Lisa I. Pilkington

A synthesis, in silico, in vitro and in vivo study of thieno[2,3-b]pyridine anticancer analogues

The anticancer activity of the thieno[2,3-b]pyridines was explored by altering the ring size of the cyclo-aliphatic moiety. Five-, six-, seven- and eight-membered derivatives were tested against the NCI60 tumour cell panel. According to this assay the most active derivative 9a has a cyclooctane moiety, which suggests that larger aliphatic ring systems are favourable. For the most sensitive tumour cell line MB-MDA-435, derivative 9a has a GI50 = 70 nM and a LC50 = 925 nM. To explore the biological mechanism of the thieno[2,3-b]pyridines five derivatives were tested against tyrosyl-DNA phosphodiesterase I (TDP1), a phospholipase D enzyme, using a biochemical assay. The most potent derivative for TDP1 was 9d, giving an excellent IC50 at 0.5 ± 0.1 μM. Also, derivative 12 was tested against 97 kinases and no or very limited activity was found, excluding this class of biomolecular targets. Finally, a mouse xenograft study using derivative 12 was encouraging but the tumour size/mass reduction was not quite statistically significant.

Enantioselective Synthesis, Stereochemical Correction, and Biological Investigation of the Rodgersinine Family of 1,4-Benzodioxane Neolignans

The enantioselective synthesis and chiroptic analysis of all members of the rodgersinine family of 1,4-benzodioxane neolignans has been achieved. ECD spectra and optical rotation analysis determined that the previously published stereochemistry of trans-rodgersinines A and B was incorrect. The cis-rodgersinines A and B did not follow the model ECD study commonly used to assign the absolute stereochemistry of 1,4-benzodioxane natural products. This finding has implications on the absolute stereochemistry of other natural products of this type. Additionally, the rodgersinines were found to have anti-HCV activities.

Synthesis and cytotoxicity of thieno[2,3-b]quinoline-2-carboxamide and cycloalkyl[b]thieno[3,2-e]pyridine-2-carboxamide derivatives.

Seventy nine derivatives of thieno[2,3-b]quinolines, tetrahydrothieno[2,3-b]quinoline, dihydrocyclopenta[b]thieno[3,2-e]pyridine, cyclohepta[b]thieno[3,2-e]pyridine and hexahydrocycloocta[b]thieno[3,2-e]pyridine were either synthesized or obtained commercially and tested for their antiproliferative activity against HCT116, MDA-MB-468 and MDA-MB-231 human cancer cell lines. The most potent eight compounds were active against all cell lines with IC50 values in the 80-250nM range. In general hexahydrocycloocta[b]thieno[3,2-e]pyridines were most active with increasing activity observed as larger cycloalkyl rings were fused to the pyridine ring.

Synthesis and antiproliferative activity of 2-chlorophenyl carboxamide thienopyridines

3-Amino-2-arylcarboxamide-thieno[2,3-b]pyridines are a known class of antiproliferative compounds with activity against the phospholipase C enzyme. To further investigate the structure activity relationships of these derivatives a series of analogues were prepared modifying key functional groups. It was determined that modification of the 3-amino and 2-aryl carboxamide functionalities resulted in complete elimination of activity, whilst modification at C-5 allowed compounds of greater activity to be prepared.

Investigation into Improving the Aqueous Solubility of the Thieno[2,3-b]pyridine Anti-Proliferative Agents

It is now established that the thieno[2,3-b]pyridines are a potent class of antiproliferatives. One of the main issues encountered for their clinical application is their low water solubility. In order to improve this, two strategies were pursued. First, a morpholine moiety was tethered to the molecular scaffold by substituting the sulphur atom with nitrogen, resulting in a 1H-pyrrolo[2,3-b]pyridine core structure. The water solubility was increased by three orders of magnitude, from 1.2 µg/mL (1-thieno[2,3-b]pyridine) to 1.3 mg/mL (3-pyrrolo[2,3-b]pyridine), however, it was only marginally active against cancer cells. The second strategy involved loading a very potent thieno[2,3-b]pyridine derivative (2) into a cholesteryl-poly(allylamine) polymer matrix for water solubilisation. Suppression of human pancreatic adenocarcinoma (BxPC-3) viability was observed to an IC50 value of 0.5 μg/mL (1.30 μM) in conjunction with the polymer, which is a five-fold (×5) increase in potency as compared to the free drug alone, demonstrating the utility of this formulation approach.

GPCR Modulation of Thieno[2,3-b]pyridine Anti-Proliferative Agents

A panel of docking scaffolds was developed for the known molecular targets of the anticancer agents, thieno[2,3-b]pyridines, in order to glean insight into their mechanism of action. The reported targets are the copper-trafficking antioxidant 1 protein, tyrosyl DNA phosphodiesterase 1, the colchicine binding site in tubulin, adenosine A2A receptor, and, finally, phospholipase C-δ1. According to the panel, the A2A receptor showed the strongest binding, inferring it to be the most plausible target, closely followed by tubulin. To investigate whether the thieno[2,3-b]pyridines modulate G protein-coupled receptors (GPCRs) other than A2A, a screen against 168 GPCRs was conducted. According to the results, ligand 1 modulates five receptors in the low µM region, four as an antagonist; CRL-RAMP3 (IC50—11.9 µM), NPSR1B (IC50—1.0 µM), PRLHR (IC50—9.3 µM), and CXCR4 (IC50—6.9 µM). Finally, one agonist, GPRR35, was found (EC50 of 7.5 µM). Molecular modelling showed good binding to all of the receptors investigated; however, none of these surpass the A2A receptor. Furthermore, the newly-identified receptors are relatively modestly expressed in the cancer cell lines most affected by the thieno[2,3-b]pyridines, making them less likely to be the main targets of the mechanism of action for this compound class. Nevertheless, new modulators against GPCRs are of an interest as potential hits for further drug development.

Synthesis and biological activity of benzamide DNA minor groove binders.

A range of di- and triaryl benzamides were synthesised to investigate the effect of the presence and nature of a polar sidechain, bonding and substitution patterns and functionalisation of benzylic substituents. These compounds were tested for their antiproliferative activity as well as their DNA binding activity. The most active compounds in all assays were unsymmetrical triaryl benzamides with a bulky or alkylating benzylic substituent and a polar amino sidechain.

Total synthesis of panicein A2

Summary The first total synthesis of the unusual aromatic sesquiterpene panicein A2 is reported and the structure of the natural product has been confirmed. When tested by the NCI against a range of human cancer cell lines, it was found that panicein A2 exhibits very little antiproliferative activity at 10 μM – an observation that is at odds with the earlier report that stated panicein A2 exhibits in vitro cytotoxicity against a number of tumour cell lines.

Antimicrobial synergy of cationic grafted poly(para-phenylene ethynylene) and poly(para-phenylene vinylene) compounds with UV or metal ions against Enterococcus faecium

The rise in multidrug resistant bacteria is an area of growing concern and it is essential to identify new biocidal agents. Cationic grafted compounds were investigated for their antimicrobial properties using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests. Synergy testing was carried out using the compounds in the presence of ultraviolet (UV). Fractional inhibitory concentration (FIC) and fractional bactericidal concentration (FBC) tests were carried out using the cationic molecules in conjunction with metal ion solutions of gold, silver, palladium, platinum, rhodium, titanium, tin, vanadium and molybdenum. Individually, the cationic compounds containing quaternary amines, polyphenylene vinylene (PPV) with long polyacrylate grafts (PPV-g-PMETAC (HMw)), polyphenylene ethylene (PPE) with long polyacrylate grafts (PPE-g-PMETAC (HMw)), polyphenylene vinylene (PPV) with short polyacrylate grafts (PPV-g-PMETAC (LMw)) and polyphenylene ethylene (PPE) with short polyacrylate grafts (PPE-g-PMETAC (LMw)) were effective against Enterococcus faecium. The most successful compound under UV was PPV-g-PMETAC (HMw). Following the FICs, palladium and rhodium ion solutions caused a synergistic reaction with all four tested compounds. The presence of conjugated bonds in the cationic molecules increased its antimicrobial activity. These results suggest that the chemical backbone of the compounds, alongside the chain lengths and chain attachment affect the antimicrobial efficacy of a compound. These factors should be taken into consideration when formulating new biocidal combinations.

Lignans: A Chemometric Analysis

The physicochemical properties of classical lignans, neolignans, flavonolignans and carbohydrate-lignan conjugates (CLCs) were analysed to assess their ADMET profiles and establish if these compounds are lead-like/drug-like and thus have potential to be or act as leads in the development of future therapeutics. It was found that while no studied compounds were lead-like, a very large proportion (>75%) fulfilled all the requirements to be deemed as present in drug-like space and almost all compounds studied were in the known drug space. Principal component analysis was an effective technique that enabled the investigation of the relationship between the studied molecular descriptors and was able to separate the lignans from their sugar derivatives and flavonolignans, primarily according to the parameters that are considered when defining chemical space (i.e., number of hydrogen bond donors, acceptors, rotatable bonds, polar surface area and molecular weight). These results indicate that while CLCs and flavonolignans are less drug-like, lignans show a particularly high level of drug-likeness, an observation that coupled with their potent biological activities, demands future pursuit into their potential for use as therapeutics.