Design, synthesis and X-ray crystallographic study of NAmPRTase inhibitors as anti-cancer agents

Identification of new FK866 analogues with potent anticancer activity against pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal diseases for which chemotherapy has not been very successful yet. FK866 ((E)-N-(4-(1-benzoylpiperidin-4-yl)butyl)-3-(pyridin-3-yl)acrylamide) is a well-known NAMPT (nicotinamide phosphoribosyltransferase) inhibitor with anti-cancer activities, but it failed in phase II clinical trials. We found that FK866 shows anti-proliferative activity in three PDAC cell lines, as well as in Jurkat T-cell leukemia cells. More than 50 FK866 analogues were synthesized that introduce substituents on the phenyl ring of the piperidine benzamide group of FK866 and exchange its buta-1,4-diyl tether for 1-oxyprop-3-yl, (E)-but-2-en-1,4-diyl and 2- and 3-carbon tethers. The pyridin-3-yl moiety of FK866 was exchanged for chlorinated and fluorinated analogues and for pyrazin-2-yl and pyridazin-4-yl groups. Several compounds showed low nanomolar or sub-nanomolar cell growth inhibitory activity. Our best cell anti-proliferative compounds were the 2,4,6-trimethoxybenzamide analogue of FK866 ((E)-N-(4-(1-(2,4,6-trimethoxybenzoyl)piperidin-4-yl)butyl)-3-(pyridin-3-yl)acrylamide) (9), the 2,6-dimethoxybenzamide (8) and 2-methoxybenzamide (4), which exhibited an IC50 of 0.16 nM, 0.004 nM and 0.08 nM toward PDAC cells, respectively.

Small Molecule Regulators Targeting NAD+ Biosynthetic Enzymes

Nicotinamide adenine dinucleotide (NAD+) is a key player in many metabolic pathways as an activated carrier of electrons. In addition to being the cofactor for redox reactions, NAD+ also serves as the substrate for various enzymatic transformations such as adenylation and ADP-ribosylation. Maintaining cellular NAD+ homeostasis has been suggested as an effective anti-aging strategy. Given the importance of NAD+ in regulating a broad spectrum of cellular events, small molecules targeting NAD+ metabolism have been pursued as therapeutic interventions for the treatment of mitochondrial disorders and agerelated diseases. In this article, small molecule regulators of NAD+ biosynthetic enzymes will be reviewed. The focus will be given to the discovery and development of these molecules, the mechanism of action as well as their therapeutic potentials.

Electrooxidation Is a Promising Approach to Functionalization of Pyrazole-Type Compounds

The review summarizes for the first time the poorly studied electrooxidative functionalization of pyrazole derivatives leading to the C-Cl, C-Br, C-I, C-S and N-N coupling products with applied properties. The introduction discusses some aspects of aromatic hydrogen substitution. Further, we mainly consider our works on effective synthesis of the corresponding halogeno, thiocyanato and azo compounds using cheap, affordable and environmentally promising electric currents.

Direct oxidative coupling of N-acyl pyrroles with alkenes by ruthenium(ii)-catalyzed regioselective C2-alkenylation

Ruthenium(ii)-catalyzed oxidative coupling by C2-alkenylation of N-acyl pyrroles with alkenes has been described. The acyl unit was found to be an effective chelating group for the activation of aryl C-H bonds ortho to the directing group. The alkenylation reaction of benzoyl pyrroles occurred regioselectively at the C2-position of the pyrrole ring, without touching the benzene ring. The reaction provides exclusively monosubstituted pyrroles under the optimized conditions. Disubstituted pyrroles could be obtained using higher loadings of the ruthenium(ii)-catalyst and the additives.

Cinnamamide: An insight into the pharmacological advances and structure-activity relationships

The cinnamamide (cinnamic acid amide and cinnamide) is a privileged scaffold present widely in a number of natural products. The scaffold acts as a useful template for designing and arriving at newly drug-like molecules with potential pharmacological activity. An attempt has been made to review the extensive occurrence of cinnamamide scaffold in many lead compounds reported for treating various diseases, their binding interactions with the therapeutic targets as well as mechanism of action and their structure-activity relationships. The discoveries of cinnamamide systems and some examples of unusual cinnamamides having an aromatic, aliphatic, and heterocyclic or other rings condensed to the basic cinnamamide structure also have been extensively covered in this review.

Structure-Based Design of Potent Nicotinamide Phosphoribosyltransferase Inhibitors with Promising in Vitro and in Vivo Antitumor Activities

Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) has the potential to directly limit NAD production in cancer cells and is an effective strategy for cancer treatment. Using a structure-based strategy, we have designed a new class of potent small-molecule inhibitors of NAMPT. Several designed compounds showed promising antiproliferative activities in vitro. (E)-N-(5-((4-(((2-(1H-Indol-3-yl)ethyl)(isopropyl)amino)methyl)phenyl)amino)pentyl)-3-(pyridin-3-yl)acrylamide, 30, bearing an indole moiety, has an IC50 of 25.3 nM for binding to the NAMPT protein and demonstrated promising inhibitory activities in the nanomolar range against several cancer cell lines (MCF-7 GI50 = 0.13 nM; MDA-MB-231 GI50 = 0.15 nM). Triple-negative breast cancer is the most malignant subtype of breast cancer with no effective targeted treatments currently available. Significant antitumor efficacy of compound 30 was achieved (TGI was 73.8%) in an orthotopic MDA-MB-231 triple-negative breast cancer xenograft tumor model. This paper reports promising lead molecules for the inhibition of NAMPT which could serve as a basis for further investigation.

Identification of nicotinamide phosphoribosyltransferase (NAMPT) inhibitors with no evidence of CYP3A4 time-dependent inhibition and improved aqueous solubility

Herein we report the optimization efforts to ameliorate the potent CYP3A4 time-dependent inhibition (TDI) and low aqueous solubility exhibited by a previously identified lead compound from our NAMPT inhibitor program (1, GNE-617). Metabolite identification studies pinpointed the imidazopyridine moiety present in 1 as the likely source of the TDI signal, and replacement with other bicyclic systems was found to reduce or eliminate the TDI finding. A strategy of reducing the number of aromatic rings and/or lowering cLogD7.4 was then employed to significantly improve aqueous solubility. These efforts culminated in the discovery of 42, a compound with no evidence of TDI, improved aqueous solubility, and robust efficacy in tumor xenograft studies.

Fragment-based identification of amides derived from trans-2-(pyridin-3-yl)cyclopropanecarboxylic acid as potent inhibitors of human nicotinamide phosphoribosyltransferase (NAMPT)

Potent, trans-2-(pyridin-3-yl)cyclopropanecarboxamide-containing inhibitors of the human nicotinamide phosphoribosyltransferase (NAMPT) enzyme were identified using fragment-based screening and structure-based design techniques. Multiple crystal structures were obtained of initial fragment leads, and this structural information was utilized to improve the biochemical and cell-based potency of the associated molecules. Many of the optimized compounds exhibited nanomolar antiproliferative activities against human tumor lines in in vitro cell culture experiments. In a key example, a fragment lead (13, KD = 51 μM) was elaborated into a potent NAMPT inhibitor (39, NAMPT IC50 = 0.0051 μM, A2780 cell culture IC50 = 0.000 49 μM) which demonstrated encouraging in vivo efficacy in an HT-1080 mouse xenograft tumor model.

Fragment-based design of 3-aminopyridine-derived amides as potent inhibitors of human nicotinamide phosphoribosyltransferase (NAMPT)

The fragment-based identification of two novel and potent biochemical inhibitors of the nicotinamide phosphoribosyltransferase (NAMPT) enzyme is described. These compounds (51 and 63) incorporate an amide moiety derived from 3-aminopyridine, and are thus structurally distinct from other known anti-NAMPT agents. Each exhibits potent inhibition of NAMPT biochemical activity (IC50=19 and 15 nM, respectively) as well as robust antiproliferative properties in A2780 cell culture experiments (IC50=121 and 99 nM, respectively). However, additional biological studies indicate that only inhibitor 51 exerts its A2780 cell culture effects via a NAMPT-mediated mechanism. The crystal structures of both 51 and 63 in complex with NAMPT are also independently described.

Identification of amides derived from 1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid as potent inhibitors of human nicotinamide phosphoribosyltransferase (NAMPT)

Potent, 1H-pyrazolo[3,4-b]pyridine-containing inhibitors of the human nicotinamide phosphoribosyltransferase (NAMPT) enzyme were identified using structure-based design techniques. Many of these compounds exhibited nanomolar antiproliferation activities against human tumor lines in in vitro cell culture experiments, and a representative example (compound 26) demonstrated encouraging in vivo efficacy in a mouse xenograft tumor model derived from the A2780 cell line. This molecule also exhibited reduced rat retinal exposures relative to a previously studied imidazo-pyridine-containing NAMPT inhibitor. Somewhat surprisingly, compound 26 was only weakly active in vitro against mouse and monkey tumor cell lines even though it was a potent inhibitor of NAMPT enzymes derived from these species. The compound also exhibited only minimal effects on in vivo NAD levels in mice, and these changes were considerably less profound than those produced by an imidazo-pyridine-containing NAMPT inhibitor. The crystal structures of compound 26 and the corresponding PRPP-derived ribose adduct in complex with NAMPT were also obtained.

Medicinal chemistry of nicotinamide phosphoribosyltransferase (NAMPT) inhibitors

Nicotinamide phoshophoribosyltransferase (NAMPT) plays a key role in the replenishment of the NAD pool in cells. This in turn makes this enzyme an important player in bioenergetics and in the regulation of NAD-using enzymes, such as PARPs and sirtuins. Furthermore, there is now ample evidence that NAMPT is secreted and has a role as a cytokine. An important role of either the intracellular or extracellular form of NAMPT has been shown in cancer, inflammation, and metabolic diseases. The first NAMPT inhibitors (FK866 and CHS828) have already entered clinical trials, and a surge in interest in the synthesis of novel molecules has occurred. The present review summarizes the recent progress in this field.

PBEF/NAMPT/visfatin: a promising drug target for treating rheumatoid arthritis?

NAMPT, also known as pre-B-cell colony-enhancing factor and visfatin, has been proposed to be involved in preventing apoptosis in cancer cells and, as such, has received a great deal of attention in recent years and stimulated the development to specific inhibitors for treating cancer. The role of NAMPT inhibitors as potential therapeutic agents for other diseases has not been studied extensively. Here, we describe their applicability for treating rheumatoid arthritis. We summarize current knowledge of NAMPT expression in healthy and diseased tissues, thereafter, we focus on pathological mechanisms relevant to rheumatoid arthritis that involve the NAMPT pathway and review the current status of NAMPT inhibitors being evaluated in clinical trials.