The discovery of a dual MAO-B/SSAO inhibitor PXS-5131 is reported. The compound offers a compact and rigid three-dimensional structure with superior selectivity over MAO-A. Potency and selectivity are linked to both the double bond geometry and stereochemistry of the allylamine moiety, highlighting the importance of optimal set up of these features in the class of amine oxidase inhibitors. PXS-5131 possesses an attractive preclinical pharmacokinetic profile and has anti-inflammatory properties in models of acute inflammation and neuroinflammation.

Dear Editor, In this study, measurement of target inhibition of lysyl oxidase-like 2 (LOXL2) in a high throughput manner from tissue lysates and bloodwas achieved by the tailored design of an activity-based probe (ABP), PXS-5878. Effective inhibition of LOXL2 enzymatic activity in vitro, in vivo and in a phase 1 study in healthy humans was demonstrated by a novel small molecule, PXS-5338. In contrast to the encouraging results obtainedwith PXS-5338, our study also revealed the inability of a LOXL2 antibody (AB0023) to effectively inhibit the target, thereby providing a plausible explanation for the failure of the corresponding humanised antibody, simtuzumab, in the clinic. Lysyl oxidases are a family of five enzymes critically responsible for the formation of cross-linked collagen and elastin, the hallmarks of fibrosis and stroma.1,2 One member in particular, LOXL2, has excellent pre-clinical target validation, is upregulated in various fibrotic diseases and cancer,3 and acts as a biomarker for disease severity and progression in humans.4,5 Despite overwhelming target rationale, the failure of the LOXL2 antibody simtuzumab to achieve positive clinical endpoints6,7 has undoubtedly hampered progress in the field and cast doubt over the validity of LOXL2 inhibition as a viable therapeutic approach. This may now be overcome with the use of an ABP to interrogate the extent of target engagement achieved by the small molecule LOXL2 inhibitor PXS-5338, providing crucial information lacking from previous trials. The ability to confirm sufficient target engagement in humans is of vital importance for successful clinical candidate progression, potentially reducing attrition rates due to inappropriate dosing regimens. PXS-5878 (Figure 1A), a novel biotinylated ABP, was designed to potently and irreversibly bind to unoccupied lysyl oxidase active sites (Figure 1B,C). Binding is blocked by pre-treatment with a lysyl oxidase inhibitor (Figure 1D,E) and the irreversible nature of inhibition

Lysyl oxidase-like 2 (LOXL2) is a secreted enzyme that catalyzes the formation of cross-links in extracellular matrix proteins, namely, collagen and elastin, and is indicated in fibrotic diseases. Herein, we report the identification and subsequent optimization of a series of indole-based fluoroallylamine inhibitors of LOXL2. The result of this medicinal chemistry campaign is PXS-5120A (12k), a potent, irreversible inhibitor that is >300-fold selective for LOXL2 over LOX. PXS-5120A also shows potent inhibition of LOXL3, an emerging therapeutic target for lung fibrosis. Key to the development of this compound was the utilization of a compound oxidation assay. PXS-5120A was optimized to show negligible substrate activity in vitro for related amine oxidase family members, leading to metabolic stability. PXS-5120A, in a pro-drug form (PXS-5129A, 12o), displayed anti-fibrotic activity in models of liver and lung fibrosis, thus confirming LOXL2 as an important target in diseases where collagen cross-linking is implicated.

Fibrosis is characterized by the excessive deposition of extracellular matrix and crosslinked proteins, in particular collagen and elastin, leading to tissue stiffening and disrupted organ function. Lysyl oxidases are key players during this process, as they initiate collagen crosslinking through the oxidation of the ε-amino group of lysine or hydroxylysine on collagen side-chains, which subsequently dimerize to form immature, or trimerize to form mature, collagen crosslinks. The role of LOXL2 in fibrosis and cancer is well documented, however the specific enzymatic function of LOXL2 and LOXL3 during disease is less clear. Herein, we describe the development of PXS-5153A, a novel mechanism based, fast-acting, dual LOXL2/LOXL3 inhibitor, which was used to interrogate the role of these enzymes in models of collagen crosslinking and fibrosis. PXS-5153A dose-dependently reduced LOXL2-mediated collagen oxidation and collagen crosslinking in vitro. In two liver fibrosis models, carbon tetrachloride or streptozotocin/high fat diet-induced, PXS-5153A reduced disease severity and improved liver function by diminishing collagen content and collagen crosslinks. In myocardial infarction, PXS-5153A improved cardiac output. Taken together these results demonstrate that, due to their crucial role in collagen crosslinking, inhibition of the enzymatic activities of LOXL2/LOXL3 represents an innovative therapeutic approach for the treatment of fibrosis.

Lysyl Oxidase-like 2 (LOXL2), a member of the lysyl oxidase family of amine oxidases is known to be important in normal tissue development and homeostasis, as well as the onset and progression of solid tumors. Here we tested the anti-tumor properties of two generations of novel small molecule LOXL2 inhibitor in the MDA-MB-231 human model of breast cancer. We confirmed a functional role for LOXL2 activity in the progression of primary breast cancer. Inhibition of LOXL2 activity inhibited the growth of primary tumors and reduced primary tumor angiogenesis. Dual inhibition of LOXL2 and LOX showed a greater effect and also led to a lower overall metastatic burden in the lung and liver. Our data provides the first evidence to support a role for LOXL2 specific small molecule inhibitors as a potential therapy in breast cancer.

Idiopathic pulmonary fibrosis (IPF) is a chronic disease characterised by a progressive decline in lung function which can be attributed to excessive scarring, inflammation and airway remodelling. Mannose-6-phosphate (M6P) is a strong inhibitor of fibrosis and its administration has been associated with beneficial effects in tendon repair surgery as well as nerve repair after injury. Given this promising therapeutic approach we developed an improved analogue of M6P, namely PXS64, and explored its anti-fibrotic effects in vitro. Normal human lung fibroblasts (NHLF) and human lung fibroblast 19 cells (HF19) were exposed to active recombinant human TGF-β1 to induce increases in fibrotic markers. rhTGF-β1 increased constitutive protein levels of fibronectin and collagen in the NHLF cells, whereas HF19 cells showed increased levels of fibronectin, collagen as well as αSMA (alpha smooth muscle actin). PXS64 demonstrated a robust inhibitory effect on all proteins analysed. IPF patient fibroblasts treated with PXS64 presented an improved phenotype in terms of their morphological appearance, as well as a decrease in fibrotic markers (collagen, CTGF, TGF-β3, tenascin C, αSMA and THBS1). To explore the cell signalling pathways involved in the anti-fibrotic effects of PXS64, proteomics analysis with iTRAQ labelling was performed and the data demonstrated a specific antagonistic effect on the TGF-β1 pathway. This study shows that PXS64 effectively inhibits the production of extracellular matrix, as well as myofibroblast differentiation during fibrosis. These results suggest that PXS64 influences tissue remodelling by inhibiting TGF-β1 signalling in NHLF and HF19 cell lines, as well as in IPF patient fibroblasts. Thus PXS64 is a potential candidate for preclinical application in pulmonary fibrosis.

Semicarbazide-sensitive amine oxidase (SSAO), also known as vascular adhesion protein-1 (VAP-1), is a member of the copper-dependent amine oxidase family that is associated with various forms of inflammation and fibrosis. To investigate the therapeutic potential of SSAO/VAP-1 inhibition, potent and selective inhibitors with drug-like properties are required. PXS-4681A [(Z)-4-(2-(aminomethyl)-3-fluoroallyloxy)benzenesulfonamide hydrochloride] is a mechanism-based inhibitor of enzyme function with a pharmacokinetic and pharmacodynamic profile that ensures complete, long-lasting inhibition of the enzyme after a single low dose in vivo. PXS-4681A irreversibly inhibits the enzyme with an apparent Ki of 37 nM and a kinact of 0.26 min(-1) with no observed turnover in vitro. It is highly selective for SSAO/VAP-1 when profiled against related amine oxidases, ion channels, and seven-transmembrane domain receptors, and is superior to previously reported inhibitors. In mouse models of lung inflammation and localized inflammation, dosing of this molecule at 2 mg/kg attenuates neutrophil migration, tumor necrosis factor-α, and interleukin-6 levels. These results demonstrate the drug-like properties of PXS-4681A and its potential use in the treatment of inflammation.

Oxygenated 4-arylisoflavans and 4-heteroarylisoflavans were synthesized in good yields via BF3·OEt2 catalyzed arylation reactions of 4′,7-diacetoxyisoflavan-4-ol 8 with activated aryl and heteroaryl compounds. These reactions were found to produce stereoselectively the trans isomers. Similar reactions of 4′,7-diacetoxyflavan-4-ol 16 afforded the corresponding 4-arylflavans and 4-heteroarylflavans as mixtures of cis/trans isomers.

AbstractA facile method for the oxidative dimerization of methoxy‐substituted isoflavones is presented.

Kudzuisoflavone-A was successfully synthesised via oxidative dimerisation of daidzein in the presence of cuprous chloride. Appropriately substituted isoflavones also undergo regioselective oxidative dimerisation when treated with thallium trifluoroacetate to give novel 6′,6′″-biisoflavones in good yield. A rationale for the regioselectivity is proposed.

A new class of 3-fluoroallyl amine-based SSAO/VAP-1 inhibitors is reported. These compounds have excellent selectivity over diamine oxidase, MAO-A and MAO-B. Synthesis and SAR studies leading to compound 28 (PXS-4159A) are reported. The pharmacokinetic profile of 28 in the rat, together with activity in a murine model of lung inflammation are also disclosed.

Halogenated flavones, isoflavones and indoles were subjected to a one-pot Sonogashira coupling reaction to generate a series of new biheterocyclic compounds. The methodology can be readily adapted to the synthesis of a wide variety of substituted biheterocycles.

Halogenated indoles, benzofurans and flavones were subjected to a one-pot Suzuki-Miyaura coupling reaction to generate a series of new biheterocycles.The methodology may be readily adapted to the synthesis of a wide variety of substituted biheterocycles.

Abstractinvolving in situ conversion of an aryl halide into a boronate ester intermediate followed by addition of a second equivalent of aryl halide together with an appropiate Pd‐catalyst; (11 examples)