• Idelalisib as upfront therapy for CLL caused an early hepatotoxicity in a subset of primarily younger patients with IGHV-mutated disease.• Multiple lines of evidence suggest that this adverse effect is immune mediated, perhaps through inhibition of regulatory T cells.Idelalisib is a small-molecule inhibitor of PI3Kd with demonstrated efficacy for the treatment of relapsed/refractory chronic lymphocytic leukemia (CLL). To evaluate idelalisib as front-line therapy, we enrolled 24 subjects in a phase 2 study consisting of 2 months of idelalisib monotherapy followed by 6 months of combination therapy with idelalisib and the anti-CD20 antibody ofatumumab. After a median follow-up period of 14.7 months, hepatotoxicity was found to be a frequent and often severe adverse event. A total of 19 subjects (79%) experienced either grade ‡1 ALT or AST elevation during the study, and 13 subjects (54%) experienced grade ‡3 transaminitis. The median time to development of transaminitis was 28 days, occurring before ofatumumab introduction. Younger age and mutated immunoglobulin heavy chain status were significant risk factors for the development of hepatotoxicity. Multiple lines of evidence suggest that this hepatotoxicity was immune mediated. A lymphocytic infiltrate was seen on liver biopsy specimens taken from 2 subjects with transaminitis, and levels of the proinflammatory cytokines CCL-3 and CCL-4 were higher in subjects experiencing hepatotoxicity. All cases of transaminitis resolved either by holding the drug, initiating immunosuppressants, or both, and rates of recurrent toxicity were lower in patients taking steroids when idelalisib was reinitiated. A decrease in peripheral blood regulatory T cells was seen in patients experiencing toxicity on therapy, which is consistent with an immune-mediated mechanism. These results suggest that caution should be taken as drugs within this class are developed for CLL, particularly in younger patients who have not received prior disease-specific therapy. This study was registered at www.clinicaltrials.gov as #NCT02135133. (Blood. 2016;128(2):195-203)

Summary Oncogenic mutations in the small Ras GTPases KRas, HRas, or NRas render the encoded proteins constitutively GTP-bound and active, which promote cancer [1]. Ras proteins share ~85% amino acid identity [2], are activated by [3] and signal through [4] the same proteins, and can exhibit functional redundancy [5][6]. Nevertheless, manipulating expression or activation of each isoform yields different cellular responses [7–10] and tumorigenic phenotypes [11–13], even when different ras genes are expressed from the same locus [6]. We now report a novel regulatory mechanism hardwired into the very sequence of RAS genes that underlies how such similar proteins impact tumorigenesis differently. Specifically, despite their high sequence similarity, KRAS is poorly translated compared to HRAS due to enrichment in genomically underrepresented, or rare, codons. Converting rare to common codons increased KRas expression and tumorigenicity to mirror that of HRas. Furthermore, in a genome-wide survey similar gene pairs with opposing codon bias were identified that not only manifested dichotomous protein expression, but were also enriched in key signaling protein classes and pathways. Thus, synonymous nucleotide differences affecting codon usage account for differences between HRas and KRas expression and function, and may represent a broader regulation strategy in cell signaling.

Ibrutinib, approved by the US Food and Drug Administration (FDA), is an inhibitor of Bruton tyrosine kinase (BTK). [1][2][3][4][5] Ibrutinib use is associated with atrial fibrillation (AF), with an incidence of 5% to 6% after 18 months on therapy [4][5][6] and up to 16% with longer follow-up. 2,7Prompted by an episode of unexplained ventricular tachycardia (VT) in a patient taking ibrutinib, we hypothesized that ibrutinib use may be associated with ventricular arrhythmias (VAs). To further investigate, we gathered 4 cases of VAs in ibrutinib-treated patients, mined the FDA Adverse Event Reporting System (FAERS) for additional reports of VAs in patients receiving ibrutinib, and estimated incidence rates of VAs in clinical trials of ibrutinib. Individual patients were enrolled on data collection protocols approved by institutional review boards or collected from publicly available data. We obtained adverse events (AEs) for ibrutinib reported to the FAERS from the fourth quarter of 2013 (ibrutinib was approved by the FDA in November 2013) to the fourth quarter of 2015. Additional details were requested for AE reports with the following preferred search terms: ventricular arrhythmia, ventricular fibrillation (VF), Brugada syndrome, right bundle branch block, cardiac arrest, cardiac death, cardiac fibrillation, cardiorespiratory arrest, conduction disorder, sudden death, sudden cardiac death, ventricular extrasystoles, and ventricular tachycardia. If dates of ibrutinib discontinuation, cardiac events, or death were redacted, we used the date when the patient was last seen alive or when the event was filed. Patients for whom there was not enough information to determine the timing of ibrutinib administration or for whom ibrutinib was discontinued before the event were excluded. Clinical trial data were drawn from published results. Median time on therapy was assumed to be mean time on therapy to calculate total time on therapy for the group of interest. Statistical analysis was performed by using STATA 14 (STATA, College Station, TX).Our index patient was a 60-year-old man who had chronic lymphocytic leukemia (CLL) and no prior cardiac history. He was a vigorous exerciser with resting sinus bradycardia. Two months after beginning ibrutinib, he reported new palpitations. He experienced syncope 86 days after initiating ibrutinib. Frequent premature ventricular contractions (PVCs) and nonsustained VT were identified ( Figure 1A). An exercise stress test was negative for ischemic changes, but polymorphic VT occurred when he transferred from stretcher to treadmill ( Figure 1B). Cardiac catheterization and echocardiogram were normal. Electrophysiologic studies induced PVCs originating from the moderator band but could not ablate the focus; therefore, he was started on antiarrhythmics and a cardioverter-defibrillator was implanted. Ibrutinib was resumed at discharge. Attempted downtitration of his quinidine later resulted in an increase in PVCs. He has since been maintained on ibrutinib, quinidine, and metoprolol for 28 mont...

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