AGRYLIN Capsule Ref.[10742] Active ingredients: Anagrelide

In blood withdrawn from normal volunteers treated with anagrelide, a disruption was found in the postmitotic phase of megakaryocyte development and a reduction in megakaryocyte size and ploidy. At therapeutic doses, anagrelide does not produce significant changes in white cell counts or coagulation parameters, and may have a small, but clinically insignificant effect on red cell parameters. The active metabolite, 3-hydroxy anagrelide, has similar potency and efficacy to that of anagrelide in the platelet lowering effect; however, exposure (measured by plasma AUC) to 3-hydroxy anagrelide is approximately 2-fold higher compared to anagrelide. Anagrelide and 3-hydroxy anagrelide inhibit cyclic AMP phosphodiesterase 3 (PDE3) and 3-hydroxy anagrelide is approximately forty times more potent than anagrelide (IC_50s = 0.9 and 36 nM, respectively). PDE3 inhibition does not alter platelet production. PDE3 inhibitors, as a class can inhibit platelet aggregation. However, significant inhibition of platelet aggregation is observed only at doses of anagrelide higher than those typically required to reduce platelet count. PDE3 inhibitors have cardiovascular (CV) effects including vasodilation, positive inotropy and chronotropy.

Cardiac Electrophysiology

The effect of anagrelide dose (0.5 mg and 2.5 mg single doses) on the heart rate and QTc interval prolongation potential was evaluated in a double-blind, randomized, placebo- and active-controlled, cross-over study in 60 healthy adult men and women.

A dose-related increase in heart rate was observed, with the maximum increase occurring around the time of maximal drug concentration (0.5–4 hours). The maximum change in mean heart rate occurred at 2 hours after administration and was +7.8 beats per minute (bpm) for 0.5 mg and +29.1 bpm for 2.5 mg.

Dose-related increase in mean QTc was observed. The maximum mean (95% upper confidence bound) change in QTcI (individual subject correction) from placebo after baseline-correction was 7.0 (9.8) ms and 13.0 (15.7) ms following anagrelide doses of 0.5 mg and 2.5 mg, respectively.

Dose proportionality has been found in the dose range 0.5 mg to 2.5 mg.

Absorption

Following oral administration of AGRYLIN, at least 70% is absorbed from the gastrointestinal tract. In fasted subjects, anagrelide peak plasma concentrations occur within about 1 hour after administration.

Pharmacokinetic data obtained from healthy volunteers comparing the pharmacokinetics of anagrelide in the fed and fasted states showed that administration of a 1 mg dose of anagrelide with food decreased the C_max by 14%, but increased the AUC by 20%. Food decreased the C_max of the active metabolite 3-hydroxy anagrelide by 29%, although it had no effect on the AUC.

Metabolism

Anagrelide is primarily metabolized by CYP1A2 to the active metabolite, 3-hydroxy anagrelide, which is subsequently metabolized by CYP1A2 to the inactive metabolite, RL603. Less than 1% of the administered dose is recovered in the urine as anagrelide, and approximately 3% and 16-20% of the administered dose is recovered as 3-hydroxy anagrelide and RL603, respectively.

Elimination

Anagrelide and 3-hydroxy anagrelide are eliminated with plasma half-lives of approximately 1.5 and 2.5 hours, respectively. Anagrelide and 3-hydroxy anagrelide do not accumulate in plasma when the clinical dose regimens are administered.

Drug Interactions

Aspirin

In two pharmacodynamic interaction studies in healthy subjects, co-administration of single-dose anagrelide 1 mg and aspirin 900 mg or repeat-dose anagrelide 1 mg once daily and aspirin 75 mg once daily showed greater ex vivo anti-platelet aggregation effects than administration of aspirin alone. Co-administered anagrelide 1 mg and aspirin 900 mg single-doses had no effect on bleeding time, prothrombin time (PT) or activated partial thromboplastin time (aPTT).

Digoxin or warfarin

In vivo interaction studies in humans have demonstrated that anagrelide does not affect the pharmacokinetic properties of digoxin or warfarin, nor does digoxin or warfarin affect the pharmacokinetic properties of anagrelide.

Specific Populations

Pediatric

Dose-normalized C_max and AUC of anagrelide were higher in children and adolescents (age range 7 through 16 years) with essential thrombocythemia, by 17% and 56%, respectively, than in adult patients (19 through 57 years).

Geriatric

C_max and AUC of anagrelide were 36% and 61% higher, respectively, in elderly patients (age range 65 through 75 years), than in younger adults (age range 22 through 50 years), but C_max and AUC of the active metabolite, 3-hydroxy anagrelide, were 42% and 37% lower, respectively, in the elderly patients.

Renal Impairment

Pharmacokinetic study at a single dose of 1 mg anagrelide in subjects with severe renal impairment (creatinine clearance <30 mL/min) showed no significant effects on the pharmacokinetics of anagrelide.

Hepatic Impairment

A pharmacokinetic study at a single dose of 1 mg anagrelide in subjects with moderate hepatic impairment (Child Pugh score 7-9) showed a 2-fold increase in mean anagrelide C_max and an 8-fold increase in total exposure (AUC) to anagrelide compared with healthy subjects. Additionally, subjects with moderate hepatic impairment showed 24% lower mean 3-hydroxy anagrelide C_max and 77% higher mean 3-hydroxy anagrelide AUC compared to healthy subjects.

In a two-year rat carcinogenicity study a higher incidence of uterine adenocarcinoma, relative to controls, was observed in females receiving 30 mg/kg/day (at least 174 times human AUC exposure after a 1 mg twice daily dose). Adrenal pheochromocytomas were increased relative to controls in males receiving 3 mg/kg/day and above, and in females receiving 10 mg/kg/day and above (at least 10 and 18 times respectively human AUC exposure after a 1 mg twice daily dose).

Anagrelide hydrochloride was not mutagenic in the bacterial mutagenesis (Ames) assay or the mouse lymphoma cell (L5178Y, TK+/-) forward mutation assay, and was not clastogenic in the in vitro chromosome aberration assay using human lymphocytes or the in vivo mouse micronucleus test.

Anagrelide hydrochloride at oral doses up to 240 mg/kg/day (233 times the recommended human dose of 10 mg/day based on body surface area) had no effect on fertility and reproductive function of male rats. However, in fertility studies in female rats, oral doses of 30 mg/kg/day (29 times the recommended maximum human dose based on body surface area) or higher resulted in increased pre- and post-implantation loss and a decrease in the number of live embryos.

In the 2-year rat study, a significant increase in non-neoplastic lesions was observed in anagrelide treated males and females in the adrenal (medullary hyperplasia), heart (myocardial hypertrophy and chamber distension), kidney (hydronephrosis, tubular dilation and urothelial hyperplasia), and bone (femur enostosis). Vascular effects were observed in tissues of the pancreas (arteritis/periarteritis, intimal proliferation, and medial hypertrophy), kidney (arteritis/periarteritis, intimal proliferation, and medial hypertrophy), sciatic nerve (vascular mineralization), and testes (tubular atrophy and vascular infarct) in anagrelide-treated males.

Clinical Studies in Adult Patients

A total of 942 patients with myeloproliferative neoplasms including 551 patients with Essential Thrombocythemia (ET), 117 patients with Polycythemia Vera (PV), 178 patients with Chronic Myelogenous Leukemia (CML), and 96 patients with other myeloproliferative neoplasms (OMPN), were treated with AGRYLIN in three clinical trials. Patients with OMPN included 87 patients who had Myeloid Metaplasia with Myelofibrosis (MMM), and 9 patients who had unclassified myeloproliferative neoplasms.

Patients were enrolled in clinical trials if their platelet count was ≥900,000/µL on two occasions or ≥650,000/µL on two occasions with documentation of symptoms associated with thrombocythemia. The mean duration of AGRYLIN therapy for ET, PV, CML, and OMPN patients was 65, 67, 40, and 44 weeks, respectively; 23% of patients received treatment for 2 years. Patients were treated with AGRYLIN starting at doses of 0.5-2.0 mg every 6 hours. The dose was increased if the platelet count was still high, but to no more than 12 mg each day. Efficacy was defined as reduction of platelet count to or near physiologic levels (150,000-400,000/µL). The criteria for defining subjects as “responders” were reduction in platelets for at least 4 weeks to ≤600,000/µL, or by at least 50% from baseline value. Subjects treated for less than 4 weeks were not considered evaluable. The results are depicted graphically below:

^* × 10³/µL
^† Nine hundred and forty-two subjects with myeloproliferative neoplasms were enrolled in three research studies. Of these, 923 had platelet counts measured over the duration of the studies.

AGRYLIN was effective in phlebotomized patients as well as in patients treated with other concomitant therapies including hydroxyurea, aspirin, interferon, radioactive phosphorus, and alkylating agents.

Clinical Study in Pediatric Patients

An open-label safety and PK/PD study was conducted in 18 pediatric patients 7 through 16 years of age (8 children 7 through 11 years of age and 10 adolescents 12 through 16 years of age, mean age of 12 years; 8 males and 10 females) with thrombocythemia secondary to ET as compared to 17 adult patients (mean age of 66 years, 9 males and 8 females). Prior to entry on to the study, 17 of 18 pediatric patients and 12 of 17 adult patients had received AGRYLIN treatment for an average of 2 years. The median starting total daily dose, determined by retrospective chart review, for pediatric and adult patients with ET who had received AGRYLIN prior to study entry was 1 mg for each of the three age groups (7 through 11 and 12 through 16 years of age and adults). The starting dose for 6 AGRYLIN-naive patients at study entry was 0.5 mg once daily. At study completion, the median total daily maintenance doses were similar across age groups, median of 1.75 mg for children of 7 through 11 years of age, 2.25 mg in adolescents 12 through 16 years of age, and 1.5 mg for adults.