Essential thrombocythemia is a chronic myeloproliferative neoplasm characterized by sustained thrombocytosis, bone marrow megakaryocytic hyperplasia and an increased risk of thrombosis and hemorrhage. The goal of treatment is to prevent the development of vascular complications without increasing the risk of transformation. Patients aged>60 years or a history of thrombosis have a high risk of thrombosis while those with a platelet count>1,500x10(9)/l have a higher risk of hemorrhage. Patients with low-risk essential thrombocythemia can be managed appropriately with low-dose of acetylsalicylic acid or even observation only, while patients with a high-risk disease are candidates to receive cytoreductive treatment, hydroxyurea being the first choice therapy. Anagrelide is the most suitable option for patients with resistance or intolerance to hydroxyurea. All patients must be submitted to a rigorous control of cardiovascular risk factors.

Although anagrelide is widely used for the treatment of essential thrombocythemia (ET) in the USA and Europe, it is not licensed in Japan. Existing literature has reported differences in polymorphism and activity of CYP1A2 in Japanese and non-Japanese ethnic groups, which may alter anagrelide metabolism. We intended to identify the optimum dosage of anagrelide in treatment-naïve Japanese patients with ET and assess its long-term safety and efficacy. Twelve patients with ET and a platelet count of ≥ 80 × 10(4)/μL were enrolled. Anagrelide was administered at an initial dose of 0.5 mg/day (weeks 1-4), then increased to 1.0 mg/day (weeks 5-8). During the following maintenance (weeks 9-52) and continuation periods (weeks 53-104), the dose was adjusted according to patient safety data and to maintain target platelet counts (<60 × 10(4)/μL). Increasing the dose led to a decrease in mean platelet count, and target platelet counts were maintained in 11 patients. Adverse events were mild or moderate, and none led to discontinuation. This cohort of Japanese patients exhibited higher pharmacokinetic exposures of anagrelide and its active metabolite than those previously documented in non-Japanese patients. These differences were modest, suggesting specific dosing regimens for Japanese patients are not required.

This study investigates whether the response criteria proposed by the European LeukemiaNet (ELN) to evaluate cytoreductive therapies in essential thrombocythemia (ET) correlate with clinically relevant outcomes in patients receiving anagrelide. We evaluated 154 ET patients treated with anagrelide (upfront in 87) for a median of 2.9 years. Complete response (CR), partial response, and no response were observed in 56, 30.5, and 13.5 % patients, respectively. Only 38 patients (25 %) achieved a sustained CR. Overall, the aggregated time on CR and without CR was 200.1 and 333.6 person-years, respectively. The incidence rate of thrombosis and hemorrhage was independent of the CR status. The only factor associated with shorter survival after anagrelide start was the patient's age, whereas achieving a CR with anagrelide had no predictive value for subsequent survival. In conclusion, CR according to the ELN definition is not associated with any measurable clinical benefit in ET patients treated with anagrelide.

RAD001 is currently used as an immunosuppressant and anticancer drug. Megakaryocyte (MK) differentiation includes development from pluripotent stem cells to proliferation and differentiation toward MK formation and platelet maturation. Our preliminary assay showed that RAD001 might stimulate MK differentiation; however, the exact regulatory mechanisms needed to be elucidated. By the ex vivo assay, RAD001 induced MK differentiation in human haematopoietic stem cells, with both the stimulation of CFU-GM colony formation and CD61 surface marker expression. Then, BALB/c mice were orally administrated with or without agrylin and/or RAD001 for 15 days. The platelet count and bone marrow CFU-MK colony formation were eliminated by agrylin, but unchanged in RAD001 and RAD001 plus agrylin mice. An ex vivo assay of bone marrow-derived stem cells demonstrated that RAD001 increased the number of CFU-MK colonies. The MK count in bone section indicated the decreased effect by agrylin and then recovered by RAD001. The level of plasma thrombopoietin was also enhanced in RAD001-treated mice. The effect of RAD001 on human leukaemic K562 and HEL cells showed the growth inhibition and MK differentiation activities; including morphological observation, CD41 and CD61 expression, and platelet factor 4 secretion. In RAD001-treated HEL cells, p-STAT3 expression, STAT3 translocation, and STAT3-DNA binding activity were up-regulated. Furthermore, STAT3 siRNA decreased the p-STAT3 and CD61 expression, as well as the CD61 fluorescence intensity, indicating that STAT3 may be critical in RAD001-mediated MK differentiation. Conclusion, the present study demonstrated that RAD001 might have the capacity to induce MK differentiation through the up-regulation of STAT3 signalling.

High platelet counts in essential thrombocythemia (ET) can be effectively lowered by treatment with either anagrelide or hydroxyurea. In 259 previously untreated, high-risk patients with ET, diagnosed according to the World Health Organization classification system, the efficacy and tolerability of anagrelide compared with hydroxyurea were investigated in a prospective randomized noninferiority phase 3 study in an a priori-ordered hypothesis. Confirmatory proof of the noninferiority of anagrelide was achieved after 6 months using the primary end point criteria and was further confirmed after an observation time of 12 and 36 months for platelet counts, hemoglobin levels, leukocyte counts (P < .001), and ET-related events (HR, 1.19 [95% CI, 0.61-2.30], 1.03 [95% CI, 0.57-1.81], and 0.92 [95% CI, 0.57-1.46], respectively). During the total observation time of 730 patient-years, there was no significant difference between the anagrelide and hydroxyurea group regarding incidences of major arterial (7 vs 8) and venous (2 vs 6) thrombosis, severe bleeding events (5 vs 2), minor arterial (24 vs 20) and venous (3 vs 3) thrombosis and minor bleeding events (18 vs 15), or rates of discontinuation (adverse events 12 vs 15 or lack of response 5 vs 2). Disease transformation into myelofibrosis or secondary leukemia was not reported. Anagrelide as a selective platelet-lowering agent is not inferior compared with hydroxyurea in the prevention of thrombotic complications in patients with ET diagnosed according to the World Health Organization system. This trial was registered at http://www.clinicaltrials.gov as #NCT01065038.

EXELS is an ongoing phase IV non-interventional study; 3643 high-risk patients with essential thrombocythemia (ET) were recruited across 13 European countries. We report patient characteristics and cytoreductive treatment patterns of ET across Europe. Hydroxycarbamide (HC; 64.3%) and anagrelide (22.0%) were the two main cytoreductive treatments prescribed. The proportions of patients taking either HC or anagrelide varied across countries, as did the number of patients receiving anti-aggregatory therapy in addition to cytoreductive treatment. This real-world evidence demonstrates that, generally, treatment patterns of ET across Europe adhere to expert recommendations, with some notable variations between countries.

The median age of patients diagnosed with essential thrombocythaemia (ET) is 65-70 years but the management of very elderly patients (aged >80 years) with ET has not been well characterized.This study aimed to document the treatment patterns of very elderly patients with ET in a multinational, real-world setting.EXELS (Evaluation of Xagrid Efficacy and Long-term Safety) is a phase IV observational study, designed to monitor the efficacy and safety of cytoreductive therapies in clinical practice. In total, 3,598 high-risk patients with ET were recruited from May 2005 to April 2009, in 13 European countries. Data were collected at registration and every 6 months thereafter for 5 years. This analysis was performed on a data-cut taken approximately 2 years after the last patient was registered.In total, 395 patients aged >80 years at registration into EXELS were included in the analysis; of these, 42.2 % had experienced a previous thrombohaemorrhagic event.At registration, the most frequently prescribed cytoreductive therapy for patients aged >80 years was hydroxycarbamide (HC), which accounted for 82.8 % of patients whereas anagrelide use was less frequent (8.6 %). Very elderly patients were more likely to be switched from anagrelide than from HC (47.1 vs. 17.4 %; 95 % confidence interval for difference in proportion 12.4-46.9; Chi-squared test p < 0.001). Median platelet count during treatment was ~430 × 10(9)/L. In patients aged >80 years, the main reason for switch was intolerance/side effects (34.1 %); 0/16 patients reported treatment with anagrelide was non-efficacious compared with 8/57 (14 %) patients receiving HC, and 7/16 (43.8 %) anagrelide patients switched because of intolerance versus 18/57 (31.6 %) patients receiving HC. At least one predefined clinical event (PDE) was experienced by 27.3 % of patients aged >80 years. The most common PDEs reported in the very elderly age group were death (non-PDE related; 11.1 %), other cardiovascular symptoms (5.8 %), haematological transformation (3.8 %), congestive heart failure (3.3 %), myocardial infarction and angina (2.8 %), and thromboembolic events (6.3 %).Well-tolerated and effective cytoreductive therapy has been achieved in patients aged >80 years by following individual treatment modalities that appear in agreement with the recent European LeukemiaNet (ELN) guidelines.

Essential thrombocythaemia (ET) is a rare clonal myeloproliferative disorder characterized by a sustained elevation in platelet count and megakaryocyte hyperplasia. Anagrelide is used in the treatment of ET, where it has been shown to reduce platelet count. Anagrelide is metabolized by cytochrome P450 (CYP) 1A2, and previous studies of the effect of food on the bioavailability and pharmacokinetics of anagrelide were conducted prior to the identification of the active metabolite, 3-hydroxyanagrelide.The objectives of this study were to determine the effect of food and caffeine on the pharmacokinetics of anagrelide and its active metabolite, 3-hydroxyanagrelide, to monitor electrocardiogram (ECG) parameters following drug administration, and to document the relationship between palpitations, ECG changes and caffeine intakeThirty-five healthy subjects who received 1 mg of anagrelide following either a 10-h fast or within 30 min of a standardized breakfast, including two cups of coffee, were studied.Time to maximum (peak) plasma concentration (C(max)) of anagrelide was 4.0 h in the fed and 1.5 h in the fasted group (p < 0.05); similar results were observed for 3-hydroxyanagrelide. The mean C(max) of anagrelide was 4.45 ± 2.32 ng/mL and 5.08 ± 2.99 ng/mL in the fed/caffeine and fasted groups, respectively; peak concentrations were higher for 3-hydroxyanagrelide in both the fed/caffeine and fasted groups. The most frequent adverse events (AEs) were headache (60 %) and palpitations (40 %). There were no serious AEs and all ECGs were normal, although significant reductions in PR interval, QRS length and QT interval were observed in both groups. Heart rate increased after anagrelide administration in both fed/caffeine and fasted states (p < 0.01); however, increased heart rate was significantly more frequent in the fed/caffeine state than in the fasted state (p < 0.001 for heart rate increase in the first hour after drug administration). There was a trend towards a greater heart rate increase in subjects reporting palpitations than in those without (mean heart rate ± SD at 1 h: 10.1 ± 6.4 vs. 8.0 ± 8.4 beats/min [p = 0.35]; at 4 h: 12.7 ± 7.5 vs. 9.1 ± 8.8 beats/min [p = 0.10], respectively).We conclude that food/caffeine delayed absorption of anagrelide. Anagrelide was generally well tolerated and had small effects on ECG parameters and heart rate. Caffeine may be implicated in a higher increase in heart rate and increased frequency of palpitations observed following administration of anagrelide with food/caffeine versus fasting.

A simple, rapid, and stability-indicating reverse-phase liquid chromatographic assay method was developed for Anagrelide Hydrochloride (ANG) in the presence of its degradation products generated from forced decomposition studies. The HPLC separation was achieved on a C18 Inertsil column (250 mm × 4.6 mm i.d. particle size is 5 μm), using solution A, a mixture of 0.03 M potassium di-hydrogen phosphate pH-adjusted to 3.0 using ortho-phosphoric acid (buffer): methanol: acetonitrile (90:5:5, v/v/v), and solution B, which contains a mixture of buffer: acetonitrile (10:90, v/v). The UV detector was operated at 251 nm while column temperature was maintained at 40°C, and the gradient program had the flow rate of 1.0 mL min(-1). The developed method was validated as per ICH guidelines with respect to specificity, linearity, precision, accuracy, robustness, and limit of quantification. The method was found to be simple, specific, precise, accurate, and reproducible. Selectivity was validated by subjecting the stock solution of ANG to acidic, basic, photolysis, oxidative, and thermal degradation. The calibration curve was found to be linear in the concentration range of 0.05-152 μg mL(-1) (R(2) = 0.9991). The peaks of degradation products did not interfere with that of pure ANG. The utility of the developed method was examined by analyzing the tablets containing ANG.

During long term follow-up of a cohort of patients with essential thrombocythemia (ET) and polycythemia vera (PV) a higher than expected incidence of myelofibrosis (MF) was noted. In order to test if the explanation could be found in the diagnostic criteria a re-evaluation of diagnosis using the 2008 WHO diagnostic criteria for ET and MF was performed.This prospective study of 60 patients with ET and PV was set up in 1998 to evaluate the long-term efficacy and tolerability of anagrelide treatment. Bone marrow trephine biopsies were requested from study start, after 2 and 7 years of follow-up. A blinded re-evaluation of the bone marrow trephines was performed. The 2008 WHO bone marrow criteria were used for diagnosis and fibrosis grading.Of 40 patients with an initial diagnosis of ET, 21 were confirmed as 'true ET' whereas 17 were reclassified as primary myelofibrosis (PMF) (12 PMF-0, 3 PMF-1, 2 PMF-2) and 2 as myeloproliferative neoplasms of uncertain origin. After 7 years of follow-up, 19 of 21 patients with 'true ET' were alive, none had transformed to MF, leukemia, or myelodysplastic syndrome. In contrast, 4/17 patients reclassified as PMF had died, two patients transformed to myelodysplastic syndrome and 7 patients progressed to overt MF.We conclude that a blinded re-evaluation of bone marrow trephines from study start and after 7 years of follow-up using 2008 World Health Organization criteria was able to differentiate between true ET and PMF with a marked difference in follow-up outcome.