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

Inhibition of NAMPT as a therapeutic strategy to suppress tumor growth in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, progressive lung disease driven by mutations in the TSC1 or TSC2 genes, leading to constitutive mTORC1 activation and uncontrolled cell proliferation. Current therapies, like rapamycin effectively stabilize disease progression but mainly exert cytostatic effects and promote autophagy, a survival mechanism in LAM cells. These limitations highlight the need for the development of innovative therapies to achieve more effective and lasting results. To explore alternative therapeutic targets, we investigated the role of nicotinamide phosphoribosyltransferase (NAMPT), a key regulator of NAD+ biosynthesis, in LAM and TSC2-deficient cells using a potent inhibitor, FK866. Our study demonstrates that FK866 depletes NAD+ levels in these cells, exerting a dual effect by activating AMPK and subsequently inhibiting mTORC1 signaling while suppressing autophagy. Unlike rapamycin, FK866 does not induce compensatory Akt activation, significantly inhibits LAM cell proliferation and induces apoptosis. Additionally, using an in vivo chicken egg chorioallantoic membrane (CAM) model, we showed that FK866 treatment significantly reduces LAM tumor growth compared to controls suggesting that NAMPT inhibition disrupts metabolic and survival pathways critical for TSC2-deficient cell viability and tumor progression. Our results establish NAMPT as a promising therapeutic target for LAM, offering a two-prong strategy to suppress tumor growth and enhance apoptosis, providing an alternative to current mTOR-based therapies.

Inhibitors of NAD+ Production in Cancer Treatment: State of the Art and Perspectives

The addiction of tumors to elevated nicotinamide adenine dinucleotide (NAD+) levels is a hallmark of cancer metabolism. Obstructing NAD+ biosynthesis in tumors is a new and promising antineoplastic strategy. Inhibitors developed against nicotinamide phosphoribosyltransferase (NAMPT), the main enzyme in NAD+ production from nicotinamide, elicited robust anticancer activity in preclinical models but not in patients, implying that other NAD+-biosynthetic pathways are also active in tumors and provide sufficient NAD+ amounts despite NAMPT obstruction. Recent studies show that NAD+ biosynthesis through the so-called "Preiss-Handler (PH) pathway", which utilizes nicotinate as a precursor, actively operates in many tumors and accounts for tumor resistance to NAMPT inhibitors. The PH pathway consists of three sequential enzymatic steps that are catalyzed by nicotinate phosphoribosyltransferase (NAPRT), nicotinamide mononucleotide adenylyltransferases (NMNATs), and NAD+ synthetase (NADSYN1). Here, we focus on these enzymes as emerging targets in cancer drug discovery, summarizing their reported inhibitors and describing their current or potential exploitation as anticancer agents. Finally, we also focus on additional NAD+-producing enzymes acting in alternative NAD+-producing routes that could also be relevant in tumors and thus become viable targets for drug discovery.

Drug discovery targeting nicotinamide phosphoribosyltransferase (NAMPT): Updated progress and perspectives

Nicotinamide phosphoribosyltransferase (NAMPT) is a key rate-limiting enzyme in the nicotinamide adenine dinucleotide (NAD+) salvage pathway, primarily catalyzing the synthesis of nicotinamide mononucleotide (NMN) from nicotinamide (NAM), phosphoribosyl pyrophosphate (PRPP), and adenosine triphosphate (ATP). Metabolic diseases, aging-related diseases, inflammation, and cancers can lead to abnormal expression levels of NAMPT due to the pivotal role of NAD+ in redox metabolism, aging, the immune system, and DNA repair. In addition, NAMPT can be secreted by cells as a cytokine that binds to cell membrane receptors to regulate intracellular signaling pathways. Furthermore, NAMPT is able to reduce therapeutic efficacy by enhancing acquired resistance to chemotherapeutic agents. Recently, a few novel activators and inhibitors of NAMPT for neuroprotection and anti-tumor have been reported, respectively. However, NAMPT activators are still in preclinical studies, and only five NAMPT inhibitors have entered the clinical stage, unfortunately, three of which were terminated or withdrawn due to safety concerns. Novel drug design strategies such as proteolytic targeting chimera (PROTAC), antibody-drug conjugate (ADC), and dual-targeted inhibitors also provide new directions for the development of NAMPT inhibitors. In this perspective, we mainly discuss the structure, biological function, and role of NAMPT in diseases and the currently discovered activators and inhibitors. It is our hope that this work will provide some guidance for the future design and optimization of NAMPT activators and inhibitors.

New Analogues of the Nicotinamide Phosphoribosyltransferase Inhibitor FK866 as Potential Anti-Pancreatic Cancer Agents

BACKGROUND

During the past two decades, many nicotinamide phosphoribosyltransferase (NAMPT) inhibitors were prepared and tested because this enzyme is overexpressed in pancreatic cancer. Although FK866 is a well-known, strong NAMPT inhibitor, it suffers severe drawbacks.

OBJECTIVE

Our work aimed to synthesize efficient NAMPT inhibitors featuring better pharmacokinetic properties than the pyridine-containing FK866. To this aim, the new anticancer agents were based on benzene, pyridazine, or benzothiazole moieties as a cap group instead of the pyridine unit found in FK866 and other NAMPT inhibitors.

METHODS

The new compounds, prepared exploiting standard heterocycle chemistry and coupling reactions (e.g., formation of amides, ureas, and cyanoguanidines, copper-mediated azide-alkyne cycloaddition), have been fully characterized using NMR and HRMS analyses. Their activity has been evaluated using cytotoxicity and intracellular NAD depletion assays in the human pancreatic cancer cell line MiaPaCa-2.

RESULTS

Among the 14 products obtained, compound 28, bearing a pyridazine unit as the cap group and a thiophene moiety as the tail group, showed 6.7 nanomolar inhibition activity in the intracellular NAD depletion assay and 43 nanomolar inhibition in the MiaPaCa-2 cells cytotoxicity assay, comparable to that observed for FK866.

CONCLUSION

The positive results observed for some newly synthesized molecules, particularly those carrying a thiophene unit as a tail group, indicate that they could act as in vivo anti-pancreatic cancer agents.

Iminosugar-Based Nicotinamide Phosphoribosyltransferase (NAMPT) Inhibitors as Potential Anti-Pancreatic Cancer Agents

The nicotinamide phosphoribosyltransferase (NAMPT) is considered a very promising therapeutic target because it is overexpressed in pancreatic cancer. Although many inhibitors have been prepared and tested, clinical trials have shown that NAMPT inhibition may result in severe haematological toxicity. Therefore, the development of conceptually new inhibitors is an important and challenging task. We synthesized ten β-d-iminoribofuranosides bearing various heterocycle-based chains carbon-linked to the anomeric position starting from non-carbohydrate derivatives. They were then submitted to NAMPT inhibition assays, as well as to pancreatic tumor cells viability and intracellular NAD⁺ depletion evaluation. The biological activity of the compounds was compared to that of the corresponding analogues lacking the carbohydrate unit to assess, for the first time, the contribution of the iminosugar moiety to the properties of these potential antitumor agents.

Synthesis and structure-activity relationship of new nicotinamide phosphoribosyltransferase inhibitors with antitumor activity on solid and haematological cancer

Cancer cells are highly dependent on Nicotinamide phosphoribosyltransferase (NAMPT) activity for proliferation, therefore NAMPT represents an interesting target for the development of anti-cancer drugs. Several compounds, such as FK866 and CHS828, were identified as potent NAMPT inhibitors with strong anti-cancer activity, although none of them reached the late stages of clinical trials. We present herein the preparation of three libraries of new inhibitors containing (pyridin-3-yl)triazole, (pyridin-3-yl)thiourea and (pyridin-3/4-yl)cyanoguanidine as cap/connecting unit and a furyl group at the tail position of the compound. Antiproliferative activity in vitro was evaluated on a panel of solid and haematological cancer cell lines and most of the synthesized compounds showed nanomolar or sub-nanomolar cytotoxic activity in MiaPaCa-2 (pancreatic cancer), ML2 (acute myeloid leukemia), JRKT (acute lymphobalistic leukemia), NMLW (Burkitt lymphoma), RPMI8226 (multiple myeloma) and NB4 (acute myeloid leukemia), with lower IC₅₀ values than those reported for FK866. Notably, compounds 35a, 39a and 47 showed cytotoxic activity against ML2 with IC₅₀ = 18, 46 and 49 pM, and IC₅₀ towards MiaPaCa-2 of 0.005, 0.455 and 2.81 nM, respectively. Moreover, their role on the NAD⁺ synthetic pathway was demonstrated by the NAMPT inhibition assay. Finally, the intracellular NAD⁺ depletion was confirmed in vitro to induced ROS accumulation that cause a time-dependent mitochondrial membrane depolarization, leading to ATP loss and cell death.

Anticancer Activities of Novel Nicotinamide Phosphoribosyltransferase Inhibitors in Hematological Malignancies

Targeting cancer cells that are highly dependent on the nicotinamide adenine dinucleotide (NAD+) metabolite is a promising therapeutic strategy. Nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme catalyzing NAD⁺ production. Despite the high efficacy of several developed NAMPT inhibitors (i.e., FK866 (APO866)) in preclinical studies, their clinical activity was proven to be limited. Here, we report the synthesis of new NAMPT Inhibitors, JJ08, FEI191 and FEI199, which exhibit a broad anticancer activity in vitro. Results show that these compounds are potent NAMPT inhibitors that deplete NAD⁺ and NADP(H) after 24 h of drug treatment, followed by an increase in reactive oxygen species (ROS) accumulation. The latter event leads to ATP loss and mitochondrial depolarization with induction of apoptosis and necrosis. Supplementation with exogenous NAD⁺ precursors or catalase (ROS scavenger) abrogates the cell death induced by the new compounds. Finally, in vivo administration of the new NAMPT inhibitors in a mouse xenograft model of human Burkitt lymphoma delays tumor growth and significantly prolongs mouse survival. The most promising results are collected with JJ08, which completely eradicates tumor growth. Collectively, our findings demonstrate the efficient anticancer activity of the new NAMPT inhibitor JJ08 and highlight a strong interest for further evaluation of this compound in hematological malignancies.