Defective One- or Two-electron Reduction of the Anticancer Anthracycline Epirubicin in Human Heart RELATIVE IMPORTANCE OF VESICULAR SEQUESTRATION AND IMPAIRED EFFICIENCY OF ELECTRON ADDITION

One-electron quinone reduction and two-electron carbonyl reduction convert the anticancer anthracycline doxorubicin to reactive oxygen species (ROS) or a secondary alcohol metabolite that contributes to inducing a severe form of cardiotoxicity. The closely related analogue epirubicin induces less cardiotoxicity, but the determinants of its different behavior have not been elucidated. We developed a translational model of the human heart and characterized whether epirubicin exhibited a defective conversion to ROS and secondary alcohol metabolites. Small myocardial samples from cardiac surgery patients were reconstituted in plasma that contained clinically relevant concentrations of doxorubicin or epirubicin. In this model only doxorubicin formed ROS, as detected by fluorescent probes or aconitase inactivation. Experiments with cell-free systems and confocal laser scanning microscopy studies of H9c2 cardiomyocytes suggested that epirubicin could not form ROS because of its protonation-dependent sequestration in cytoplasmic acidic organelles and the consequent limited localization to mitochondrial one-electron quinone reductases. Accordingly, blocking the protonation-sequestration mechanism with the vacuolar H+-ATPase inhibitor bafilomycin A1 relocalized epirubicin to mitochondria and increased its conversion to ROS in human myocardial samples. Epirubicin also formed ∼60% less alcohol metabolites than doxorubicin, but this was caused primarily by its higher Km and lower Vmax values for two-electron carbonyl reduction by aldo/keto-reductases of human cardiac cytosol. Thus, vesicular sequestration and impaired efficiency of electron addition have separate roles in determining a defective bioactivation of epirubicin to ROS or secondary alcohol metabolites in the human heart. These results uncover the molecular determinants of the reduced cardiotoxicity of epirubicin and serve mechanism-based guidelines to improving antitumor therapies

Posaconazole and midostaurin in patients with FLT3-mutated acute myeloid leukemia: Pharmacokinetic interactions and clinical facts in a real life study

: Midostaurin is used in combination with chemotherapy to treat patients with newly diagnosed FLT3-mutated acute myeloid leukemia. Chemotherapy-induced neutropenia exposes these patients to a significant risk of invasive fungal infections (IFIs). International guidelines recommend primary antifungal prophylaxis with posaconazole (PCZ) but nested analysis of a phase III trial showed that strong PCZ inhibition of CYP3A4 diminished midostaurin metabolism and increased midostaurin plasma levels; however, midostaurin-related adverse events (AEs) were only moderately exacerbated. We conducted a prospective multicenter real-life study to evaluate (i) how often concerns around PCZ-midostaurin interactions made the hematologist prescribe antifungals other than PCZ, (ii) how remarkably PCZ increased midostaurin plasma levels, and (iii) how significantly PCZ-midostaurin interactions influenced hematologic and safety outcomes of induction therapy. Although the hematologists were blinded to pharmacokinetic findings, as many as 16 of 35 evaluable patients were prescribed antifungal prophylaxis with micafungin, weak CYP3A4 inhibitor, in place of PCZ (p < 0.001 for deviation from guidelines). In the 19 patients managed as per guidelines, PCZ-midostaurin interactions were more remarkable than previously characterized, such that at the end of induction therapy midostaurin minimum plasma concentration (Cmin ) was greater than three times higher than reported; moreover, midostaurin Cmin , maximum plasma concentration, and area under the curve were more than or equal to four times higher with PCZ than micafungin. Hematologic outcomes (complete remission and duration of severe neutropenia) and safety outcomes (midostaurin-related any grade or grade ≥3 AEs) were nonetheless similar for patients exposed to PCZ or micafungin, as was the number of breakthrough IFIs. In waiting for randomized phase III trials of new prophylaxis regimens, these findings show that PCZ should remain the antifungal of choice for the midostaurin-treated patient

Mechanisms and clinical course of cardiovascular toxicity of cancer treatment II. Hematology

Session II of the Second International Colloquium on Cardio-Oncology, chaired by Dr Breccia (Rome, Italy) and Dr Jurczak (Krakow, Poland), focused on mechanisms and clinical course of cardiovascular toxicity of cancer treatment. Whereas the venerable anthracyclines keep challenging patients and clinicians with risk of left ventricular dysfunction and heart failure, other newer drugs cause substantially different clinical phenotypes of cardiovascular toxicity. In particular, Session II not only focused on arterial thrombosis and venous thromboembolism, but also hypertension or cardiomyopathy or atrial fibrillation induced by many otherwise life-saving drugs. Dr Breccia (Rome, Italy) reviewed incidence, mechanisms, risk factors, and principles for prevention of cardiovascular events induced by tyrosine kinase inhibitors of hematologic interest, such as those used to treat chronic myeloid leukemia. Dr Carver (Philadelphia) reviewed the incidence, predisposing factors, and principles for proactive management of cardiovascular events in patients treated by conventional chemotherapy or new drugs for treatment of multiple myeloma. Dr Szmit (Warsaw, Poland) discussed on how coagulation disorders should be classified according to patient- or drug-related factors and how they should be diagnosed and treated in patients with solid or hematologic tumors. Dr Minotti (Rome. Italy) illustrated some potential pitfalls of accelerated drug development and approval and their possible impact on clinical incidence of cardiovascular events induced by tyrosine kinase inhibitors of hematologic interest. Session II therefore offered a broad perspective of the risk-benefit ratio of new drugs that are plagued with concerns about cardiovascular events. (C) 2019 Elsevier Inc. All rights reserved