Exploring the anticancer activity and the mechanism of action of pyrrolomycins F obtained by microwave-assisted total synthesis.

Pyrrolomycins (PMs) are a family of naturally occurring antibiotic agents, isolated from the fermentation broth of Actinosporangium and Streptomyces species. Pursuing our studies on pyrrolomycins, we performed the total synthesis of the F-series pyrrolomycins (1-4) by microwave-assisted synthesis (MAOS), thus obtaining the title compounds in excellent yields (63-69%). Considering that there is no evidence so far of the anticancer effect of this class of compounds, we investigated PMs for their antiproliferative activity against HCT116 and MCF-7 cancer cell lines. PMs showed anticancer activity at submicromolar level with a minimal effect on normal epithelial cell line (hTERT RPE-1), and they were able to induce several morphological changes including elongated cells, cytoplasm vacuolization, long and thin filopodia as well as the appearance of tunneling nanotubes (TNTs). These data suggest that PMs could act by impairing the cell membranes and the cytoskeleton organization, with subsequent increase of ROS generation and the activation of different forms of non-apoptotic cell death.

Peptidomimetics: An Overview of Recent Medicinal Chemistry Efforts toward the Discovery of Novel Small Molecule Inhibitors.

The use of peptides as therapeutics has often been associated with several drawbacks such as poor absorption, low stability to proteolytic digestion, and fast clearance. Peptidomimetics are developed by modifications of native peptides with the aim of obtaining molecules that are more suitable for clinical development and, for this reason, are widely used as tools in medicinal chemistry programs. The effort to disclose innovative peptidomimetic therapies is recurrent and constantly evolving as demonstrated by the new lead compounds in clinical trials. Synthetic strategies for the development of peptidomimetics have also been implemented with time. This perspective highlights some of the most recent efforts for the design and synthesis of peptidomimetic agents together with their biological evaluation toward a panel of targets.

Pyrrolidine in Drug Discovery: A Versatile Scaffold for Novel Biologically Active Compounds.

The five-membered pyrrolidine ring is one of the nitrogen heterocycles used widely by medicinal chemists to obtain compounds for the treatment of human diseases. The great interest in this saturated scaffold is enhanced by (1) the possibility to efficiently explore the pharmacophore space due to sp3-hybridization, (2) the contribution to the stereochemistry of the molecule, (3) and the increased three-dimensional (3D) coverage due to the non-planarity of the ring-a phenomenon called "pseudorotation". In this review, we report bioactive molecules with target selectivity characterized by the pyrrolidine ring and its derivatives, including pyrrolizines, pyrrolidine-2-one, pyrrolidine-2,5-diones and prolinol described in the literature from 2015 to date. After a comparison of the physicochemical parameters of pyrrolidine with the parent aromatic pyrrole and cyclopentane, we investigate the influence of steric factors on biological activity, also describing the structure-activity relationship (SAR) of the studied compounds. To aid the reader's approach to reading the manuscript, we have planned the review on the basis of the synthetic strategies used: (1) ring construction from different cyclic or acyclic precursors, reporting the synthesis and the reaction conditions, or (2) functionalization of preformed pyrrolidine rings, e.g., proline derivatives. Since one of the most significant features of the pyrrolidine ring is the stereogenicity of carbons, we highlight how the different stereoisomers and the spatial orientation of substituents can lead to a different biological profile of drug candidates, due to the different binding mode to enantioselective proteins. We believe that this work can guide medicinal chemists to the best approach in the design of new pyrrolidine compounds with different biological profiles.

Bioactive pyrrole-based compounds with target selectivity.

The discovery of novel synthetic compounds with drug-like properties is an ongoing challenge in medicinal chemistry. Natural products have inspired the synthesis of compounds for pharmaceutical application, most of which are based on N-heterocyclic motifs. Among these, the pyrrole ring is one of the most explored heterocycles in drug discovery programs for several therapeutic areas, confirmed by the high number of pyrrole-based drugs reaching the market. In the present review, we focused on pyrrole and its hetero-fused derivatives with anticancer, antimicrobial, and antiviral activities, reported in the literature between 2015 and 2019, for which a specific target was identified, being responsible for their biological activity. It emerges that the powerful pharmaceutical and pharmacological features provided by the pyrrole nucleus as pharmacophore unit of many drugs are still recognized by medicinal chemists.

New Imidazo[2,1-b][1,3,4]Thiadiazole Derivatives Inhibit FAK Phosphorylation and Potentiate the Antiproliferative Effects of Gemcitabine Through Modulation of the Human Equilibrative Nucleoside Transporter-1 in Peritoneal Mesothelioma.

BACKGROUND/AIM: A new class of imidazo[2,1-b][1,3,4]thiadiazole compounds have recently been evaluated as inhibitors of phosphorylation of focal adhesion kinase (FAK) in pancreatic cancer. FAK is overexpressed in mesothelioma and has recently emerged as an interesting target for the treatment of this disease. MATERIALS AND METHODS: Ten imidazo[2,1-b][1,3,4]thiadiazole compounds characterized by indole bicycle and a thiophene ring, were evaluated for their cytotoxic activity in two primary cell cultures of peritoneal mesothelioma, MesoII and STO cells. RESULTS: Compounds 1a and 1b showed promising antitumor activity with IC50 values in the range of 0.59 to 2.81 µM in both cell lines growing as monolayers or as spheroids. Their antiproliferative and antimigratory activity was associated with inhibition of phospho-FAK, as detected by a specific ELISA assay in STO cells. Interestingly, these compounds potentiated the antiproliferative activity of gemcitabine, and these results might be explained by the increase in the mRNA expression of the key gemcitabine transporter human equilibrative nucleoside transporter-1 (hENT-1). CONCLUSION: These promising results support further studies on new imidazo[2,1-b][1,3,4]thiadiazole compounds as well as on the role of both FAK and hENT-1 modulation in order to develop new drug combinations for peritoneal mesothelioma.

Impact of hypoxia on chemoresistance of mesothelioma mediated by the proton-coupled folate transporter, and preclinical activity of new anti-LDH-A compounds.

BACKGROUND: Expression of proton-coupled folate transporter (PCFT) is associated with survival of mesothelioma patients treated with pemetrexed, and is reduced by hypoxia, prompting studies to elucidate their correlation. METHODS: Modulation of glycolytic gene expression was evaluated by PCR arrays in tumour cells and primary cultures growing under hypoxia, in spheroids and after PCFT silencing. Inhibitors of lactate dehydrogenase (LDH-A) were tested in vitro and in vivo. LDH-A expression was determined in tissue microarrays of radically resected malignant pleural mesothelioma (MPM, N = 33) and diffuse peritoneal mesothelioma (DMPM, N = 56) patients. RESULTS: Overexpression of hypoxia marker CAIX was associated with low PCFT expression and decreased MPM cell growth inhibition by pemetrexed. Through integration of PCR arrays in hypoxic cells and spheroids and following PCFT silencing, we identified the upregulation of LDH-A, which correlated with shorter survival of MPM and DMPM patients. Novel LDH-A inhibitors enhanced spheroid disintegration and displayed synergistic effects with pemetrexed in MPM and gemcitabine in DMPM cells. Studies with bioluminescent hypoxic orthotopic and subcutaneous DMPM athymic-mice models revealed the marked antitumour activity of the LDH-A inhibitor NHI-Glc-2, alone or combined with gemcitabine. CONCLUSIONS: This study provides novel insights into hypoxia/PCFT-dependent chemoresistance, unravelling the potential prognostic value of LDH-A, and demonstrating the preclinical activity of LDH-A inhibitors.

New Synthetic Nitro-Pyrrolomycins as Promising Antibacterial and Anticancer Agents.

: Pyrrolomycins (PMs) are polyhalogenated antibiotics known as powerful biologically active compounds, yet featuring high cytotoxicity. The present study reports the antibacterial and antitumoral properties of new chemically synthesized PMs, where the three positions of the pyrrolic nucleus were replaced by nitro groups, aiming to reduce their cytotoxicity while maintaining or even enhancing the biological activity. Indeed, the presence of the nitro substituent in diverse positions of the pyrrole determined an improvement of the minimal bactericidal concentration (MBC) against Gram-positive (i.e., Staphylococcus aureus) or -negative (i.e., Pseudomonas aeruginosa) pathogen strains as compared to the natural PM-C. Moreover, some new nitro-PMs were as active as or more than PM-C in inhibiting the proliferation of colon (HCT116) and breast (MCF 7) cancer cell lines and were less toxic towards normal epithelial (hTERT RPE-1) cells. Altogether, our findings contribute to increase the knowledge of the mode of action of these promising molecules and provide a basis for their rationale chemical or biological manipulation.

3-(6-Phenylimidazo [2,1-b][1,3,4]thiadiazol-2-yl)-1H-Indole Derivatives as New Anticancer Agents in the Treatment of Pancreatic Ductal Adenocarcinoma.

A new series of imidazo[2,1-b][1,3,4]thiadiazole derivatives was efficiently synthesized and screened for their in vitro antiproliferative activity on a panel of pancreatic ductal adenocarcinoma (PDAC) cells, including SUIT-2, Capan-1 and Panc-1. Compounds 9c and 9l, showed relevant in vitro antiproliferative activity on all three pre-clinical models with half maximal inhibitory concentration (IC50) ranging from 5.11 to 10.8 µM, while the compounds 9e and 9n were active in at least one cell line. In addition, compound 9c significantly inhibited the migration rate of SUIT-2 and Capan-1 cells in the scratch wound-healing assay. In conclusion, our results will support further studies to increase the library of imidazo [2,1-b][1,3,4] thiadiazole derivatives for deeper understanding of the relationship between biological activity of the compounds and their structures in the development of new antitumor compounds against pancreatic diseases.

To Combine or Not Combine: Drug Interactions and Tools for Their Analysis. Reflections from the EORTC-PAMM Course on Preclinical and Early-phase Clinical Pharmacology.

Combination therapies are used in the clinic to achieve cure, better efficacy and to circumvent resistant disease in patients. Initial assessment of the effect of such combinations, usually of two agents, is frequently performed using in vitro assays. In this review, we give a short summary of the types of analyses that were presented during the Preclinical and Early-phase Clinical Pharmacology Course of the Pharmacology and Molecular Mechanisms Group, European Organization for Research and Treatment on Cancer, that can be used to determine the efficacy of drug combinations. The effect of a combination treatment can be calculated using mathematical equations based on either the Loewe additivity or Bliss independence model, or a combination of both, such as Chou and Talalay's median-drug effect model. Interactions can be additive, synergistic (more than additive), or antagonistic (less than additive). Software packages CalcuSyn (also available as CompuSyn) and Combenefit are designed to calculate the extent of the combined effects. Interestingly, the application of machine-learning methods in the prediction of combination treatments, which can include pharmacogenomic, genetic, metabolomic and proteomic profiles, might contribute to further refinement of combination regimens. However, more research is needed to apply appropriate rules of machine learning methods to ensure correct predictive models.

A Brief Guide to Performing Pharmacological Studies In Vitro: Reflections from the EORTC-PAMM Course "Preclinical and Early-phase Clinical Pharmacology".

One aim of cell-based in vitro assays is to identify the best drug candidate to develop using the best tumor cell model. This is challenging in every anticancer drug discovery process. Briefly, we summarize the parameters to be taken into account when performing in vitro cell assays, in order to obtain reliable and reproducible results, which was fundamentally discussed by lecturers at the educational course on preclinical and early-phase clinical pharmacology studies, at the 40th Winter Meeting of the Pharmacology and Molecular Mechanisms Group of the European Organization for Research and Treatment of Cancer. Moreover, specific cellular sensitivity tests are described. In addition to monolayer in vitro cell models for the screening of new potential candidate drugs, three-dimensional tumor/cell tissue models are emerging as new pre-clinical tools that more closely reflect the in vivo microenvironment. Therefore, the use of different in vitro models for drug screening can enhance the predictability and reliability of pre-clinical drug-discovery phases and target validation.

Biological Evaluation of the Antiproliferative and Anti-migratory Activity of a Series of 3-(6-Phenylimidazo[2,1-b][1,3,4]thiadiazol-2-yl)-1H-indole Derivatives Against Pancreatic Cancer Cells.

Heterocyclic rings are recognized as key components of many natural, semi-synthetic and synthetic molecules with a broad spectrum of biological activities. Among these molecules, the indole and imidazo[2,1-b][1,3,4]thiadiazole systems have recently been described as useful scaffolds for the design of anticancer agents. Herein the antitumor activity of a series of 3-(6-phenylimidazo[2,1-b][1,3,4]thiadiazol-2-yl)-1H-indoles, designed as hybrid structures, was assessed. Seven out of 10 compounds (1a-g) were submitted to National Cancer Institute (NCI). Remarkably, compound 1g showed antiproliferative activity against the full panel of sixty human cancer lines, with half-maximal inhibitory concentration of between 1.67 and 10.3 µM. Further studies showed antiproliferative activity of 1a-g and of three additional compounds 1h, 1i and 1l, with different substituents on the indole nucleus and phenyl ring, against three pancreatic cancer cell lines. In particular, derivatives 1g and 1h inhibited both proliferation and migration of SUIT-2 cells at concentrations lower than 10 µM. In conclusion, new indole derivatives are characterized by in vitro antitumor activity, supporting future mechanistic studies.

Pharmacogenetics of treatments for pancreatic cancer.

Introduction: Despite clinical efforts, pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. The scarcity of effective therapies can be reflected by the lack of reliable biomarkers to adapt anticancer drugs prescription to tumors' and patients' features. Areas covered: Pharmacogenetics should provide the way to select patients who may benefit from a specific therapy that best matches individual and tumor genetic profile, but it has not yet led to gains in outcome. This review describes PDAC pharmacogenetics findings, critically reappraising studies on polymorphisms and -omics profiles correlated to response to gemcitabine, FOLFIRINOX, and nab-paclitaxel combinations, as well as limitations of targeted therapies. Further, we question whether personalized approaches will benefit patients to any significant degree, supporting the need of new strategies within well-designed trials and validated genomic tests for treatment decision-making. Expert opinion: A major challenge in PDAC is the identification of subgroups of patients who will benefit from treatments. Minimally-invasive tests to analyze biomarkers of drug sensitivity/toxicity should be developed alongside anticancer treatments. However, progress might fall below expectations because of tumor heterogeneity and clonal evolution. Whole-genome sequencing and liquid biopsies, as well as prospective validation in selected cohorts, should overcome the limitations of traditional pharmacogenetic approaches.