DPI 201-106 for severe congestive heart failure

The positive inotropic agent DPI-201106 selectively reverses ABCB1-mediated multidrug resistance in cancer cell lines

The overexpression of ABCB1 in cancer cells is a major factor contributing to the development of multidrug resistance (MDR) and treatment failure in cancer patients. Therefore, re-sensitization of MDR cancer cells to anticancer drugs remains an important aspect in chemotherapy. The progress in developing clinically applicable synthetic inhibitors of ABCB1 has been slow, mostly due to complications associated with intrinsic toxicities and unforeseen drug-drug interactions. Here, we explored the drug-repositioning approach for cancer therapy by targeting ABCB1-mediated MDR in human cancer cells. We found that DPI-201106, a positive inotropic agent, selectively inhibits the drug efflux function of ABCB1, and in doing so, re-sensitizes ABCB1-overexpressing MDR cancer cells to conventional anticancer drugs. Furthermore, the ATPase activity of ABCB1 and docking analysis of DPI-201106 in the drug-binding pocket of ABCB1 were determined to confirm the interaction between DPI-201106 and ABCB1 protein. In summary, we revealed an additional action and a potential clinical application of DPI-201106 to reverse ABCB1-mediated MDR in human cancer cells, which may be beneficial for cancer patients who have developed multidrug resistance and no longer respond to conventional chemotherapy, and should be further investigated.

Pharmacologic Management of Acute Heart Failure: A Review

Because of improved social and medical standards in the western world, the average age of the population continues to increase. This altering demographic profile has its impact on the surgical population, resulting in a dramatic increase in the number of patients with exten sive cardiovascular disease, presenting for either car diac or noncardiac surgery. As a result, the incidence of perioperative acute congestive heart failure (CHF) is a major clinical problem at the present time. For the pharmacologic management of acute CHF, the β-adreno ceptor agonists continue to be the mainstay of therapy, due to their short duration of action and hemodynamic controlability by continuous intravenous infusion. Mono therapy with the phosphodiesterase type III (PDE) inhibi tors appears to be the treatment of choice in selected patients with high systemic vascular resistance or re sidual β-adrenoceptor blockade. Combination therapy especially deserves attention, because this approach allows the enhancement of contractile force, possibly without the side effects associated with the administra tion of high concentrations of one agent alone. New developments including ultrashort-acting PDE inhibi tors, calcium-dependent calcium sensitizers, and cal cium promotors are anxiously awaited.

Lack of desensitization and enhanced efficiency of calcium channel promoter in conscious dogs with heart failure

The goal of this study was to compare responses to a calcium promoter, BAY y 5959, and dobutamine (Dob) in heart failure (HF). Dogs (n = 9) were chronically instrumented and studied in the conscious state before and after pacing-induced HF. In the control state, BAY y 5959 (20 microgram. kg-1. min-1) increased the first derivative of left ventricular (LV) pressure (dP/dt) by 83 +/- 8% and mean arterial pressure (MAP) by 8 +/- 2% and decreased heart rate (HR) by 30 +/- 3%. With Dob (10 microgram. kg-1. min-1) LV dP/dt rose similarly (+80 +/- 6%), but HR also rose (+25 +/- 4%) (P < 0.05 vs. BAY y 5959). After HF developed, BAY y 5959 still increased LV dP/dt by 108 +/- 8% and MAP by 21 +/- 2% and decreased HR by 28 +/- 4%, whereas Dob increased LV dP/dt by only 50 +/- 7% (P < 0.05 vs. BAY y 5959) and MAP by 7 +/- 3%, and HR did not change (+3 +/- 3%) (P < 0.05 vs. BAY y 5959). In HF, cardiac work increased more (P < 0. 05) with BAY y 5959 (+105 +/- 13%) compared with Dob (+47 +/- 11%), yet myocardial oxygen consumption increased similarly with the two drugs. Accordingly, mechanical efficiency increased more (P < 0.05) with BAY y 5959 (+73 +/- 14%) than with Dob (+17 +/- 12%). These data indicate that 1) increases in contractility mediated directly by Ca2+ are relatively resistant to desensitization in HF; and 2) the calcium-channel promoter can produce increases in myocardial contractility and cardiac work similar to those of Dob at a significantly lower oxygen cost, thereby enhancing mechanical efficiency in HF.

Characterization of the inotropic and arrhythmogenic action of the sodium channel activator BDF 9148: a comparison to its S-enantiomer BDF 9196, to its congener DPI 201-106, to norepinephrine, and to ouabain

Positive inotropic substances which enhance the myocardial cAMP level or inhibit the Na+/K(+)-ATPase are known for their proarrhythmic side-effects. This study was performed to investigate the inotropic and arrhythmogenic action of the Na(+)-channel activator BDF 9148 (racemate) in comparison to its S-enantiomer BDF 9196, its congener DPI 201-106 (racemate), to norepinephrine, and to ouabain. In 30 open-chest dogs, the effects of these substances on the first derivative of left ventricular pressure (dP/dt, Millar-tip catheter) and anterior systolic wall thickening (AWT, sonomicrometry) were studied. Concomitantly, myocardial excitability, conduction times, and refractory period were assessed with a transmural, three-dimensional, 16-electrode array in the anterior wall. For the study of the Na(+)-channel activators, alpha- and beta-adrenergic and muscarinic receptors were blocked. A first set of measurements was performed during normoperfusion with administration of BDF 9148 (1 mg/kg, n = 8), BDF 9196 (0.5 mg/kg, n = 8), and DPI 201-106 (1 mg/kg, n = 8), respectively. A second set of measurements was performed with administration of the threefold dosage of either substance. With a severe stenosis on the left anterior descending coronary artery, a final set of measurements was performed, again using the higher dosage of either substance. For the study of norepinephrine (0.5 micrograms/kg/min i.v., n = 6) and ouabain (40 micrograms/kg i.v., n = 4), measurements were performed during normoperfusion in additional animals. Under normal conditions, either Na(+)-channel activator induced increases in dP/dtmax (lower dosage: 45-84%, higher dosage: by 93-117%) and AWT (lower dosage: by 24-37%, higher dosage: by 19-56%). Under ischemic conditions, either drug increased dP/dtmax by 60-98% and AWT by 45-102%. Excitability, conduction times, and refractory period did not change significantly in response to the Na(+)-channel activators, neither under normal nor under ischemic conditions. There was no significant difference in the incidence of spontaneous ventricular extrasystoles before and after administration of either Na(+)-channel activator. In contrast, an equi-inotropic dosage of norepinephrine (increases in dP/dtmax by 148% and AWT by 42%) increased excitability, decreased conduction times and refractory period, and increased the incidence of spontaneous ventricular extrasystoles. Ouabain induced only a moderate increase in dP/dtmax by 56% and AWT by 24%, but elicited sustained and complex ventricular arrhythmias. Excitability was markedly increased, whereas conduction times and refractory period changed only little.(ABSTRACT TRUNCATED AT 400 WORDS)

Current status of non-digitalis positive inotropic drugs

Considerable effort and resources have been directed at the development and study of positive inotropic drugs over the past 10-15 years. Much has been learned about the physiology and pharmacology of myocardial contraction, the application of agents to augment contractility, and, importantly, the general and specific limitations of positive inotropic therapy. Studies on acute inotropic intervention have now shown that a drug's ability to augment overall cardiac performance is heavily dependent on its effects on vasculature, vascular control, and ventricular-vascular coupling. The clinical research on new agents has served to remind us how difficult it is to formulate the "ideal" positive inotropic or cardiovascular support drug for the critical care setting. The vast effort to develop a chronically and orally administrable drug to replace or even supplement digitalis has generally been disappointing. The dopaminergic agents (e.g., ibopamine, levodopa) act primarily via vasodilation and their effectiveness and role in managing heart failure remain unresolved. The initial excitement about the phosphodiesterase III inhibitors (e.g., amrinone, milrinone, enoximone) has been tempered by the results of large well-designed trials indicating variable effectiveness and a prominent adverse effect profile. During long-term oral administration none of these agents has been shown to improve clinical status or exercise capacity beyond that achieved by digoxin, when administered either separately or in combination with digoxin. The Prospective Randomized Milrinone Survival Evaluation (PROMISE) trial, showing that repeated oral administration of milrinone can increase mortality in heart failure, is having a devastating effect on the further development of this class of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Similar oxygen cost of myocardial contractility between DPI 201-106 and epinephrine despite different subcellular mechanisms of action in dog hearts

The effects of DPI 201-106 (a novel, cyclic AMP-independent positive inotropic agent with Ca(2+)-sensitizing and Na(+)-channel agonistic mechanisms) on myocardial mechanics and energetics were assessed in the excised cross-circulated dog left ventricle. In the first protocol, the relation between left ventricular oxygen consumption (VO2) and systolic pressure-volume area (PVA) was analyzed before and during administration of DPI 201-106. The reciprocal of the slope of the VO2-PVA relation has been shown to reflect the contractile efficiency, and the VO2-intercept consists of the oxygen cost of contractility-dependent excitation-contraction coupling and basal metabolism. DPI 201-106 increased Emax (contractility index) and elevated the VO2-PVA relation in a parallel manner, i.e., the VO2-intercept increased without a change in the slope. In the second protocol, the increase in the VO2-intercept of the VO2-PVA relation for a unit increase in Emax (i.e., oxygen cost of enhanced contractility) was compared between DPI 201-106 and epinephrine in a paired manner in each heart. Epinephrine significantly abbreviated the time to end systole, whereas DPI 201-106 did not, suggesting that the mechanism of inotropic action differed between the two drugs. However, the oxygen cost of enhanced contractility was the same between the two drugs in each heart. Therefore, DPI 201-106 did not alter the contractile efficiency nor spare the oxygen cost of enhanced contractility as compared to epinephrine under the present experimental conditions. This suggests that the Ca(2+)-sensitizing effect of DPI 201-106, if any, is too small to spare the oxygen cost of contractility in the blood-perfused, non-failing dog heart.

Inotropic and electrophysiological effects of BDF 9148, a congener of DPI 201-106, in guinea-pig atria and papillary muscles

1. BDF 9148 is a newly synthesized congener of DPI 201-106 in which the piperazidinyl moiety has been replaced by an azetidine-3-oxy-moiety. The inotropic effect of both drugs was studied as well as their influence on the action potential, by use of standard microelectrode techniques. 2. BDF 9148 increased the contractile force of guinea-pig atria and papillary muscles. The EC50 was 1.32 X 10(-7) mol l-1 and 0.7 X 10(-6) mol l-1 respectively. DPI 201-106 was effective in a similar concentration-range, the EC50 being 2.6 X 10(-7) mol l-1 for atria and 2.8 X 10(-7) mol l-1 for papillary muscles. 3. Both drugs caused a concentration-dependent prolongation of the relaxation time of the isometric contraction curve. With 10(-6) mol l-1 BDF 9148, the mean increase was 39.1 +/- 4.4 ms in atria and 39.4 +/- 7.5 ms in papillary muscles while 10(-6) mol l-1 DPI 201-106 caused increases of 56.7 +/- 2.5 ms and 79.3 +/- 11.7 ms, respectively. The effect of BDF 9148 was not prevented by propranolol, but was reversed by 3 X 10(-6) mol l-1 tetrodotoxin. Pretreatment of atria with 3 X 10(-8) mol l-1 BDF shifted the concentration-response curve of ouabain to the left and reduced the EC50 of the glycoside from 3.21 X 10(-7) mol l-1 to 2 X 10(-7) mol l-1. 4. BDF 9148 and DPI 201-106 concentration-dependently increased the action potential duration of papillary muscles and their functional refractory period. The drugs did not modify the resting potential, the action potential amplitude or the maximum depolarization velocity.5. All effects of BDF 9148 persisted after washout. The lipophilic drug accumulated in the tissues and the tissue drug concentration was little reduced by washout of BDF 9148 from the organ bath.6. In contrast to DPI 201-106, which had a prominent negative chronotropic effect in right atria, BDF 9148 caused only a slight reduction of the beating frequency with the largest (3 x 10 5mol 11) concentration.7. The results are consistent with BDF 9148 being a sodium channel activator with much weaker influence on the beating frequency than the parent compound DPI 201-106.

Inotropic response to DPI 201-106 in the failing human heart

1. The present study was designed to characterize the positive inotropic response to DPI 201-106 in isolated papillary muscle strips obtained from heart failure patients undergoing surgery. 2. The positive inotropic responses to isoprenaline and milrinone and cardiac beta-adrenoceptor density were also determined. 3. DPI 201-106 increased the force of contraction in papillary muscle strips from patients with moderate (NYHA II-III) and severe (NYHA IV) heart failure, in a concentration-dependent manner. This positive inotropic effect was more pronounced in tissues from NYHA IV patients. Furthermore, these responses were greater than those produced by milrinone or isoprenaline. The positive inotropic effects of isoprenaline and milrinone were reduced in NYHA IV compared to NYHA II-III. Consistently, there was also a smaller density of beta-adrenoceptors in myocardium from NYHA IV than in NYHA II-III. The positive inotropic effect of Ca2+ was similar in tissues from both groups of patients. 4. The positive inotropic effect of DPI 201-106 was not antagonized by adenosine or carbachol, whereas both compounds reduced the positive inotropic effect of isoprenaline. 5. DPI 201-106 did not increase the Ca2+ -sensitivity of chemically skinned ventricular fibres, whereas a significant increase of the Ca2+ -sensitivity was obtained with trifluoperazine. 6. It is concluded that DPI 201-106 produces significant positive inotropic effects in tissue excised from the failing human heart. The lack of inhibition by adenosine and carbachol might contribute to its greater effectiveness in NYHA IV than NYHA II-III and indicates that its mechanism of action is cyclic AMP-independent. A sensitization of the contractile proteins to Ca2+ does not appear to be important for the positive inotropic action of DPI 201-106 in the failing human heart.

Cardiac and hemodynamic profile of the new cardiotonic agent, DPI 201-106, in the conscious dog

The cardiac and hemodynamic effects of increasing doses (0.1-3 mg/kg i.v.) of the novel cardiotonic agent, DPI 201-106 (DPI), were investigated over a 60 min period in conscious dogs chronically instrumented for the measurement of arterial pressure, heart rate, left ventricular pressure (LVP), LV (+) dP/dtmax and cardiac output. LV (+) dP/dtmax, cardiac output and stroke volume were significantly increased by DPI whereas the total peripheral resistance was significantly decreased. These effects were dose-dependent in intensity and in duration. The mean arterial pressure and heart rate remained unaffected, except by the 3 mg/kg dose, which increased them slightly. Autonomic blockade with hexamethonium, atropine and propranolol did not alter the positive inotropic properties of DPI but unmasked its intrinsic bradycardic effect. At equipotent positive inotropic doses, DPI (0.3 mg/kg), milrinone (40 micrograms/kg) and dobutamine (5 micrograms/kg per min) induced similar increases in cardiac output and similar decreases in total peripheral resistance, but only dobutamine and milrinone accelerated the heart rate, whereas ouabain (17.5 micrograms/kg) induced a strong rise in the total peripheral resistance and markedly lowered the heart rate and cardiac output. After coadministration of DPI and ouabain, LV (+) dP/dtmax was further increased whereas the ouabain-induced bradycardia, the rise in the total peripheral resistance and the decrease in cardiac output were reinforced, halved and unaltered, respectively. We conclude that (a) DPI exhibits potent and direct positive inotropic properties, associated with a peripheral vasodilating action, and almost no positive chronotropic effects, and (b) coadministration of DPI and ouabain results in synergistic positive inotropic effects.

New mechanisms for positive inotropic agents: focus on the discovery and development of imazodan

Intense efforts during the last decade to identify a useful positive inotropic agent to replace digitalis for the treatment of congestive heart failure have led to the discovery of several dozen potential substitutes, of which a number are currently undergoing clinical trials. In addition to producing a variety of new therapeutic entities, research in this area has also yielded valuable new information regarding the fundamental events that regulate calcium homeostasis and contractile function in the cardiac cell. For example, several of these new inotropic agents, including the calcium-channel stimulator BAY-k 8644, the sodium-channel stimulator DPI-201-186, and the sodium-calcium exchange inhibitor dichlorobenzamil, have provided considerable insight into the role of sodium and calcium in regulating contractility and the molecular events that mediate potential-dependent ion channels. Likewise, the discovery and development of agents like imazodan, amrinone, enoximone, and other selective type III phosphodiesterase inhibitors have provided new information regarding multiple molecular forms of cyclic nucleotide phosphodiesterase, compartmentation of cyclic AMP, and the importance of soluble vs. membrane-bound phosphodiesterases.

Interactions of DPI 201-106, a novel cardiotonic agent, with cardiac calcium channels

The interaction of DPI 201-106, a novel cardiotonic agent, with the calcium entry blocker receptor complex was studied using porcine cardiac sarcolemmal membranes. DPI 201-106 and the chemically-related calcium antagonist, cinnarizine, produce concentration-dependent inhibition of nitrendipine, gallopamil and diltiazem binding to their respective sites in these vesicles. This effect of DPI 201-106 is not stereoselective since resolved stereoisomers of this compound display equal potency in inhibiting each of the binding reactions. Equilibrium ligand binding studies revealed that DPI 201-106 and cinnarizine cause mixed inhibitory patterns at the aralkylamine and benzothiazepine sites (i.e. both Kd and Bmax values were affected) while mainly increasing Kd at the dihydropyridine site. The kinetics of ligand dissociation from the three calcium entry blocker receptors, together with measurements of dihydropyridine association kinetics, further demonstrate that DPI 201-106 interacts at a unique site in the receptor complex and allosterically modulates binding of nitrendipine, gallopamil and diltiazem. The functional consequences of the above interactions with the calcium channel were studied in isolated cardiac preparations. In guinea-pig atria, DPI 201-106 increased force of contraction. This inotropic effect is seen only with the S(-) enantiomer and is unaltered by nitrendipine-, verapamil- or diltiazem-pretreatment, indicating DPI 201-106 does not act as a stimulant of this channel. Furthermore, DPI 201-106 did not alter the inotropic action of Bay K 8644, a calcium channel stimulant. Spontaneous rate of guinea-pig right atria is decreased by both DPI 201-106 and cinnarizine. In addition, potassium-induced contractures in cat papillary muscles are reduced by both agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasodilator and inotropic drugs for the treatment of chronic heart failure: distinguishing hype from hope

During the past 10 years, more than 80 orally active vasodilator and inotropic agents have been tested in the clinical setting to evaluate their potential utility in the treatment of chronic heart failure. Although the initial reports of all of these drugs suggested that each represented a major therapeutic advance, only three agents--digoxin, captopril and enalapril--have produced consistent long-term hemodynamic and clinical benefits in these severely ill patients. Most of the other drugs that have been tested have not (to date) distinguished themselves from placebo therapy in large-scale, controlled trials, even though these agents produce hemodynamic effects that closely resemble those seen with digitalis and the converting-enzyme inhibitors. These observations suggest that the hemodynamic derangements that characteristically accompany the development of left ventricular dysfunction cannot be considered to be the most important pathophysiologic abnormality in chronic heart failure. Although cardiac contractility is usually depressed in this disease, positive inotropic agents do not consistently improve the clinical status of these patients. Similarly, although the systemic vessels are usually markedly constricted, drugs that ameliorate this vasoconstriction do not consistently relieve symptoms, enhance exercise capacity or prolong life. Hence, correction of the central hemodynamic abnormalities seen in heart failure may not necessarily provide a rational basis for drug development, and future advances in therapy are likely to evolve only by attempting to understand and modify the basic physiologic derangements in this disorder.