketones with thiosemicarbazides RNHC(S)NHNH 2 and R=CH 3 , C 6 H 5 were prepared in good yield. The reaction of [PdCl 2 (cod)] with cod = 1,5-cyclooctadiene or K 2 [PtCl 4 ] resulted in a total of 17 Pd(II) and Pt(II) complexes isolated in excellent purity, as demonstrated by 1 H, 13 C, and, where applicable, 195 Pt NMR spectroscopy combined with CHNS analysis. The cytotoxicity of the title compounds was studied on four human glioblastoma cell lines (GaMG, U87, U138, and U343). The most active compound, with a Pd(II) metal centre, a 2-quinolinyl ring, and methyl groups on both the proximal C and distal N atoms exhibited an EC 50 value of 2.1 μM on the GaMG cell lines, thus being slightly more active than cisplatin (EC 50 3.4 μM) and significantly more potent than temozolomide (EC 50 67.1 μM). Surprisingly, the EC 50 values were inversely correlated with the lipophilicity, as determined with the "shake-flask method", and decreased with the length of the alkyl substituents (C 1 > C 8 > C 10 ). Correlation with the different structural motifs showed that for the most promising anticancer activity, a maximum of two aromatic rings (either quinolinyl or pyridyl plus phenyl) combined with one methyl group are favoured and the Pd(II) complexes are slightly more potent than their Pt(II) analogues.

Glioblastoma leads to a fatal course within two years in more than two thirds of patients. An essential cornerstone of therapy is chemotherapy with temozolomide (TMZ). The effect of TMZ is counteracted by the cellular repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). The MGMT promoter methylation, the main regulator of MGMT expression, can change from primary tumor to recurrence, and TMZ may play a significant role in this process. To identify the potential mechanisms involved, three primary stem-like cell lines (one astrocytoma with the mutation of the isocitrate dehydrogenase (IDH), CNS WHO grade 4 (HGA)), and two glioblastoma (IDH-wildtype, CNS WHO grade 4) were treated with TMZ. The MGMT promoter methylation, migration, proliferation, and TMZ-response of the tumor cells were examined at different time points. The strong effects of TMZ treatment on the MGMT methylated cells were observed. Furthermore, TMZ led to a loss of the MGMT promoter hypermethylation and induced migratory rather than proliferative behavior. Cells with the unmethylated MGMT promoter showed more aggressive behavior after treatment, while HGA cells reacted heterogenously. Our study provides further evidence to consider the potential adverse effects of TMZ chemotherapy and a rationale for investigating potential relationships between TMZ treatment and change in the MGMT promoter methylation during relapse.