Mitochondria-targeted metformin (mitomet) inhibits lung cancer in cellular models and in mice by enhancing the generation of reactive oxygen species

Lung cancer is the leading cause of cancer-related mortality in the United States. Although some epidemiological studies have shown an inverse relationship between the use of metformin, a widely used antidiabetic drug, and the incidence of lung cancer, the real benefits of the drug are unclear as the efficacy is low and the outcomes are quite heterogeneous. To develop a more potent form of metformin, we synthesized mitochondria-targeted metformin (mitomet) and tested its efficacy in in vitro and in vivo models of lung cancer. Mitomet was cytotoxic to transformed bronchial cells and several non-small cell lung cancer (NSCLC) cell lines but relatively safe to normal bronchial cells, and these effects were mediated mainly via induction of mitochondrial reactive oxygen species. Studies using isogenic A549 cells showed that mitomet was selectively toxic to those cells deficient in the tumor suppressor gene LKB1, which is widely mutated in NSCLC. Mitomet also significantly reduced the multiplicity and size of lung tumors induced by a tobacco smoke carcinogen in mice. Overall, our findings showed that mitomet, which was about 1000 and 100 times more potent than metformin, in killing NSCLC cells and reducing the multiplicity and size of lung tumors in mice, respectively, is a promising candidate for the chemoprevention and treatment of lung cancer, in particular against LKB1-deficient lung cancers which are known to be highly aggressive.

Structural modifications that increase gut restriction of bile acid derivatives

Bile acid derivatives have been investigated as possible therapeutics for a wide array of conditions, including several for which gut-restricted analogs would likely be preferred. These include the prevention of Clostridioides difficile infection (CDI) and the treatment of inflammatory bowel disease (IBD). The design of gut-restricted bile acid analogs, however, is complicated by the highly efficient enterohepatic circulation system that typically reabsorbs these compounds from the digestive tract for subsequent return to the liver. Herein, we report that incorporation of a sulfate group at the 7-position of the bile acid scaffold reduces oral bioavailability and increases fecal recovery in two pairs of compounds designed to inhibit the germination of C. difficile spores. A different approach was necessary for designing gut-restricted bile acid-based TGR5 agonists for the treatment of IBD, as the incorporation of a 7-sulfate group reduces activity at this receptor. Instead, building on our previous discovery that incorporation of a 7-methoxy group into chenodeoxycholic acid derivatives greatly increases their TGR5 receptor potency, we determined that an N-methyl-d-glucamine group could be conjugated to the scaffold to obtain a compound with an excellent mix of potency at the TGR5 receptor, low oral exposure, and good fecal recovery.

Ultrasound assisted synthesis of 3-alkynyl substituted 2-chloroquinoxaline derivatives: Their in silico assessment as potential ligands for N-protein of SARS-CoV-2

In view of recent global pandemic the 3-alkynyl substituted 2-chloroquinoxaline framework has been explored as a potential template for the design of molecules targeting COVID-19. Initial in silico studies of representative compounds to assess their binding affinities via docking into the N-terminal RNA-binding domain (NTD) of N-protein of SARS-CoV-2 prompted further study of these molecules. Thus building of a small library of molecules based on the said template became essential for this purpose. Accordingly, a convenient and environmentally safer method has been developed for the rapid synthesis of 3-alkynyl substituted 2-chloroquinoxaline derivatives under Cu-catalysis assisted by ultrasound. This simple and straightforward method involved the coupling of 2,3-dichloroquinoxaline with commercially available terminal alkynes in the presence of CuI, PPh₃ and K₂CO₃ in PEG-400. Further in silico studies revealed some remarkable observations and established a virtual SAR (Structure Activity Relationship) within the series. Three compounds appeared as potential agents for further studies.

7-Methylation of Chenodeoxycholic Acid Derivatives Yields a Substantial Increase in TGR5 Receptor Potency

TGR5 agonists are potential therapeutics for a variety of conditions including type 2 diabetes, obesity, and inflammatory bowel disease. After screening a library of chenodeoxycholic acid (CDCA) derivatives, it was determined that a range of modifications could be made to the acid moiety of CDCA which significantly increased TGR5 agonist potency. Surprisingly, methylation of the 7-hydroxyl of CDCA led to a further dramatic increase in potency, allowing the identification of 5.6 nM TGR5 agonist 17.

A novel SIRT1 inhibitor, 4bb induces apoptosis in HCT116 human colon carcinoma cells partially by activating p53

The NAD+-dependent protein deacetylase SIRT1 has emerged as an important target for epigenetic therapeutics of colon cancer as its increased expression is associated with cancer progression. Additionally, SIRT1 represses p53 function via deacetylation, promoting tumor growth. Therefore, inhibition of SIRT1 is of great therapeutic interest for the treatment of colon cancer. Here, we report discovery of a novel quinoxaline based small molecule inhibitor of human SIRT1, 4bb, investigated its effect on viability of colon cancer cells and molecular mechanism of action. In vitro, 4bb is a significantly more potent SIRT1 inhibitor, compared to β-naphthols such as sirtinol, cambinol. Increasing concentration of 4bb decrease viability of colon cancer cells but, does not affect the viability of normal dermal fibroblasts depicting cancer cell specificity. Further, 4bb treatment increased p53 acetylation, Bax expression and induced caspase 3 cleavage suggesting that the death of HCT116 colon cancer cells occur through intrinsic pathway of apoptosis. Overall, our results presents 4bb as a new class of human SIRT1 inhibitor and suggest that inhibition of SIRT1 by 4bb induces apoptosis of colon cancer cells at least in part via activating p53 by preventing p53 deacetylation, increasing Bax expression and inducing caspases. Therefore, this molecule provide an opportunity for lead optimization and may help in development of novel, non-toxic epigenetic therapeutics for colon cancer.

A metal catalyst-free and one-pot synthesis of (3,4-dihydro-2H-benzo[b][1,4]oxazin-2-yl)methanol derivatives in water

Regioselective synthesis of (3,4-dihydro-2H-benzo[b][1,4]oxazin-2-yl)methanols have been accomplished via a greener method.

NaSH in the construction of thiophene ring fused with N-heterocycles: a rapid and inexpensive synthesis of novel small molecules as potential inducers of apoptosis

A facile construction of a thiophene ring fused with N-heterocycles has been achieved via the reaction of NaSH with 2-chloro-3-alkynyl quinoxalines/pyrazines leading to novel 2-substituted thieno[2,3-b]pyrazine/quinoxaline derivatives as potential inducers of apoptosis. Some of them showed encouraging pharmacological properties when tested in zebrafish.

Construction and functionalization of pyranone ring fused with pyran moiety: design and synthesis of novel pyrano[4,3-b]pyran-5(4H)-ones as potential inhibitors of sirtuins

Novel pyrano[4,3-b]pyran-5(4H)-one based small molecules were designed as potential inhibitors of sirtuins (i.e., yeast sir2, a homolog of human SIRT1). Elegant synthesis of these compounds was performed via a multi-step sequence consisting of MCR, Sandmeyer type iodination, Sonogashira type coupling followed by iodocyclization and then Pd-mediated various C-C bond forming reactions. The overall strategy involved the construction of a pyran ring followed by the fused pyranone moiety and subsequent functionalization at C-8 position of the resultant core pyrano[4,3-b]pyran-5(4H)-one framework. The crystal structure analysis of a representative iodolactonized product (6d) is presented. Some of the synthesized compounds showed promising inhibitory activities when tested against yeast sir2 in vitro. The compound 6g showed dose dependent inhibition (IC50=78.05μM) of yeast sir2 and good interactions with this protein in silico.

Transition metal free hydrolysis/cyclization strategy in a single pot: synthesis of fused furo N-heterocycles of pharmacological interest

A transition metal free tandem two-step strategy has been developed involving hydrolysis of 2-chloro-3-alkynyl quinoxalines/pyrazines followed by in situ cyclization of the corresponding 2-hydroxy-3-alkynyl intermediates in a single pot leading to fused furo N-heterocycles as potential inhibitors of sirtuins. A representative compound showed promising pharmacological properties in vitro and in vivo.