A Quinquennial Review of Potent LSD1 Inhibitors Explored for the Treatment of Different Cancers, with Special Focus on SAR Studies

Cancer bears a significant share of global mortality. The enzyme Lysine Specific Demethylase 1 (LSD1, also known as KDM1A), since its discovery in 2004, has captured the attention of cancer researchers due to its overexpression in several cancers like acute myeloid leukaemia (AML), solid tumours, etc. The Lysine Specific Demethylase (LSD1) downregulation is reported to have an effect on cancer proliferation, migration, and invasion. Therefore, research to discover safer and more potent LSD1 inhibitors can pave the way for the development of better cancer therapeutics. These efforts have resulted in the synthesis of many types of derivatives containing diverse structural nuclei. The present manuscript describes the role of Lysine Specific Demethylase 1 (LSD1) in carcinogenesis, reviews the LSD1 inhibitors explored in the past five years and discusses their comprehensive structural activity characteristics apart from the thorough description of LSD1. Besides, the potential challenges, opportunities, and future perspectives in the development of LSD1 inhibitors are also discussed. The review suggests that tranylcypromine derivatives are the most promising potent LSD1 inhibitors, followed by triazole and pyrimidine derivatives with IC₅₀ values in the nanomolar and sub-micromolar range. A number of potent LSD1 inhibitors derived from natural sources like resveratrol, protoberberine alkaloids, curcumin, etc. are also discussed. The structural-activity relationships discussed in the manuscript can be exploited to design potent and relatively safer LSD1 inhibitors as anticancer agents.

Recent advances of LSD1/KDM1A inhibitors for disease therapy

Lysine-specific demethylase 1 (LSD1/KDM1A) dysregulation is closely associated with the pathological processes of various diseases, especially hematologic malignancies. Significant progresses have been made in the field of LSD1-targeted drug discovery. Nine LSD1 inhibitors including tranylcypromine, ORY-1001, ORY-2001, GSK-2879552, IMG-7289, INCB059872, TAK-418, CC-90011 and SP-2577 have entered clinical stage for disease treatment as either mono- or combinational therapy. This review updates LSD1 inhibitors reported during 2022. Design strategies, structure-activity relationship studies, binding model analysis and modes of action are highlighted. In particular, the unique multiple-copies binding mode of quinazoline derivatives paves new ways for the development of reversible LSD1 inhibitors by blocking the substrate entrance. The design strategy of clinical candidate TAK-418 also provides directions for further optimization of novel irreversible LSD1 inhibitors with low hematological side effects. The influence of the stereochemistry on the potency against LSD1 and its homolog LSD2 is briefly discussed. Finally, the challenges and prospects of LSD1-targeted drug discovery are also given.

LSD1 inhibitors for cancer treatment: Focus on multi-target agents and compounds in clinical trials

Histone lysine-specific demethylase 1 (LSD1/KDM1A) was first identified in 2004 as an epigenetic enzyme able to demethylate specific lysine residues of histone H3, namely H3K4me1/2 and H3K9me1/2, using FAD as the cofactor. It is ubiquitously overexpressed in many types of cancers (breast, gastric, prostate, hepatocellular, and esophageal cancer, acute myeloid leukemia, and others) leading to block of differentiation and increase of proliferation, migration and invasiveness at cellular level. LSD1 inhibitors can be grouped in covalent and non-covalent agents. Each group includes some hybrid compounds, able to inhibit LSD1 in addition to other target(s) at the same time (dual or multitargeting compounds). To date, 9 LSD1 inhibitors have entered clinical trials, for hematological and/or solid cancers. Seven of them (tranylcypromine, iadademstat (ORY-1001), bomedemstat (IMG-7289), GSK-2879552, INCB059872, JBI-802, and Phenelzine) covalently bind the FAD cofactor, and two are non-covalent LSD1 inhibitors [pulrodemstat (CC-90011) and seclidemstat (SP-2577)]. Another TCP-based LSD1/MAO-B dual inhibitor, vafidemstat (ORY-2001), is in clinical trial for Alzheimer's diseases and personality disorders. The present review summarizes the structure and functions of LSD1, its pathological implications in cancer and non-cancer diseases, and the identification of LSD1 covalent and non-covalent inhibitors with different chemical scaffolds, including those involved in clinical trials, highlighting their potential as potent and selective anticancer agents.

LSD1 inhibitors from the roots of Pueraria lobata

One new 6a,11a-dehydropterocarpan derivative, 6-O-methyl-anhydrotuberosin (1), one new 6a-hydroxypterocarpan, (6aR,11aR,11bR)-hydroxytuberosone (7), and seven known compounds including two 6a,11a-dehydropterocarpans (2 and 4), two coumestans (3 and 5), one isoflavonoid (6) and two other phenolic compounds (8 and 9) were isolated from the roots of Pueraria lobata. The structures of the isolated compounds were elucidated with spectroscopic and spectrometric methods (1 D and 2DNMR, HRESIMS). Compounds 1, 2, 4-5 showed potent LSD1 inhibitory activities with IC₅₀ values ranging from 1.73 to 4.99 μM. Furthermore, compound 2 showed potent cytotoxicity against gastric cancer cell lines MGC-803 and BGC-823, and lung cancer cell lines H1299 and H460.

Epigenetic compounds targeting pharmacological target lysine specific demethylase 1 and its impact on immunotherapy, chemotherapy and radiotherapy for treatment of tumor recurrence and resistance

It has been proven that metastatic recurrence and therapeutic resistance are linked. Due to the variability of individuals and tumors, as well as the tumor's versatility in avoiding therapies, therapy resistance is more difficult to treat. Therapy resistance has significantly restricted the clinical feasibility and efficacy of tumor therapy, despite the discovery of novel compounds and therapy combinations with increasing efficacy. In several tumors, lysine specific demethylase 1 (LSD1) has been associated to metastatic recurrence and therapeutic resistance. For researchers to better comprehend how LSD1-mediated tumor therapy resistance occurs and how to overcome it in various tumors, this study focused on the role of LSD1 in tumor recurrence and therapeutic resistance. The importance of therapeutically targeted LSD1 was also discussed. Most gene pathway signatures are related to LSD1 inhibitor sensitivity. However, some gene pathway signatures, especially in AML, negatively correlate with LSD1 inhibitor sensitivity, but targeting LSD1 makes the therapy-resistant tumor sensitive to physiological doses of conventional therapy. We propose that combining LSD1 inhibitor with traditional tumor therapy can help patients attain a complete response and prevent cancer relapse.

Design Two Novel Tetrahydroquinoline Derivatives against Anticancer Target LSD1 with 3D-QSAR Model and Molecular Simulation

Lysine-specific demethylase 1 (LSD1) is a histone-modifying enzyme, which is a significant target for anticancer drug research. In this work, 40 reported tetrahydroquinoline-derivative inhibitors targeting LSD1 were studied to establish the three-dimensional quantitative structure-activity relationship (3D-QSAR). The established models CoMFA (Comparative Molecular Field Analysis (q² = 0.778, Rpred2 = 0.709)) and CoMSIA (Comparative Molecular Similarity Index Analysis (q² = 0.764, Rpred2 = 0.713)) yielded good statistical and predictive properties. Based on the corresponding contour maps, seven novel tetrahydroquinoline derivatives were designed. For more information, three of the compounds (D1, D4, and Z17) and the template molecule 18x were explored with molecular dynamics simulations, binding free energy calculations by MM/PBSA method as well as the ADME (absorption, distribution, metabolism, and excretion) prediction. The results suggested that D1, D4, and Z17 performed better than template molecule 18x due to the introduction of the amino and hydrophobic groups, especially for the D1 and D4, which will provide guidance for the design of LSD1 inhibitors.

Identification of novel indole derivatives as highly potent and efficacious LSD1 inhibitors

Lysine-specific demethylase 1 (LSD1) is a FAD-dependent histone demethylase to catalyze the demethylation of H3K4 and H3K9 and thus is an attractive target for therapeutic cancer. Starting with a high micromolar compound 17i, structure-based optimization of novel indole derivatives is described by a bioelectronic isosteric strategy. Grounded by molecular modeling, medicinal chemistry has efficiently yielded low nanomolar LSD1 inhibitors. One of the compounds, B35, exhibited excellent LSD1 inhibition (IC50 = 0.050 ± 0.005 μM) and anti-proliferation against A549 cells (IC50 = 0.74 ± 0.14 μM). The further PK studies indicated compound B35 possessed favorable metabolic stability, in which the plasma t1/2 of p.o. and i.v. were 6.27 ± 0.72 h and 8.78 ± 1.31 h, respectively. Additionally, inhibitor B35 shows a strong antitumor effect and good safety in vivo. Meanwhile, compound B35 regulated genes are closely associated with transcriptional dislocation in cancer and PI3K/AKT pathway involving IGFBP3. Taken together, B35 could be a potent LSD1 inhibitor for further drug development.

Design, synthesis and biological evaluation of 2-aminopyrimidine-based LSD1 inhibitors

AZD9291, with excellent pharmaceutical properties, has been reported to have certain LSD1 inhibitory activity. Therefore, we carried out structural optimization based on the AZD9291 skeleton to increase the LSD1 inhibitory potential of the compound. Then, a series of 2-aminopyrimidine derivatives were designed and synthesized as LSD1 inhibitors, and their structure-activity relationships were studied. The most promising compound, X43, with an IC₅₀ of 0.89 μM showed remarkable LSD1 selectivity not only to EGFR^wt (>100-fold) but also to MAO-A/B (>50-fold). Further studies showed that X43 inhibited LSD1 activity and induced the apoptosis of A549 cells in a dose-dependent manner. Meanwhile, compound X43 showed a superior ability to inhibit the proliferation of A549 and THP-1 cells, with IC₅₀ values of 1.62 μM and 1.21 μM, respectively. Then, analyses of the stability of human liver microsomes, CYP inhibition and in vivo pharmacokinetics in rats showed that X43 had favorable profiles in vitro and in vivo and the potential for further study. Our findings suggested that a 2-aminopyrimidine-based LSD1 inhibitor deserves further investigation as a treatment for LSD1-overexpressing cancer.

Annual review of lysine-specific demethylase 1 (LSD1/KDM1A) inhibitors in 2021

Lysine-specific demethylase 1 (LSD1/KDM1A) has emerged as a promising epigenetic target for disease treatment. Several LSD1 inhibitors have advanced into clinical trials. Following our last annual review on LSD1 inhibitors in 2020 (Eur. J. Med. Chem. 2021, 214, 113254), in this review we aim to update LSD1 inhibitors including natural products, synthetic compounds and cyclic peptides reported during 2021. Design strategies, structure-activity relationships, binding model analysis and modes of action are highlighted. In particular, two FDA-approved antihypertensive drugs raloxifene and fenoldopam were repurposed as reversible LSD1 inhibitors. The clinical candidate TAK-418 for treating neurodevelopmental disorders and PET imaging agent [¹⁸F]30 for LSD1 were identified. Moreover, dual inhibitors targeting both LSD1 and HDAC6 or tubulin displayed enhanced anti-cancer effects than single agents. These compounds further enrich the structural types of LSD1 inhibitors.

Machine-Learning-Enabled Virtual Screening for Inhibitors of Lysine-Specific Histone Demethylase 1

A machine learning approach has been applied to virtual screening for lysine specific demethylase 1 (LSD1) inhibitors. LSD1 is an important anti-cancer target. Machine learning models to predict activity were constructed using Morgan molecular fingerprints. The dataset, consisting of 931 molecules with LSD1 inhibition activity, was obtained from the ChEMBL database. An evaluation of several candidate algorithms on the main dataset revealed that the support vector regressor gave the best model, with a coefficient of determination (R2) of 0.703. Virtual screening, using this model, identified five predicted potent inhibitors from the ZINC database comprising more than 300,000 molecules. The virtual screening recovered a known inhibitor, RN1, as well as four compounds where activity against LSD1 had not previously been suggested. Thus, we performed a machine-learning-enabled virtual screening of LSD1 inhibitors using only the structural information of the molecules.

Design, synthesis, and biological evaluation of coumarin analogs as novel LSD1 inhibitors

The abnormal expression of lysine-specific histone demethylase 1 (LSD1) is associated with different cancer types, and it is increasingly recognized as a potential therapeutic target in oncology. Here, utilizing core hopping and conformational restriction strategies, we designed and synthesized a series of coumarin analogs that were shown to be potent LSD1 inhibitors in the enzyme assay. Furthermore, several potent compounds were selected to evaluate their antiproliferative activity on A549 cells and MGC-803 cells with high expression of LSD1. Among them, YX10 showed an anticlonogenic effect on A549 cells and MGC-803 cells, with IC₅₀ values of 1.52 ± 0.16 and 0.98 ± 0.18 μM, respectively. Modeling suggested that the inhibitors would bind to the active site of the protein located around the key residues of Asp555 and Lys661. Meanwhile, a preliminary druggability evaluation showed that compound YX10 showed favorable liver microsomal and moderate plasma stability and weak inhibitory activity against cytochrome P450 isoforms at 10 μM. All the results indicated that compound YX10 could represent a promising lead compound for further development.

Design, synthesis, and biological evaluation of 5-aminotetrahydroquinoline-based LSD1 inhibitors acting on Asp375

The abnormal expression of lysine-specific histone demethylase 1 (LSD1) is associated with different cancer types, and LSD1 inhibitory activity seems to have high therapeutic potential in cancer treatment. Here, we report the design, synthesis, and biochemical evaluation of novel 5-aminotetrahydroquinoline-based LSD1 inhibitors. Among them, compounds A6, A8, B1-B5, and C4 showed preferable inhibitory effects on LSD1, with IC₅₀  = 0.19-0.82 µM. Several potent compounds were selected to evaluate their antiproliferative activity on A549 cells and MCF-7 cells with a high expression of LSD1. The potential binding modes of the compounds were revealed through molecular docking to rationalize the potency of compounds toward LSD1. Our data recognized that the 5-aminotetrahydroquinoline scaffold may serve as a starting point for developing potent LSD1 inhibitors for cancer therapy.

Discovery of higenamine as a potent, selective and cellular active natural LSD1 inhibitor for MLL-rearranged leukemia therapy

Natural products are a rich source of lead compounds and have shown promise for epigenetic drug discovery. In this work, we discovered higenamine from our natural product library as a potent, selective and cellular active natural LSD1 inhibitor. Higenamine shows acceptable potency against LSD1 and high selectivity towards LSD1 over MAOA/B. Higenamine significantly increases expression of LSD1 substrates H3K4me1 and H3K4me2 in MLL-rearranged leukemia cells MV4-11 and MOLM-13, but nearly had no effect on LSD1 and H3K4Me3. Meanwhile, higenamine dose-dependently suppresses the levels of HOXA9 and MEIS1 that are overexpressed in leukemia cell lines. Notably, higenamine induces cell differentiation of MV4-11 and MOLM-13 cells accompanying by increased expression of CD11b, CD14 and CD86. Higenamine promotes cell apoptosis, inhibits colony formation, but does not inhibit proliferation of leukemia cells significantly. In addition, the expression levels of p53 are dramatically changed by higenamine in an LSD1-dependent manner in MV4-11 cells. Taken together, higenamine could be employed as a starting point for the development of more selective and potent LSD1 inhibitors. Our work firstly reveals the non-classical epigenetic regulation mechanism of higenamine in cancers, and also demonstrates the efficacy of higenamine for MLL-rearranged leukemia therapy.

Targeting LSD1 for acute myeloid leukemia (AML) treatment

Targeted therapy for acute myeloid leukemia (AML) is an effective strategy, but currently there are very limited therapeutic targets for AML treatment. Histone lysine specific demethylase 1 (LSD1) is highly expressed in many cancers, impedes the differentiation of cancer cells, promotes the proliferation, metastasis and invasion of cancer cells, and is associated with poor prognosis. Targeting LSD1 has been recognized as a promising strategy for AML treatment in recent years. Based on these features, in the review, we discussed the main epigenetic drugs targeting LSD1 for AML therapy. Thus, this review focuses on the progress of LSD1 inhibitors in AML treatment, particularly those such as tranylcypromine (TCP), ORY-1001, GSK2879552, and IMG-7289 in clinical trials. These inhibitors provide novel scaffolds for designing new LSD1 inhibitors. Besides, combined therapies of LSD1 inhibitors with other drugs for AML treatment are also highlighted.

Exploration of 5-cyano-6-phenylpyrimidin derivatives containing an 1,2,3-triazole moiety as potent FAD-based LSD1 inhibitors

Histone lysine specific demethylase 1 (LSD1) has become a potential therapeutic target for the treatment of cancer. Discovery and develop novel and potent LSD1 inhibitors is a challenge, although several of them have already entered into clinical trials. Herein, for the first time, we reported the discovery of a series of 5-cyano-6-phenylpyrimidine derivatives as LSD1 inhibitors using flavin adenine dinucleotide (FAD) similarity-based designing strategy, of which compound 14q was finally identified to repress LSD1 with IC₅₀ = 183 nmol/L. Docking analysis suggested that compound 14q fitted well into the FAD-binding pocket. Further mechanism studies showed that compound 14q may inhibit LSD1 activity competitively by occupying the FAD binding sites of LSD1 and inhibit cell migration and invasion by reversing epithelial to mesenchymal transition (EMT). Overall, these findings showed that compound 14q is a suitable candidate for further development of novel FAD similarity-based LSD1 inhibitors.

Natural products as LSD1 inhibitors for cancer therapy

Natural products generally fall into the biologically relevant chemical space and always possess novel biological activities, thus making them a rich source of lead compounds for new drug discovery. With the recent technological advances, natural product-based drug discovery is now reaching a new era. Natural products have also shown promise in epigenetic drug discovery, some of them have advanced into clinical trials or are presently being used in clinic. The histone lysine specific demethylase 1 (LSD1), an important class of histone demethylases, has fundamental roles in the development of various pathological conditions. Targeting LSD1 has been recognized as a promising therapeutic option for cancer treatment. Notably, some natural products with different chemotypes including protoberberine alkaloids, flavones, polyphenols, and cyclic peptides have shown effectiveness against LSD1. These natural products provide novel scaffolds for developing new LSD1 inhibitors. In this review, we mainly discuss the identification of natural LSD1 inhibitors, analysis of the co-crystal structures of LSD1/natural product complex, antitumor activity and their modes of action. We also briefly discuss the challenges faced in this field. We believe this review will provide a landscape of natural LSD1 inhibitors.

Natural protoberberine alkaloids, identified as potent selective LSD1 inhibitors, induce AML cell differentiation

Natural protoberberine alkaloids were first identified and characterized as potent, selective and cellular active lysine specific demethylase 1 (LSD1) inhibitors. Due to our study, isoquinoline-based tetracyclic scaffold was identified as the key structural element for their anti-LSD1 activity, subtle changes of substituents attached to the core structure led to dramatic changes of the activity. Among these protoberberine alkaloids, epiberberine potently inhibited LSD1 (IC₅₀ = 0.14 ± 0.01 μM) and was highly selective to LSD1 over MAO-A/B. Furthermore, epiberberine could induce the expression of CD86, CD11b and CD14 in THP-1 and HL-60 cells, confirming its cellular activity of inducing acute myeloid leukemia (AML) cells differentiation. Moreover, epiberberine prolonged the survival of THP-1 cells bearing mice and inhibited the growth of AML cells in vivo without obvious global toxicity. These findings give the potential application of epiberberine in AML treatment, and the isoquinoline-based tetracyclic scaffold could be used for further development of LSD1 inhibitors.

HFIP-Promoted de Novo Synthesis of Biologically Relevant Nonnatural α-Arylated Amino Esters and Dipeptide Mimetics

Amino acids are fundamental building blocks, which have been extensively used in drug design and organic synthesis. However, nonnatural amino acids are relatively less studied. In this work, the authors report the first HFIP-promoted de novo synthesis of nonnatural α-arylated amino esters and dipeptide mimetics (27 examples, up to 99 % yield) from readily available amines, ethyl glyoxylate and electron-rich arenes under mild conditions, in which one C-C bond, one C-N bond and one chiral center were established simultaneously. The reaction was also performed on a gram scale, giving compound 4 a in 96 % yield. In addition, this protocol was successfully applied to the late-stage elaboration of drug molecules, such as tranylcypromine (TCP or PCPA) and troxipide. Interestingly, compound 4 h inactivated histone lysine specific demethylase 1 (LSD1) potently with an IC₅₀ value of 0.296 μm. To the best of our knowledge, compound 4 h is the first LSD1 inhibitor derived from nonnatural α-arylated amino esters, and therefore could be used as a hit compound for the development of new LSD1 inhibitors. The synthesized nonnatural α-arylated amino esters and dipeptide mimetics as unique building blocks may have potential synthetic utilities.

LSD1/KDM1A inhibitors in clinical trials: advances and prospects

Histone demethylase LSD1 plays key roles during carcinogenesis, targeting LSD1 is becoming an emerging option for the treatment of cancers. Numerous LSD1 inhibitors have been reported to date, some of them such as TCP, ORY-1001, GSK-2879552, IMG-7289, INCB059872, CC-90011, and ORY-2001 currently undergo clinical assessment for cancer therapy, particularly for small lung cancer cells (SCLC) and acute myeloid leukemia (AML). This review is to provide a comprehensive overview of LSD1 inhibitors in clinical trials including molecular mechanistic studies, clinical efficacy, adverse drug reactions, and PD/PK studies and offer prospects in this field.

LSD1/KDM1A, a Gate-Keeper of Cancer Stemness and a Promising Therapeutic Target

A new exciting area in cancer research is the study of cancer stem cells (CSCs) and the translational implications for putative epigenetic therapies targeted against them. Accumulating evidence of the effects of epigenetic modulating agents has revealed their dramatic consequences on cellular reprogramming and, particularly, reversing cancer stemness characteristics, such as self-renewal and chemoresistance. Lysine specific demethylase 1 (LSD1/KDM1A) plays a well-established role in the normal hematopoietic and neuronal stem cells. Overexpression of LSD1 has been documented in a variety of cancers, where the enzyme is, usually, associated with the more aggressive types of the disease. Interestingly, recent studies have implicated LSD1 in the regulation of the pool of CSCs in different leukemias and solid tumors. However, the precise mechanisms that LSD1 uses to mediate its effects on cancer stemness are largely unknown. Herein, we review the literature on LSD1's role in normal and cancer stem cells, highlighting the analogies of its mode of action in the two biological settings. Given its potential as a pharmacological target, we, also, discuss current advances in the design of novel therapeutic regimes in cancer that incorporate LSD1 inhibitors, as well as their future perspectives.

Insights into novel emerging epigenetic drugs in myeloid malignancies

Epigenetics has been defined as ‘a stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence’ and several epigenetic regulators are recurrently mutated in hematological malignancies. Epigenetic modifications include changes such as DNA methylation, histone modifications and RNA associated gene silencing. Transcriptional regulation, chromosome stability, DNA replication and DNA repair are all controlled by these modifications. Mutations in genes encoding epigenetic modifiers are a frequent occurrence in hematologic malignancies and important in both the initiation and progression of cancer. Epigenetic modifications are also frequently reversible, allowing excellent opportunities for therapeutic intervention. The goal of epigenetic therapies is to reverse epigenetic dysregulation, restore the epigenetic balance, and revert malignant cells to a more normal condition. The role of epigenetic therapies thus far is most established in hematologic malignancies, with several agents already approved by the US Food and Drug Administration. In this review, we discuss pharmacological agents targeting epigenetic regulators.

Identifying the novel inhibitors of lysine-specific demethylase 1 (LSD1) combining pharmacophore-based and structure-based virtual screening

Lysine-specific demethylase 1 (LSD1) has been reported to connect with a range of solid tumors. Thus, the exploration of LSD1 inhibitors has emerged as an effective strategy for cancer treatment. In this study, we constructed a pharmacophore model based on a series of flavin adenine dinucleotide (FAD)-competing inhibitors bearing triazole - dithiocarbamate scaffold combining docking, structure-activity relationship (SAR) study, and molecular dynamic (MD) simulation. Meanwhile, another pharmacophore model was also constructed manually, relying on several speculated substrate-competing inhibitors and reported putative vital interactions with LSD1. On the basis of the two pharmacophore models, multi-step virtual screenings (VSs) were performed against substrate-binding pocket and FAD-binding pocket, respectively, combining pharmacophore-based and structure-based strategy to exploit novel LSD1 inhibitors. After bioassay evaluation, four compounds among 21 hits with diverse and novel scaffolds exhibited inhibition activity at the range of 3.63-101.43 μM. Furthermore, substructure-based enrichment was performed, and four compounds with a more potent activity were identified. After that, the time-dependent assay proved that the most potent compound with IC₅₀ 2.21 μM inhibits LSD1 activity in a manner of time-independent. In addition, the compound exhibited a cellular inhibitory effect against LSD1 in MGC-803 cells and may inhibit cell migration and invasion by reversing EMT in cultured gastric cancer cells. Considering the binding mode and SAR of the series of compounds, we could roughly deem that these compounds containing 3-methylxanthine scaffold act through occupying substrate-binding pocket competitively. This study presented a new starting point to develop novel LSD1 inhibitors.

Lysine-Specific Demethylase 1A as a Promising Target in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic malignancy characterized by the accumulation of incompletely differentiated progenitor cells (blasts) in the bone marrow and blood, and by suppression of normal hematopoiesis. It has recently become apparent that the AML genome is characterized by recurrent mutations and dysregulations in epigenetic regulators. These mutations frequently occur before the onset of full blown leukemia, at the pre-leukemic phase, and persist in residual disease that remains after therapeutic intervention, thus suggesting that targeting the AML epigenome may help to eradicate minimal residual disease and prevent relapse. Within the AML epigenome, lysine-specific demethylase 1 A (LSD1) is a histone demethylase that is found frequently overexpressed, albeit not mutated, in AML. LSD1 is a required constituent of critical transcription repressor complexes like CoREST and nucleosome remodeling and deacetylase (NuRD), and abrogation of LSD1 expression results in impaired self-renewal and proliferation, and increased differentiation and apoptosis in AML models and primary cells, particularly in AMLs with MLL- and AML1-rearrangements, or erythroid and megakaryoblastic differentiation block. On this basis, a number of LSD1 inhibitors have been developed in the past decade, and few of them are currently being tested in clinical trials for patients with AML, along with other malignancies. To date, the most promising application of this therapeutic strategy appears to be combination therapy of LSD1 inhibitors with all-trans retinoic acid (ATRA) to reactivate myeloid differentiation in cells that are not spontaneously susceptible to ATRA treatment. In this review, we provide an overview of LSD1 function in normal hematopoiesis and leukemia, and of the current clinical application of LSD1 inhibitors for the treatment of patients with AML.

Advances toward LSD1 inhibitors for cancer therapy. Future Med Chem. 2017;9:1227-1242. [PMID: 28722477 DOI: 10.4155/fmc-2017-0068]

LSD1 has become an important biologically validated epigenetic target for cancer therapy since its identification in 2004. LSD1 mediates many cellular signaling pathways and is involved in the initiation and development of cancers. Aberrant overexpression of LSD1 has been observed in different types of cancers, and inactivation by small molecules suppresses cancer cell differentiation, proliferation, invasion and migration. To date, a large number of LSD1 inhibitors have been reported, RG6016, GSK-2879552, INCB059872, IMG-7289 and CC-90011 are currently undergoing clinical assessment for the treatment of acute myeloid leukemia, small-cell lung cancer, etc. In this review, we briefly highlight recent advances of LSD1 inhibitors mainly covering the literatures from 2015 to 2017 and tentatively propose our perspectives on the design of new LSD1 inhibitors for cancer therapy.