Novel leucine ureido derivatives as inhibitors of aminopeptidase N (APN)

Aminopeptidase N (APN/CD13) over expressed on tumor cells, plays a critical role in tumor invasion, metastasis, and tumor angiogenesis. Here we described the design, synthesis and preliminary activity studies of novel leucine ureido derivatives as aminopeptidase N (APN/CD13) inhibitors. The results showed that compound 8c had the most potent inhibitory activity against APN with the IC₅₀ value to 0.06 ± 0.041 μM, which could be used for further anticancer agent research.     

Novel 3-phenylpropane-1,2-diamine derivates as inhibitors of aminopeptidase N (APN)

Aminopeptidase N (APN) is an essential peptidase involved in the process of tumor invasion and metastasis. Here we describe a novel class of inhibitor with 3-phenylpropane-1,2-diamine as scaffold to APN. Preliminary activity evaluation with enzyme inhibition studies showed that compound 12i exhibited potent and selective inhibitory activity towards APN with the IC(50) value 15.5+/-1.2microM.     

Novel aminopeptidase N (APN/CD13) inhibitors derived from chloramphenicol amine

Aminopeptidase N (APN) is involved in different physiological and pathological processes of tumor cells, including proliferation, invasion, apoptosis and metastasis. Herein one series of compounds derived from commercially available (1S,2S)-2-amino-1-(4-nitrophenyl) propane-1,3-diol have been designed and synthesized. Furthermore, preliminary activity evaluation showed that some compounds elicited moderate inhibitory activity against APN with compounds 10e (IC(50)=6.1±0.5 μM) possessing the best efficacy, which could be used as the lead compound in the future for anticancer agents research.     

Design and synthesis of novel chloramphenicol amine derivatives as potent aminopeptidase N (APN/CD13) inhibitors

Herein we report a series of novel chloramphenicol amine derivatives as aminopeptidase N (APN)/CD13 inhibitors. All compounds were synthesized starting from commercially available (1S,2S)-2-amino-1-(4-nitrophenyl) propane-1,3-diol. The preliminary biological screening showed that some compounds exhibited potent inhibitory activity against APN. It should be noted that one compound, 13b (IC₅₀ = 7.1 μM), possess similar APN inhibitory activity compared with Bestatin (IC₅₀ = 3.0 μM).     

Novel leucine ureido derivatives as aminopeptidase N inhibitors using click chemistry

The over-expression of aminopeptidase N on diverse malignant cells is associated with the tumor angiogenesis and metastasis. In this report, one new series of leucine ureido derivatives containing the triazole moiety was designed, synthesized and evaluated as APN inhibitors. Among them, compound 13v showed the best APN inhibition with an IC₅₀ value of 0.089?±?0.007?μM, which was two orders of magnitude lower than that of bestatin (IC₅₀?=?9.4?±?0.5?μM). Compound 13v also showed dose-dependent anti-angiogenesis activities. Even at the lower concentration (10?μM), compound 13v presented similar anti-angiogenesis activity compared with bestatin at 100?μM in both the human umbilical vein endothelial cells (HUVECs) capillary tube formation assay and the rat thoracic aorta rings test. Moreover, compared with bestatin, 13v exhibited comparable, if not better in vivo anti-metastasis activity in a mouse H22 pulmonary metastasis model.     

Novel hydroxamic acid-related phosphinates: inhibition of neutral aminopeptidase N (APN)

Here we describe the inhibitory activity toward neutral aminopeptidase of three new families of phosphinate inhibitors related in structure to hydroxamic acids. These compounds, even as racemic mixtures, are good inhibitors of APN and show strong structure activity relationship (SAR) depending on the substituents in P1 and P1' positions.     

Synthesis of a novel series of L-isoserine derivatives as aminopeptidase N inhibitors

A series of novel L-isoserine derivatives were synthesised and evaluated for their ability to inhibit aminopeptidase N (APN)/CD13. In our preliminary biological results, some of these compounds possessed a potent inhibitory activity against the APN. Within this series, compound 14b not only showed similar enzyme inhibition (IC₅₀ of 12.2?μM) compared with the positive control bestatin (half maximal inhibitory concentration (IC₅₀) of 7.3?μM), but also had a potent antiproliferative activity against human cancer cell lines cells.     

Synthesis of a novel series of L-isoserine derivatives as aminopeptidase N inhibitors

A series of novel L-isoserine derivatives were synthesised and evaluated for their ability to inhibit aminopeptidase N (APN)/CD13. In our preliminary biological results, some of these compounds possessed a potent inhibitory activity against the APN. Within this series, compound 14b not only showed similar enzyme inhibition (IC?? of 12.2 μM) compared with the positive control bestatin (half maximal inhibitory concentration (IC??) of 7.3 μM), but also had a potent antiproliferative activity against human cancer cell lines cells.     

Leucine ureido derivatives as aminopeptidase N inhibitors using click chemistry. Part II

Aminopeptidase N (APN) has been proved to be deeply associated with cancer angiogenesis, metastasis and invasion. Therefore, APN gains increasing attention as a promising anti-tumor target. In the current study, we report the design, synthesis, biological evaluation and structure-activity relationship of one new series of leucine ureido derivatives containing the 1,2,3-triazole moiety. Among them, compound 31f was identified as the best APN inhibitor with IC₅₀ value being two orders of magnitude lower than that of the positive control bestatin. Compound 31f possessed selective cytotoxicity to several tumor cell lines over the normal cell line human umbilical vein endothelial cells (HUVECs). Notably, when combined with 5-fluorouracil (5-Fu), 31f exhibited synergistic anti-proliferation effect against several tumor cell lines. At the same concentration, 31f exhibited much better anti-angiogenesis activities than bestatin in the HUVECs capillary tube formation assay and the rat thoracic aorta rings test. In the in vitro anti-invasion assay, 31f also exhibited superior potency over bestatin. Moreover, considerable in vivo antitumor potencies of 31f alone or in combination with 5-Fu were observed without significant toxic signs in a mouse heptoma H22 tumor transplant model.     

Novel aminopeptidase N inhibitors derived from 1,3,4-thiadiazole scaffold

The aminopeptidase N (APN/CD13), overexpressed in tumor cells, plays a critical role in angiogenesis. In this study, we report the synthesis and in vitro enzyme inhibition assay of 1,3,4-thiadiazole scaffold compounds. These new compounds have potent inhibitory activities toward APN with IC(50) values in the micromol rang.     

First synthesis of alpha-aminoalkyl-(N-substituted)thiocarbamoyl-phosphinates: inhibitors of aminopeptidase N (APN/CD13) with the new zinc-binding group

OO-Di-trimethylsilyl esters of alpha-N-benzyloxycarbonylaminoalkylphosphinates (III) undergo triethylamine catalyzed addition to isothiocyanates to give after hydrolysis, a series of new alpha-aminoalkyl-(N-substituted)thiocarbamoyl-phosphinates. Thiocarbamoyl-phosphinate moiety can be included in the structures of the metalloproteinase inhibitors as the zinc-binding group and the new compounds reported here are good inhibitors of important aminopeptidase N(CD13) with IC(50) in range of 10.56-0.25 microM.     

Novel inhibitors of enkephalin-degrading enzymes. II: N5'-substituted-4-thioxohydantoic acids as aminopeptidase inhibitors

Some 2-substituted-(2'-aminophenyl)-4-thioxohydantoic acids (o-amino PTC-amino acids) have antinociceptive activity when administered (icv) alone (IC50 = 0.04-0.87 microM/animal) and show a striking prolongation of the antinociceptive action of (D-Ala-2 D-Leu5)-enkephalin (DADL) in combination. The effects are thought to be mediated via opioid receptors since they are naloxone-reversible. Although inhibitors of the enkephalin degrading puromycin-insensitive, bestatin-sensitive aminopeptidase (possibly aminopeptidase M) their action is weak (IC50 = 32 microM leucine, 536 microM, glycine) and they might be considered to have a direct antinociceptive effect on opioid receptors. The titled compounds constitute novel 'lead' compounds for the development of potent aminopeptidase M inhibitors.     

Design, synthesis and biological evaluation of novel L-lysine ureido derivatives as aminopeptidase N inhibitors

As the exopeptidase over-expressed in the cell surface of endothelial cells, aminopeptidase N (APN/CD13) is an essential target for tumor angiogenesis and metastasis. Based on the previous work of L-lysine amide derivatives in our laboratory, we designed and synthesized two series of L-lysine ureido derivatives as APN inhibitors. Within these compounds, one compound, 5d (IC?? = 4.51 μM), showed similar inhibitory effect compared with Bestatin (IC?? = 5.87 μM).     

Design,synthesis and biological evaluation of novel L-isoserine tripeptide derivatives as aminopeptidase N inhibitors

Aminopeptidase N (APN/CD13) is one of the essential proteins for tumour invasion, angiogenesis and metastasis as it is over-expressed on the surface of different tumour cells. Based on our previous work that L-isoserine dipeptide derivatives were potent APN inhibitors, we designed and synthesized L-isoserine tripeptide derivatives as APN inhibitors. Among these compounds, one compound 16l (IC₅₀?=?2.51?±?0.2 µM) showed similar inhibitory effect compared with control compound Bestatin (IC₅₀?=?6.25?±?0.4 µM) and it could be used as novel lead compound for the APN inhibitors development as anticancer agents in the future.     

Engineered Thermoplasma acidophilum factor F3 mimics human aminopeptidase N (APN) as a target for anticancer drug development

Human aminopeptidase N (hAPN) is an appealing objective for the development of anti-cancer agents. The absence of mammalian APN experimental structure negatively impinges upon the progression of structure-based drug design. Tricorn interacting factor F3 (factor F3) from Thermoplasma acidophilum shares 33% sequence identity with hAPN. Engineered factor F3 with two point directed mutations resulted in a protein with an active site identical to hAPN. In the present work, the engineered factor F3 has been co-crystallized with compound D24, a potent APN inhibitor introduced by our lab. Such a holo-form experimental structure helpfully insinuates a more bulky pocket than Bestatin-bound Escherichia coli APN. This evidence discloses that compound D24 targetting the structure of E. coli APN cannot bind to the activity cleft of factor F3 with high affinity. Thus, there is a potential risk of inefficiency to design hAPN targeting drug while using E. coli APN as the target model. We do propose here now that engineered factor F3 can be employed as a reasonable alternative of hAPN for drug design and development.     

Novel pyridazinone derivatives as butyrylcholinesterase inhibitors

In the current study, forty-four new [3-(2/3/4-methoxyphenyl)-6-oxopyridazin-1(6H)-yl]methyl carbamate derivatives were synthesized and evaluated for their ability to inhibit electric eel acetylcholinesterase (EeAChE) and equine butyrylcholinesterase (eqBuChE) enzymes. According to the inhibitory activity results, [3-(2-methoxyphenyl)-6-oxopyridazin-1(6H)-yl]methyl heptylcarbamate (16c, eqBuChE, IC₅₀ = 12.8 μM; EeAChE, no inhibition at 100 μM) was the most potent eqBuChE inhibitor among the synthesized compounds and was found to be a moderate inhibitor compared to donepezil (eqBuChE, IC₅₀ = 3.25 μM; EeAChE, IC₅₀ = 0.11 μM). Kinetic and molecular docking studies indicated that compounds 16c and 14c (hexylcarbamate derivative, eqBuChE, IC₅₀ = 35 μM; EeAChE, no inhibition at 100 μM) were mixed-type inhibitors which accommodated within the catalytic active site (CAS) and peripheral anionic site (PAS) of hBuChE through stable hydrogen bonding and π-π stacking. Furthermore, it was determined that [3-(2-methoxyphenyl)-6-oxopyridazin-1(6H)-yl]methyl (4-methylphenyl)carbamate 7c (eqBuChE, IC₅₀ = 34.5 μM; EeAChE, 38.9% inhibition at 100 μM) was the most active derivative against EeAChE and a competitive inhibitor binding to the CAS of hBuChE. As a result, 6-(2-methoxyphenyl)pyridazin-3(2H)-one scaffold is important for the inhibitory activity and compounds 7c, 14c and 16c might be considered as promising lead candidates for the design and development of selective BuChE inhibitors for Alzheimer’s disease treatment.     

Novel potent 2,5-pyrrolidinedione peptidomimetics as aminopeptidase N inhibitors. Design, synthesis and activity evaluation

A series of novel aminopeptidase N inhibitors with 2,5-pyrrolidinedione scaffold were chemically synthesized. Their preliminary biological activities in enzyme kinetics and cell assay in vitro and anti-metastasis profile in vivo were also evaluated. The results indicated that all the compounds displayed potent inhibitory activity against aminopeptidase N. Compound 8f inhibited aminopeptidase N activity with IC(50) value of 1.0μM and displayed better activity profile in vivo than that of bestatin.     

Synthesis and biological evaluation of pyrido[2,3-d]pyrimidine-2,4-dione derivatives as eEF-2K inhibitors

A small molecule library of pyrido[2,3-d]pyrimidine-2,4-dione derivatives 6–16 was synthesized from 6-amino-1,3-disubstituted uracils 18, characterized, and screened for inhibitory activity against eukaryotic elongation factor-2 kinase (eEF-2K). To understand the binding pocket of eEF-2K, structural modifications of the pyrido[2,3-d]pyrimidine were made at three regions (R¹, R², and R³). A homology model of eEF-2K was created, and compound 6 (A-484954, Abbott laboratories) was docked in the catalytic domain of eEF-2K. Compounds 6 (IC₅₀ = 420 nM) and 9 (IC₅₀ = 930 nM) are found to be better molecules in this preliminary series of pyrido[2,3-d]pyrimidine analogs. eEF-2K activity in MDA-MB-231 breast cancer cells is significantly reduced by compound 6, to a lesser extent by compound 9, and is unaffected by compound 12. Similar inhibitory results are observed when eEF-2K activity is stimulated by 2-deoxy-d-glucose (2-DOG) treatment, suggesting that compounds 6 and 9 are able to inhibit AMPK-mediated activation of eEF-2K to a notable extent. The results of this work will shed light on the further design and optimization of novel pyrido[2,3-d]pyrimidine analogs as eEF-2K inhibitors.     

S-Benzylisothiourea derivatives as small-molecule inhibitors of indoleamine-2,3-dioxygenase

S-Benzylisothiourea 3a was discovered by its ability to inhibit indoleamine-2,3-dioxygenase (IDO) in our screening program. Subsequent optimization of the initial hit 3a lead to the identification of sub-μM inhibitors 3r and 10h, both of which suppressed kynurenine production in A431 cells. Synthesis and structure–activity relationship of S-benzylisothiourea analogues as small-molecule inhibitors of IDO are described.