Small-molecule LOXL2 inhibition as a novel antifibrotic strategy for the treatment of myocardial fibrosis

To the Editor, Myocardial fibrosis is a defining feature of adverse cardiac remodeling. It plays a central role in the progression of heart failure. The condition is characterized by excessive accumulation and abnormal cross-linking fibrillar fibers. This leads to increased myocardial stiffness, impaired diastolic filling, and ultimately a reduction in cardiac performance[1]. Lysyl oxidases are copper-dependent enzymes, which are responsible for catalyzing the cross-linking of collagen and elastin fibers. This is the process that significantly influences myocardial stiffness and resistance to matrix degradation. Among this enzyme family, lysyl oxidase-like 2 (LOXL2) has gained increasing attention as a mediator of fibrosis. Studies of patients with heart failure due to hypertension or aortic stenosis have reported increased levels of myocardial and circulating LOXL2. These increased levels are associated with left ventricular hypertrophy and adverse cardiac remodeling[2]. These findings suggest that LOXL2 is not only a marker of fibrosis but may also represent a promising therapeutic target. Recent data from clinical trials provide evidence that selective small-molecule inhibition of LOXL2 can decrease the extent of myocardial fibrosis. Earlier antibody-based approaches were ultimately unsuccessful. This may largely be due to insufficient inhibition of enzymatic activity. In contrast, small-molecule inhibitors directly target the active site of LOXL2, thereby preventing collagen cross-linking and fibrosis. In experimental models of MI, LOXL2 inhibition reduces collagen cross-link density without lowering total collagen content, which implies an improvement in extracellular matrix quality rather than nonspecific matrix loss[3]. Along with this, improvements were seen in left ventricular systolic function and chamber remodeling, supporting a functional benefit of this strategy. Early-phase clinical studies show that oral LOXL2 inhibitors can maintain sustained target engagement with acceptable safety and pharmacokinetic profiles. Once-daily dosing was sufficient to produce prolonged enzyme inhibition, even though LOXL2 is rapidly renewed. This finding helps explain why earlier antibody-based approaches were unsuccessful, as their limitations appear to be related to drug design rather than the relevance of LOXL2 as a target[4]. Despite these advances, several issues need to be resolved before LOXL2 inhibition can be used in routine cardiovascular care. At present, clinical evidence is mainly limited to phase 1 studies in healthy volunteers, and solid efficacy data in patients with established myocardial fibrosis are still missing. Other translational challenges include the fact that some LOXL2-targeting strategies failed in clinical trials despite promising preclinical results – for example, antibody inhibitors showed lack of therapeutic efficacy or even enhanced fibroblast invasion in humanized models of fibrosis, underscoring uncertainty in how findings translate from models to patients[5]. In addition, selecting appropriate patient populations and identifying the optimal timing of treatment is also essential for successful clinical translation. To summarize, selective small-molecule inhibition of LOXL2 appears to be a promising approach for treating myocardial fibrosis. This strategy targets a key driver of myocardial stiffening that is not adequately addressed by current therapies of heart failure. But further clinical studies are needed to determine whether LOXL2 inhibition can meaningfully alter the progression of heart fibrosis and whether it can be used long term as an intervention. This letter to the Editor adheres to the Transparency in the Reporting of Artificial Intelligence in Research (TITAN) guideline[6].