Myeloperoxidase (MPO) is a heme-containing peroxidase enzyme primarily expressed in neutrophils, monocytes, and macrophages. It plays a central role in innate immunity by generating hypochlorous acid (HOCl), a potent oxidant critical for microbial killing. However, excessive MPO activity contributes to chronic inflammation and oxidative stress, particularly in atherosclerosis and other cardiovascular diseases. Elevated plasma levels of MPO and its oxidation products correlate with increased risk of coronary artery disease and heart failure. MPO also modifies low-density lipoprotein (LDL) and high-density lipoprotein (HDL), promoting plaque formation and endothelial dysfunction. Furthermore, emerging evidence suggests MPO may drive atrial fibrosis in heart failure through oxidative remodeling of cardiac tissue.
Given the pathological roles of MPO, developing selective inhibitors has become a promising therapeutic strategy. The focus here is on designing reversible, non-covalent inhibitors that bind above the heme pocket of native MPO, thereby preventing the interaction with hydrogen peroxide (H₂O₂) without altering the enzyme’s redox state. Early leads such as triazolopyridine compounds 1–3 demonstrated moderate potency in inhibiting MPO-mediated chlorination using the AminoPhenyl Fluorescein (APF) assay but suffered from poor selectivity against thyroid peroxidase (TPO) and time-dependent inhibition of cytochrome P450 3A4 (TD-CYP3A4). These liabilities prompted a structural redesign centered on a substituted pyrazole scaffold.
The crystal structure of compound 3 bound to MPO revealed a hydrophobic pocket formed by residues Phe366, Phe407, Met411, and Val410, which could be exploited for enhanced binding. Replacing the phenyl ring in 3 with a pyrazole ring yielded lead compound 4, showing improved potency and better access to this region. Molecular overlay confirmed that the pyrazole ring adopts a rotated conformation compared to the phenyl group, enabling edge-to-face interactions with Phe366 and positioning the fluorophenyl substituent into a small lipophilic cavity.ALG2 Antibody In Vivo This orientation allowed for strategic introduction of diverse substituents via alkylation at the pyrazole nitrogen.303760-60-3 References
Structure-activity relationship (SAR) studies led to the identification of piperidine derivative 17, which exhibited an IC₅₀ of 2.PMID:34414559 4 μM in human neutrophil assays and excellent selectivity over TPO (>8,000-fold). Further optimization focused on extending into the larger hydrophobic pocket between Phe407 and Met411. To achieve this, macrocyclic analogs were designed to bridge two distal hydrophobic regions within the active site. Multiple macrocyclization strategies—including Ullmann coupling, Mitsunobu reactions, and intramolecular Suzuki-Miyaura condensation—were explored. Among these, the Suzuki-Miyaura approach proved most versatile, enabling efficient ring closure across diverse scaffolds regardless of linker complexity.
Notably, macrocycle 30, featuring a benzyl-substituted pentane linker, emerged as one of the most potent inhibitors with an APF IC₅₀ of just 5 nM. X-ray crystallography confirmed that the pendant benzyl group occupies the hydrophobic cleft near Val410, Pro220, and Asp218, validating the design hypothesis. Despite increased lipophilicity leading to stronger TD-CYP3A4 inhibition, compound 30 maintained >1,500-fold selectivity over TPO and showed favorable metabolic stability in human liver microsomes (t₁/₂ > 120 min). Pharmacokinetic profiling in mice revealed a half-life of 1.2 hours after IV administration, although oral bioavailability remained limited due to poor permeability.
In conclusion, this work demonstrates how rational design based on MPO crystal structures enables the development of highly potent and selective pyrazole-based macrocyclic inhibitors. While oral absorption remains a challenge, the advanced potency and selectivity of compounds like 30 support their potential utility in targeting MPO-driven pathology in cardiovascular disease.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com