Pan-lysyl oxidase inhibitor PXS-5505 ameliorates multiple-organ fibrosis by inhibiting collagen crosslinks in rodent models of systemic sclerosis

Background/Purpose: Systemic sclerosis (SSc) is characterised by progressive multiple-organ fibrosis leading to morbidity and mortality. Lysyl oxidases play a vital role in the cross-linking of collagens and subsequent build-up of fibrosis in the extracellular matrix. As such, their inhibition provides a novel treatment paradigm for SSc. Experimental Approach: Lysyl oxidases are upregulated in preclinical models of fibrosis in skin, lung, heart, kidney and liver. A novel small molecule pan-lysyl oxidase inhibitor, PXS-5505, currently in clinical development for bone fibrosis treatment was evaluated in in vivo rodent models resembling the fibrotic conditions in SSc. Key Results: Both lysyl oxidase and lysyl oxidase-like 2 (LOXL2) expression was elevated in the skin and lung of SSc patients. Once-a-day oral application of PXS-5505 inhibited lysyl oxidase activity in the skin and LOXL2 activity in the lung. PXS-5505 exhibited anti-fibrotic effects in the SSc skin mouse model, reducing dermal thickness and α-smooth muscle actin compared to the disease controls. Similarly, in the bleomycin-induced mouse lung model, PXS-5505 reduced tissue fibrosis toward normal levels. The anti-fibrotic efficacy of PXS-5505 in the bleomycin exposed lungs was mediated by its ability to normalise collagen/elastin crosslink formation, a direct consequence of lysyl oxidase inhibition. PXS-5505 also reduced area of fibrosis in rodent models of the ischaemia-reperfusion heart, the unilateral ureteral obstruction kidney and the CCl4-induced fibrotic liver. Conclusion/Implication: PXS-5505 consistently demonstrates potent anti-fibrotic efficacy in multiple models of organ fibrosis relevant to the pathogenesis of SSc, suggesting that it may be efficacious as a novel approach for treating SSc.

Dysregulation of Lysyl Oxidases Expression in Diabetic Nephropathy and Renal Cell Carcinoma

: Lysyl oxidases (LOXs) are amino oxidase enzymes that catalyze the oxidative deamination of lysine and hydroxylysine residues to form allysine, the first step towards the development of the final cross-linking reaction in collagens, a crucial macromolecule that reinforces extracellular matrices. Basement membranes are specialized extracellular matrices that are essential components of the glomerular filtration barrier, which also support tubular epithelial cells. Lysyl oxidases are post-translational enzymes indispensable for tissue architecture, participating actively in the development and function of kidneys. The differential expression and dysregulation of these enzymes promote diabetic nephropathy, one of the major complications observed in end-stage renal diseases. In addition, these enzymes act as transcription factors that trigger the epithelial-mesenchymal transition responsible for the generation of different cancers. In the kidney, the expression studies in physiological conditions identified LOXL1 and LOXL2 as constituent proteins of glomerular basement membranes. Besides, LOX and LOXL2 are upregulated in fibrosis and renal cell carcinoma. The current review summarizes the physiological expression of LOXs enzymes in the nephrons, including glomerulus and tubules. Their roles in renal diseases are particularly highlighted in diabetic nephropathy and renal cell carcinoma, two pathophysiological conditions where these enzymes have been demonstrated to participate. The focus of the present study is to describe and discuss the current understanding in this field. The current potential of LOXs enzymes as a biomarker and pharmacological target to kidney diseases that involves extracellular matrix cross-linking enzymes is also discussed. LOXs isoforms and their capacity as therapeutic targets could be used for diagnostic and prognostic purposes and in treating these renal complications.

The Expression Patterns and Roles of Lysyl Oxidases in Aortic Dissection

Background: Lysyl oxidases (LOXs), including LOX, LOXL1, LOXL2, LOXL3, and LOXL4, catalyze the formation of a cross-link between elastin (ELN) and collagen. Multiple LOX mutations have been shown to be associated with the occurrence of aortic dissection (AD) in humans, and LOX-knockout mice died during the perinatal period due to aortic aneurysm and rupture. However, the expression levels and roles of other LOX members in AD remain unknown.Methods: A total of 33 aorta samples of AD and 15 normal aorta were collected for LOXs mRNA and protein levels detection. We also analyzed the datasets of AD in GEO database through bioinformatics methods. LOXL2 and LOXL3 were knocked down in primary cultured human aortic smooth muscle cells (HASMCs) via lentivirus.Results: Here, we show that the protein levels of LOXL2 and LOXL3 are upregulated, while LOXL4 is downregulated in AD subjects compared with non-AD subjects, but comparable protein levels of LOX and LOXL1 are detected. Knockdown of LOXL2 suppressed MMP2 expression, the phosphorylation of AKT (p-AKT) and S6 (p-S6), but increased the mono-, di-, tri-methylation of H3K4 (H3K4me1/2/3), H3K9me3, and p-P38 levels in HASMCs. These results indicate that LOXL2 is involved in regulation of the extracellular matrix (ECM) in HASMCs. In contrast, LOXL3 knockdown inhibited PCNA and cyclin D1, suppressing HASMC proliferation. Our results suggest that in addition to LOX, LOXL2 and LOXL3 are involved in the pathological process of AD by regulating ECM and the proliferation of HASMCs, respectively. Furthermore, we found that LOXL2 and LOXL4 was inhibited by metformin and losartan in HASMCs, which indicated that LOXL2 and LOXL4 are the potential targets that involved in the therapeutic effects of metformin and losartan on aortic or aneurysm expansion.Conclusions: Thus, differential regulation of LOXs might be a novel strategy to prevent or treat AD.

An in situ activity assay for lysyl oxidases

The lysyl oxidase family of enzymes (LOXs) catalyze oxidative deamination of lysine side chains on collagen and elastin to initialize cross-linking that is essential for the formation of the extracellular matrix (ECM). Elevated expression of LOXs is highly associated with diverse disease processes. To date, the inability to detect total LOX catalytic function in situ has limited the ability to fully elucidate the role of LOXs in pathobiological mechanisms. Using LOXL2 as a representative member of the LOX family, we developed an in situ activity assay by utilizing the strong reaction between hydrazide and aldehyde to label the LOX-catalyzed allysine (-CHO) residues with biotin-hydrazide. The biotinylated ECM proteins are then labeled via biotin-streptavidin interaction and detected by fluorescence microscopy. This assay detects the total LOX activity in situ for both overexpressed and endogenous LOXs in cells and tissue samples and can be used for studies of LOXs as therapeutic targets.

Lysyl oxidase inhibitors attenuate cyclosporin A-induced nephropathy in mouse

Calcineurin inhibitors, such as Cyclosporin (CsA), are the mainstay of anti-rejection therapy in solid organ transplants but can paradoxically induce progressive nephropathy characterised by renal dysfunction and interstitial fibrosis. Lysyl oxidases (LOXs), a group of enzymes that catalyse extracellular matrix (ECM) crosslinking, were shown to implicate in tissue scarring. It is hypothesized that inhibition of these enzymes may render therapeutic effects against CsA-induced nephropathy. In this study, 6-to-8 weeks old C57BL/6 J mice were administered saline or CsA (30 mg/kg/day s.c) for 16 weeks. At 8 weeks, CsA-treated animals were divided into 5 groups respectively treated with: (1) vehicle, (2) PXS-5505 (Pan-LOX inhibitor), (3) PXS-5382 (LOX-like 2 inhibitor), (4) PXS-5505 for 4 weeks then PXS-5382 for 4 weeks (sequential therapy), and (5) Telmisartan (standard therapy). Our results indicate that CsA administration significantly increased the levels of blood urea nitrogen, glomerular and tubular injury, tubulointerstitial fibrosis, inflammation and oxidative stress in mouse kidney. These changes were associated with upregulated mRNA expression of LOX and LOXL2. Administration of Pan-LOX or LOXL2 inhibitors or the sequential therapy suppressed the expression of ECM proteins (α-SMA, FN and COL1A), matrix metalloproteases (MMP)2 and 9, inflammatory markers (TNFα and MCP-1) and TGF-β1-Smad3 signalling. Among all regimens including telmisartan, only Pan-LOX inhibitor PXS-5505 was able to attenuate uraemia. Collectively, our study suggests that Pan-LOX and LOXL2 inhibition can attenuate progressive nephropathy due to CsA administration.

A Novel In Situ Activity Assay for Lysyl Oxidases

The lysyl oxidase family of enzymes (LOXs) catalyze oxidative deamination of lysine side chains on collagen and elastin to initialize cross-linking that is essential for the formation of the extracellular matrix (ECM). Elevated expression of LOXs is highly associated with diverse disease processes. To date, the inability to detect total LOX catalytic function in situ has limited the ability to fully elucidate the role of LOXs in pathobiological mechanisms. Using LOXL2 as a representative member of the LOX family, we developed an in situ activity assay by utilizing the strong reaction between hydrazide and aldehyde to label the LOX-catalyzed allysine (-CHO) residues with biotin-hydrazide. The biotinylated ECM proteins are then labeled via biotin-streptavidin interaction and detected by fluorescence microscopy. This assay detects the total LOX activity in situ for both overexpressed and endogenous LOXs in cells and tissue samples and can be used for studies of LOXs as therapeutic targets.

Evaluation of a Pan-Lysyl Oxidase Inhibitor, Pxs-5505, in Myelofibrosis: A Phase I, Randomized, Placebo Controlled Double Blind Study in Healthy Adults

BACKGROUND: Myeloproliferative neoplasms (MPNs) are clonal stem cell neoplasms characterized by terminal expansion of the myeloid cell lineage and include essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF). MF carries the worst prognosis and is characterized by reactive bone marrow fibrosis. Currently bone marrow transplant is the only known therapy that can reverse fibrosis and alter the disease course. Lysyl oxidases (LOX, LOXL1-4) are copper amine oxidase enzymes that facilitate the cross-linking of collagen and elastin through deamination and oxidization of lysine residues, yielding highly reactive aldehydes. This is essential for fibrotic tissue formation. An earlier study identified an important role for LOX in the development of MF in mice (Eliades et al, J. Biol. Chem. 2011; PMID: 21665949). Furthermore, small molecule pan-LOX inhibitors reduced spleen size and bone marrow fibrosis in mouse models of MF (Leiva et al, Int J. Hemat. 2019; PMID: 31637674). This provides clinical rationale for the use of pan-lysyl oxidase inhibition in MF. A Phase 1 study was conducted to establish the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of PXS-5505, a pan-lysyl oxidase inhibitor. Plasma levels of LOX and LOXL2 were investigated in a separate cohort of MPN patients, with the ultimate goal to develop PXS-5505-based therapy in MF patients. METHODS: PXS-5505 was dosed orally in a Phase I, randomized, placebo-controlled, single ascending (Part A) and multiple ascending dose (Part B) double-blind study in healthy male volunteers. Plasma LOX and LOXL2 levels were also measured in a separate cohort of MPN patients using ELISA-based Single Molecule Array technology (Simoa; Quanterix). RESULTS: Forty subjects were enrolled in Part A and 16 were enrolled in Part B. In Part A, there were 5 cohorts consisting of 8 subjects (6 active, 2 placebo) with doses of 10, 50, 100, 200 or 300 mg administered once. In Part B, there were 2 cohorts of 8 subjects each (6 active, 2 placebo) at doses of 100 or 200 mg daily for 14 days. There were no significant treatment-related adverse events. Mean age in Part A was 32.0 years (SD 11.14) and 32.1 years (SD 12.14) in Part B. Cmax and AUC increased linearly across the dose range of 10 to 300 mg for single dose administration. In multiple dosing at 200 mg daily, Cmax was 916 ng/mL and AUC0-24 was 7421 hr*ng/mL on Day 14, with median Tmax of 1 hour and t1/2 of 7 hours. When measured in plasma, LOX was dose-dependently inhibited and achieved very strong inhibition (median 80%) with a 200 mg dose around Tmax. The 300 mg dosing did not significantly increase inhibition. Multiple daily doses of 100-200 mg resulted in 60-70% and 50-60% inhibition of plasma LOX at 12 and 24 hours. Average LOX plasma levels were 3.61 ng/mL (range: 3.20-13.42 ng/mL; SD: 2.92 ng/mL). We measured plasma LOX and LOXL2 levels in a separate MPN cohort of 9 ET, 8 PV, and 13 MF patients (mean age 61.4, range:24-84, 65% males). LOXL2 levels were higher in MF (mean 415 pg/mL) compared to ET (mean 209 pg/mL) and PV (mean 322 pg/ml), although this was not significant. However, LOXL2 levels in all MPN patients (mean 333 pg/mL) were significantly higher than LOXL2 levels in normal controls (mean 152 pg/mL, p<0.01). There were no significant differences in LOX levels in the two groups. DISCUSSION: PXS-5505 demonstrated an excellent safety profile and was well tolerated in healthy human subjects. PK/PD properties are consistent with preclinical data and support once or twice daily >100 mg dosing over 14 days. PXS-5505 achieves long-lasting, strong inhibition of lysyl oxidases. Plasma LOXL2 levels are higher in MF patients compared to healthy controls, and we found no significant disease associations of LOX or LOXL2 among MPN subtypes in our small cohort. LOXL2 is likely a more sensitive MF biomarker as it is present at low concentrations in the blood, while LOX is constantly produced from major organs making detection due to disease more difficult. Based on previous mouse studies, it is possible that LOX levels would be higher in MF patients when compared to age-matched controls, which we will investigate further. We will open a Phase IB/II study of PXS-5505 in MF patients resistant to ruxolitinib. Disclosures Neuberg: Madrigak Pharmaceuticals: Current equity holder in publicly-traded company; Celgene: Research Funding; Pharmacyclics: Research Funding. Ravid:Pharmaxis: Research Funding. Jarolimek:Pharmaxis Ltd: Current Employment. Charlton:Pharmaxis Ltd: Current Employment. Hobbs:Novartis: Honoraria; Constellation: Honoraria, Research Funding; Jazz: Honoraria; Celgene/BMS: Honoraria; Merck: Research Funding; Incyte: Research Funding; Bayer: Research Funding.