Warnings for Agrylin
Included as part of the "PRECAUTIONS" Section
Precautions for Agrylin
Please see BOX WARNING.
General
The decision to treat asymptomatic young adults with thrombocythemia secondary to myeloproliferative neoplasms should be individualized.
Abrupt treatment discontinuation or substantial reduction of AGRYLIN (anagrelide hydrochloride capsules) treatment dose should be avoided due to the risk of sudden increase in platelet counts, which may lead to potentially fatal thrombotic complications, such as cerebral infraction (BOX WARNING; DOSAGE AND ADMINISTRATION, Discontinuation). Thrombotic complications have been reported in patients following sudden treatment withdrawal, dose interruption (including medical procedures), and in patients at maintenance doses but in which platelet counts were above 600,000/mcL. Sudden discontinuation or interruption of AGRYLIN (anagrelide hydrochloride capsules) treatment is followed by an increase in platelet count. Following discontinuation of AGRYLIN, an increase in platelet count can be observed within four days. Patients should be advised how to recognize early signs and symptoms suggestive of thrombotic complications, such as cerebral infarction, and if symptoms occur to seek medical assistance.
Carcinogenesis And Mutagenesis
In a two-year rat carcinogenicity study, a higher incidence of uterine adenocarcinoma, relative to controls, was observed in females receiving the dose of 30mg/kg/day (at least 174 times human AUC exposure after a 1mg twice daily dose). Adrenal benign and malignant phaeochromocytomas were increased relative to controls in males at all dose levels (receiving 3mg/kg/day and above), and in females receiving the doses of 10 and 30mg/kg/day (at least 10 and 18 times respectively human AUC exposure after a 1mg twice daily dose).
Anagrelide produced no detectable or reproducible increases in gene mutational activity in studies conducted in vitro with mutant strains of Salmonella typhimurium in the Ames test, or in a mouse lymphoma mutagenesis assay, with or without a rat hepatic drug metabolising enzyme system.
In addition, no clastogenic activity was seen in vitro using cultured human peripheral lymphocytes or in vivo in a mouse bone marrow erythrocyte micronucleus assay. At the concentrations and doses employed in these studies, there was no indication that anagrelide was a potential mutagen either directly or after metabolic activation.
Cardiovascular
Due to the positive inotropic and chronotropic effects and cardiovascular side-effects (ADVERSE REACTIONS) of AGRYLIN, it should be used with caution in patients with known or suspected heart disease, and only if the potential benefits of therapy outweigh the potential risks.
A pre-treatment cardiovascular examination (including investigations such as echocardiograph, electrocardiogram) is recommended for all patients, along with careful monitoring during treatment and further investigations carried out as necessary. In humans, therapeutic doses of AGRYLIN may cause cardiovascular effects, including vasodilation, tachycardia, palpitations, Prinzmetal angina and congestive heart failure.
Anagrelide has been shown to increase the heart rate, resulting in an apparent increase in QTc interval of the electrocardiogram in healthy volunteers. The clinical impact of this effect is unknown (CLINICAL PHARMACOLOGY, Pharmacodynamics – Effects On Heart Rate And QTc Interval).
Caution should be taken when using anagrelide in patients with known risk factors for prolongation of the QT interval, such as congenital long QT syndrome, a known history of acquired QTc prolongation, medicinal products that can prolong QTc interval and hypokalemia, as cases of Torsades de pointes have been reported post market.
Care should also be taken in populations that may have a higher maximum plasma concentration (Cmax) of anagrelide or its active metabolite, 3-hydroxy-anagrelide, e.g., hepatic impairment (CLINICAL PHARMACOLOGY, Special Populations And Conditions) or use with CYP1A2 inhibitors (Drug-Drug Interactions).
Cases of pulmonary hypertension have been reported in patients treated with anagrelide. Patients should be evaluated for signs and symptoms of underlying cardiopulmonary disease prior to initiating and during anagrelide therapy.
Driving And Operating Machinery
Caution should be used when driving vehicles or machinery.
Hematologic
Use of concomitant AGRYLIN and acetylsalicylic acid has been associated with major hemorrhagic events (Drug-Drug Interactions).
Hepatic/Biliary/Pancreatic
Hepatic metabolism represents the major route of anagrelide clearance and liver function may therefore be expected to influence this process. AGRYLIN has not been studied in patients with severe hepatic impairment and is contraindicated (CONTRAINDICATIONS). Exposure to anagrelide is increased 8-fold in patients with moderate hepatic impairment (DOSAGE AND ADMINISTRATION; CLINICAL PHARMACOLOGY, Special Populations And Conditions – Hepatic Insufficiency). It is recommended that patients with mild and moderate hepatic impairment receive AGRYLIN only if, in the physician's judgment, the potential benefits of therapy outweigh the potential risks. Patients with mild or moderate hepatic impairment should be carefully and regularly monitored for cardiovascular effects and hepatic toxicity while receiving AGRYLIN (WARNINGS AND PRECAUTIONS, Cardiovascular, and Adverse Reactions). In patients with moderate hepatic impairment, a dosage reduction is required (DOSAGE AND ADMINISTRATION, Error! Reference source not found.).
Monitoring And Laboratory Tests
AGRYLIN therapy requires close clinical supervision of the patient. To monitor the effect of AGRYLIN and prevent the occurrence of thrombocytopenia, platelet counts should be performed every two days during the first week of treatment and at least weekly thereafter, until the maintenance dosage is reached. Typically, platelet count begins to respond within 7 to 14 days at the proper dosage. The time to complete response, defined as platelet count ≤600,000/mcL, ranged from 4 to 12 weeks. Most patients will experience an adequate response at a dose of 1.5 to 3.0mg/day.
In the event of dosage interruption or treatment withdrawal, the rebound in platelet count is variable, but platelet counts typically will start to rise within four days and return to baseline levels in one to two weeks, possibly rebounding above baseline values. Therefore, platelets should be monitored frequently (BOX WARNING, WARNINGS AND PRECAUTIONS).
In patients with hepatic insufficiency or renal insufficiency, liver function and kidney function tests should be performed at least once per month or when deemed necessary in the physician’s judgement (DOSAGE AND ADMINISTRATION). Electrolytes (potassium, magnesium and calcium) should also be monitored.
As cases of hepatitis have been reported from post-marketing surveillance, it is recommended that liver functions (ALT and AST) tests are performed before anagrelide treatment is initiated and at regular intervals thereafter (DOSAGE AND ADMINISTRATION; WARNINGS AND PRECAUTIONS, Hepatic/Biliary/Pancreatic; CLINICAL PHARMACOLOGY, Special Populations And Conditions).
Renal
It is recommended that patients with renal insufficiency (GFR1 <30 ml/min/1.73 m2) receive AGRYLIN when, in the physician's judgment, the potential benefits of therapy outweigh the potential risks. These patients should be monitored closely for signs of renal toxicity while receiving AGRYLIN (ADVERSE REACTIONS).
Respiratory
Interstitial Lung Diseases
Interstitial lung diseases (including allergic alveolitis, eosinophilic pneumonia and interstitial pneumonitis) have been reported to be associated with the use of anagrelide in post-marketing reports. Most cases presented with progressive dyspnea associated with lung infiltrations. The time of onset ranges from 1 week to several years after initiating anagrelide. In most cases, the symptoms improved after discontinuation of anagrelide (ADVERSE REACTIONS, Post- Market Adverse Reactions).
Sensitivity/Resistance
Due to the presence of lactose, patients with hereditary problems of galactose intolerance, glucose-galactose malabsorption or the Lapp lactase deficiency should not take AGRYLIN (see CONTRAINDICATIONS).
1 Glomerular filtration rate
Special Populations
Pregnant Women
AGRYLIN is not recommended in women who are or may become pregnant. Women of childbearing potential should be instructed that they must not be pregnant and that they should use contraception while taking AGRYLIN. AGRYLIN may cause fetal harm when administered to a pregnant woman. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential harm to the fetus. There are no adequate and well-controlled studies in pregnant women. AGRYLIN should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
In female pregnant rats administered AGRYLIN, implantation losses, reduction in fetal survival and body weight were observed at doses in excess of the therapeutic range (Nonclinical Toxicology, Reproductive And Developmental Toxicology).
Breast-feeding
It is not known whether this drug is excreted in human milk; however, excretion of anagreliderelated material into milk has been demonstrated in rats (CLINICAL PHARMACOLOGY, Pharmacokinetics). Because many drugs are excreted in human milk and because of the potential for serious adverse reaction in nursing infants from AGRYLIN, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Pediatrics
Pediatrics (<16 years of age): No data are available to Health Canada; therefore, Health Canada has not authorized an indication for pediatric use.
Geriatrics
The safety and effectiveness of AGRYLIN have not been evaluated in studies specific to the elderly. Pharmacokinetic (PK) differences between elderly and younger patients with essential thrombocythemia (ET) have been observed (CLINICAL PHARMACOLOGY, Special Populations and Conditions – Geriatrics; Dosage And Administration).
Nonclinical Toxicology
General Toxicology
Acute Toxicity
Acute oral doses of anagrelide as high as 2,500mg/kg in mice and 1,500mg/kg in the rat, caused decreased activity immediately after administration; all animals recovered within 1 to 2 days. Intraperitoneal administration of 500mg/kg of anagrelide to mice, resulted in the death of all animals within 3 days, while administration of 250mg/kg caused decreased activity with recovery by 2 days.
In dogs, diarrhea was observed 4 to 5 days after a single oral dose of 10mg/kg of anagrelide and after 1 to 2 days with doses of ≥50mg/kg. Emesis was also observed, 2 days after a dose of 100mg/kg and on the day of dosing with doses of ≥500mg/kg; all animals recovered.
Single oral doses of 200mg/kg of anagrelide in rhesus monkeys caused soft stools and a transient decrease in food consumption after 3 days; all animals recovered.
These results indicate that the acute oral LD50 is >2,500mg/kg in mice, >1,500mg/kg in the rat, >800mg/kg in dogs, and >200mg/kg in primates (rhesus monkey).
Long-Term Toxicity
Anagrelide was administered daily to rats by oral gavage for 27 days at doses of 50 to 1,000mg/kg/day. Findings included flushing of the ears, feet, and nose. Drug-related changes seen at 1,000mg/kg/day consisted of decreased platelet counts, retarded body weight gains in males, and mild fibrosis and myocarditis along with labored respiration and/or rales; one female died. In a 94-day study, administration of 4 to 12mg/kg/day of anagrelide resulted in dose-related intestinal tract lesions and increased liver, adrenal, and thyroid weights relative to body weight at the highest dose.
Administration of escalating oral doses up to 3,200mg/kg over a period of 7 days in dogs resulted in a decrease in food consumption, in females at doses as low as 100mg/kg, and in males at doses as low as 800mg/kg. Clinical signs of gastrointestinal upset were evident; all dogs exhibited loose stools, diarrhea, and ultimately vomited as the dose was increased. In a 28-day repeat-dose study in the dog, the only abnormalities reported with oral doses were diarrhea and vomiting at doses of 500 to 800mg/kg/day.
Multidose studies were performed in primates using oral doses of 10mg/kg/day for 14 days or 4 to 12mg/kg/day of anagrelide for up to 92 days of treatment. Clinical signs related to anagrelide treatment consisted of diarrhea, emesis, soft and/or loose stools and decreased food consumption.
Chronic toxicity studies were carried out for up to 12 months in rats and dogs. In the rat, doses of 120.5, 361.5, and 1,205mg/kg/day of anagrelide were administered orally by diet. Treatment-related findings included the following: hunched posture; dilated vagina in females; increases and decreases in body weight; increased food consumption; mild transient increases in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH), decreased platelet counts in females; changes in serum chemistry indicative of mild to moderate liver and kidney damage in all groups; increased cholesterol, decreased triglycerides, decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in males, increased creatinine in males, marginal increases in basal urea nitrogen (BUN) and creatinine in females, increased urine volume; liver and kidneys in all treated rats and adrenals in males were significantly increased in weight relative to body weight and/or brain weight; focal hyperplasia at the highest dose and pheochromocytomas at doses ≥361.5mg/kg/day. There were 24 deaths during the study (see Table 5); though none were attributed to anagrelide treatment, necropsy findings indicated kidney and liver damage.
Table 6: Unscheduled Deaths
|
Anagrelide (mg/kg/day) |
|
0 |
120.5 |
361.5 |
1,205 |
| Cause of Death * |
|
|
|
|
| Leukemia |
|
1M |
1M |
|
| Nephropathy |
|
2M |
|
|
| Inflammation/infection and/or hemorrhage/thrombi |
1M |
2M |
2M |
2M; 1F |
| Heart failure |
|
|
|
1M |
| Accident |
|
1M |
1F |
|
| Unknown |
|
1F |
3M |
5M |
| Total |
1M |
6M; 1F |
6M; 1F |
8M; 1F |
| * Animals may have had more than one finding at necropsy/histopathology |
In the chronic dog toxicity study, repeated exposure to 10 to 600mg/kg/day of anagrelide were associated with a variety of toxicities, including: diarrhea and emesis; significant reductions in red cell counts, hemoglobin, hematocrit, and platelet counts; a tendency toward increased kidney weight in both sexes and increased liver weight in females; dose-related cardiac changes consisting of minimal to marked hemorrhage and chronic inflammation were present in the myocardium of the right atrium and left AV valves along with proliferative changes in some cardiac vessels.
Carcinogenicity
At the concentrations and doses employed in the non-clinical carcinogenicity studies, there was no indication that anagrelide was a potential mutagen either directly or after metabolic activation (WARNINGS AND PRECAUTIONS, Carcinogenesis And Mutagenesis).
Reproductive and Developmental Toxicology
A comprehensive range of fertility, embryofetal development, and pre- and post-natal toxicity studies were performed in rats at oral doses of 30 to 900mg/kg/day of anagrelide.
In a fertility and early embryofetal development study in which female rats were dosed for 15 days prior to pairing, during pairing and up to and including Day 6 of gestation, an increase in the incidences of both pre- and post-implantation losses, leading to a decrease in the mean number of embryos per female was observed at 30mg/kg/day. The No Observed Effect Level (NOEL) was considered to be 10mg/kg/day. These data are consistent with an earlier study assessing fertility in rats which showed evidence of reduced implantations and increased resorptions at all doses tested (60, 120 and 240mg/kg/day).
In the embryofetal development and pre- and post-natal studies, females were dosed from Days 6 to 15 or 18 of gestation, Day 6 gestation through Day 7 lactation, or Day 15 gestation to Day 21 lactation. The average number of live pups was significantly reduced on Day 1 postpartum in the 60 and 120mg/kg/day dosage groups; Days 4 and 21 postpartum in the 120 and 240mg/kg/day dosage groups and Day 7 postpartum in the 120mg/kg/day dosage group. Average body weights of pups were significantly reduced in all anagrelide-treated groups at Day 1 postpartum; in the 120 and 240mg/kg/day groups on Days 4 and 7 postpartum, and in the 240mg/kg/day group on Day 14 postpartum. Administration of anagrelide did not adversely affect the averages for implantations and live litter sizes, number of dams with all stillbirths, number of dams with all pups dying during lactation, sex ratios, or clinical and necropsy observations of the pups.
Doses of 240mg/kg/day and higher were associated with an increase in the incidence of pups dying on Days 1 to 4 postpartum, a decrease in the percentage of pups surviving to Day 7 postpartum, and a decrease in the average pup weight/litter.
Fetal body weights were significantly reduced by 5 to 7% in groups receiving 300 and 900mg/kg/day. Significant reversible delays in fetal ossification occurred in groups given doses of 100mg/kg/day or higher. No fetal malformations were attributable to doses of anagrelide as high as 900mg/kg/day. Deaths occurred when rats were continued to be dosed during delivery and early lactation.
In embryofetal development studies with rabbits, oral doses of 30 to 480mg/kg of anagrelide, administered from Days 6 to 18 of gestation revealed that doses of ≥60mg/kg/day caused body weight loss, severe decreases in food consumption, decreased live litter sizes, and increased number and percentages of resorptions per litter. Deaths occurred in all dosed groups and there were two deformed fetuses, one at 30 and another at 240mg/kg/day. A second study of similar design employed doses of 1 to 20mg/kg/day. Body weight gains were significantly increased with 10 or 20mg/kg/day while food consumption significantly decreased during dosing. There were no deaths, abortions, premature deliveries, changes in litter parameters, or fetal malformations with oral doses of ≤20mg/kg/day.
Detailed Pharmacology
Clinically, AGRYLIN (anagrelide hydrochloride capsules) was found to be an effective, highly specific platelet-reducing agent. Anagrelide's effects on platelets are fully reversible. Moreover, it has no clinically significant effect on the other formed elements in the blood. These findings were demonstrated both preclinically and clinically.
Preclinical pharmacology data that are available demonstrate anagrelide's specificity toward platelets. While anagrelide was found to be a potent inhibitor of platelet aggregation, it had no significant effect on other cellular components of the blood. Additional significant pharmacologic effects attributed to anagrelide administration are hypotension and positive inotropic activity.
Mechanism Of Action
Anagrelide is a highly selective platelet-lowering agent. In vitro studies of human megakaryocytopoiesis suggested that, in vivo, its thrombocytopenic activity results primarily from an inhibitory effect on the post-mitotic phase of megakaryotic maturation. Anagrelide inhibited thrombopoietin-induced megakaryocytopoiesis in a dose-dependent manner with an estimated IC50 of approximately 30nM (= 7.7ng/mL), consistent with the in vivo Cmax of 7-13ng/mL after doses of 0.5-1mg. Three in vivo studies in humans (published in abstract form) have confirmed that anagrelide decreases circulating platelet counts in thrombocythemic subjects by inhibiting megakaryocyte maturation and ploidy.
Effect On Platelet Count
An effect on platelet count was demonstrated in only a few animal studies. In one rat study, a decreased platelet count was found in male Sprague-Dawley rats treated at 1,000mg/kg for 27 days. In another rat study, decreased platelet counts were observed in all female rats dosed for 1 year with 120.5, 361.5, and 1,205mg/kg/day of anagrelide hydrochloride. Platelet counts were decreased from pre-study values by 30 to 54% in male beagle dogs, and by 23 to 40% in females treated for 1 year at doses of 10, 300, and 600mg/kg/day.
Anti-thrombotic Studies
The ability of anagrelide to inhibit thrombosis was demonstrated in four different animal models: rat, rabbit, dog, and rhesus monkey. Anagrelide was found to be a potent, broadspectrum platelet aggregation inhibitor whose effects are dose-related. It is 50 times more potent than acetylsalicylic acid as an anticoagulant and was found to have a synergistic effect on platelet aggregation inhibition when administered in conjunction with heparin.
Cardiovascular Pharmacology
Preclinical cardiovascular information was obtained during the course of studies conducted in four different animal models: rat, guinea pig, ferret, and dog.
The key findings in these studies was that anagrelide has a significant direct positive inotropic effect and direct vasodilatory effect; and causes dose-related decreases in mean blood pressure and reflexogenic increases in heart rate. Anagrelide was also shown to be a potent vasodilator and cardiotonic agent in dogs. All of these effects were seen at doses higher than the recommended clinical dose of 2.0mg/day.
General Pharmacology Studies
General pharmacologic effects of anagrelide were studied in five different animal models: rat, guinea pig, ferret, rabbit, and dog. The overall conclusions from these studies were that anagrelide causes the following:
- simple competitive antagonism of peripheral 5-HT receptors in the rat fundus model
- a decrease in diuresis sodium and chlorine excretion in the volume-loaded normotensive rat
- a dose-related prolongation of bleeding time in the guinea pig extracorporeal shunt model
- no behavioural or neurological changes in the conscious dog model
- weak airway dilation in the anesthetized dog model
- inhibition of both cyclic AMP (cAMP) phosphodiesterase (PDE) and cyclic GMP PDE activity in a study of supernatant and sonicate models
- inhibition of cAMP PDE activity in another study of supernatant and sonicate models
- an increase in cAMP level and cAMP-dependent protein kinase (cA-PK) ratio in the washed human platelet model
- inhibition of platelet PDE and resultant elevation of cAMP in the intact platelet model
Pharmacokinetics
Studies on the absorption, distribution, metabolism, and excretion (ADME) in four different species (rat, dog, monkey, and human) revealed that the orally-administered anagrelide is generally well absorbed, widely distributed to tissues, extensively metabolized, and excreted in the urine.
In a study with pregnant or post-partum female rats administered 14C-labelled anagrelide, anagrelide-related material was partitioned into milk and was still being secreted in milk at the final sampling time of 24 hours.
The monkey most closely resembled man in the route, rate, and extent of excretion. Human and animal urinary metabolite profiles were qualitatively similar. Each of the 3 main metabolites present in human urine were present in animal urine, but quantities were generally smaller.
Oral administration of 14C-labelled anagrelide in the monkey resulted in rapid absorption with peak plasma levels occurring 4 to 8 hours after dosing. Capsule dose absorption from the intestinal tract was 76%. The main route of elimination was the urine; by 6 days after drug administration, the mean cumulative urinary excretion level of the dosed radioactivity was 61%.
A secondary route of elimination was in feces, the mean cumulative fecal excretion level over 6 days after drug administration was 31% in monkeys. The amount of parent compound detected in the urine as unchanged drug was less than 3%. Bioavailability in the primate was 92%, with a terminal half-life of 2 days for total radioactivity.