Littérature scientifique sur le sujet « Istaroxime »

Background/Aims: Istaroxime is a validated inotropic Na+/K+ ATPase inhibitor currently in development for the treatment of various cardiac conditions. Recent findings established that this steroidal drug exhibits potent apoptotic responses in prostate tumors in vitro and in vivo, by affecting key signaling orchestrating proliferation and apoptosis, such as c-Myc and caspase 3, Rho GTPases and actin cytoskeleton dynamics. In the present study we examined whether istaroxime is affecting cell motility and analyzed the underlying mechanism in prostate tumor cells. Methods: Migration was assessed by transwell and wound healing assays, Orai1 and Stim1 abundance by RT-PCR and confocal immunofluorescence microscopy, Fura-2 fluorescence was utilized to determine intracellular Ca2+ and Western blotting for FAK/pFAK measurements. Results: We observed strong inhibition of cell migration in istaroxime treated DU-145 prostate cancer cells. Istaroxime further decreased Orai1 and Stim1 transcript levels and downregulated Orai1 protein expression. Moreover, SOCE was significantly decreased upon istaroxime treatment. Furthermore, istaroxime strikingly diminished phosphorylated FAK levels. Interestingly, the efficacy of istaroxime on the inhibition of DU-145 cell migration was further enhanced by blocking Orai1 with 2-APB and FAK with the specific inhibitor PF-00562271. These results provide strong evidence that istaroxime prevents cell migration and motility of DU-145 prostate tumor cells, an effect at least partially attributed to Orai1 downregulation and FAK de-activation. Conclusion: Collectively our results indicate that this enzyme inhibitor, besides its pro-apoptotic action, affects motility of cancer cells, supporting its potential role as a strong candidate for further clinical cancer drug development.

Current therapeutic strategies for acute heart failure (AHF) are based on traditional inotropic agents that are often associated with untoward effects; therefore, finding new effective approaches with a safer profile is dramatically needed. Istaroxime is a novel compound, chemically unrelated to cardiac glycosides, that is currently being studied for the treatment of AHF. Its effects are essentially related to its inotropic and lusitropic positive properties exerted through a dual mechanism of action: activation of the sarcoplasmic reticulum Ca2+ ATPase isoform 2a (SERCA2a) and inhibition of the Na+/K+-ATPase (NKA) activity. The advantages of istaroxime over the available inotropic agents include its lower arrhythmogenic action combined with its capability of increasing systolic blood pressure without augmenting heart rate. However, it has a limited half-life (1 hour) and is associated with adverse effects including pain at the injection site and gastrointestinal issues. Herein, we describe the main mechanism of action of istaroxime and we present a systematic overview of both clinical and preclinical trials testing this drug, underlining the latest insights regarding its adoption in clinical practice for AHF.

Lo scompenso cardiaco è una delle principali cause di morte improvvisa nei paesi sviluppati ed è noto che il cuore scompensato sia caratterizzato da una ridotta contrattilità causata da un’alterazione della dinamica del calcio tra il sarcoplasma e il reticolo sarcoplasmatico. In questo ambito, istaroxime è un farmaco in fase 2 preclinica che combina l’inibizione della pompa Na+/K+ e la stimolazione di SERCA2a, mostrando effetti promettenti per il trattamento dello scompenso cardiaco acuto. Tuttavia, l’uso di istaroxime è limitato al trattamento i.v. a causa della sua breve emivita (⁓ 1 h) e dalla sua estensiva metabolizzazione a livello epatico portando alla formazione di una molecola chiamata PST3093. Il primo obiettivo del mio progetto di tesi mirava allo studio del PST3093, il principale metabolita di istaroxime, per capire se fosse dotato di attività farmacologica e per comprendere meglio gli effetti in vivo dell’istaroxime. Sulla base dei risultati ottenuti, il secondo obiettivo era quello di sviluppare degli analoghi del PST3093, stimolatori di SERCA2a e dotati di un gruppo metabolicamente stabile per la somministrazione orale. Effetti in vivo e in vitro dei derivati del PST3093 venivano valutati in un modello di ratto con cardiomiopatia diabetica indotta da streptozotocina (STZ), in quanto caratterizzato da disfunzione diastolica associata a down-regolazione di SERCA2a. Innanzitutto, venivano studiati gli effetti del PST3093 sull’attività di SERCA2a e della pompa Na+/K+, sulla dinamica del calcio intracellulare in miociti ventricolari isolati e sull’emodinamica nei ratti STZ. A differenza di istaroxime, il PST3093 risultava uno stimolatore “selettivo” di SERCA2a, privo di effetti sulla pompa Na+/K+¸ con un profilo meno aritmogenico del composto di origine. Il PST3093 risultava attivo a concentrazioni nanomolari in preparazioni cardiache di cavia e di ratto STZ e, similmente a istaroxime, stimolava SERCA2a solo in presenza del fosfolambano, diminuendone l’inibizione su SERCA2a. L’infusione del composto (effetto acuto) nei ratti STZ migliorava complessivamente le prestazioni cardiache e revertiva molte anomalie causate da STZ. Grazie alla collaborazione con un gruppo di chimici del nostro dipartimento, sono stati sintetizzati dei derivati del PST3093 privi di attività inibitoria sulla pompa Na+/K+ e formulati per essere utilizzati nel trattamento cronico (orale) dello scompenso cardiaco. Molti di loro mantenevano l’azione stimolatoria su SERCA2a a dosi nanomolari. Il composto 5 e il composto 8 venivano selezionati per ulteriori analisi in cardiomiociti isolati e in vivo (in acuto). Entrambi i composti, stimolando SERCA2a, promuovevano la compartimentalizzazione nel calcio intracellulare e, in seguito a infusione, ripristinavano la funzione diastolica nei ratti STZ. Infine, venivano valutati gli effetti cronici in vivo del composto 8 nei ratti STZ dopo somministrazione orale. Venivano testate due diverse dosi (40 o 80 mg/kg) e gli effetti venivano valutati dopo 1 o 4 somministrazioni (1 al giorno), per valutare eventuali effetti dose-dipendenti e, indirettamente, esplorare la sua farmacocinetica. Il composto 8 migliorava in maniera dose-dipendente la disfunzione diastolica causata da STZ e la sua farmacocinetica risultava comparabile a quella del PST3093. Analisi delle interazioni molecolari con 50 diversi ligandi escludevano effetti off-target del composto 8. Infine, veniva valutata la tossicità in topo. Il composto 8 risultava meno tossico di PST3093 e istaroxime In conclusione, PST3093 e i suoi derivati agivano come stimolatori “selettivi” di SERCA2a. Mentre il PST3093 prolungava gli effetti benefici dati dall’infusione dell’istaroxime, i suoi derivati possono essere considerati il prototipo di una nuova classe farmacodinamica per la terapia dello scompenso cardiaco. In particolare, il composto 8 risultava un possibile candidato per la terapia cronica.
Heart failure (HF) is one of the leading causes of sudden death in developed countries and it is known that failing hearts are characterized by reduced contractile properties caused by impaired Ca2+ cycling between the sarcoplasm and sarcoplasmic reticulum (SR). In this field, istaroxime is a small-molecule drug under phase 2 clinical trial that, combining inhibition of Na+/K+ ATPase and SERCA2a stimulation, shows an interesting profile for acute HF treatment. However, istaroxime use is restricted to acute i.v. infusion because of its plasma half-life of about 1 hour in humans and its extensive hepatic metabolism to a molecule, named PST3093. The first aim of my thesis project dealt with the investigation whether PST3093, the main metabolite of istaroxime, may, on its own, be endowed with pharmacological activity and at least partially explain in vivo istaroxime effects. In light of the results, the second aim was to develop PST3093 analogues with metabolically stable groups, with the purpose to generate orally administrable SERCA2a stimulators. In vivo and in vitro effects of PST3093 follow-on compounds were evaluated by using streptozotocin (STZ)-treated rats developing diabetic cardiomyopathy with diastolic dysfunction associated to SERCA2a downregulation. Firstly, we characterized PST3093 effects on SERCA2a and Na+/K+ ATPase activities, intracellular Ca2+ dynamics in isolated ventricular myocytes and in vivo hemodynamic effects in STZ rats. At variance with its parent compound, PST3093 is a “selective” (i.e. devoid of Na+/K+ ATPase inhibition) SERCA2a stimulator, showing a safer profile than istaroxime. It is active at nanomolar concentrations in cardiac preparations from normal guinea pig and STZ rats and, similarly to istaroxime, it stimulates SERCA2a only in the presence of phospholamban (PLN), thus relieving its inhibitory activity on SERCA2a. In-vivo PST3093 i.v. infusion (acute effects) in STZ rats improved overall cardiac performance and reversed most STZ-induced abnormalities. Thanks to a collaboration with chemists of our Department, we synthesized a panel of PST3093 derivatives devoid of Na+/K+ ATPase inhibitory activity to develop a class of compounds suitable for chronic (oral) HF treatment. Most of them retained SERCA2a stimulatory action with nanomolar potency. Two selected PST3093 analogues, compound 5 and compound 8, were further characterized in isolated cardiomyocytes and their acute in vivo effects were firstly evaluated after i.v. infusion in STZ rats. Both compounds, stimulating SERCA2a, improved intracellular Ca2+ handling (promoting SR Ca2+ compartmentalization) and restored diastolic function following acute i.v. infusion in STZ rats. Finally, we evaluated chronic in vivo effects of compound 8 in STZ rats after oral administration at two dosages (40 or 80 mg/kg) at 1 or 4 daily doses to evaluate potential dose-dependent effects and to indirectly explore its pharmacokinetic in rats. Compound 8 dose-dependently ameliorated STZ-induced diastolic dysfunction and its pharmacokinetic was comparable to that of PST3093, i.e. longer than istaroxime one. Off-target effects of compound 8 were excluded based on the analysis of its molecular interaction with a panel of 50 ligands. Acute toxicity in mice was finally evaluated, showing a safer profile of compound 8 than PST3093 and istaroxime. In conclusion, PST3093 and its derivatives act as “selective” SERCA2a stimulators. While PST3093 is suitable to prolong the cardiac beneficial effect of istaroxime infusion, PST3093 derivatives can be considered the prototype of a novel pharmacodynamic class for the ino-lusitropic approach of HF. In particular, compound 8 seems to be a favourable drug candidate for chronic HF therapy.

The current positive inotropic interventions for the management of heart failure (HF) are all associated to an unchanged or increased long term mortality, which limit their use. Istaroxime (IST) is a novel positive inotrope able to inhibit Na+, K+ ATPase and to stimulate SERCA pump. We employed IST as a tool to assess the role of a mild SERCA stimulation as a positive inotropic intervention. In a guinea pig model of HF, where the sarcoplasmic reticulum (SR) function was deranged, IST was able to restore an optimal SR function, increase the SR Ca2+ content and to improve all the EC coupling parameters considered. The comparison if IST and digoxin, a pure inhibitor of Na+, K+ ATPase, in mouse ventricular myocytes, showed that IST was less pro-arrhythmic than digoxin, as already observed in guinea pig. Digoxin induced a rapid accumulation of cytosolic Ca2+, while IST did not, and neither compound directly affected SR Ca2+ leakage, suggesting that a better compartmentalization of the ion was achieved in the presence of IST by the stimulation of SERCA pump. We concluded that the mild stimulation of SERCA is associated to a reduced pro-arrhythmic effect, and that it might represent a promising target for a new class of positive inotropic interventions associated to a reduced long term mortality.

Inotropic agents are substances used to improve cardiac output and end-organ perfusion in severe forms of acute heart failure. However, inappropriate use of inotropic agents may be associated with severe adverse effects and death. Despite clear indications to restrict their use to acute heart failure patients presenting with signs of end-organ hypoperfusion, the current use of inotropes is very frequent and often unnecessary. This chapter reviews mechanisms of action of current and future inotropes (including catecholamines, phosphodiesterase-III inhibitors, calcium sensitizers, cardiac myosin activators, and istaroxime) and discusses their clinical use in acute heart failure.

Inotropic agents are substances used to improve cardiac output and end-organ perfusion in severe forms of acute heart failure. However, inappropriate use of inotropic agents may be associated with severe adverse effects and death. Despite clear indications to restrict their use to acute heart failure patients presenting with signs of end-organ hypoperfusion, the current use of inotropes is very frequent and often unnecessary. This chapter reviews mechanisms of action of current and future inotropes (including catecholamines, phosphodiesterase-III inhibitors, calcium sensitizers, cardiac myosin activators, and istaroxime) and discusses their clinical use in acute heart failure.