The European Medicines Agency Review of Gilteritinib (Xospata) for the Treatment of Adult Patients with Relapsed or Refractory Acute Myeloid Leukemia with an FLT3 Mutation.

On October 24, 2019, a marketing authorization valid through the European Union (EU) was issued for gilteritinib monotherapy for adult patients who have relapsed or refractory acute myeloid leukemia (AML) with an Fms-like tyrosine kinase 3 (FLT3) mutation. Gilteritinib inhibits FLT3 receptor signaling and proliferation in cells exogenously expressing FLT3 including FLT3 internal tandem duplication (ITD), FLT3 D835Y, and FLT3 ITD D835Y, and it induced apoptosis in leukemic cells expressing FLT3 ITD. The recommended starting dose of gilteritinib is 120 mg (three 40 mg tablets) once daily. Gilteritinib was evaluated in one, phase III, open-label, multicenter, randomized study of gilteritinib (n = 247, gilteritinib arm) versus salvage chemotherapy (n = 124, salvage chemotherapy arm) in patients with relapsed or refractory AML with FLT3 mutation. Overall survival (OS) was statistically significantly different between the two groups with a median OS of 9.3 months in the gilteritinib arm compared with 5.6 months for salvage chemotherapy (hazard ratio, 0.637; 95% confidence interval, 0.490-0.830; p = .0004 one-sided log-rank test). The most common adverse reactions with gilteritinib treatment were blood creatine phosphokinase increase, alanine aminotransferase increase, aspartate aminotransferase increase, blood alkaline phosphatase increase, diarrhea, fatigue, nausea, constipation, cough, peripheral edema, dyspnea, dizziness, hypotension, pain in extremity, asthenia, arthralgia, and myalgia. The objective of this article is to summarize the scientific review of the application leading to regulatory approval in the EU. IMPLICATIONS FOR PRACTICE: Xospata was approved in the European Union as monotherapy for the treatment of adult patients with relapsed or refractory acute myeloid leukemia (AML) with an Fms-like tyrosine kinase 3 (FLT3) mutation. Gilteritinib resulted in a clinically meaningful and statistically significant improvement of overall survival compared with salvage chemotherapy. At the time of the marketing authorization of gilteritinib, there were no approved standard therapies specifically for adult patients diagnosed with relapsed or refractory AML with FLT3 mutation. In terms of safety, the overall accepted safety profile was considered manageable.

Sustained diacylglycerol accumulation resulting from prolonged G protein-coupled receptor agonist-induced phosphoinositide breakdown in hepatocytes.

Studies in various cells have led to the idea that agonist-stimulated diacylglycerol (DAG) generation results from an early, transient phospholipase C (PLC)-catalyzed phosphoinositide breakdown, while a more sustained elevation of DAG originates from phosphatidylcholine (PC). We have examined this issue further, using cultured rat hepatocytes, and report here that various G protein-coupled receptor (GPCR) agonists, including vasopressin (VP), angiotensin II (Ang.II), prostaglandin F2alpha, and norepinephrine (NE), may give rise to a prolonged phosphoinositide hydrolysis. Preincubation of hepatocytes with 1-butanol to prevent conversion of phosphatidic acid (PA) did not affect the agonist-induced DAG accumulation, suggesting that phospholipase D-mediated breakdown of PC was not involved. In contrast, the GPCR agonists induced phosphoinositide turnover, assessed by accumulation of inositol phosphates, that was sustained for up to 18 h, even under conditions where PLC was partially desensitized. Pretreatment of hepatocytes with wortmannin, to inhibit synthesis of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate (PIP2), prevented agonist-induced inositol phosphate and DAG accumulation. Upon VP stimulation the level of PIP) declined, but only transiently, while increases in inositol 1,4,5-trisphosphate (InsP3) and DAG mass were sustained, suggesting that efficient resynthesis of PIP2 allowed sustained PLC activity. This was confirmed when cells were pretreated with wortmannin to prevent resynthesis of PIP2. Furthermore, metabolism of InsP3 was rapid, compared to that of DAG, with a more than 20-fold difference in half-life. Thus, rapid metabolism of InsP3 and efficient resynthesis of PIP2 may account for the larger amount of DAG generated and the more sustained time course, compared to InsP3. The results suggest that DAG accumulation that is sustained for many hours in response to VP, Ang.II, NE, and prostaglandin F2alpha in hepatocytes is mainly due to phosphoinositide breakdown.

Ca2+-dependent elevation of inositol 1,4,5-trisphosphate level induced by freezing or homogenization of tissues and cells.

Various cells and tissues contain high basal levels of inositol 1,4,5-trisphosphate, raising questions about the functional significance of inositol 1,4,5-trisphosphate in some tissues such as the heart. We used intact tissue and isolated cells from heart and liver of adult rats to examine if different fixation procedures might artificially elevate the level of inositol 1,4,5-trisphosphate. The basal level of inositol 1,4,5-trisphosphate in intact, freeze-clamped cardiac tissue from adult rats was 10 times higher than in isolated, non-frozen cardiomyocytes, while freeze-clamped liver contained approximately 4 times higher inositol 1,4,5-trisphosphate levels than isolated, non-frozen hepatocytes. Stimulation with norepinephrine induced a significant increase in the inositol 1,4,5-trisphosphate level in isolated cardiomyocytes, whereas no significant increase was observed in freeze-clamped cardiac tissue. Freezing of isolated cardiomyocytes or hepatocytes before extraction increased basal inositol 1,4,5-trisphosphate levels 3 times. In cellular homogenates prepared in the presence of EGTA and stored at 4 degrees , readdition of calcium resulted in a time-dependent increase in inositol 1,4,5-trisphosphate mass and a decrease in the mass of phosphatidylinositol 4,5-bisphosphate (PIP(2)). The reaction was essentially complete within 30 sec. in homogenates from cardiomyocytes, while PIP(2) hydrolysis was slower in hepatocyte homogenates. Perfusion of intact rat hearts with EGTA present during the last 2 min. of perfusion, followed by freeze-clamping, resulted in basal inositol 1,4,5-trisphosphate levels comparable to those in isolated cardiomyocytes, and norepinephrine stimulation increased inositol 1,4,5-trisphosphate mass by approximately 80%. The presence of EGTA did not significantly affect PIP(2) levels in perfused hearts. The results suggest that freezing or homogenization of intact tissue and isolated cells may result in Ca(2+)-dependent activation of phospholipase C, leading to high basal inositol 1,4,5-trisphosphate levels that may mask agonist-induced changes.