Imidazo[1,2-a]quinoxalines for melanoma treatment with original mechanism of action.

The malignant transformation of melanocytes causes several thousand deaths each year, making melanoma an important public health concern. Melanoma is the most aggressive skin cancer, which incidence has regularly increased over the past decades. We described here the preparation of new compounds based on the 1-(3,4-dihydroxyphenyl)imidazo[1,2-a]quinoxaline structure. Different positions of the quinoxaline moiety were screened to introduce novel substituents in order to study their influence on the biological activity. Several alkylamino or alkyloxy groups were also considered to replace the methylamine of our first generation of Imiqualines. Imidazo[1,2-a]pyrazine derivatives were also designed as potential minimal structure. The investigation on A375 melanoma cells displayed interesting in vitro low nanomolar cytotoxic activity. Among them, 9d (EAPB02303) is particularly remarkable since it is 20 times more potent than vemurafenib, the reference clinical therapy used on BRAF mutant melanoma. Contrary to the first generation, EAPB02303 does not inhibit tubulin polymerization, as confirmed by an in vitro assay and a molecular modelisation study. The mechanism of action for EAPB02303 highlighted by a transcriptomic analysis is clearly different from a panel of 12 well-known anticancer drugs. In vivoEAPB02303 treatment reduced tumor size and weight of the A375 human melanoma xenografts in a dose-dependent manner, correlated with a low mitotic index but not with necrosis.

Vegetable Oil-based Hybrid Submicron Particles Loaded with JMV5038: A Promising Formulation against Melanoma.

The aim of this work was to carry out a preformulation study on JMV5038 as a new potent cytotoxic agent, and to develop its formulation within vegetable oil-based hybrid submicron particles (HNP) in order to obtain a versatile dosage form against melanoma. JMV5038 was first characterized through physico-chemical tests and it exhibited high melting point and logP value, an important pH-sensitivity that led to the formation of well-identified degradation products at low pH, as well as a substantial solubility value in silylated castor oil (ICO). Then, JMV5038-loaded HNP were formulated through a thermostabilized emulsion process based on the sol-gel cross-linking of ICO. They showed high loading efficiency and their in vitro release kinetic assessed in a biorelevant PBS/octanol biphasic system showed a constant sustained release over one month. The cytotoxic activity and cytocompatibility of HNP were evaluated on A375 melanoma cells and NIH 3T3 cells, respectively. JMV5038-loaded HNP exhibited a slightly enhanced cytotoxic activity of JMV5038 on melanoma cells while demonstrating their safety on NIH 3T3 cells. In conclusion, JMV5038-loaded HNP proved to be an efficient and safe drug subcutaneous delivery system that will be interesting to evaluate through preclinical studies.

Imidazopyridine-fused [1,3]diazepinones: modulations of positions 2 to 4 and their impacts on the anti-melanoma activity.

A series of 19 novel pyrido-imidazodiazepinones, with modulations of positions 2, 3 and 4 of the diazepine ring were synthesised and screened for their in vitro cytotoxic activities against two melanoma cell lines (A375 and MDA-MB-435) and for their potential toxicity against NIH-3T3 non-cancerous cells. Selected compounds were also evaluated on the NCI-60 cell line panel. The SAR study revealed that the molecular volume and the cLogP of compounds modified at position 2 were significantly correlated with the activity of these compounds on melanoma cell lines. Moreover, introduction of a heterocyclic group at position 2 or an azido-alkyl chain at position 4 led to compounds displaying a significantly different activity profile on the NCI-60 cell line panel, compared to phenyl-substituted compounds at position 2 of the diazepinone. This study provides us crucial information for the development of new derivatives active against melanoma.

New imidazoquinoxaline derivatives: Synthesis, biological evaluation on melanoma, effect on tubulin polymerization and structure-activity relationships.

Microtubules are considered as important targets of anticancer therapy. EAPB0503 and its structural imidazo[1,2-a]quinoxaline derivatives are major microtubule-interfering agents with potent anticancer activity. In this study, the synthesis of several new derivatives of EAPB0503 is described, and the anticancer efficacy of 13 novel derivatives on A375 human melanoma cell line is reported. All new compounds show significant antiproliferative activity with IC50 in the range of 0.077-122µM against human melanoma cell line (A375). Direct inhibition of tubulin polymerization assay in vitro is also assessed. Results show that compounds 6b, 6e, 6g, and EAPB0503 highly inhibit tubulin polymerization with percentages of inhibition of 99%, 98%, 90%, and 84% respectively. Structure-activity relationship studies within the series are also discussed in line with molecular docking studies into the colchicine-binding site of tubulin.

Lysosomes and unfolded protein response, determinants of differential resistance of melanoma cells to vinca alkaloids.

On account of its strong ability to become chemoresistant after a primary response to drugs, malignant melanoma (MM) remains a therapeutic challenge. This study focuses on acquired resistance to vinca alkaloids (VAs) using VA-resistant MM cell lines (CAL1R-VCR, CAL1R-VDS, and CAL1R-VRB), established by long-term continuous exposure of parental CAL1-wt cells to vincristine (VCR), vindesine (VDS), or vinorelbine (VRB), respectively. Transcriptomic profiling using rma and rdam methods led to distinguish two cell groups: CAL1R-VCR and CAL1R-VDS, CAL1R-VRB, and CAL1-wt. mgsa of the specifically altered genes in the first group evidenced the GO terms 'lysosomal lumen' and 'vacuolar lumen' linked to underexpressed genes, and 'endoplasmic reticulum (ER) stress response' associated with overexpressed genes. A specific reduction of lysosomal enzymes, independent of acidic vacuole organelle (AVO) turnover, was observed (LTG probe) in CAL1R-VCR and CAL1R-VDS cells. It was associated with the specific lowering of cathepsin B and L, known to be involved in the lysosomal pathway of apoptosis. Confirming gene profiling, the same groups (CAL1R-VCR and CAL1R-VDS, CAL1-wt and CAL1R-VRB) could be distinguished regarding the VA-mediated changes on mean size areas and on acidic compartment volumes. These two parameters were reduced in CAL1R-VCR and CAL1R-VDS cells, suggesting a smaller AVO accumulation and thus a reduced sensitivity to lysosomal membrane permeabilization-mediated apoptosis. In addition, 'ER stress response' inhibition by tauroursodeoxycholic acid induced a higher VA sensitization of the first cell group. In conclusion, lysosomes and unfolded protein response could be key determinants of the differential resistance of MM to VAs.

Differential involvement of glutathione S-transferase mu 1 and multidrug resistance protein 1 in melanoma acquired resistance to vinca alkaloids.

On account of its extreme intrinsic resistance to apoptosis and of its strong ability to become chemoresistant after a primary response to drugs, malignant melanoma (MM) is still a therapeutic challenge. We previously showed that glutathione S-transferase mu 1 (GSTM1) acts in synergy with multidrug resistance protein 1 (MRP1) to protect GSTM1-transfected human CAL1 melanoma cells from toxic effects of vincristine (VCR). Herein, we investigated the role of these proteins in the acquired resistance of CAL1 cells to vinca alkaloids (VAs). Resistant lines were established by continuous exposure (>1 year) of parental CAL1-wt cells to VCR, vindesine (VDS), or vinorelbine (VRB): CAL1R-VCR, CAL1R-VDS, CAL1R-VRB, respectively. All resistant lines displayed more than 10-fold increase in resistance to their selection VA, and specifically expressed GSTM1. Suggesting a direct interaction between this protein and VAs, each VA specifically decreased the GSTM1-mediated glutathione conjugation activity in cell lysates. Curcumin (GSTM1 inhibitor), BSO (glutathione synthesis inhibitor), and MK571 (MRP1 inhibitor) considerably reversed the acquired resistance to VCR and VDS, but not to VRB. Microarray data analysis revealed similar gene expression patterns of CAL1R-VCR and CAL1R-VDS, and a distinct one for CAL1R-VRB. These data suggest a differential involvement of GSTM1 and MRP1 in acquired resistance to VAs. A coordinated expression and activity of GSTM1 and MRP1 is required to protect CAL1 cells from VCR and VDS, while the simple expression of GSTM1 is sufficient, possibly by a direct drug/protein interaction, to confer resistance against VRB.