Pixantrone: novel mode of action and clinical readouts

<p><b>Introduction</b>: Pixantrone is a first-in-class aza-anthracenedione approved as monotherapy for treatment of relapsed or refractory aggressive diffuse B-cell non-Hodgkin’s lymphoma (NHL), a patient group which is notoriously difficult to treat. It has a unique chemical structure and pharmacologic properties distinguishing it from anthracyclines and anthracenediones.</p> <p><b>Areas covered</b>: The chemical structure and mode of action of pixantrone versus doxorubicin and mitoxantrone; preclinical evidence for pixantrone’s therapeutic effect and cardiac tolerability; efficacy and safety of pixantrone in clinical trials; ongoing and completed trials of pixantrone alone or as combination therapy; and the risk of cardiotoxicity of pixantrone versus doxorubicin and mitoxantrone.</p> <p><b>Expert commentary</b>: Currently, pixantrone is the only approved therapy for multiply relapsed or refractory NHL, an area with few available effective treatment options. Pixantrone is currently being investigated as combination therapy with other drugs including several targeted therapies, with the ultimate goal of improved survival in heavily pretreated patients. In order for pixantrone to be acknowledged in the treatment of aggressive NHL, the perception of pixantrone as an anthracycline-like agent that has anthracycline-like activity and cardiotoxicity needs to be changed. Further data from ongoing clinical trials will help in confirming pixantrone as an effective and safe option.</p

Circulating microparticles (MPs).

<p>Total MPs (A), platelet (CD61⁺)- (B), endothelial (CD54⁺)- (C) and erythrocyte- (D) derived MPs from control, spironolactone (Spiro), Provinols™ (Prov), aldosterone-salt (Aldo-salt), Aldo-salt Spiro and Aldo-salt Prov (n = 4–5 for each group). Values are means ± SEM, *<i>P</i><0.05 <i>vs</i> control rats. ^#<i>P</i><0.05 ^##<i>P</i><0.01 <i>vs</i> Aldo-salt rats.</p

Endothelial function in small mesenteric arteries.

<p>A: Flow-induced dilatation in small mesenteric arteries from control, aldosterone-salt (Aldo-salt), aldosterone-salt spironolactone (Aldo-salt Spiro) and aldosterone-salt Provinols™ (Aldo-salt Prov) calculated as Δdiameter. Absolute values for baseline diameters were 133±9, 136±7, 142±5 and 153±6 µm, respectively. *<i>P</i><0.05 Aldo-salt <i>vs</i> control. B: NO-dependent dilatation calculated as the difference between the dilatation in basal conditions and the dilatation in the presence of nitro-L-arginine (L-NA, 100 µM). Absolute values for baseline diameters ere 133±4, 135±4, 143±6 and 154±4 µm, respectively. n = 5 for each group. Values are means ± SEM. <i>*P<0.05</i> Aldo-salt <i>vs</i> control vessels.</p

Effects of treatment by spironolactone (Spiro) or Provinols™ (Prov) on blood pressure, carotid diameter and organ weights in aldosterone-salt (Aldo-salt) treated rats.

<p>DAP: diastolic arterial pressure; SAP: systolic arterial pressure; MAP: mean arterial blood pressure; PP: pulse pressure.</p><p>Values are means ± SEM.</p>*<p><i>P</i><0.05 <i>vs</i> Control.</p>#<p><i>P</i><0.05 <i>vs</i> Aldo-salt.</p

Contractile effects of KCl (80 mM) and endothelium-dependent relaxation to acetylcholine in rat mesenteric resistance arteries.

<p>Spironolactone  =  Spiro; Provinols™  =  Prov; Aldosterone-salt  =  Aldo-salt.</p><p>Values are means ± SEM (n = 4–6).</p>*<p><i>P</i><0.05 <i>vs</i> Spiro.</p

NO production, iNOS and NFκB pathways.

<p>Quantification of the amplitude of NO-Fe(DETC)₂ signal per µl in blood (A) and per mg of dried sample in aorta (B). Values are means ± SEM, *<i>P</i><0.05 <i>vs</i> control rats, #P<0.05 <i>vs</i> Aldo-salt rats (n = 4–5 for each group). Western blot (C) and densitometric analysis revealing iNOS (D), NFκB p65 (E) expression and phosphorylated I-κB alpha (P-IκB; F) in aortae. Values are means ± SEM, *<i>P</i><0.05 <i>vs</i> control rats, ^#<i>P</i><0.05 <i>vs</i> Aldo-salt rats.</p

Carotid artery incremental elastic modulus-wall stress (Einc-WS) curves.

<p><b>A.</b> Einc-WS curves from Control, aldosterone-salt (Aldo-salt), Aldo-salt spironolactone (Aldo-salt Spiro) and Aldo-salt Provinols™ (Aldo-salt Prov) rats (n = 5 for each group). <b>B.</b> Mean value of WS at 1500 kPa of Einc. Values are means ± SEM, *<i>P</i><0.05 <i>vs</i> control rats.</p

Shear stress and microparticle formation.

<p>(A) Phospholipid-related procoagulant activity (PPA) values are expressed as a ratio between sheared and unsheared data from blood samples treated with aldosterone (Aldo), aldosterone plus spironolactone (Aldo+Spiro) and aldosterone plus Provinols™ (Aldo+Prov) groups (n = 4–5 for each group). Values are means ± SEM, *<i>P</i><0.05 vs control (PBS). #P<0.05 vs aldosterone-treated samples. (B-E). Mineralocorticoid receptor antagonist activity. VSMCs were preincubated with spironolactone (Spiro), Provinols™ (Prov) or fulvestrant (Fluv) for 1 hour, and then aldosterone (Aldo) was added for 24 hours for protein analysis. Changes in MDM2 (C), gp91 (D) and CT-1 (E) protein expression were assayed by Western Blotting and normalized with β-actin in triplicate. A representative Western blot (B) and the histograms with bars represent the means ± SEM of triplicates in three independent experiments. *<i>P</i><0.01 vs Control.</p

Effects of treatment by Spironolactone (Spiro) or Provinols™ (Prov) on aortic medial composition in aldosterone-salt (Aldo-salt) treated rats.

<p>Values are means ± SEM <i>P</i><0.05 <i>vs</i> Control, ^#<i>P</i><0.05 <i>vs</i> Aldo-salt.</p

Superoxide anion and nitrotyrosine staining in aorta.

<p>Quantification of the amplitude of O₂^–CMH signal (A) and immunohistochemical staining for nitrotyrosine (B-E) in aortae (n = 4–5 for each group). Values are means ± SEM, *<i>P</i><0.05 <i>vs</i> control rats, ^#<i>P</i><0.05 <i>vs</i> Aldo-salt rats.</p