JTV-519, a novel cardioprotective agent, improves the contractile recovery after ischaemia-reperfusion in coronary perfused guinea-pig ventricular muscles

Mitochondrial and Sarcoplasmic Reticulum Interconnection in Cardiac Arrhythmia

Ca²⁺ plays a pivotal role in mitochondrial energy production, contraction, and apoptosis. Mitochondrial Ca²⁺-targeted fluorescent probes have demonstrated that mitochondria Ca²⁺ transients are synchronized with Ca²⁺ fluxes occurring in the sarcoplasmic reticulum (SR). The presence of specialized proteins tethering SR to mitochondria ensures the local Ca²⁺ flux between these organelles. Furthermore, communication between SR and mitochondria impacts their functionality in a bidirectional manner. Mitochondrial Ca²⁺ uptake through the mitochondrial Ca²⁺ uniplex is essential for ATP production and controlled reactive oxygen species levels for proper cellular signaling. Conversely, mitochondrial ATP ensures the proper functioning of SR Ca²⁺-handling proteins, which ensures that mitochondria receive an adequate supply of Ca²⁺. Recent evidence suggests that altered SR Ca²⁺ proteins, such as ryanodine receptors and the sarco/endoplasmic reticulum Ca²⁺ ATPase pump, play an important role in maintaining proper cardiac membrane excitability, which may be initiated and potentiated when mitochondria are dysfunctional. This recognized mitochondrial role offers the opportunity to develop new therapeutic approaches aimed at preventing cardiac arrhythmias in cardiac disease.

Synthesis and pharmacological characterization of mitochondrial KATP channel openers with enhanced mitochondriotropic effects

Mitochondria play a key role for deciding fate of cells and thus are considered an attractive target for pharmacological interventions focused on containment of myocardial ischemia/reperfusion (I/R) injury. Notably, the activation of mitochondrial potassium (mitoK) channels produces a mild depolarization of mitochondrial membrane, that contributes to reduce the driving force to calcium uptake and prevents the formation of mitochondrial transition membrane pore (MPTP); these events underlie anti-ischemic cardioprotection. However, an ideal mitoK channel opener should possess the fundamental requirement to be delivered at mitochondrial level; therefore, to improve the mitochondrial delivery of a previously characterized spirocyclic benzopyrane F81, new compounds have been developed. The three original triphenylphosphonium (TPP⁺)-derivatives of F81 (1-3), were evaluated for their cardioprotective activity on both isolated cardiac mitochondria and cardiac H9c2 cell line. Compound 1 was further investigated in an in vivo infarct model. This work confirms that the TPP⁺ strategy applied to mitoKATP openers could foster mitochondrial delivery and enhance the cardioprotective effects of mitochondrial activators of potassium channels.

K201 (JTV519) is a Ca2+-Dependent Blocker of SERCA and a Partial Agonist of Ryanodine Receptors in Striated Muscle

K201 (JTV-519) may prevent abnormal Ca(2+) leak from the sarcoplasmic reticulum (SR) in the ischemic heart and skeletal muscle (SkM) by stabilizing the ryanodine receptors (RyRs; RyR1 and RyR2, respectively). We tested direct modulation of the SR Ca(2+)-stimulated ATPase (SERCA) and RyRs by K201. In isolated cardiac and SkM SR microsomes, K201 slowed the rate of SR Ca(2+) loading, suggesting potential SERCA block and/or RyR agonism. K201 displayed Ca(2+)-dependent inhibition of SERCA-dependent ATPase activity, which was measured in microsomes incubated with 200, 2, and 0.25 µM Ca(2+) and with the half-maximal K201 inhibitory doses (IC50) estimated at 130, 19, and 9 µM (cardiac muscle) and 104, 13, and 5 µM (SkM SR). K201 (≥5 µM) increased RyR1-mediated Ca(2+) release from SkM microsomes. Maximal K201 doses at 80 µM produced ∼37% of the increase in SkM SR Ca(2+) release observed with the RyR agonist caffeine. K201 (≥5 µM) increased the open probability (Po) of very active ("high-activity") RyR1 of SkM reconstituted into bilayers, but it had no effect on "low-activity" channels. Likewise, K201 activated cardiac RyR2 under systolic Ca(2+) conditions (∼5 µM; channels at Po ∼0.3) but not under diastolic Ca(2+) conditions (∼100 nM; Po < 0.01). Thus, K201-induced the inhibition of SR Ca(2+) leak found in cell-system studies may relate to potentially potent SERCA block under resting Ca(2+) conditions. SERCA block likely produces mild SR depletion in normal conditions but could prevent SR Ca(2+) overload under pathologic conditions, thus precluding abnormal RyR-mediated Ca(2+) release.

Altered myocardial calcium cycling and energetics in heart failure--a rational approach for disease treatment

Cardiomyocyte function depends on coordinated movements of calcium into and out of the cell and the proper delivery of ATP to energy-utilizing enzymes. Defects in calcium-handling proteins and abnormal energy metabolism are features of heart failure. Recent discoveries have led to gene-based therapies targeting calcium-transporting or -binding proteins, such as the cardiac sarco(endo)plasmic reticulum calcium ATPase (SERCA2a), leading to improvements in calcium homeostasis and excitation-contraction coupling. Here we review impaired calcium cycling and energetics in heart failure, assessing their roles from both a mutually exclusive and interdependent viewpoint, and discuss therapies that may improve the failing myocardium.

Dysfunctional ryanodine receptors in the heart: new insights into complex cardiovascular diseases

Calcium dependent signaling is highly regulated in cardiomyocytes and determines the force of cardiac muscle contraction. The cardiac ryanodine receptors (RyR2) play important roles in health and disease. Modulation of RyR2 by phosphorylation is required for sympathetic regulation of cardiac function. Abnormal regulation of RyR2 contributes to heart failure, and atrial and ventricular arrhythmias. RyR2 channels are oxidized, nitrosylated, and hyperphosphorylated by protein kinase A (PKA) in heart failure, resulting in "leaky" channels. These leaky RyR2 channels contribute to depletion of calcium from the sarcoplasmic reticulum, resulting in defective cardiac excitation-contraction coupling. In this review, we discuss both the importance of PKA and calcium/calmodulin-dependent kinase II (CaMKII) regulation of RyR2 in health, and how altered phosphorylation, nitrosylation and oxidation of RyR2 channels lead to cardiac disease. Correcting these defects using either genetic manipulation (knock-in) in mice, or specific and novel small molecules ameliorates the RyR2 dysfunction, reducing the progression to heart failure and the incidence of arrhythmias.

Calcium cycling proteins and heart failure: mechanisms and therapeutics

Ca2+-dependent signaling is highly regulated in cardiomyocytes and determines the force of cardiac muscle contraction. Ca2+ cycling refers to the release and reuptake of intracellular Ca2+ that drives muscle contraction and relaxation. In failing hearts, Ca2+ cycling is profoundly altered, resulting in impaired contractility and fatal cardiac arrhythmias. The key defects in Ca2+ cycling occur at the level of the sarcoplasmic reticulum (SR), a Ca2+ storage organelle in muscle. Defects in the regulation of Ca2+ cycling proteins including the ryanodine receptor 2, cardiac (RyR2)/Ca2+ release channel macromolecular complexes and the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a)/phospholamban complex contribute to heart failure. RyR2s are oxidized, nitrosylated, and PKA hyperphosphorylated, resulting in "leaky" channels in failing hearts. These leaky RyR2s contribute to depletion of Ca2+ from the SR, and the leaking Ca2+ depolarizes cardiomyocytes and triggers fatal arrhythmias. SERCA2a is downregulated and phospholamban is hypophosphorylated in failing hearts, resulting in impaired SR Ca2+ reuptake that conspires with leaky RyR2 to deplete SR Ca2+. Two new therapeutic strategies for heart failure (HF) are now being tested in clinical trials: (a) fixing the leak in RyR2 channels with a novel class of Ca2+-release channel stabilizers called Rycals and (b) increasing expression of SERCA2a to improve SR Ca2+ reuptake with viral-mediated gene therapy. There are many potential opportunities for additional mechanism-based therapeutics involving the machinery that regulates Ca2+ cycling in the heart.

Altered sarcoplasmic reticulum calcium cycling--targets for heart failure therapy

Cardiac myocyte function is dependent on the synchronized movements of Ca(2+) into and out of the cell, as well as between the cytosol and sarcoplasmic reticulum. These movements determine cardiac rhythm and regulate excitation-contraction coupling. Ca(2+) cycling is mediated by a number of critical Ca(2+)-handling proteins and transporters, such as L-type Ca(2+) channels (LTCCs) and sodium/calcium exchangers in the sarcolemma, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), ryanodine receptors, and cardiac phospholamban in the sarcoplasmic reticulum. The entry of Ca(2+) into the cytosol through LTCCs activates the release of Ca(2+) from the sarcoplasmic reticulum through ryanodine receptor channels and initiates myocyte contraction, whereas SERCA2a and cardiac phospholamban have a key role in sarcoplasmic reticulum Ca(2+) sequesteration and myocyte relaxation. Excitation-contraction coupling is regulated by phosphorylation of Ca(2+)-handling proteins. Abnormalities in sarcoplasmic reticulum Ca(2+) cycling are hallmarks of heart failure and contribute to the pathophysiology and progression of this disease. Correcting impaired intracellular Ca(2+) cycling is a promising new approach for the treatment of heart failure. Novel therapeutic strategies that enhance myocyte Ca(2+) homeostasis could prevent and reverse adverse cardiac remodeling and improve clinical outcomes in patients with heart failure.

The effect of K201 on isolated working rabbit heart mechanical function during pharmacologically induced Ca2+ overload

BACKGROUND AND PURPOSE

Reduced cardiac contractility has been associated with disrupted myocardial Ca(2+) signalling. The 1,4 benzothiazepine K201 (JTV-519) acts on several Ca(2+) handling proteins and improves cardiac contractility in vivo in a variety of animal models of myocardial dysfunction. However, it is unclear whether this improvement depends on the systemic effects of K201 or if K201 reverses the effects of Ca(2+) dysregulation, regardless of the cause.

EXPERIMENTAL APPROACH

The effect of K201 on cardiac mechanical function was assessed in isolated working hearts from adult rabbits, using a ventricular pressure-volume catheter. In separate experiments, the effect of K201 was investigated in hearts following pharmacologically induced Ca(2+) overload using elevated extracellular [Ca(2+) ] ([Ca(2+) ](o) ) and β-adrenoceptor stimulation.

KEY RESULTS

K201 induced a concentration-dependent decline in systolic function (peak pressure, dP/dt(max) and preload recruitable stroke work), lusitropy (reduced dP/dt(min) and increased end diastolic pressure) and stroke volume, independent of decreased heart rate. In separate experiments, mechanical function in hearts exposed to 4.5 mmol·L(-1) [Ca(2+) ](o) and 150 nmol·L(-1) isoprenaline declined until cessation of aortic flow (in 6 out of 11 hearts). However, all hearts perfused with the addition of 1 µmol·L(-1) K201 maintained aortic flow and demonstrated significantly improved peak systolic pressures, dP/dt(max) and dP/dt(min) .

CONCLUSIONS AND IMPLICATIONS

K201 significantly improved mechanical function of the heart during Ca(2+) overload. This suggests that K201 can limit the detrimental effects of elevated intracellular Ca(2+) and exert beneficial effects on cardiac contractile function, independent of systemic effects previously observed in vivo.

Effects of K201 on repolarization and arrhythmogenesis in anesthetized chronic atrioventricular block dogs susceptible to dofetilide-induced torsade de pointes

The novel antiarrhythmic drug K201 (4-[3-{1-(4-benzyl)piperidinyl}propionyl]-7-methoxy-2,3,4,5-tetrahydro-1,4-benzothiazepine monohydrochloride) is currently in development for treatment of atrial fibrillation. K201 not only controls intracellular calcium release by the ryanodine receptors, but also possesses a ventricular action that might predispose to torsade de pointes arrhythmias. The anti- and proarrhythmic effects of K201 were investigated in the anesthetized canine chronic atrioventricular block model. Two doses of K201 (0.1 and 0.3mg/kg/2 min followed by 0.01 and 0.03 mg/kg/30 min i.v.) were tested in 4 serial experiments in dogs with normally conducted sinus rhythm (n=10) and in torsade de pointes-susceptible dogs with chronic atrioventricular block. Susceptibility was assessed with dofetilide (0.025 mg/kg/5 min i.v.). Beat-to-beat variability of repolarization was quantified as short-term variability of left ventricular monophasic action potential duration. In dogs with normally conducted sinus rhythm, both doses of K201 prolonged ventricular repolarization whereas only the higher dose prolonged atrial repolarization. At chronic atrioventricular block, dofetilide induced torsade de pointes in 9 of 10 dogs. K201 did neither suppress nor prevent dofetilide-induced torsade de pointes. K201 dose-dependently prolonged ventricular repolarization. In contrary to the lower dose, the higher dose did increase beat-to-beat variability of repolarization (from 1.2 ± 0.3 to 2.9 ± 0.8 ms, P<0.05) and resulted in spontaneous, repetitive torsade de pointes arrhythmias in 1 of 7 dogs; Programmed electrical stimulation resulted in torsade de pointes in 2 more dogs. In conclusion, both doses of K201 showed a class III effect. No relevant antiarrhythmic effects against dofetilide-induced torsade de pointes were seen. Only at the higher dose a proarrhythmic signal was observed.

The ryanodine receptor in cardiac physiology and disease

According to the American Heart Association it is estimated that the United States will spend close to $39 billion in 2010 to treat over five million Americans suffering from heart failure. Patients with heart failure suffer from dyspnea and decreased exercised tolerance and are at increased risk for fatal ventricular arrhythmias. Food and Drug Administration -approved pharmacologic therapies for heart failure include diuretics, inhibitors of the renin-angiotensin system, and β-adrenergic receptor antagonists. Over the past 20 years advances in the field of ryanodine receptor (RyR2)/calcium release channel research have greatly advanced our understanding of cardiac physiology and the pathogenesis of heart failure and arrhythmias. Here we review the key observations, controversies, and discoveries that have led to the development of novel compounds targeting the RyR2/calcium release channel for treating heart failure and for preventing lethal arrhythmias.

Chronic heart rate reduction with ivabradine improves systolic function of the reperfused heart through a dual mechanism involving a direct mechanical effect and a long-term increase in FKBP12/12.6 expression

AIMS

To investigate the adaptations of left ventricular function and calcium handling to chronic heart rate reduction with ivabradine in the reperfused heart.

METHODS AND RESULTS

Rabbits underwent 20 min coronary artery occlusion followed by 3 weeks of reperfusion. Throughout reperfusion, rabbits received ivabradine (10 mg/kg/day) or vehicle (control). Ivabradine reduced heart rate by about 20% and improved both ejection fraction (+35%) and systolic displacement (+26%) after 3 weeks of treatment. Interestingly, this was associated with a two-fold increase expression of FKBP12/12.6. There was no difference in the expressions of phospholamban, SERCA2a, calsequestrin, ryanodine, phospho-ryanodine, and Na(2+)/Ca(2+) exchanger in the two groups. Infarct scar and vascular density were similar in both groups. Administration of a single intravenous bolus of ivabradine (1 mg/kg) in control rabbits at 3 weeks of reperfusion also significantly improved acutely ejection fraction and systolic displacement.

CONCLUSION

Chronic heart rate reduction protects the myocardium against ventricular dysfunction induced by myocardial ischaemia followed by 3 weeks of reperfusion. Beyond pure heart rate reduction, ivabradine improves global and regional systolic function of the reperfused heart through a dual mechanism involving a direct mechanical effect and a long-term adaptation in calcium handling, as supported by the increase in FKBP12/12.6 expression.

Effect of K201, a novel antiarrhythmic drug on calcium handling and arrhythmogenic activity of pulmonary vein cardiomyocytes

BACKGROUND AND PURPOSE

Pulmonary veins are the most important focus for the generation of atrial fibrillation. Abnormal calcium homeostasis with ryanodine receptor dysfunction may underlie the arrhythmogenic activity in pulmonary veins. The preferential ryanodine receptor stabilizer (K201) possesses antiarrhythmic effects through calcium regulation. The purpose of this study was to investigate the effects of K201 on the arrhythmogenic activity and calcium regulation of pulmonary vein cardiomyocytes.

EXPERIMENTAL APPROACH

The ionic currents and intracellular calcium were studied in isolated single cardiomyocytes from rabbit pulmonary vein before and after the administration of K201, by the whole-cell patch clamp and indo-1 fluorimetric ratio techniques.

KEY RESULTS

K201 (0.1, 0.3, 1 microM) reduced the firing rates in pulmonary vein cardiomyocytes, decreased the amplitudes of the delayed afterdepolarizations and prolonged the action potential duration. K201 decreased the L-type calcium currents, Na(+)/Ca(2+) exchanger currents, transient inward currents and calcium transients. K201 (1 microM, but not 0.1 microM or 0.3 microM) also reduced the sarcoplasmic reticulum calcium content. Moreover, both the pretreatment and administration of K201 (0.3 microM) decreased the isoprenaline (10 nM)-induced arrhythmogenesis in pulmonary veins.

CONCLUSIONS AND IMPLICATIONS

K201 reduced the arrhythmogenic activity of pulmonary vein cardiomyocytes and attenuated the arrhythmogenicity induced by isoprenaline. These findings may reveal the anti-arrhythmic potential of K201.

K201, a multi-channel blocker, inhibits clofilium-induced torsades de pointes and attenuates an increase in repolarization

K201 (JTV519) is a 1,4-benzothiazepine derivative that exhibits a strong cardioprotective action and acts as a multiple-channel blocker, including as a K+ channel blocker. An experimental model of prolongation of the QT interval and torsades de pointes can be induced in rabbits by treatment with clofilium in the presence of the alpha1-adrenoreceptor agonist methoxamine. In this study we examined the effects of K201 with and without methoxamine on the QT and QTc intervals, and determined whether K201 inhibits clofilium-induced torsades de pointes in the presence of methoxamine (15 microg/kg/min) in rabbits (n=74). Administration of K201 (0, 40, 100, 200 and 400 microg/kg/min) with and without methoxamine prolonged the QT interval in a dose-dependent manner, and torsades de pointes did not occur in any animals. However, clofilium (50 microg/kg/min) with methoxamine induced torsades de pointes in all animals (6/6). Torsades de pointes occurred at rates of 100%, 67%, 40% and 0% at K201 concentrations of 0, 50, 200 and 400 microg/kg/min, respectively, in the clofilium-infused torsades de pointes model. Therefore, 400 microg/kg/min of K201 completely inhibited clofilium-induced torsades de pointes and attenuated the increase of repolarization caused by clofilium; the inhibitory effects of K201 may be related to its pharmacological properties as an alpha1-adrenoceptor blocker. Overall, our results show that K201 causes prolongation of the QT and QTc intervals, but does not induce torsades de pointes, with and without alpha1-adrenoceptor stimulation. Furthermore, K201 inhibits clofilium-induced torsades de pointes, despite QT prolongation, suggesting that QT prolongation alone is not a proarrhythmic signal.

Stabilisation of calstabin2 – a new approach in sudden cardiac death

Calstablin2 stabilises the ryanodine receptor (RyR2), preventing aberrant activation of the channels during the resting phase of the cardiac muscle. Loss of this stabilisation may be associated with cardiac arrhythmias, the sudden death occasionally observed in people with structurally normal hearts, as well as the atrial fibrillation in heart failure. Calstabin2-deficient mice have structurally normal hearts but exhibit exercise-induced cardiac ventricular arrhythmias that cause sudden death. In arrhythmias, the calstabin2 stabiliser JTV519 did not prevent arrhythmias in calstabin2-/- mice, but reduced the arrhythmias in calstabin2+/- mice, illustrating the antiarrhythmic potential of stabilising calstablin2. Familial polymorphic ventricular tachycardia in humans has been linked to missense mutants in the hRyR2 gene. In HEK293 cells, these RyR2 mutants showed less binding of 35S-calstabin2 than the wild type, indicating a reduced binding affinity. In human atrial fibrillation and heart failure, where there is excessive disassociation of calstabin2 from the RyR2 receptor in vitro, JTV519 is able to reverse this. In conclusion, calstabin2 is an important new target in sudden cardiac death associated with structurally normal hearts, and in the treatment of atrial fibrillation and heart failure.

Reversal of P-glycoprotein mediated multidrug resistance by a newly synthesized 1,4-benzothiazipine derivative, JTV-519

A newly synthesized 1,4-benzothiazipine derivate, 4-[3-(4-benzylpiperidin-1-yl) propionyl]-7-methoxy-2,3,4,5-tetrahydro-1, 4-benzothiazepine monohydrochloride (JTV-519) was examined for its ability to reverse P-glycoprotein (P-gp) and multidrug resistance protein 1 (MRP1) mediated multidrug resistance (MDR) in K562/MDR and KB/MRP cells, respectively. JTV-519 at 3 microM reversed the resistance of K562/MDR cells to vincristine (VCR), taxol, etoposide (VP16), adriamycin (ADM) and actinomycin D and at 0.5 or 1 microM reversed their resistance to STI571. JTV-519 at 10 microM enhanced the accumulation of ADM in K562/MDR cells to the level in parental K562 cells and inhibited the efflux of ADM from K562/MDR cells. Photoaffinity labeling of P-gp with 3H-azidopine was almost completely inhibited by 500 microM JTV-519. JTV-519 at 3 microM also partially reversed the resistance of KB/MRP cells to VCR and at 500 microM partially inhibited the photoaffinity labeling of MRP1 with (125)I-II-azidophenyl agosterol A (125I-azidoAG-A). These results suggest that JTV-519 reversed the resistance to the anti-cancer agents in P-gp and MRP1 overexpressing multidrug-resistant cells by directly binding to P-gp and MRP1, and competitively inhibiting transport of the anti-cancer agents.

A novel cardioprotective agent, JTV-519, is abolished by nitric oxide synthase inhibitor on myocardial metabolism in ischemia-reperfused rabbit hearts

We investigated the effect of a novel cardioprotective agent, JTV-519, with or without a nitric oxide synthase inhibitor, L-NAME, on the myocardial metabolism and contraction during ischemia and reperfusion by means of phosphorus 31-nuclear magnetic resonance (31P-NMR) in Langendorff rabbit hearts. After 20 min normothermic global ischemia, postischemic reperfusion was carried out for 30 min. JTV-519 was administered from 40 min prior to the global ischemia. Twenty-one hearts were divided into three experimental groups consisting of 7 hearts each: a control group, a JTV-519 group perfused with JTV-519, and a JTV-519+L-NAME group perfused with a combination of JTV-519 and L-NAME. During ischemia, the JTV-519 group showed a significant inhibition of the decrease in adenosine triphosphate (ATP) compared with both the control and JTV-519+L-NAME groups (p<0.01); the levels of ATP were 20+/-6, 56+/-9, and 40+/-4% in the control group, JTV-519 group, and JTV-519+L-NAME group, respectively. Both the JTV-519 group and JTV-519+L-NAME group showed a significant inhibition of the increase in left ventricular end-diastolic pressure (LVEDP) compared with the control group (p<0.01). After postischemic reperfusion, the JTV-519 group again showed a significant improvement of ATP as compared with both the control and JTV-519+L-NAME groups (p<0.01); the ATP levels were 52+/-4, 82+/-3, and 64+/-3% in the control group, JTV-519 group, and JTV-519+L-NAME group. In conclusion, JTV-519 has a significant beneficial effect on myocardial energy metabolism during both ischemia and reperfusion. This beneficial effect was dependent on NO synthase. Furthermore, JTV-519 showed significant potential for improving myocardial relaxation during ischemia. This effect was not dependent on NO synthase.

Reversal of cisplatin resistance by the 1,4-benzothiazepine derivative, JTV-519

The 1,4-benzothiazepine derivative JTV-519 is a new type of calcium ion channel modulator. We examined the modulatory effect of JTV-519 on the antitumor activity of several platinum compounds (cisplatin, carboplatin, and nedaplatin) in a human cancer cell line resistant to cisplatin (PC-14 / CDDP) in vitro. PC-14 / CDDP cells showed 8-fold resistance to cisplatin compared with the parental PC-14 cells as determined by dye formation [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT] assay. In PC-14 / CDDP, but not PC-14 cells, augmentation of cytotoxicity was observed when a nontoxic concentration (10 mM) of JTV-519 was combined with the platinum compounds. Increased intracellular cisplatin accumulation was observed in PC-14 / CDDP cells in the presence of JTV-519 as measured by atomic absorption assay. Therefore, increased cisplatin accumulation was considered to be a possible mechanism underlying the reversing effect of JTV-519 on cisplatin resistance. These results suggest that JTV-519 is a potent agent reversing cisplatin resistance.