Synthesis and biological evaluation of new disubstituted analogues of 6-methoxy-3-(3′,4′,5′-trimethoxybenzoyl)-1H-indole (BPR0L075), as potential antivascular agents

Structural Investigations of Aroylindole Derivatives through 3D-QSAR and Multiple Pharmacophore Modeling for the Search of Novel Colchicines Inhibitor

Background :

The ligand and structure based integrated strategies are being repeatedly and effectively employed for the precise search and design of novel ligands against various disease targets. Aroylindole derivative has a similar structural analogy as Combretastatin A-4, and exhibited potent anticancer activity on several cancer cell lines.

Objective:

To identify structural features of aroylindole derivatives through 3D-QSAR and multiple pharmacophore modelling for the search of novel colchicines inhibitor via virtual screening.

Method:

The present study utilizes ligand and structure based methodology for the establishment of structure activity correlation among trimethoxyaroylindole derivatives and the search of novel colchicines inhibitor via virtual screening. The 3D-QSAR studies were performed using Phase module and provided details of relationship between structure and biological activity. A single ligand based pharmacophore model was generated from Phase on compound 3 and compound 29 and three energetically optimized structure based pharmacophore models were generated from epharmacophore for co-crystallized ligand, compound 3 and compound 29 with protein PBD ID 1SA0, 5EYP and 5LYJ. These pharmacophoric features containing hit-like compounds were collected from commercially available ZINC database and screened using virtual screening workflow.

Results and Discussion:

The 3D-QSAR model studies with good PLSs statistics for factor four was characterized by the best prediction coefficient Q2 (0.8122), regression R2 (0.9405), SD (0.2581), F (102.7), P (1.56e-015), RMSE (0.402), Stability (0.5411) and Pearson-r (0.9397). The generated epharmacophores have GH scores over 0.5 and AUAC ≥ 0.7 indicated that all the pharmacophores were suitable for pharmacophore-based virtual screening. The virtual screened compounds ZINC12323179, ZINC01642724, and ZINC14238006 have showed similar structural alignment as co-crystallized ligand and showed the hydrogen bonding of ligand with ASN101, SER178, THR179, VAL238, CYS241 amino acid of protein.

Conclusion:

The study illustrates that the ligand and structure based pharmacophoric approach is beneficial for identification of structurally diverse hits, having better binding affinity on colchicines binding site as novel anticancer agents.

Phase I Dose-Escalation Study of SCB01A, a Microtubule Inhibitor with Vascular Disrupting Activity, in Patients with Advanced Solid Tumors

LESSONS LEARNED

SCB01A is a novel microtubule inhibitor with vascular disrupting activity. This first-in-human study demonstrated SCB01A safety, pharmacokinetics, and preliminary antitumor activity. SCB01A is safe and well tolerated in patients with advanced solid malignancies with manageable neurotoxicity.

BACKGROUND

SCB01A, a novel microtubule inhibitor, has vascular disrupting activity.

METHODS

In this phase I dose-escalation and extension study, patients with advanced solid tumors were administered intravenous SCB01A infusions for 3 hours once every 21 days. Rapid titration and a 3 + 3 design escalated the dose from 2 mg/m² to the maximum tolerated dose (MTD) based on dose-limiting toxicity (DLT). SCB01A-induced cellular neurotoxicity was evaluated in dorsal root ganglion cells. The primary endpoint was MTD. Safety, pharmacokinetics (PK), and tumor response were secondary endpoints.

RESULTS

Treatment-related adverse events included anemia, nausea, vomiting, fatigue, fever, and peripheral sensorimotor neuropathy. DLTs included grade 4 elevated creatine phosphokinase (CPK) in the 4 mg/m² cohort; grade 3 gastric hemorrhage in the 6.5 mg/m² cohort; grade 2 thromboembolic event in the 24 mg/m² cohort; and grade 3 peripheral sensorimotor neuropathy, grade 3 elevated aspartate aminotransferase, and grade 3 hypertension in the 32 mg/m² cohort. The MTD was 24 mg/m² , and average half-life was ~2.5 hours. The area under the curve-dose response relationship was linear. Nineteen subjects were stable after two cycles. The longest treatment lasted 24 cycles. SCB01A-induced neurotoxicity was reversible in vitro.

CONCLUSION

The MTD of SCB01A was 24 mg/m² every 21 days; it is safe and tolerable in patients with solid tumors.

Tubulin inhibitors targeting the colchicine binding site: a perspective of privileged structures

The vital roles of microtubule in mitosis and cell division make it an attractive target for antitumor therapy. Colchicine binding site of tubulin is one of the most important pockets that have been focused on to design tubulin-destabilizing agents. Over the past few years, a large number of colchicine binding site inhibitors (CBSIs) have been developed inspired by natural products or synthetic origins, and many moieties frequently used in these CBSIs are structurally in common. In this review, we will classify the CBSIs into classical CBSIs and nonclassical CBSIs according to their spatial conformations and binding modes with tubulin, and highlight the privileged structures from these CBSIs in the development of tubulin inhibitors targeting the colchicine binding site.

Synthesis and biological evaluation of isomeric methoxy substitutions on anti-cancer indolyl-pyridinyl-propenones: Effects on potency and mode of activity

Certain indolyl-pyridinyl-propenone analogues kill glioblastoma cells that have become resistant to conventional therapeutic drugs. Some of these analogues induce a novel form of non-apoptotic cell death called methuosis, while others primarily cause microtubule disruption. Ready access to 5-indole substitution has allowed characterization of this position to be important for both types of mechanisms when a simple methoxy group is present. We now report the syntheses and biological effects of isomeric methoxy substitutions on the indole ring. Additionally, analogues containing a trimethoxyphenyl group in place of the pyridinyl moiety were evaluated for anticancer activity. The results demonstrate that the location of the methoxy group can alter both the potency and the mechanism of cell death. Remarkably, changing the methoxy from the 5-position to the 6-position switched the biological activity from induction of methuosis to disruption of microtubules. The latter may represent a prototype for a new class of mitotic inhibitors with potential therapeutic utility.

Synthesis of a 2-aryl-3-aroyl indole salt (OXi8007) resembling combretastatin A-4 with application as a vascular disrupting agent

The natural products colchicine and combretastatin A-4 are potent inhibitors of tubulin assembly, and they have inspired the design and synthesis of a large number of small-molecule, potential anticancer agents. The indole-based molecular scaffold is prominent among these SAR modifications, leading to a rapidly increasing number of agents. The water-soluble phosphate prodrug 33 (OXi8007) of 2-aryl-3-aroylindole-based phenol 8 (OXi8006) was prepared by chemical synthesis and found to be strongly cytotoxic against selected human cancer cell lines (GI₅₀ = 36 nM against DU-145 cells, for example). The free phenol, 8 (OXi8006), was a strong inhibitor (IC₅₀ = 1.1 μM) of tubulin assembly. The corresponding phosphate prodrug 33 (OXi8007) also demonstrated pronounced interference with tumor vasculature in a preliminary in vivo study utilizing a SCID mouse model bearing an orthotopic PC-3 (prostate) tumor as imaged by color Doppler ultrasound. The combination of these results provides evidence that the indole-based phosphate prodrug 33 (OXi8007) functions as a vascular disrupting agent that may prove useful for the treatment of cancer.

Synthesis and biological evaluation of indole-based, anti-cancer agents inspired by the vascular disrupting agent 2-(3'-hydroxy-4'-methoxyphenyl)-3-(3″,4″,5″-trimethoxybenzoyl)-6-methoxyindole (OXi8006)

The discovery of a 2-aryl-3-aroyl indole-based small-molecule inhibitor of tubulin assembly (referred to as OXi8006) inspired the design, synthesis, and biological evaluation of a series of diversely functionalized analogues. In the majority of examples, the pendant 2-aryl ring contained a 3-hydroxy-4-methoxy substitution pattern, and the fused aryl ring featured a 6-methoxy group. Most of the variability was in the 3-aroyl moiety, which was modified to incorporate methoxy (33-36), nitro (25-27), halogen (28-29), trifluoromethyl (30), or trifluoromethoxy (31-32) functionalities. In two analogues (34 and 36), the methoxy substitution pattern in the fused aryl ring varied, while in another derivative (35) the phenolic moiety was translocated from the pendant 2-aryl ring to position-7 of the fused aryl ring. Each of the compounds were evaluated for their cytotoxicity (in vitro) against the SK-OV-3 (ovarian), NCI-H460 (lung), and DU-145 (prostate) human cancer cell lines and for their ability to inhibit tubulin assembly. Four of the compounds (30, 31, 35, 36) proved to be potent inhibitors of tubulin assembly (IC50 <5μM), and three of these compounds (31, 35, 36) were strongly cytotoxic against the three cancer cell lines. The most active compound (36) in this series, which incorporated a methoxy group at position-7, was comparable in terms of inhibition of tubulin assembly and cytotoxicity to the lead compound OXi8006.

Indole molecules as inhibitors of tubulin polymerization: potential new anticancer agents

Agents that interfere with tubulin function have a broad anti-tumor spectrum and they represent one of the most significant classes of anticancer agents. In the past few years, several small synthetic molecules that have an indole nucleus as a core structure have been identified as tubulin inhibitors. Among these, several aroylindoles, arylthioindoles, diarylindoles and indolylglyoxyamides have shown good inhibition towards the tubulin polymerization. This article reviews the synthesis, biological activities and SARs of these main classes of indoles. Brief mention has also been made about the fused indole analogs as tubulin inhibitors.

Discovery of 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105), a tubulin polymerization inhibitor with potent antiproliferative and tumor vascular disrupting properties

A structure-activity relationship (SAR) guided design of novel tubulin polymerization inhibitors has resulted in a series of benzo[b]furans with exceptional potency toward cancer cells and activated endothelial cells. The potency of early lead compounds has been substantially improved through the synergistic effect of introducing a conformational bias and additional hydrogen bond donor to the pharmacophore. Screening of a focused library of potent tubulin polymerization inhibitors for selectivity against cancer cells and activated endothelial cells over quiescent endothelial cells has afforded 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105, 8) as a potent and selective antiproliferative. Because of poor solubility, 8 is administered as its disodium phosphate ester prodrug 9 (BNC105P), which is rapidly cleaved in vivo to return the active 8. 9 exhibits both superior vascular disrupting and tumor growth inhibitory properties compared with the benchmark agent combretastatin A-4 disodium phosphate 5 (CA4P).

Domino approach to 2-aroyltrimethoxyindoles as novel heterocyclic combretastatin A4 analogues

Two series of 2-aroyltrimethoxyindoles were designed to investigate the effects of the replacement of the trimethoxyphenyl ring of phenstatin with a trimethoxyindole moiety. These compounds were efficiently prepared through a domino palladium-catalyzed sequence from 2-gem-dibromovinylanilines substituted by three methoxy groups and arylboronic acids under carbon monoxide atmosphere. These novel heterocyclic combretastatin A4 analogues were evaluated for their cell growth inhibitory properties and their ability to inhibit the tubulin polymerization.

Synthesis and evaluation of 3-aroylindoles as anticancer agents: metabolite approach

BPR0L075 (2) is a potential anticancer drug candidate designed from Combretastatin A-4 (1) based on the bioisosterism principle. Metabolites of 2, proposed from in vitro human microsome studies, were synthesized, leading to the identification of metabolite-derived analogue 10 with 40-350 pM potency against various cancer cell lines. Insights gained from the major inactive metabolite of 2 led to the development of 29, with better pharmacokinetics and improved potency in the tumor xenograft model than 2.