imatinib 400 MG Oral Tablet

INDICATIONS AND USAGE Imatinib mesylate tablets are a kinase inhibitor indicated for the treatment of: • Newly diagnosed adult and pediatric patients with Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) in chronic phase. ( 1.1 ) • Patients with Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) in blast crisis (BC), accelerated phase (AP), or in chronic phase (CP) after failure of interferon-alpha therapy. ( 1.2 ) • Adult patients with relapsed or refractory Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL). ( 1.3 ) • Pediatric patients with newly diagnosed Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL) in combination with chemotherapy. ( 1.4 ) • Adult patients with myelodysplastic/myeloproliferative diseases (MDS/MPD) associated with platelet-derived growth factor receptor (PDGFR) gene re-arrangements. ( 1.5 ) • Adult patients with aggressive systemic mastocytosis (ASM) without the D816V c-Kit mutation or with c-Kit mutational status unknown. ( 1.6 ) • Adult patients with hypereosinophilic syndrome (HES) and/or chronic eosinophilic leukemia (CEL) who have the FIP1L1-PDGFRα fusion kinase (mutational analysis or fluorescence in situ hybridization [FISH] demonstration of CHIC2 allele deletion) and for patients with HES and/or CEL who are FIP1L1-PDGFRα fusion kinase negative or unknown. ( 1.7 ) • Adult patients with unresectable, recurrent and/or metastatic dermatofibrosarcoma protuberans (DFSP). ( 1.8 ) • Patients with Kit (CD117) positive unresectable and/or metastatic malignant gastrointestinal stromal tumors (GIST). ( 1.9 ) • Adjuvant treatment of adult patients following resection of Kit (CD117) positive GIST. ( 1.10 ) 1.1 Newly Diagnosed Philadelphia Positive Chronic Myeloid Leukemia (Ph+ CML) Newly diagnosed adult and pediatric patients with Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) in chronic phase. 1.2 Ph+ CML in Blast Crisis (BC), Accelerated Phase (AP) or Chronic Phase (CP) After Interferon-alpha (IFN) Therapy Patients with Philadelphia chromosome positive chronic myeloid leukemia in blast crisis, accelerated phase, or in chronic phase after failure of interferon-alpha therapy. 1.3 Adult Patients With Ph+ Acute Lymphoblastic Leukemia (ALL) Adult patients with relapsed or refractory Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL). 1.4 Pediatric Patients With Ph+ Acute Lymphoblastic Leukemia (ALL) Pediatric patients with newly diagnosed Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL) in combination with chemotherapy. 1.5 Myelodysplastic/Myeloproliferative Diseases (MDS/MPD) Adult patients with myelodysplastic/myeloproliferative diseases associated with platelet-derived growth factor receptor (PDGFR) gene re-arrangements. 1.6 Aggressive Systemic Mastocytosis (ASM) Adult patients with aggressive systemic mastocytosis without the D816V c-Kit mutation or with c-Kit mutational status unknown. 1.7 Hypereosinophilic Syndrome (HES) and/or Chronic Eosinophilic Leukemia (CEL) Adult patients with hypereosinophilic syndrome and/or chronic eosinophilic leukemia who have the FIP1L1-PDGFRα fusion kinase (mutational analysis or fluorescence in situ hybridization [FISH] demonstration of CHIC2 allele deletion) and for patients with HES and/or CEL who are FIP1L1-PDGFRα fusion kinase negative or unknown. 1.8 Dermatofibrosarcoma Protuberans (DFSP) Adult patients with unresectable, recurrent and/or metastatic dermatofibrosarcoma protuberans. 1.9 Kit+ Gastrointestinal Stromal Tumors (GIST) Patients with Kit (CD117) positive unresectable and/or metastatic malignant gastrointestinal stromal tumors. 1.10 Adjuvant Treatment of GIST Adjuvant treatment of adult patients following complete gross resection of Kit (CD117) positive GIST.

DOSAGE AND ADMINISTRATION Adults with Ph+ CML CP ( 2.2 ): 400 mg/day Adults with Ph+ CML AP or BC ( 2.2 ): 600 mg/day Pediatrics with Ph+ CML CP ( 2.3 ): 340 mg/m 2 /day Adults with Ph+ ALL ( 2.4 ): 600 mg/day Pediatrics with Ph+ ALL ( 2.5 ) 340 mg/m 2 /day Adults with MDS/MPD ( 2.6 ): 400 mg/day Adults with ASM ( 2.7 ): 100 mg/day or 400 mg/day Adults with HES/CEL ( 2.8 ): 100 mg/day or 400 mg/day Adults with DFSP ( 2.9 ): 800 mg/day Adults with metastatic and/or unresectable GIST ( 2.10 ): 400 mg/day Adjuvant treatment of adults with GIST ( 2.11 ): 400 mg/day Patients with mild to moderate hepatic impairment ( 2.12 ): 400 mg/day Patients with severe hepatic impairment ( 2.12 ): 300 mg/day All doses of imatinib mesylate tablets should be taken with a meal and a large glass of water. Doses of 400 mg or 600 mg (imatinib as free base) should be administered once daily, whereas a dose of 800 mg (imatinib as free base) should be administered as 400 mg (imatinib as free base) twice a day. Imatinib mesylate tablets can be dissolved in water or apple juice for patients having difficulty swallowing. Daily dosing of 800 mg (imatinib as free base) and above should be accomplished using the 400 mg tablet (imatinib as free base) to reduce exposure to iron. 2.1 Drug Administration The prescribed dose should be administered orally, with a meal and a large glass of water. Doses of 400 mg or 600 mg (imatinib as free base) should be administered once daily, whereas a dose of 800 mg (imatinib as free base) should be administered as 400 mg (imatinib as free base) twice a day. For patients unable to swallow the film-coated tablets, the tablets may be dispersed in a glass of water or apple juice. The required number of tablets should be placed in the appropriate volume of beverage (approximately 50 mL for a 100-mg tablet, and 200 mL for a 400-mg tablet) and stirred with a spoon. The suspension should be administered immediately after complete disintegration of the tablet(s). For daily dosing of 800 mg (imatinib as free base) and above, dosing should be accomplished using the 400-mg (imatinib as free base) tablet to reduce exposure to iron. Treatment may be continued as long as there is no evidence of progressive disease or unacceptable toxicity. 2.2 Adult Patients With Ph+ CML CP, AP, or BC The recommended dose of imatinib mesylate tablets is 400 mg/day (imatinib as free base) for adult patients in chronic phase CML and 600 mg/day (imatinib as free base) for adult patients in accelerated phase or blast crisis. In CML, a dose increase from 400 mg to 600 mg (imatinib as free base) in adult patients with chronic phase disease, or from 600 mg to 800 mg (imatinib as free base) (given as 400 mg twice daily) in adult patients in accelerated phase or blast crisis may be considered in the absence of severe adverse drug reaction and severe non-leukemia related neutropenia or thrombocytopenia in the following circumstances: disease progression (at any time), failure to achieve a satisfactory hematologic response after at least 3 months of treatment, failure to achieve a cytogenetic response after 6 to 12 months of treatment, or loss of a previously achieved hematologic or cytogenetic response. 2.3 Pediatric Patients With Ph+ CML CP The recommended dose of imatinib mesylate tablets for children with newly diagnosed Ph+ CML is 340 mg/m 2 /day (imatinib as free base) (not to exceed 600 mg). Imatinib mesylate tablets treatment can be given as a once daily dose or the daily dose may be split into two–one portion dosed in the morning and one portion in the evening. There is no experience with imatinib mesylate treatment in children under 1 year of age. 2.4 Adult Patients With Ph+ ALL The recommended dose of imatinib mesylate tablets is 600 mg/day (imatinib as free base) for adult patients with relapsed/refractory Ph+ ALL. 2.5 Pediatric Patients With Ph+ ALL The recommended dose of imatinib mesylate tablets to be given in combination with chemotherapy to children with newly diagnosed Ph+ ALL is 340 mg/m 2 /day (not to exceed 600 mg). Imatinib mesylate tablets treatment can be given as a once daily dose. 2.6 Adult Patients With MDS/MPD Determine PDGFRb gene rearrangements status prior to initiating treatment. The recommended dose of imatinib mesylate tablets is 400 mg/day (imatinib as free base) for adult patients with MDS/MPD. 2.7 Adult Patients With ASM Determine D816V c-Kit mutation status prior to initiating treatment. The recommended dose of imatinib mesylate tablets is 400 mg/day (imatinib as free base) for adult patients with ASM without the D816V c-Kit mutation. If c-Kit mutational status is not known or unavailable, treatment with imatinib mesylate tablets 400 mg/day (imatinib as free base) may be considered for patients with ASM not responding satisfactorily to other therapies. For patients with ASM associated with eosinophilia, a clonal hematological disease related to the fusion kinase FIP1L1-PDGFRα, a starting dose of 100 mg/day (imatinib as free base) is recommended. Dose increase from 100 mg to 400 mg (imatinib as free base) for these patients may be considered in the absence of adverse drug reactions if assessments demonstrate an insufficient response to therapy. 2.8 Adult Patients With HES/CEL The recommended dose of imatinib mesylate tablets is 400 mg/day (imatinib as free base) for adult patients with HES/CEL. For HES/CEL patients with demonstrated FIP1L1-PDGFRα fusion kinase, a starting dose of 100 mg/day (imatinib as free base) is recommended. Dose increase from 100 mg to 400 mg (imatinib as free base) for these patients may be considered in the absence of adverse drug reactions if assessments demonstrate an insufficient response to therapy. 2.9 Adult Patients With DFSP The recommended dose of imatinib mesylate tablets is 800 mg/day (imatinib as free base) for adult patients with DFSP. 2.10 Adult Patients With Metastatic and/or Unresectable GIST The recommended dose of imatinib mesylate tablets is 400 mg/day (imatinib as free base) for adult patients with unresectable and/or metastatic, malignant GIST. A dose increase up to 800 mg daily (imatinib as free base) (given as 400 mg twice daily) may be considered, as clinically indicated, in patients showing clear signs or symptoms of disease progression at a lower dose and in the absence of severe adverse drug reactions. 2.11 Adult Patients With Adjuvant GIST The recommended dose of imatinib mesylate tablets is 400 mg/day (imatinib as free base) for the adjuvant treatment of adult patients following complete gross resection of GIST. In clinical trials, one year of imatinib mesylate tablets and three years of imatinib mesylate tablets were studied. In the patient population defined in Study 2, three years of imatinib mesylate tablets is recommended [see Clinical Studies ( 14.8 )] . The optimal treatment duration with imatinib mesylate tablets is not known. 2.12 Dose Modification Guidelines Concomitant Strong CYP3A4 inducers: The use of concomitant strong CYP3A4 inducers should be avoided (e.g., dexamethasone, phenytoin, carbamazepine, rifampin, rifabutin, rifampacin, phenobarbital). If patients must be coadministered a strong CYP3A4 inducer, based on pharmacokinetic studies, the dosage of imatinib mesylate tablets should be increased by at least 50%, and clinical response should be carefully monitored [ see Drug Interactions ( 7.1 ) ]. Hepatic Impairment: Patients with mild and moderate hepatic impairment do not require a dose adjustment and should be treated per the recommended dose. A 25% decrease in the recommended dose should be used for patients with severe hepatic impairment [ see Use in Specific Populations ( 8.6 ) ]. Renal Impairment: Patients with moderate renal impairment (creatinine clearance [CrCL] = 20 to 39 mL/min) should receive a 50% decrease in the recommended starting dose and future doses can be increased as tolerated. Doses greater than 600 mg (imatinib as free base) are not recommended in patients with

WARNINGS AND PRECAUTIONS • Edema and severe fluid retention have occurred. Weigh patients regularly and manage unexpected rapid weight gain by drug interruption and diuretics. ( 5.1 , 6.1 ) • Cytopenias, particularly anemia, neutropenia, and thrombocytopenia, have occurred. Manage with dose reduction, dose interruption, or discontinuation of treatment. Perform complete blood counts weekly for the first month, biweekly for the second month, and periodically thereafter. ( 5.2 ) • Severe congestive heart failure and left ventricular dysfunction have been reported, particularly in patients with comorbidities and risk factors. Monitor and treat patients with cardiac disease or risk factors for cardiac failure. ( 5.3 ) • Severe hepatotoxicity, including fatalities may occur. Assess liver function before initiation of treatment and monthly thereafter or as clinically indicated. Monitor liver function when combined with chemotherapy known to be associated with liver dysfunction. ( 5.4 ) • Grade 3/4 hemorrhage has been reported in clinical studies in patients with newly diagnosed CML and with GIST. GI tumor sites may be the source of GI bleeds in GIST. ( 5.5 ) • Gastrointestinal (GI) perforations, some fatal, have been reported. ( 5.6 ) • Cardiogenic shock/left ventricular dysfunction has been associated with the initiation of imatinib mesylate in patients with conditions associated with high eosinophil levels (e.g., HES, MDS/MPD, and ASM). ( 5.7 ) • Bullous dermatologic reactions (e.g., erythema multiforme and Stevens-Johnson syndrome) have been reported with the use of imatinib mesylate. ( 5.8 ) • Hypothyroidism has been reported in thyroidectomy patients undergoing levothyroxine replacement. Closely monitor TSH levels in such patients. ( 5.9 ) • Fetal harm can occur when administered to a pregnant woman. Apprise women of the potential harm to the fetus, and to use effective contraception. ( 5.10 , 8.1 ) • Growth retardation occurring in children and pre-adolescents receiving imatinib mesylate has been reported. Close monitoring of growth in children under imatinib mesylate treatment is recommended. ( 5.11 , 6.2 ) • Tumor Lysis Syndrome. Close monitoring is recommended. ( 5.12 ) • Reports of motor vehicle accidents have been received in patients receiving imatinib mesylate. Caution patients about driving a car or operating machinery. ( 5.13 ) • Renal Toxicity. A decline in renal function may occur in patients receiving imatinib mesylate tablets. Evaluate renal function at baseline and during therapy, with attention to risk factors for renal dysfunction. ( 5.14 ) 5.1 Fluid Retention and Edema Imatinib mesylate is often associated with edema and occasionally serious fluid retention [ see Adverse Reactions ( 6.1 ) ]. Weigh and monitor patients regularly for signs and symptoms of fluid retention. Investigate unexpected rapid weight gain carefully and provide appropriate treatment. The probability of edema was increased with higher imatinib mesylate dose and age greater than 65 years in the CML studies. Severe superficial edema was reported in 1.5% of newly diagnosed CML patients taking imatinib mesylate, and in 2% to 6% of other adult CML patients taking imatinib mesylate. In addition, other severe fluid retention (e.g., pleural effusion, pericardial effusion, pulmonary edema, and ascites) reactions were reported in 1.3% of newly diagnosed CML patients taking imatinib mesylate, and in 2% to 6% of other adult CML patients taking imatinib mesylate. Severe fluid retention was reported in 9% to 13.1% of patients taking imatinib mesylate for GIST [see Adverse Reactions ( 6.1 )]. In a randomized trial in patients with newly diagnosed Ph+CML in chronic phase comparing imatinib mesylate and nilotinib, severe (Grade 3 or 4) fluid retention occurred in 2.5% of patients receiving imatinib mesylate and in 3.9% of patients receiving nilotinib 300 mg twice daily. Effusions (including pleural effusion, pericardial effusion, ascites) or pulmonary edema were observed in 2.1% (none were Grade 3 or 4) of patients in the imatinib mesylate arm and 2.2% (0.7% Grade 3 or 4) of patients in the nilotinib 300 mg twice daily arm. 5.2 Hematologic Toxicity Treatment with imatinib mesylate tablets is associated with anemia, neutropenia, and thrombocytopenia. Perform complete blood counts weekly for the first month, biweekly for the second month, and periodically thereafter as clinically indicated (for example, every 2 to 3 months). In CML, the occurrence of these cytopenias is dependent on the stage of disease and is more frequent in patients with accelerated phase CML or blast crisis than in patients with chronic phase CML. In pediatric CML patients the most frequent toxicities observed were Grade 3 or 4 cytopenias, including neutropenia, thrombocytopenia, and anemia. These generally occur within the first several months of therapy [ see Dosage and Administration ( 2.14 ) ]. 5.3 Congestive Heart Failure and Left Ventricular Dysfunction Congestive heart failure and left ventricular dysfunction have been reported in patients taking imatinib mesylate. Cardiac adverse reactions were more frequent in patients with advanced age or co-morbidities, including previous medical history of cardiac disease. In an international randomized Phase 3 study in 1106 patients with newly diagnosed Ph+ CML in chronic phase, severe cardiac failure and left ventricular dysfunction were observed in 0.7% of patients taking imatinib mesylate compared to 0.9% of patients taking IFN + Ara-C. In another randomized trial with newly diagnosed Ph+ CML patients in chronic phase that compared imatinib mesylate and nilotinib, cardiac failure was observed in 1.1% of patients in the imatinib mesylate arm and 2.2% of patients in the nilotinib 300 mg twice daily arm and severe (Grade 3 or 4) cardiac failure occurred in 0.7% of patients in each group. Carefully monitor patients with cardiac disease or risk factors for cardiac or history of renal failure. Evaluate and treat any patient with signs or symptoms consistent with cardiac or renal failure. 5.4 Hepatotoxicity Hepatotoxicity, occasionally severe, may occur with imatinib mesylate [ see Adverse Reactions ( 6.1 ) ] . Cases of fatal liver failure and severe liver injury requiring liver transplants have been reported with both short-term and long-term use of imatinib mesylate. Monitor liver function (transaminases, bilirubin, and alkaline phosphatase) before initiation of treatment and monthly, or as clinically indicated. Manage laboratory abnormalities with imatinib mesylate interruption and/or dose reduction [ see Dosage and Administration ( 2.13 ) ] . When imatinib mesylate is combined with chemotherapy, liver toxicity in the form of transaminase elevation and hyperbilirubinemia has been observed. Additionally, there have been reports of acute liver failure. Monitoring of hepatic function is recommended. 5.5 Hemorrhage In a trial of imatinib mesylate versus IFN+Ara-C in patients with the newly diagnosed CML, 1.8% of patients had Grade 3/4 hemorrhage. In the Phase 3 unresectable or metastatic GIST studies, 211 patients (12.9%) reported Grade 3/4 hemorrhage at any site. In the Phase 2 unresectable or metastatic GIST study, 7 patients (5%) had a total of 8 CTC Grade 3/4 hemorrhages; gastrointestinal (GI) (3 patients), intra-tumoral (3 patients) or both (1 patient). Gastrointestinal tumor sites may have been the source of GI hemorrhages. In a randomized trial in patients with newly diagnosed Ph+ CML in chronic phase comparing imatinib mesylate and nilotinib, GI hemorrhage occurred in 1.4% of patients in the imatinib mesylate arm, and in 2.9% of patients in the nilotinib 300 mg twice daily arm. None of these events were Grade 3 or 4 in the imatinib mesylate arm; 0.7% were Grade 3 or 4 in the nilotinib 300 mg twice daily arm. In addition, gastric antral vascular ectasia has been reported in postmarketing experience. 5.6 Gastrointestinal Disorders Imatinib mesylate is sometimes as

CONTRAINDICATIONS None. None ( 4 ).

CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Imatinib mesylate is a protein-tyrosine kinase inhibitor that inhibits the BCR-ABL tyrosine kinase, the constitutive abnormal tyrosine kinase created by the Philadelphia chromosome abnormality in CML. Imatinib inhibits proliferation and induces apoptosis in BCR-ABL positive cell lines as well as fresh leukemic cells from Philadelphia chromosome positive chronic myeloid leukemia. Imatinib inhibits colony formation in assays using ex vivo peripheral blood and bone marrow samples from CML patients. In vivo, imatinib inhibits tumor growth of BCR-ABL transfected murine myeloid cells as well as BCR-ABL positive leukemia lines derived from CML patients in blast crisis. Imatinib is also an inhibitor of the receptor tyrosine kinases for platelet-derived growth factor (PDGF) and stem cell factor (SCF), c-kit, and inhibits PDGF- and SCF-mediated cellular events. In vitro, imatinib inhibits proliferation and induces apoptosis in GIST cells, which express an activating c-Kit mutation. 12.3 Pharmacokinetics The pharmacokinetics of imatinib mesylate have been evaluated in studies in healthy subjects and in population pharmacokinetic studies in over 900 patients. The pharmacokinetics of imatinib mesylate tablets are similar in CML and GIST patients. Absorption and Distribution Imatinib is well absorbed after oral administration with C max achieved within 2 to 4 hours post-dose. Mean absolute bioavailability is 98%. Mean imatinib AUC increases proportionally with increasing doses ranging from 25 mg to 1,000 mg. There is no significant change in the pharmacokinetics of imatinib on repeated dosing, and accumulation is 1.5- to 2.5-fold at steady state when imatinib mesylate is dosed once-daily. At clinically relevant concentrations of imatinib, binding to plasma proteins in in vitro experiments is approximately 95%, mostly to albumin and α1-acid glycoprotein. Elimination Metabolism CYP3A4 is the major enzyme responsible for metabolism of imatinib. Other cytochrome P450 enzymes, such as CYP1A2, CYP2D6, CYP2C9, and CYP2C19, play a minor role in its metabolism. The main circulating active metabolite in humans is the N-demethylated piperazine derivative, formed predominantly by CYP3A4. It shows in vitro potency similar to the parent imatinib. The plasma AUC for this metabolite is about 15% of the AUC for imatinib. The plasma protein binding of N-demethylated metabolite CGP74588 is similar to that of the parent compound. Human liver microsome studies demonstrated that imatinib mesylate is a potent competitive inhibitor of CYP2C9, CYP2D6, and CYP3A4/5 with K i values of 27, 7.5, and 8 μM, respectively. Excretion Imatinib elimination is predominately in the feces, mostly as metabolites. Based on the recovery of compound(s) after an oral 14 C-labeled dose of imatinib, approximately 81% of the dose was eliminated within 7 days, in feces (68% of dose) and urine (13% of dose). Unchanged imatinib accounted for 25% of the dose (5% urine, 20% feces), the remainder being metabolites. Following oral administration in healthy volunteers, the elimination half-lives of imatinib and its major active metabolite, the N-demethyl derivative (CGP74588), are approximately 18 and 40 hours, respectively. Typically, clearance of imatinib in a 50-year-old patient weighing 50 kg is expected to be 8 L/h, while for a 50-year-old patient weighing 100 kg the clearance will increase to 14 L/h. The inter-patient variability of 40% in clearance does not warrant initial dose adjustment based on body weight and/or age but indicates the need for close monitoring for treatment-related toxicity. Specific Populations Hepatic Impairment The effect of hepatic impairment on the pharmacokinetics of both imatinib and its major metabolite, CGP74588, was assessed in 84 patients with cancer and varying degrees of hepatic impairment [see Use in Specific Populations (8.6) ] at imatinib doses ranging from 100 mg to 800 mg. Exposure to both imatinib and CGP74588 was comparable between each of the mildly and moderately hepatically-impaired groups and the normal group. Patients with severe hepatic impairment tend to have higher exposure to both imatinib and its metabolite than patients with normal hepatic function. At steady state, the mean C max /dose and AUC/dose for imatinib increased by about 63% and 45%, respectively, in patients with severe hepatic impairment compared to patients with normal hepatic function. The mean C max /dose and AUC/dose for CGP74588 increased by about 56% and 55%, respectively, in patients with severe hepatic impairment compared to patients with normal hepatic function. Dose reductions are necessary for patients with severe hepatic impairment [see Dosage and Administration (2.12) ] . Renal Impairment The effect of renal impairment on the pharmacokinetics of imatinib was assessed in 59 cancer patients with varying degrees of renal impairment [see Use in Specific Populations (8.7) ] at single and steady state imatinib doses ranging from 100 to 800 mg/day. The mean exposure to imatinib (dose normalized AUC) in patients with mild and moderate renal impairment increased 1.5-to 2-fold compared to patients with normal renal function. The AUCs did not increase for doses greater than 600 mg in patients with mild renal impairment. The AUCs did not increase for doses greater than 400 mg in patients with moderate renal impairment. Two patients with severe renal impairment were dosed with 100 mg/day and their exposures were similar to those seen in patients with normal renal function receiving 400 mg/day. Dose reductions are necessary for patients with moderate and severe renal impairment [see Dosage and Administration (2.12) ] . Pediatric Use As in adult patients, imatinib was rapidly absorbed after oral administration in pediatric patients, with a C max of 2 to 4 hours. Apparent oral clearance was similar to adult values (11.0 L/hr/m 2 in children vs. 10.0 L/hr/m 2 in adults), as was the half-life (14.8 hours in children vs. 17.1 hours in adults). Dosing in children at both 260 mg/m 2 and 340 mg/m 2 achieved an AUC similar to the 400 mg dose in adults. The comparison of AUC on Day 8 vs Day 1 at 260 mg/m 2 and 340 mg/m 2 dose levels revealed a 1.5- and 2.2-fold drug accumulation, respectively, after repeated once-daily dosing. Mean imatinib AUC did not increase proportionally with increasing dose. Based on pooled population pharmacokinetic analysis in pediatric patients with hematological disorders (CML, Ph+ ALL, or other hematological disorders treated with imatinib), clearance of imatinib increases with increasing BSA. After correcting for the BSA effect, other demographics, such as age, body weight, and body mass index did not have clinically significant effects on the exposure of imatinib. The analysis confirmed that exposure of imatinib in pediatric patients receiving 260 mg/m 2 once daily (not exceeding 400 mg once daily) or 340 mg/m 2 once daily (not exceeding 600 mg once daily) were similar to those in adult patients who received imatinib 400 mg or 600 mg once daily. Drug Interactions Agents Inducing CYP3A Metabolism Pretreatment of healthy volunteers with multiple doses of rifampin followed by a single dose of imatinib mesylate, increased imatinib mesylate oral-dose clearance by 3.8-fold, which significantly (p less than 0.05) decreased mean C max and AUC. Similar findings were observed in patients receiving 400 to 1,200 mg/day imatinib mesylate concomitantly with enzyme-inducing anti-epileptic drugs (EIAED) (e.g., carbamazepine, oxcarbamazepine, phenytoin, fosphenytoin, phenobarbital, and primidone). The mean dose normalized AUC for imatinib in the patients receiving EIAED's decreased by 73% compared to patients not receiving EIAED. Concomitant administration of imatinib mesylate and St. John's Wort led to a 30% reduction in the AUC of imatinib. Consider alternative therapeutic agents with less enzyme induction potential in patients when rifampin or ot