Temozolomide

12.1 Mechanism of Action Temozolomide is not directly active but undergoes rapid nonenzymatic conversion at physiologic pH to the reactive compound 5-(3-methyltriazen-1-yl)-imidazole-4-carboxamide (MTIC). The cytotoxicity of MTIC is thought to be primarily due to DNA alkylation, mainly at the O 6 and N 7 positions of guanine, which causes DNA double strand breaks and results in programmed cell death.

1 INDICATIONS AND USAGE TEMODAR is an alkylating drug indicated for the treatment of adults with: Newly diagnosed glioblastoma concomitantly with radiotherapy and then as maintenance treatment. ( 1.1 ) Anaplastic astrocytoma. ( 1.2 ) Adjuvant treatment of adults with newly diagnosed anaplastic astrocytoma. ( 1.2 ) Treatment of adults with refractory anaplastic astrocytoma. ( 1.2 ) 1.1 Newly Diagnosed Glioblastoma TEMODAR is indicated for the treatment of adults with newly diagnosed glioblastoma, concomitantly with radiotherapy and then as maintenance treatment. 1.2 Anaplastic Astrocytoma TEMODAR is indicated for the: adjuvant treatment of adults with newly diagnosed anaplastic astrocytoma; treatment of adults with refractory anaplastic astrocytoma.

2 DOSAGE AND ADMINISTRATION Administer either orally or intravenously. ( 2.4 ) Newly Diagnosed Glioblastoma : 75 mg/m 2 once daily for 42 to 49 days concomitant with focal radiotherapy followed by initial maintenance dose of 150 mg/m 2 once daily for Days 1 to 5 of each 28-day cycle for 6 cycles. May increase maintenance dose to 200 mg/m 2 for Cycles 2 to 6 based on toxicity. ( 2.1 ) Provide Pneumocystis pneumonia (PCP) prophylaxis during concomitant phase and continue in patients who develop lymphopenia until resolution to Grade 1 or less. ( 2.1 ) Adjuvant Treatment of Newly Diagnosed Anaplastic Astrocytoma: Beginning 4 weeks after the end of radiotherapy, administer TEMODAR orally in a single dose on days 1-5 of a 28-day cycle for 12 cycles. The recommended dosage for Cycle 1 is 150 mg/m 2 per day and for Cycles 2 to 12 is 200 mg/m 2 if patient experienced no or minimal toxicity in Cycle 1. ( 2.2 ) Refractory Anaplastic Astrocytoma: Initial dose of 150 mg/m 2 once daily on Days 1 to 5 of each 28-day cycle. ( 2.2 ) 2.1 Monitoring to Inform Dosage and Administration Prior to dosing, withhold TEMODAR until patients have an absolute neutrophil count (ANC) of 1.5 x 10 9 /L or greater and a platelet count of 100 x 10 9 /L or greater. For concomitant radiotherapy, obtain a complete blood count prior to initiation of treatment and weekly during treatment. For the 28-day treatment cycles, obtain a complete blood count prior to treatment on Day 1 and on Day 22 of each cycle. Perform complete blood counts weekly until recovery if the ANC falls below 1.5 x 10 9 /L and the platelet count falls below 100 x 10 9 /L. For concomitant use with focal radiotherapy, obtain a complete blood count weekly and as clinically indicated. 2.2 Recommended Dosage and Dosage Modifications for Newly Diagnosed Glioblastoma Administer TEMODAR either orally or intravenously once daily for 42 to 49 consecutive days during the concomitant use phase with focal radiotherapy, and then once daily on Days 1 to 5 of each 28-day cycle for 6 cycles during the maintenance use phase. Provide Pneumocystis pneumonia (PCP) prophylaxis during the concomitant use phase and continue in patients who develop lymphopenia until resolution to Grade 1 or less [see Warnings and Precautions (5.3) ] . Concomitant Use Phase: The recommended dosage of TEMODAR is 75 mg/m 2 either orally or intravenously once daily for 42 to 49 days in combination with focal radiotherapy. Focal radiotherapy includes the tumor bed or resection site with a 2 to 3 cm margin. Other administration schedules have been used. Obtain a complete blood count weekly. The recommended dosage modifications due to adverse reactions during concomitant use phase are provided in Table 1 . TABLE 1: Dosage Modifications Due to Adverse Reactions During Concomitant Use Phase Adverse Reaction Interruption Discontinuation Absolute Neutrophil Count Withhold TEMODAR if ANC is greater than or equal to 0.5 × 10 9 /L and less than 1.5 × 10 9 /L. Discontinue TEMODAR if ANC is less than 0.5 × 10 9 /L. Resume TEMODAR at the same dose when ANC is greater than or equal to 1.5 × 10 9 /L. Platelet Count Withhold TEMODAR if platelet count is greater than or equal to 10 × 10 9 /L and less than 100 × 10 9 /L. Discontinue TEMODAR if platelet count is less than 10 × 10 9 /L. Resume TEMODAR at the same dose when platelet count is greater than or equal to 100 × 10 9 /L. Non-hematological Adverse Reaction (except for alopecia, nausea, vomiting) Withhold TEMODAR if Grade 2 adverse reaction occurs. Discontinue TEMODAR if Grade 3 or 4 adverse reaction occurs. Resume TEMODAR at the same dose when resolution to Grade 1 or less. Single Agent Maintenance Use Phase: Beginning 4 weeks after concomitant use phase completion, administer TEMODAR either orally or intravenously once daily on Days 1 to 5 of each 28-day cycle for 6 cycles. The recommended dosage of TEMODAR in the maintenance use phase is: Cycle 1: 150 mg/m 2 per day on days 1 to 5. Cycles 2 to 6: May increase to 200 mg/m 2 per day on days 1 to 5 before starting Cycle 2 if no dosage interruptions or discontinuations are required (Table 1). If the dose is not escalated at the onset of Cycle 2, do not increase the dose for Cycles 3 to 6. Obtain a complete blood count on Day 22 and then weekly until the ANC is above 1.5 × 10 9 /L and the platelet count is above 100 × 10 9 /L. Do not start the next cycle until the ANC and platelet count exceed these levels. The recommended dosage modifications due to adverse reactions during the maintenance use phase are provided in Table 2 . If TEMODAR is withheld, reduce the dose for the next cycle by 50 mg/m 2 per day. Permanently discontinue TEMODAR in patients who are unable to tolerate a dose of 100 mg/m 2 per day. TABLE 2: Dosage Modifications Due to Adverse Reactions During Maintenance and Adjuvant Treatment Adverse Reactions Interruption and Dose Reduction Discontinuation Absolute Neutrophil Count Withhold TEMODAR if ANC less than 1 × 10 9 /L.

6 ADVERSE REACTIONS The following clinically significant adverse reactions are described elsewhere in the labeling: Myelosuppression [see Warnings and Precautions (5.1) ] Hepatotoxicity [see Warnings and Precautions (5.2) ] Pneumocystis Pneumonia [see Warnings and Precautions (5.3) ] Secondary Malignancies [see Warnings and Precautions (5.4) ] The most common adverse reactions (≥20%) are: alopecia, fatigue, nausea, vomiting, headache, constipation, anorexia, and convulsions. ( 6.1 ) The most common Grade 3 to 4 hematologic laboratory abnormalities (≥10%) in patients with anaplastic astrocytoma are: decreased lymphocytes, decreased platelets, decreased neutrophils, and decreased leukocytes. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Merck Sharp & Dohme LLC at 1-877-888-4231 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Newly Diagnosed Glioblastoma The safety of TEMODAR was evaluated in study MK-7365-051 [see Clinical Studies (14.1) ]. Severe or life-threatening adverse reactions occurred in 49% of patients treated with TEMODAR; the most common were fatigue (13%), convulsions (6%), headache (5%), and thrombocytopenia (5%). The most common adverse reactions (≥20%) in patients treated with TEMODAR were alopecia, fatigue, nausea, anorexia, headache, constipation, and vomiting. Table 3 summarizes the adverse reactions in MK-7365-051. TABLE 3: Adverse Reactions (≥10%) in Patients with Newly Diagnosed Glioblastoma Adverse Reactions Concomitant Use Phase Maintenance Use Phase Radiation Therapy and TEMODAR N=288 One patient who was randomized to radiation therapy-only arm received radiation therapy and TEMODAR. Radiation Therapy Alone N=285 TEMODAR N=224 All Grades (%) Grade ≥3 (%) All Grades (%) Grades ≥3 (%) All Grades (%) Grade ≥3 (%) NOS = not otherwise specified. Note: Grade 5 (fatal) adverse reactions are included in the Grade ≥3 column. Skin and Subcutaneous Tissue Alopecia 69 0 63 0 55 0 Rash 19 1 15 0 13 1 General Fatigue 54 7 49 5 61 9 Anorexia 19 1 9 <1 27 1 Headache 19 2 17 4 23 4 Gastrointestinal System Nausea 36 1 16 <1 49 1 Vomiting 20 <1 6 <1 29 2 Constipation 18 1 6 0 22 0 Diarrhea 6 0 3 0 10 1 Central and Peripheral Nervous System Convulsions 6 3 7 3 11 3 Clinically relevant adverse reactions in <10% of patients are presented below: Central & Peripheral Nervous System: memory impairment, confusion Eye: v ision blurred Gastrointestinal System: stomatitis, abdominal pain General: weakness, dizziness Immune System: allergic reaction Injury: radiation injury not otherwise specified Musculoskeletal System: arthralgia Platelet, Bleeding, & Clotting: thrombocytopenia Psychiatric: insomnia Respiratory System: coughing, dyspnea Special Senses Other: taste perversion Skin & Subcutaneous Tissue: dry skin, pruritus, erythema When laboratory abnormalities and adverse reactions were combined, Grade 3 or Grade 4 neutrophil abnormalities including neutropenic reactions were observed in 8% of patients, and Grade 3 or Grade 4 platelet abnormalities including thrombocytopenic reactions were observed in 14% of patients. Newly Diagnosed Anaplastic Astrocytoma The safety of TEMODAR for the adjuvant treatment of adults with newly diagnosed anaplastic astrocytoma was derived from published literature [see Clinical Studies (14.2) ]. The safety of TEMODAR for the adjuvant treatment of patients with newly diagnosed anaplastic astrocytoma was consistent with the known safety profile of TEMODAR. Refractory Anaplastic Astrocytoma The safety of TEMODAR was evaluated in study MK-7365-006 [see Clinical Studies (14.2) ]. The most common adverse reactions (≥20%) were nausea, vomiting, headache, fatigue, constipation, and convulsions. Tables 4 and 5 summarize the adverse reactions and hematological laboratory abnormalities in MK-7365-006. TABLE 4: Adverse Reactions (≥10%) in Patients with Refractory Anaplastic Astrocytoma Adverse Reactions TEMODAR N=158 All Reactions (%) Grades 3-4 (%) Gastrointestinal System Nausea 53 10 Vomiting 42 6 Constipation 33 1 Diarrhea 16 2 General Headache 41 6 Fatigue 34 4 Asthenia 13 6 Fever 13 2 Central and Peripheral Nervous System Convulsions 23 5 Hemiparesis 18 6 Dizziness 12 1 Coordination abnormal 11 1 Amnesia 10 4 Insomnia 10 0 Cardiovascular Edema peripheral 11 1 Resistance Mechanism Infection viral 11 0 Clinically relevant adverse reactions in <10% of patients are presented below: Central and Peripheral Nervous System: paresthesia, somnolence, paresis, urinary incontinence, ataxia, dysphasia, convulsions local, gait abnormal, confusion Endocrine: adrenal hypercorticism Gastrointestinal System: abdominal pain, anorexia General: back pain Metabolic: weight increase Musculoskeletal System: mya