Repurposing Medications for Treatment of Pulmonary Arterial Hypertension: What's Old Is New Again

Integrated bioinformatics analysis and experimental animal models identify a robust biomarker and its correlation with the immune microenvironment in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) represents a substantial global risk to human health. This study aims to identify diagnostic biomarkers for PAH and assess their association with the immune microenvironment through the utilization of sophisticated bioinformatics techniques.

Methods

Based on two microarray datasets, differentially expressed genes (DEGs) were detected, and hub genes underwent a sequence of machine learning analyses. After pathways associated with PAH were assessed by gene enrichment analysis, the identified genes were validated using external datasets and confirmed in a monocrotaline (MCT)-induced rat model. In addition, three algorithms were employed to estimate the proportions of various immune cell types, and the link between hub genes and immune cells was substantiated.

Results

Using SVM, LASSO, and WGCNA, we identified seven hub genes, including (BPIFA1, HBA2, HBB, LOC441081, PI15, S100A9, and WIF1), of which only BPIFA1 remained stable in the external datasets and was validated in an MCT-induced rat model. Furthermore, the results of the functional enrichment analysis established a link between PAH and both metabolism and the immune system. Correlation assessment showed that BPIFA1 expression in the MCP-counter algorithm was negatively associated with various immune cell types, positively correlated with macrophages in the ssGSEA algorithm, and correlated with M1 and M2 macrophages in the CIBERSORT algorithm.

Conclusion

BPIFA1 serves as a modulator of PAH, with the potential to impact the immune microenvironment and disease progression, possibly through its regulatory influence on both M1 and M2 macrophages.

Multifunctional nanoparticle-mediated combining therapy for human diseases

Combining existing drug therapy is essential in developing new therapeutic agents in disease prevention and treatment. In preclinical investigations, combined effect of certain known drugs has been well established in treating extensive human diseases. Attributed to synergistic effects by targeting various disease pathways and advantages, such as reduced administration dose, decreased toxicity, and alleviated drug resistance, combinatorial treatment is now being pursued by delivering therapeutic agents to combat major clinical illnesses, such as cancer, atherosclerosis, pulmonary hypertension, myocarditis, rheumatoid arthritis, inflammatory bowel disease, metabolic disorders and neurodegenerative diseases. Combinatorial therapy involves combining or co-delivering two or more drugs for treating a specific disease. Nanoparticle (NP)-mediated drug delivery systems, i.e., liposomal NPs, polymeric NPs and nanocrystals, are of great interest in combinatorial therapy for a wide range of disorders due to targeted drug delivery, extended drug release, and higher drug stability to avoid rapid clearance at infected areas. This review summarizes various targets of diseases, preclinical or clinically approved drug combinations and the development of multifunctional NPs for combining therapy and emphasizes combinatorial therapeutic strategies based on drug delivery for treating severe clinical diseases. Ultimately, we discuss the challenging of developing NP-codelivery and translation and provide potential approaches to address the limitations. This review offers a comprehensive overview for recent cutting-edge and challenging in developing NP-mediated combination therapy for human diseases.

Efficacy of Drpitor1a, a Dynamin-Related Protein 1 inhibitor, in Pulmonary Arterial Hypertension

Rationale

Dynamin-related protein 1 (Drp1), a large GTPase, mediates mitochondrial fission. Increased Drp1-mediated fission permits accelerated mitosis, contributing to hyperproliferation of pulmonary artery smooth muscle cells (PASMC), which characterizes pulmonary arterial hypertension (PAH). We developed a Drp1 inhibitor, Drpitor1a, and tested its ability to regress PAH.

Objectives

Assess Drpitor1a's efficacy and toxicity in: a)normal and PAH human PASMC (hPASMC); b)normal rats versus rats with established monocrotaline (MCT)-induced PAH.

Methods

Drpitor1a's effects on recombinant and endogenous Drp1-GTPase activity, mitochondrial fission, and cell proliferation were studied in hPASMCs (normal=3; PAH=5). Drpitor1a's pharmacokinetics and tissue concentrations were measured (n=3 rats/sex). In a pilot study (n=3-4/sex/dose), Drpitor1a (1mg/kg/48-hours, intravenous) reduced adverse PA remodeling only in females. Consequently, we compared Drpitor1a to vehicle in normal (n=6 versus 8) and MCT-PAH (n=9 and 11) females, respectively. Drpitor1a treatment began 17-days post-MCT with echocardiography and cardiac catheterization performed 28-29 days post-MCT.

Results

Drpitor1a inhibited recombinant and endogenous Drp1 GTPase activity, which was increased in PAH hPASMC. Drpitor1a inhibited mitochondrial fission and proliferation and induced apoptosis, in PAH hPASMC but not normal hPASMC. Drpitor1a tissue levels were higher in female versus male RVs. In MCT-PAH females, Drpitor1a regressed PA obstruction, lowered pulmonary vascular resistance, and improved RV function, without hematologic, renal, or hepatic toxicity.

Conclusions

Drpitor1a inhibits Drp1 GTPase, reduces mitochondrial fission, and inhibits cell proliferation in PAH hPASMC. Drpitor1a caused no toxicity in MCT-PAH and had no significant effect on normal rats or hPASMCs. Drpitor1a is a potential PAH therapeutic which displays an interesting therapeutic sexual dimorphism.

Emerging biologics for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare pulmonary vascular disorder, wherein mean systemic arterial pressure (mPAP) becomes abnormally high because of aberrant changes in various proliferative and inflammatory signalling pathways of pulmonary arterial cells. Currently used anti-PAH drugs chiefly target the vasodilatory and vasoconstrictive pathways. However, an imbalance between bone morphogenetic protein receptor type II (BMPRII) and transforming growth factor beta (TGF-β) pathways is also implicated in PAH predisposition and pathogenesis. Compared to currently used PAH drugs, various biologics have shown promise as PAH therapeutics that elicit their therapeutic actions akin to endogenous proteins. Biologics that have thus far been explored as PAH therapeutics include monoclonal antibodies, recombinant proteins, engineered cells, and nucleic acids. Because of their similarity with naturally occurring proteins and high binding affinity, biologics are more potent and effective and produce fewer side effects when compared with small molecule drugs. However, biologics also suffer from the limitations of producing immunogenic adverse effects. This review describes various emerging and promising biologics targeting the proliferative/apoptotic and vasodilatory pathways involved in PAH pathogenesis. Here, we have discussed sotatercept, a TGF-β ligand trap, which is reported to reverse vascular remodelling and reduce PVR with an improved 6-minute walk distance (6-MWDT). We also elaborated on other biologics including BMP9 ligand and anti-gremlin1 antibody, anti-OPG antibody, and getagozumab monoclonal antibody and cell-based therapies. Overall, recent literature suggests that biologics hold excellent promise as a safe and effective alternative to currently used PAH therapeutics.

Histone deacetylase inhibitors synergize with sildenafil to suppress purine metabolism and proliferation in pulmonary hypertension

RATIONALE

Sildenafil, a well-known vasodilator known to interfere with purinergic signaling through effects on cGMP, is a mainstay in the treatment of pulmonary hypertension (PH). However, little is known regarding its effects on the metabolic reprogramming of vascular cells, which is a hallmark of PH. Purine metabolism, especially intracellular de novo purine biosynthesis is essential for vascular cell proliferation. Since adventitial fibroblasts are critical contributors to proliferative vascular remodeling in PH, in this study we aimed to investigate if sildenafil, beyond its well-known vasodilator role in smooth muscle cells, impacts intracellular purine metabolism and proliferation of fibroblasts derived from human PH patients.

METHODS

Integrated omics approaches (plasma and cell metabolomics) and pharmacological inhibitor approaches were employed in plasma samples and cultured pulmonary artery fibroblasts from PH patients.

MEASUREMENTS AND MAIN RESULTS

Plasma metabolome analysis of 27 PH patients before and after treatment with sildenafil, demonstrated a partial, but specific effect of sildenafil on purine metabolites, especially adenosine, adenine, and xanthine. However, circulating markers of cell stress, including lactate, succinate, and hypoxanthine were only decreased in a small subset of sildenafil-treated patients. To better understand potential effects of sildenafil on pathological changes in purine metabolism (especially purine synthesis) in PH, we performed studies on pulmonary fibroblasts from PAH patients (PH-Fibs) and corresponding controls (CO-Fibs), since these cells have previously been shown to demonstrate stable and marked PH associated phenotypic and metabolic changes. We found that PH-Fibs exhibited significantly increased purine synthesis. Treatment of PH-Fibs with sildenafil was insufficient to normalize cellular metabolic phenotype and only modestly attenuated the proliferation. However, we observed that treatments which have been shown to normalize glycolysis and mitochondrial abnormalities including a PKM2 activator (TEPP-46), and the histone deacetylase inhibitors (HDACi), SAHA and Apicidin, had significant inhibitory effects on purine synthesis. Importantly, combined treatment with HDACi and sildenafil exhibited synergistic inhibitory effects on proliferation and metabolic reprogramming in PH-Fibs.

CONCLUSIONS

While sildenafil alone partially rescues metabolic alterations associated with PH, treatment with HDACi, in combination with sildenafil, represent a promising and potentially more effective strategy for targeting vasoconstriction, metabolic derangement and pathological vascular remodeling in PH.

Impact of a TAK-1 inhibitor as a single or as an add-on therapy to riociguat on the metabolic reprograming and pulmonary hypertension in the SUGEN5416/hypoxia rat model

Background: Despite increasing evidence suggesting that pulmonary arterial hypertension (PAH) is a complex disease involving vasoconstriction, thrombosis, inflammation, metabolic dysregulation and vascular proliferation, all the drugs approved for PAH mainly act as vasodilating agents. Since excessive TGF-β signaling is believed to be a critical factor in pulmonary vascular remodeling, we hypothesized that blocking TGFβ-activated kinase 1 (TAK-1), alone or in combination with a vasodilator therapy (i.e., riociguat) could achieve a greater therapeutic benefit.

Methods: PAH was induced in male Wistar rats by a single injection of the VEGF receptor antagonist SU5416 (20 mg/kg) followed by exposure to hypoxia (10%O2) for 21 days. Two weeks after SU5416 administration, vehicle, riociguat (3 mg/kg/day), the TAK-1 inhibitor 5Z-7-oxozeaenol (OXO, 3 mg/kg/day), or both drugs combined were administered for 7 days. Metabolic profiling of right ventricle (RV), lung tissues and PA smooth muscle cells (PASMCs) extracts were performed by magnetic resonance spectroscopy, and the differences between groups analyzed by multivariate statistical methods.

Results:In vitro, riociguat induced potent vasodilator effects in isolated pulmonary arteries (PA) with negligible antiproliferative effects and metabolic changes in PASMCs. In contrast, 5Z-7-oxozeaenol effectively inhibited the proliferation of PASMCs characterized by a broad metabolic reprogramming but had no acute vasodilator effects. In vivo, treatment with riociguat partially reduced the increase in pulmonary arterial pressure (PAP), RV hypertrophy (RVH), and pulmonary vascular remodeling, attenuated the dysregulation of inosine, glucose, creatine and phosphocholine (PC) in RV and fully abolished the increase in lung IL-1β expression. By contrast, 5Z-7-oxozeaenol significantly reduced pulmonary vascular remodeling and attenuated the metabolic shifts of glucose and PC in RV but had no effects on PAP or RVH. Importantly, combined therapy had an additive effect on pulmonary vascular remodeling and induced a significant metabolic effect over taurine, amino acids, glycolysis, and TCA cycle metabolism via glycine-serine-threonine metabolism. However, it did not improve the effects induced by riociguat alone on pulmonary pressure or RV remodeling. None of the treatments attenuated pulmonary endothelial dysfunction and hyperresponsiveness to serotonin in isolated PA.

Conclusion: Our results suggest that inhibition of TAK-1 induces antiproliferative effects and its addition to short-term vasodilator therapy enhances the beneficial effects on pulmonary vascular remodeling and RV metabolic reprogramming in experimental PAH.

Histologic and proteomic remodeling of the pulmonary veins and arteries in a porcine model of chronic pulmonary venous hypertension

AIMS

In heart failure (HF), pulmonary venous hypertension (PVH) produces pulmonary hypertension (PH) with remodeling of pulmonary veins (PV) and arteries (PA). In a porcine PVH model, we performed proteomic-based bioinformatics to investigate unique pathophysiologic mechanisms mediating PA and PV remodeling.

METHODS AND RESULTS

Large PV were banded (PVH, n = 10) or not (Sham, n = 9) in piglets. At sacrifice, PV and PA were perfusion labelled for vessel-specific histology and proteomics. The PA and PV were separately sampled with laser-capture micro-dissection for mass spectrometry. Pulmonary vascular resistance [Wood Units; 8.6 (95% confidence interval: 6.3, 12.3) vs. 2.0 (1.7, 2.3)] and PA [19.9 (standard error of mean, 1.1) vs. 10.3 (1.1)] and PV [14.2 (1.2) vs. 7.6 (1.1)] wall thickness/external diameter (%) were increased in PVH (P < 0.05 for all). Similar numbers of proteins were identified in PA (2093) and PV (2085) with 94% overlap, but biological processes differed. There were more differentially expressed proteins (287 vs. 161), altered canonical pathways (17 vs. 3), and predicted upstream regulators (PUSR; 22 vs. 6) in PV than PA. In PA and PV, bioinformatics indicated activation of the integrated stress response and mammalian target of rapamycin signalling with dysregulated growth. In PV, there was also activation of Rho/Rho-kinase signalling with decreased actin cytoskeletal signalling and altered tight and adherens junctions, ephrin B, and caveolae-mediated endocytosis signalling; all indicating disrupted endothelial barrier function. Indeed, protein biomarkers and the top PUSR in PV (transforming growth factor-beta) suggested endothelial to mesenchymal transition in PV. Findings were similar in human autopsy specimens.

CONCLUSION

These findings provide new therapeutic targets to oppose pulmonary vascular remodeling in HF-related PH.

Mitochondrial Dysfunction in Pulmonary Hypertension

Pulmonary hypertension (PH) is a multi-etiological condition with a similar hemodynamic clinical sign and end result of right heart failure. Although its causes vary, a similar link across all the classifications is the presence of mitochondrial dysfunction. Mitochondria, as the powerhouse of the cells, hold a number of vital roles in maintaining normal cellular homeostasis, including the pulmonary vascular cells. As such, any disturbance in the normal functions of mitochondria could lead to major pathological consequences. The Warburg effect has been established as a major finding in PH conditions, but other mitochondria-related metabolic and oxidative stress factors have also been reported, making important contributions to the progression of pulmonary vascular remodeling that is commonly found in PH pathophysiology. In this review, we will discuss the role of the mitochondria in maintaining a normal vasculature, how it could be altered during pulmonary vascular remodeling, and the therapeutic options available that can treat its dysfunction.

Pathophysiology and new advances in pulmonary hypertension

Pulmonary hypertension is a progressive and often fatal cardiopulmonary condition characterised by increased pulmonary arterial pressure, structural changes in the pulmonary circulation, and the formation of vaso-occlusive lesions. These changes lead to increased right ventricular afterload, which often progresses to maladaptive right ventricular remodelling and eventually death. Pulmonary arterial hypertension represents one of the most severe and best studied types of pulmonary hypertension and is consistently targeted by drug treatments. The underlying molecular pathogenesis of pulmonary hypertension is a complex and multifactorial process, but can be characterised by several hallmarks: inflammation, impaired angiogenesis, metabolic alterations, genetic or epigenetic abnormalities, influence of sex and sex hormones, and abnormalities in the right ventricle. Current treatments for pulmonary arterial hypertension and some other types of pulmonary hypertension target pathways involved in the control of pulmonary vascular tone and proliferation; however, these treatments have limited efficacy on patient outcomes. This review describes key features of pulmonary hypertension, discusses current and emerging therapeutic interventions, and points to future directions for research and patient care. Because most progress in the specialty has been made in pulmonary arterial hypertension, this review focuses on this type of pulmonary hypertension. The review highlights key pathophysiological concepts and emerging therapeutic directions, targeting inflammation, cellular metabolism, genetics and epigenetics, sex hormone signalling, bone morphogenetic protein signalling, and inhibition of tyrosine kinase receptors.

Allopurinol treatment reduced vascular remodeling and improved vascular functions in monocrotaline-induced pulmonary hypertensive rats

Increased oxidative stress and high uric acid are implicated in the pathogenesis of pulmonary hypertension (PH). This provides opportunity to benefit from drugs like allopurinol which suppresses both contributing factors. Therefore, we aimed to investigate the effects of allopurinol in preventing as well as reversing the pathological changes occurring in monocrotaline (MCT)-induced rat model of PH. Male rats were assigned into three groups based on the follow-up time: 7, 21 and 35 days. Time-matched controls of each group received single injections of MCT (60 mg/kg) intraperitoneally. Test groups consisted of rats who were treated with MCT on day 0 plus oral allopurinol (60 mg/kg) daily for 7 or 21 days. 35-day group received allopurinol for two weeks starting on the 22nd day following MCT injection. At the end of all-time points, rats were killed and basal pulmonary perfusion pressure, Fulton index, pulmonary arterial wall thickness and pulmonary arterial relaxations along with oxidative stress markers (MDA, SOD, XO), NO and uric acid levels were measured in all groups. MCT-injected rats had evidence of raised oxidative stress (high MDA and XO, low SOD levels) which was reversed by allopurinol co-treatment in all-time groups. Marked elevation of uric acid seen in 21- and 35 day-groups was also reversed by allopurinol. Reduced NO levels of 21 and 35 days were unchanged in allopurinol treated groups. Apart from an increase in arterial wall thickening which was maintained in all-time groups, no alterations in other cardiovascular parameters were observed in 7-day group. However, basal lung perfusion pressure and Fulton index significantly increased, while arterial relaxations decreased in 21- and 35-day groups. Co-treatment with allopurinol for 21 days improved these functional alterations, whereas late allopurinol treatment failed to affect them. Our results indicate that early treatment of MCT-induced PH with allopurinol ameliorated the impaired functional characteristics via suppressing the increased oxidative stress and uric acid, while treatment started after progression of the disease had no significant effect.

Cytokine profiling in pulmonary arterial hypertension: the role of redox homeostasis and sex

Pulmonary arterial hypertension (PAH) is a fatal disease with a well-established sexual dimorphism. Activated inflammatory response and altered redox homeostasis, both known to manifest in a sex-specific manner, are implicated in the pathogenic mechanisms involved in PAH development. This study aimed to evaluate the impact of sex and plasma redox status on circulating cytokine profiles. Plasma oxidation-reduction potential (ORP), as a substitute measure of redox status, was analyzed in male and female Group 1 PAH and healthy subjects. The profiles of 27 circulating cytokines were compared in 2 PAH groups exhibiting the highest and lowest quartile for plasma ORP, correlated with clinical parameters, and used to predict patient survival. The analysis of the PAH groups with the highest and lowest ORP revealed a correlation between elevated cytokine levels and increased oxidative stress in females. In contrast, in males, cytokine expressions were increased in the lower oxidative environment (except for IL-1b). Correlations of the increased cytokine expressions with PAH severity were highly sex-dependent and corresponded to the increase in PAH severity in males and less severe PAH in females. Machine learning algorithms trained on the combined cytokine and redox profiles allowed the prediction of PAH mortality with 80% accuracy. We conclude that the profile of circulating cytokines in PAH patients is redox- and sex-dependent, suggesting the vital need to stratify the patient cohort subjected to anti-inflammatory therapies. Combined cytokine and/or redox profiling showed promising value for predicting the patients' survival.

Interplay of Low-Density Lipoprotein Receptors, LRPs, and Lipoproteins in Pulmonary Hypertension

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LDLR regulates oxidized LDL level, which is increased in lung and blood from PAH patients.

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LRP1 preserving vascular homeostasis is decreased in PAH patients.

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LRP5/6 regulating Wnt signaling is upregulated in PH.

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The LRP8 (aka ApoER2) ligand ApoE protects from PAH.

The low-density lipoprotein receptor (LDLR) gene family includes LDLR, very LDLR, and LDL receptor–related proteins (LRPs) such as LRP1, LRP1b (aka LRP-DIT), LRP2 (aka megalin), LRP4, and LRP5/6, and LRP8 (aka ApoER2). LDLR family members constitute a class of closely related multifunctional, transmembrane receptors, with diverse functions, from embryonic development to cancer, lipid metabolism, and cardiovascular homeostasis. While LDLR family members have been studied extensively in the systemic circulation in the context of atherosclerosis, their roles in pulmonary arterial hypertension (PAH) are understudied and largely unknown. Endothelial dysfunction, tissue infiltration of monocytes, and proliferation of pulmonary artery smooth muscle cells are hallmarks of PAH, leading to vascular remodeling, obliteration, increased pulmonary vascular resistance, heart failure, and death. LDLR family members are entangled with the aforementioned detrimental processes by controlling many pathways that are dysregulated in PAH; these include lipid metabolism and oxidation, but also platelet-derived growth factor, transforming growth factor β1, Wnt, apolipoprotein E, bone morpohogenetic proteins, and peroxisome proliferator-activated receptor gamma. In this paper, we discuss the current knowledge on LDLR family members in PAH. We also review mechanisms and drugs discovered in biological contexts and diseases other than PAH that are likely very relevant in the hypertensive pulmonary vasculature and the future care of patients with PAH or other chronic, progressive, debilitating cardiovascular diseases.

Inflammatory Glycoprotein 130 Signaling Links Changes in Microtubules and Junctophilin-2 to Altered Mitochondrial Metabolism and Right Ventricular Contractility

BACKGROUND

Right ventricular dysfunction (RVD) is the leading cause of death in pulmonary arterial hypertension (PAH), but no RV-specific therapy exists. We showed microtubule-mediated junctophilin-2 dysregulation (MT-JPH2 pathway) causes t-tubule disruption and RVD in rodent PAH, but the druggable regulators of this critical pathway are unknown. GP130 (glycoprotein 130) activation induces cardiomyocyte microtubule remodeling in vitro; however, the effects of GP130 signaling on the MT-JPH2 pathway and RVD resulting from PAH are undefined.

METHODS

Immunoblots quantified protein abundance, quantitative proteomics defined RV microtubule-interacting proteins (MT-interactome), metabolomics evaluated the RV metabolic signature, and transmission electron microscopy assessed RV cardiomyocyte mitochondrial morphology in control, monocrotaline, and monocrotaline-SC-144 (GP130 antagonist) rats. Echocardiography and pressure-volume loops defined the effects of SC-144 on RV-pulmonary artery coupling in monocrotaline rats (8-16 rats per group). In 73 patients with PAH, the relationship between interleukin-6, a GP130 ligand, and RVD was evaluated.

RESULTS

SC-144 decreased GP130 activation, which normalized MT-JPH2 protein expression and t-tubule structure in the monocrotaline RV. Proteomics analysis revealed SC-144 restored RV MT-interactome regulation. Ingenuity pathway analysis of dysregulated MT-interacting proteins identified a link between microtubules and mitochondrial function. Specifically, SC-144 prevented dysregulation of electron transport chain, Krebs cycle, and the fatty acid oxidation pathway proteins. Metabolomics profiling suggested SC-144 reduced glycolytic dependence, glutaminolysis induction, and enhanced fatty acid metabolism. Transmission electron microscopy and immunoblots indicated increased mitochondrial fission in the monocrotaline RV, which SC-144 mitigated. GP130 antagonism reduced RV hypertrophy and fibrosis and augmented RV-pulmonary artery coupling without altering PAH severity. In patients with PAH, higher interleukin-6 levels were associated with more severe RVD (RV fractional area change 23±12% versus 30±10%, P=0.002).

CONCLUSIONS

GP130 antagonism reduces MT-JPH2 dysregulation, corrects metabolic derangements in the RV, and improves RVD in monocrotaline rats.

Pulmonary Arterial Hypertension: Emerging Principles of Precision Medicine across Basic Science to Clinical Practice

Pulmonary arterial hypertension (PAH) is an enigmatic and deadly vascular disease with no known cure. Recent years have seen rapid advances in our understanding of the molecular underpinnings of PAH, with an expanding knowledge of the molecular, cellular, and systems-level drivers of disease that are being translated into novel therapeutic modalities. Simultaneous advances in clinical technology have led to a growing list of tools with potential application to diagnosis and phenotyping. Guided by fundamental biology, these developments hold the potential to usher in a new era of personalized medicine in PAH with broad implications for patient management and great promise for improved outcomes.

Computational repurposing of therapeutic small molecules from cancer to pulmonary hypertension

Cancer therapies are being considered for treating rare noncancerous diseases like pulmonary hypertension (PH), but effective computational screening is lacking. Via transcriptomic differential dependency analyses leveraging parallels between cancer and PH, we mapped a landscape of cancer drug functions dependent upon rewiring of PH gene clusters. Bromodomain and extra-terminal motif (BET) protein inhibitors were predicted to rely upon several gene clusters inclusive of galectin-8 (LGALS8). Correspondingly, LGALS8 was found to mediate the BET inhibitor–dependent control of endothelial apoptosis, an essential role for PH in vivo. Separately, a piperlongumine analog’s actions were predicted to depend upon the iron-sulfur biogenesis gene ISCU. Correspondingly, the analog was found to inhibit ISCU glutathionylation, rescuing oxidative metabolism, decreasing endothelial apoptosis, and improving PH. Thus, we identified crucial drug-gene axes central to endothelial dysfunction and therapeutic priorities for PH. These results establish a wide-ranging, network dependency platform to redefine cancer drugs for use in noncancerous conditions.

Mineralocorticoid receptors in pulmonary hypertension and right heart failure: From molecular biology to therapeutic targeting

Pulmonary hypertension (PH) is a devastating condition characterized by pulmonary vascular remodelling, leading to progressive increase in pulmonary artery pressure and subsequent right ventricular failure. Aldosterone and the mineralocorticoid receptor (MR), a nuclear transcription factor, are key drivers of cardiovascular disease and MR antagonists are well-established in heart failure. Now, a growing body of evidence points at a detrimental role of MR in PH. Pharmacological MR blockade attenuated PH and prevented RV failure in experimental models. Mouse models with cell selective MR deletion suggest that this effect is mediated by MR in endothelial cells. While the evidence from experimental studies appears convincing, the available clinical data on MR antagonist use in patients with PH is more controversial. Integrated analysis of clinical data together with MR-dependent molecular alterations may provide insights why some patients respond to MRA treatment while others do not. Potential ways to identify MRA 'responders' include the analysis of underlying PH causes, stage of disease, or sex, as well as new biomarkers.

Network module-based drug repositioning for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by pulmonary vascular remodeling leading to increased pulmonary vascular resistance and pulmonary arterial pressure. PAH is a highly morbid cardiopulmonary disease adversely affecting lifespan and quality of life. Despite increased awareness and advances of medical therapies in recent decades, long-term prognosis and survival remain poor for patients with PAH. Novel therapies that can target the underlying pathobiology of PAH and reverse pulmonary vascular remodeling are clearly needed. In this study, we develop a network module-based framework to examine potential drug repositioning for PAH. The rationale for this approach is that in order to have therapeutic effects, the targets of potential drugs must be significantly proximate to the disease module of interest in the human protein-protein interactome. Based on 15 existing drugs for treating PAH, our framework integrates drug-drug interactions, drug-drug chemical similarity, drug targets, and PAH disease proteins into the human interactome, and prioritizes candidate drugs for PAH. We identified 53 drugs that could potentially be repurposed for PAH. Many of these candidates have strong literature support. Compared to black-box-like machine learning models, network module-based drug repositioning can provide mechanistic insights into how repositioned drugs can target the underlying pathobiological mechanisms of PAH.

Halofuginone, a promising drug for treatment of pulmonary hypertension

BACKGROUND AND PURPOSE

Halofuginone is a febrifugine derivative originally isolated from Chinese traditional herb Chang Shan that exhibits anti-hypertrophic, anti-fibrotic and anti-proliferative effects. We sought to investigate whether halofuginone induced pulmonary vasodilation and attenuates chronic hypoxia-induced pulmonary hypertension (HPH).

EXPERIMENTAL APPROACH

Patch-clamp experiments were conducted to examine the activity of voltage-dependent Ca²⁺ channels (VDCCs) in pulmonary artery smooth muscle cells (PASMCs). Digital fluorescence microscopy was used to measure intracellular Ca²⁺ concentration in PASMCs. Isolated perfused and ventilated mouse lungs were used to measure pulmonary artery pressure (PAP). Mice exposed to hypoxia (10% O₂ ) for 4 weeks were used as model of HPH for in vivo experiments.

KEY RESULTS

Halofuginone increased voltage-gated K⁺ (K_v ) currents in PASMCs and K⁺ currents through KCNA5 channels in HEK cells transfected with KCNA5 gene. HF (0.03-1 μM) inhibited receptor-operated Ca²⁺ entry in HEK cells transfected with calcium-sensing receptor gene and attenuated store-operated Ca²⁺ entry in PASMCs. Acute (3-5 min) intrapulmonary application of halofuginone significantly and reversibly inhibited alveolar hypoxia-induced pulmonary vasoconstriction dose-dependently (0.1-10 μM). Intraperitoneal administration of halofuginone (0.3 mg·kg^-1 , for 2 weeks) partly reversed established PH in mice.

CONCLUSION AND IMPLICATIONS

Halofuginone is a potent pulmonary vasodilator by activating K_v channels and blocking VDCC and receptor-operated and store-operated Ca²⁺ channels in PASMCs. The therapeutic effect of halofuginone on experimental PH is probably due to combination of its vasodilator effects, via inhibition of excitation-contraction coupling and anti-proliferative effects, via inhibition of the PI3K/Akt/mTOR signalling pathway.

Premature closure of ductus arteriosus after a single dose of diclofenac during pregnancy

A male term neonate was admitted to the neonatal intensive care unit in the first hours of life with central cyanosis. Echocardiogram showed severe biventricular hypertrophy, markedly right-sided, tricuspid regurgitation, a patent foramen ovale and a closed ductus arteriosus (CDA). The mother recalled being treated with a single dose of intravenous diclofenac for low back pain 2 weeks earlier. The newborn was started on propranolol with symptomatic improvement and was discharged on day 10. At 1-month follow-up, he showed complete resolution of ventricular hypertrophy and suspended propranolol. In the literature, of the 22 cases of CDA after intrauterine exposure to diclofenac, 11 resolved in utero, 3 required ventilatory and inotropic support and 1 evolved to persistent pulmonary hypertension. In this case, a thorough anamnesis was key to identify the probable cause of an otherwise unexplained transient ventricular hypertrophy. This case also alerts to the fetal risks of non-steroidal anti-inflammatory drugs during the third trimester, requiring close monitoring.

Eplerenone Improves Pulmonary Vascular Remodeling and Hypertension by Inhibition of the Mineralocorticoid Receptor in Endothelial Cells

[Figure: see text].

Evolving Schema for Employing Network Biology Approaches to Understand Pulmonary Hypertension

Reductionist approaches have served as the cornerstone for traditional mechanistic endeavors in biomedical research. However, for pulmonary hypertension (PH), a relatively rare but deadly vascular disease of the lungs, the use of traditional reductionist approaches has failed to define the complexities of pathogenesis. With the development of new -omics platforms (i.e., genomics, transcriptomics, proteomics, and metabolomics, among others), network biology approaches have offered new pipelines for discovery of human disease pathogenesis. Human disease processes are driven by multiple genes that are dysregulated which are affected by regulatory networks. Network theory allows for the identification of such gene clusters which are dysregulated in various disease states. This framework may in part explain why current therapeutics that seek to target a single part of a dysregulated cluster may fail to provide clinically significant improvements. Correspondingly, network biology could further the development of novel therapeutics which target clusters of "disease genes" so that a disease phenotype can be more robustly addressed. In this chapter, we seek to explain the theory behind network biology approaches to identify drivers of disease as well as how network biology approaches have been used in the field of PH. Furthermore, we discuss an example of in silico methodology using network pharmacology in conjunction with gene networks tools to identify drugs and drug targets. We discuss similarities between the pathogenesis of PH and other disease states, specifically cancer, and how tools developed for cancer may be repurposed to fill the gaps in research in PH. Finally, we discuss new approaches which seek to integrate clinical health record data into networks so that correlations between disease genes and clinical parameters can be explored in the context of this disease.

New Pharmacologic Approaches to Bronchopulmonary Dysplasia

Bronchopulmonary Dysplasia is the most common long-term respiratory morbidity of preterm infants, with the risk of development proportional to the degree of prematurity. While its pathophysiologic and histologic features have changed over time as neonatal demographics and respiratory therapies have evolved, it is now thought to be characterized by impaired distal lung growth and abnormal pulmonary microvascular development. Though the exact sequence of events leading to the development of BPD has not been fully elucidated and likely varies among patients, it is thought to result from inflammatory and mechanical/oxidative injury from chronic ventilatory support in fragile, premature lungs susceptible to injury from surfactant deficiency, structural abnormalities, inadequate antioxidant defenses, and a chest wall that is more compliant than the lung. In addition, non-pulmonary issues may adversely affect lung development, including systemic infections and insufficient nutrition. Once BPD has developed, its management focuses on providing adequate gas exchange while promoting optimal lung growth. Pharmacologic strategies to ameliorate or prevent BPD continue to be investigated. A variety of agents, to be reviewed henceforth, have been developed or re-purposed to target different points in the pathways that lead to BPD, including anti-inflammatories, diuretics, steroids, pulmonary vasodilators, antioxidants, and a number of molecules involved in the cell signaling cascade thought to be involved in the pathogenesis of BPD.

AAV1-Mediated shRNA Knockdown of SASH1 in Rat Bronchus Attenuates Hypoxia-Induced Pulmonary Artery Remodeling

Pulmonary hypertension (PH) is a proliferative disease characterized by pulmonary arterial remodeling (PAR). SAM and SH3 domain containing 1 (SASH1) is a novel tumor suppressor gene whose biological function in PH is unclear. In this study, a hypoxia-induced pulmonary hypertension (HPH) rat model was constructed to explore the role of SASH1 in PAR. Histopathological changes in the lung tissue and hemodynamic alteration were detected in SASH1-knockdown rats through adeno-associated virus type-1 (AAV1) infection. In vitro, primary human pulmonary arterial smooth muscle cells (HPASMCs) were transfected with SASH1siRNA to investigate the effects of SASH1 on hypoxia-induced proliferation and migration. The molecular mechanisms associated with SASH1 were explored through knockdown and overexpression approaches. We found that SASH1 expression was significantly increased in rat pulmonary arteries and HPASMCs after hypoxia exposure. In vivo, silencing the SASH1 gene expression improved HPH in rats. The SASH1 downregulation inhibited proliferation and migration of hypoxia-induced HPASMCs. The protein expression of phospho-AKT (known as protein kinase B), proliferating cell nuclear antigen, and matrix metalloproteinase 9 (MMP9) in HPASMCs were increased after SASH1 overexpression, whereas these effects were inhibited by SASH1 knockdown. In conclusion, SASH1 downregulation improved hypoxia-induced PAR and PH. SASH1 may be a novel target for PH gene therapy in the era of precision medicine.

Pulmonary Hypertension in Acute and Chronic High Altitude Maladaptation Disorders

Alveolar hypoxia is the most prominent feature of high altitude environment with well-known consequences for the cardio-pulmonary system, including development of pulmonary hypertension. Pulmonary hypertension due to an exaggerated hypoxic pulmonary vasoconstriction contributes to high altitude pulmonary edema (HAPE), a life-threatening disorder, occurring at high altitudes in non-acclimatized healthy individuals. Despite a strong physiologic rationale for using vasodilators for prevention and treatment of HAPE, no systematic studies of their efficacy have been conducted to date. Calcium-channel blockers are currently recommended for drug prophylaxis in high-risk individuals with a clear history of recurrent HAPE based on the extensive clinical experience with nifedipine in HAPE prevention in susceptible individuals. Chronic exposure to hypoxia induces pulmonary vascular remodeling and development of pulmonary hypertension, which places an increased pressure load on the right ventricle leading to right heart failure. Further, pulmonary hypertension along with excessive erythrocytosis may complicate chronic mountain sickness, another high altitude maladaptation disorder. Importantly, other causes than hypoxia may potentially underlie and/or contribute to pulmonary hypertension at high altitude, such as chronic heart and lung diseases, thrombotic or embolic diseases. Extensive clinical experience with drugs in patients with pulmonary arterial hypertension suggests their potential for treatment of high altitude pulmonary hypertension. Small studies have demonstrated their efficacy in reducing pulmonary artery pressure in high altitude residents. However, no drugs have been approved to date for the therapy of chronic high altitude pulmonary hypertension. This work provides a literature review on the role of pulmonary hypertension in the pathogenesis of acute and chronic high altitude maladaptation disorders and summarizes current knowledge regarding potential treatment options.

Approaches to treat pulmonary arterial hypertension by targeting bmpr2 - from cell membrane to nucleus

Pulmonary arterial hypertension (PAH) is estimated to affect between 10-50 people per million worldwide. The lack of cure and devastating nature of the disease means that treatment is crucial to arrest rapid clinical worsening. Current therapies are limited by their focus on inhibiting residual vasoconstriction rather than targeting key regulators of the cellular pathology. Potential disease-modifying therapies may come from research directed towards causal pathways involved in the cellular and molecular mechanisms of disease. It is widely acknowledged, that targeting reduced expression of the critical bone morphogenetic protein type-2 receptor (BMPR2) and its associated signalling pathways is a compelling therapeutic avenue to explore. In this review we highlight the advances that have been made in understanding this pathway and the therapeutics that are being tested in clinical trials and the clinic to treat PAH.

Peroxisome proliferator-activated receptor agonists and reversal of vascular degeneration through DNA repair, a step toward drug-induced regenerative medicine

Endothelial dysfunction with subsequent degeneration and vasoocclusive remodeling is the hallmark of many cardiovascular disorders including pulmonary vascular disease (PVD). To date, the available treatments slows disease progression but does not prevent deterioration. Reversing such pathologies would spare many patients risky surgeries and long waiting lists for a possible organ donor. Peroxisome proliferator-activated receptor agonists were first introduced as sole insulin sensitizers, however, there is increasing body of evidence that they have different actions on DNA which might help reverse vascular degeneration. This effect appears to be mainly achieved through enhancement of DNA damage responses (DDR). The aforementioned effect could offer new insights about repurposing drugs for achieving organ or tissue regeneration, an understudied field named drug-induced regenerative medicine.

Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosamine, which, when added to serines or threonines, modulates protein function through protein O-GlcNAcylation. Glutamine-fructose-6-phosphate amidotransferase (GFAT) regulates HBP flux, and AMP-kinase phosphorylation of GFAT blunts GFAT activity and O-GlcNAcylation. While numerous studies demonstrate increased right ventricle (RV) glucose uptake in pulmonary arterial hypertension (PAH), the relationship between O-GlcNAcylation and RV function in PAH is unexplored. Therefore, we examined how colchicine-mediated AMP-kinase activation altered HBP intermediates, O-GlcNAcylation, mitochondrial function, and RV function in pulmonary artery-banded (PAB) and monocrotaline (MCT) rats. AMPK activation induced GFAT phosphorylation and reduced HBP intermediates and O-GlcNAcylation in MCT but not PAB rats. Reduced O-GlcNAcylation partially restored the RV metabolic signature and improved RV function in MCT rats. Proteomics revealed elevated expression of O-GlcNAcylated mitochondrial proteins in MCT RVs, which fractionation studies corroborated. Seahorse micropolarimetry analysis of H9c2 cardiomyocytes demonstrated colchicine improved mitochondrial function and reduced O-GlcNAcylation. Presence of diabetes in PAH, a condition of excess O-GlcNAcylation, reduced RV contractility when compared to nondiabetics. Furthermore, there was an inverse relationship between RV contractility and HgbA1C. Finally, RV biopsy specimens from PAH patients displayed increased O-GlcNAcylation. Thus, excess O-GlcNAcylation may contribute to metabolic derangements and RV dysfunction in PAH.

Repurposing of medications for pulmonary arterial hypertension

This manuscript on drug repurposing incorporates the broad experience of members of the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative as an open debate platform for academia, the pharmaceutical industry and regulatory experts surrounding the future design of clinical trials in pulmonary hypertension. Drug repurposing, use of a drug in a disease for which it was not originally developed, in pulmonary arterial hypertension has been a remarkable success story, as highlighted by positive large phase 3 clinical trials using epoprostenol, bosentan, iloprost, and sildenafil. Despite the availability of multiple therapies for pulmonary arterial hypertension, mortality rates have modestly changed. Moreover, pulmonary arterial hypertension patients are highly symptomatic and frequently end up on parental therapy and lung transplant waiting lists. Therefore, an unmet need for new treatments exists and drug repurposing may be an important avenue to address this problem.

Emerging therapies for right ventricular dysfunction and failure

Therapeutic options for right ventricular (RV) dysfunction and failure are strongly limited. Right heart failure (RHF) has been mostly addressed in the context of pulmonary arterial hypertension (PAH), where it is not possible to discern pulmonary vascular- and RV-directed effects of therapeutic approaches. In part, opposing pathomechanisms in RV and pulmonary vasculature, i.e., regarding apoptosis, angiogenesis and proliferation, complicate addressing RHF in PAH. Therapy effective for left heart failure is not applicable to RHF, e.g., inhibition of adrenoceptor signaling and of the renin-angiotensin system had no or only limited success. A number of experimental studies employing animal models for PAH or RV dysfunction or failure have identified beneficial effects of novel pharmacological agents, with most promising results obtained with modulators of metabolism and reactive oxygen species or inflammation, respectively. In addition, established PAH agents, in particular phosphodiesterase-5 inhibitors and soluble guanylate cyclase stimulators, may directly address RV integrity. Promising results are furthermore derived with microRNA (miRNA) and long non-coding RNA (lncRNA) blocking or mimetic strategies, which can target microvascular rarefaction, inflammation, metabolism or fibrotic and hypertrophic remodeling in the dysfunctional RV. Likewise, pre-clinical data demonstrate that cell-based therapies using stem or progenitor cells have beneficial effects on the RV, mainly by improving the microvascular system, however clinical success will largely depend on delivery routes. A particular option for PAH is targeted denervation of the pulmonary vasculature, given the sympathetic overdrive in PAH patients. Finally, acute and durable mechanical circulatory support are available for the right heart, which however has been tested mostly in RHF with concomitant left heart disease. Here, we aim to review current pharmacological, RNA- and cell-based therapeutic options and their potential to directly target the RV and to review available data for pulmonary artery denervation and mechanical circulatory support.

Pulmonary arterial hypertension: Rationale for using multiple vs. single drug therapy

Pulmonary arterial hypertension (PAH) is defined by a heterogenous pathobiology that corresponds to variable clinical presentation, treatment response, and prognosis across affected patients. The approach to pharmacotherapeutics in PAH has evolved since the introduction of the first prostacyclin replacement drug, which was trialed in patients with end-stage disease as a strategy by which to delay or prevent mortality. Subsequently, the aim of care in PAH has shifted toward minimizing symptoms, improving functional capacity, delaying disease progression, and prolonging life. Thus, treatments are now implemented earlier and according to the evidence base, which spans more than twenty years and includes patients at various stages of disease. Overall, the evidence supports multidrug therapy rather than monotherapy in the majority of PAH patients. Among incident patients, up-front combination therapy with ambrisentan and tadalafil or other comparable agents within these drug classes is recommended based on strong clinical trial data. In the near future, up-front triple therapy may be emerge as bona fide treatment approach in selected patients. Future goals that are already under consideration in PAH include stronger integration of pathobiological characteristics when considering the use of specific drugs, or the development of novel therapies, toward precision medicine-based clinical pharmacology.

Current and future treatments of pulmonary arterial hypertension

Therapeutic options for pulmonary arterial hypertension (PAH) have increased over the last decades. The advent of pharmacological therapies targeting the prostacyclin, endothelin, and NO pathways has significantly improved outcomes. However, for the vast majority of patients, PAH remains a life-limiting illness with no prospect of cure. PAH is characterised by pulmonary vascular remodelling. Current research focusses on targeting the underlying pathways of aberrant proliferation, migration, and apoptosis. Despite success in preclinical models, using a plethora of novel approaches targeting cellular GPCRs, ion channels, metabolism, epigenetics, growth factor receptors, transcription factors, and inflammation, successful transfer to human disease with positive outcomes in clinical trials is limited. This review provides an overview of novel targets addressed by clinical trials and gives an outlook on novel preclinical perspectives in PAH. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Autophagy in chronic lung disease

The development of chronic lung disease occurs as a consequence of multiple cellular events that involve an initial insult which often leads to the development of chronic inflammation, and the dysregulation of cellular proliferation and cell death mechanisms. Multiple cell types in the lung are key to the respiratory and protective/barrier functions necessary to manage the chronic exposures to environmental, mechanical, and oxidative stressors. Autophagy is essential to lung development and homeostasis, as well as the prevention and development of disease. The cellular process involves the collection and removal of unwanted organelles and proteins through lysosomal degradation. In recent years, investigations have addressed the roles of autophagy and selective autophagy in numerous chronic lung diseases. Here, we highlight recent advances on the role of autophagy in the pathogenesis of asthma, chronic obstructive pulmonary disease and emphysema, pulmonary arterial hypertension, and idiopathic pulmonary fibrosis.

The risk of sudden cardiac arrest and ventricular arrhythmia with rosiglitazone versus pioglitazone: real-world evidence on thiazolidinedione safety

BACKGROUND

The low cost of thiazolidinediones makes them a potentially valuable therapeutic option for the > 300 million economically disadvantaged persons worldwide with type 2 diabetes mellitus. Differential selectivity of thiazolidinediones for peroxisome proliferator-activated receptors in the myocardium may lead to disparate arrhythmogenic effects. We examined real-world effects of thiazolidinediones on outpatient-originating sudden cardiac arrest (SCA) and ventricular arrhythmia (VA).

METHODS

We conducted population-based high-dimensional propensity score-matched cohort studies in five Medicaid programs (California, Florida, New York, Ohio, Pennsylvania | 1999-2012) and a commercial health insurance plan (Optum Clinformatics | 2000-2016). We defined exposure based on incident rosiglitazone or pioglitazone dispensings; the latter served as an active comparator. We controlled for confounding by matching exposure groups on propensity score, informed by baseline covariates identified via a data adaptive approach. We ascertained SCA/VA outcomes precipitating hospital presentation using a validated, diagnosis-based algorithm. We generated marginal hazard ratios (HRs) via Cox proportional hazards regression that accounted for clustering within matched pairs. We prespecified Medicaid and Optum findings as primary and secondary, respectively; the latter served as a conceptual replication dataset.

RESULTS

The adjusted HR for SCA/VA among rosiglitazone (vs. pioglitazone) users was 0.91 (0.75-1.10) in Medicaid and 0.88 (0.61-1.28) in Optum. Among Medicaid but not Optum enrollees, we found treatment effect heterogeneity by sex (adjusted HRs = 0.71 [0.54-0.93] and 1.16 [0.89-1.52] in men and women respectively, interaction term p-value = 0.01).

CONCLUSIONS

Rosiglitazone and pioglitazone appear to be associated with similar risks of SCA/VA.

Activation of the Metabolic Master Regulator PPARγ: A Potential PIOneering Therapy for Pulmonary Arterial Hypertension

Translational research is essential to the development of reverse-remodeling strategies for the treatment of pulmonary vascular disease, pulmonary hypertension, and heart failure via mechanistic in vivo studies using animal models resembling human pulmonary arterial hypertension (PAH), cardiovascular remodeling, and progressive right heart failure. Since 2007, peroxisome proliferator-activated receptor γ (PPARγ) agonists have emerged as promising novel, antiproliferative, antiinflammatory, insulin-sensitizing, efficient medications for the treatment of PAH. However, early diabetes study results, their subsequent misinterpretations, errors in published review articles, and rumors regarding potential adverse effects in the literature have dampened enthusiasm for considering pharmacological PPARγ activation for the treatment of cardiovascular diseases, including PAH. Most recently, the thiazolidinedione class PPARγ agonist pioglitazone underwent a clinical revival, especially based on the IRIS (Insulin Resistance Intervention After Stroke) study, a randomized controlled trial in 3,876 patients without diabetes status post-transient ischemic attack/ischemic stroke who were clinically followed for 4.8 years. We discuss preclinical basic translational findings and randomized controlled trials related to the beneficial and adverse effects of PPARγ agonists of the thiazolidinedione class, with a particular focus on the last 5 years. The objective is a data-driven approach to set the preclinical and clinical study record straight. The convincing recent clinical trial data on the lack of significant toxicity in high-risk populations justify the timely conduct of clinical studies to achieve "repurposing" or "repositioning" of pioglitazone for the treatment of clinical PAH.

Rational Design of Multitarget-Directed Ligands: Strategies and Emerging Paradigms

Due to the complexity of multifactorial diseases, single-target drugs do not always exhibit satisfactory efficacy. Recently, increasing evidence indicates that simultaneous modulation of multiple targets may improve both therapeutic safety and efficacy, compared with single-target drugs. However, few multitarget drugs are on market or in clinical trials, despite the best efforts of medicinal chemists. This article discusses the systematic establishment of target combination, lead generation, and optimization of multitarget-directed ligands (MTDLs). Moreover, we analyze some MTDLs research cases for several complex diseases in recent years and the physicochemical properties of 117 clinical multitarget drugs, with the aim to reveal the trends and insights of the potential use of MTDLs.