Predictors of Early or Delayed Diastolic Dysfunction After Anthracycline-Based or Nonanthracycline Chemotherapy: A Pharmacological Appraisal

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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

MECCANISMI DI RESISTENZA AI FARMACI ANTITUMORALI

Nonostante i progressi della terapia medica dei tumori solidi e del sangue, la resistenza ai farmaci antineoplastici rimane un ostacolo principale alla guarigione di molti pazienti. Le cause di tale resistenza sono molteplici e possono essere distinte in “farmacologiche” e “cellulari”. Fattori farmacologici che possono limitare l’efficacia della terapia sono rappresentati, ad esempio, dall’impiego di dosi, vie o schemi di somministrazione inadeguati, anche in relazione al fatto che il tessuto tumorale spesso non è facilmente accessibile ai farmaci: perché localizzato in organi “santuario”, protetti da barriere (come quella ematoencefalica), oppure perché poco vascolarizzato. Le caratteristiche della resistenza cellulare sono state largamente analizzate negli ultimi anni, a partire dalla formulazione, nel 1979, da parte di Goldie e Coldman di un modello matematico, peraltro vicino a quello proponibile per diversi aspetti della resistenza batterica agli antibiotici

Ibrutinib and Bruton's tyrosine kinase inhibitors in chronic lymphocytic leukemia: focus on atrial fibrillation and ventricular tachyarrhythmias/sudden cardiac death

Background: The natural history of chronic lymphocytic leukemia (CLL) was dramatically improved by the introduction of ibrutinib, a Bruton's kinase (BTK) inhibitor. In this review we aimed to summarize and critically evaluate the association between first and second generation BTK inhibitors and the risk of atrial fibrillation (AF) and ventricular arrhythmias (VA). Summary: Since the first clinical experience, the development of AF was observed as the result of off-target effects that likely combined with patient's predisposing risk factors and concomitant cardiac morbidities. More recently both ibrutinib dose reduction and arrhythmia management allowed long-term treatment, with positive effects on progression-free survival and reduced all-cause mortality as well. Second-generation BTK inhibitors, acalabrutinib and zanubrutinib have been tested and validated in CLL. A lower occurrence of AF as compared with ibrutinib has been found, although AF has always been a secondary endpoint of all studies that probed these agents. Key Messages: For this reason, caution should be exercised before concluding that second-generation BTK inhibitors are safer than ibrutinib. Recent data on the effectiveness of ibrutinib over a follow-up of 8 years show a remarkable benefit on all-cause mortality, which is of great value also for interpreting the clinical impact of the few cases of VA and sudden cardiac death (SCD) reported for ibrutinib, independently of QT lengthening. Since a risk of VA and SCD has been recently reported also during treatment with second-generation BTK inhibitors, it appears that this risk, usually reaching its maximum size effect at long-term follow-up, likely denotes a class effect of BTK-inhibitors

FARMACI ANTIMICROTUBULARI

I microtubuli sono dei componenti del citoscheletro essenziali per lo svolgimento della normale divisione nucleare, in quanto formano il fuso mitotico, la struttura cellulare responsabile della corretta ripartizione dei cromosomi nelle cellule figlie. Inoltre, svolgono altre funzioni correlate con il mantenimento della morfologia cellulare e la regolazione di vari processi dinamici come la motilità, la fagocitosi, il trasporto assonico e la secrezione cellulare. La loro struttura altamente dinamica è stata chiarita solo recentemente; in effetti i microtubuli, costituiti dalla giustapposizione di dimeri della tubulina-alfa e -beta, sono costantemente sottoposti ad un processo di montaggio e smontaggio, in maniera che la loro lunghezza si mantenga costante (treadmilling)