Temozolomide: Package Insert and Label Information (Page 2 of 5)
6.2 Postmarketing Experience
The following adverse reactions have been identified during post-approval use of temozolomide. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to the drug exposure.
Dermatologic: Toxic epidermal necrolysis and Stevens-Johnson syndrome
Immune System: Hypersensitivity reactions, including anaphylaxis. Erythema multiforme, which
resolved after discontinuation of temozolomide and, in some cases, recurred upon rechallenge.
Hematopoietic: Prolonged pancytopenia, which may result in aplastic anemia and fatal outcomes.
Hepatobiliary: Fatal and severe hepatotoxicity, elevation of liver enzymes, hyperbilirubinemia, cholestasis, and hepatitis.
Infections: Serious opportunistic infections, including some cases with fatal outcomes, with bacterial, viral (primary and reactivated), fungal, and protozoan organisms.
Pulmonary: Interstitial pneumonitis, pneumonitis, alveolitis, and pulmonary fibrosis.
Endocrine: Diabetes insipidus
8 USE IN SPECIFIC POPULATIONS
Based on its mechanism of action [see Clinical Pharmacology (12.1)] and findings from animal studies, temozolomide can cause fetal harm when administered to a pregnant woman. Available postmarketing reports describe cases of spontaneous abortions and congenital malformations, including polymalformations with central nervous system, facial, cardiac, skeletal, and genitourinary system anomalies with exposure to temozolomide during pregnancy. These cases report similar adverse developmental outcomes to those observed in animal studies. Administration of temozolomide to rats and rabbits during the period of organogenesis caused numerous external, internal, and skeletal malformations at doses less than the maximum human dose based on body surface area (see Data). Advise pregnant women of the potential risk to a fetus.
In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.
Five consecutive days of oral administration of temozolomide at doses of 75 and 150 mg/m2 (0.38 and 0.75 times the human dose of 200 mg/m2) in rats and rabbits, respectively, during the period of organogenesis (Gestation Days 8-12) caused numerous malformations of the external and internal organs and skeleton in both species. In rabbits, temozolomide at the 150 mg/m2 dose (0.75 times the human dose of 200 mg/m2) caused embryolethality as indicated by increased resorptions.
There are no data on the presence of temozolomide or its metabolites in human milk, the effects on a breastfed child, or the effects on milk production. Because of the potential for serious adverse reactions, including myelosuppression from temozolomide in the breastfed children, advise women not to breastfeed during treatment with temozolomide and for at least 1 week after the final dose.
8.3 Females and Males of Reproductive Potential
Verify pregnancy status in females of reproductive potential prior to initiating temozolomide [see Use in Specific Populations (8.1)].
Temozolomide can cause embryo-fetal harm when administered to a pregnant woman [see Use in Specific Populations (8.1)]. Advise females of reproductive potential to use effective contraception during treatment with temozolomide and for at least 6 months after the last dose.
Because of the potential for embryofetal toxicity and genotoxic effects on sperm cells, advise male patients with pregnant partners or female partners of reproductive potential to use condoms during treatment with temozolomide and for at least 3 months after the final dose [see Use in Specific Populations (8.1), Nonclinical Toxicology (13.1)].
Advise male patients not to donate semen during treatment with temozolomide and for at least 3 months after the final dose.
Temozolomide may impair male fertility [see Nonclinical Toxicology (13.1)]. Limited data from male patients show changes in sperm parameters during treatment with temozolomide; however, no information is available on the duration or reversibility of these changes.
8.4 Pediatric Use
Safety and effectiveness of temozolomide have not been established in pediatric patients. Safety and effectiveness of temozolomide capsules were assessed, but not established, in 2 open-label studies in pediatric patients aged 3 to 18 years. In one study, 29 patients with recurrent brain stem glioma and 34 patients with recurrent high-grade astrocytoma were enrolled. In a second study conducted by the Children’s Oncology Group (COG), 122 patients were enrolled, including patients with medulloblastoma/PNET (29), high grade astrocytoma (23), low grade astrocytoma (22), brain stem glioma (16), ependymoma (14), other CNS tumors (9), and non-CNS tumors (9). The adverse reaction profile in pediatric patients was similar to adults.
8.5 Geriatric Use
In the Newly Diagnosed Glioblastoma trial, Study MK-7365-051, 15% of patients were 65 years and older. This study did not include sufficient numbers of patients aged 65 years and older to determine differences in effectiveness from younger patients. No overall differences in safety were observed between patients ≥ 65 years and younger patients.
In the Refractory Anaplastic Astrocytoma trial, Study MK-7365-0006, 4% of patients were 70 years and older. This study did not include sufficient numbers of patients aged 70 years and older to determine differences in effectiveness from younger patients. Patients 70 years and older had a higher incidence of Grade 4 neutropenia (25%) and Grade 4 thrombocytopenia (20%) in the first cycle of therapy than patients less than 70 years of age [see Warnings and Precautions (5.1), Adverse Reactions (6.1)].
8.6 Renal Impairment
No dosage adjustment is recommended for patients with creatinine clearance (CLcr) of 36 to 130 mL/min/m2 [see Clinical Pharmacology (12.3)]. The recommended dose of temozolomide has not been established for patients with severe renal impairment (CLcr < 36 mL/min/m2) or for patients with end-stage renal disease on dialysis.
8.7 Hepatic Impairment
No dosage adjustment is recommended for patients with mild to moderate hepatic impairment (Child Pugh class A and B) [see Clinical Pharmacology (12.3)]. The recommended dose of temozolomide has not been established for patients with severe hepatic impairment (Child-Pugh class C).
Dose-limiting toxicity was myelosuppression and was reported with any dose but is expected to be more severe at higher doses. An overdose of 2000 mg per day for 5 days was taken by one patient and the adverse reactions reported were pancytopenia, pyrexia, multi-organ failure, and death. There are reports of patients who have taken more than 5 days of treatment (up to 64 days), with adverse reactions reported including myelosuppression, which in some cases was severe and prolonged, and infections and resulted in death. In the event of an overdose, monitor complete blood count and provide supportive measures as necessary.
Temozolomide, USP is an alkylating drug. The chemical name of temozolomide, USP is 3,4-dihydro-3-methyl-4-oxoimidazo[5,1-d]-as -tetrazine-8-carboxamide. The structural formula of temozolomide, USP is:
The material is a white to light tan/light pink powder with a molecular formula of C6 H6 N6 O2 and a molecular weight of 194.15. The molecule is stable at acidic pH (< 5) and labile at pH > 7; hence temozolomide, USP can be administered orally. The prodrug, temozolomide, USP, is rapidly hydrolyzed to the active 5-(3-methyltriazen-1-yl) imidazole-4-carboxamide (MTIC) at neutral and alkaline pH values, with hydrolysis taking place even faster at alkaline pH.
Temozolomide capsules, USP:
Each capsule for oral use contains either 5 mg, 20 mg, 100 mg, 140 mg, 180 mg, or 250 mg of temozolomide, USP.
The inactive ingredients for temozolomide capsules, USP are as follows: colloidal silicon dioxide, ethyl alcohol, lactose anhydrous, sodium starch glycolate, stearic acid and tartaric acid.
The body of the capsules are made of gelatin and titanium dioxide, and are white opaque color. The cap is also made of gelatin, and the colors vary based on the dosage strength. The capsule body and cap are imprinted with pharmaceutical branding ink, which contains alcohol, D&C Yellow #10, FD&C Blue #1, FD&C Blue #2, FD&C Red #40, iron oxide black, n-butyl alcohol, propylene glycol and shellac.
Temozolomide Capsules USP, 5 mg : The green cap contains FD&C Blue #2, gelatin, titanium dioxide and yellow iron oxide.
Temozolomide Capsules USP, 20 mg : The yellow cap contains D&C Yellow #10, FD&C Yellow #6, gelatin and titanium dioxide.
Temozolomide Capsules USP, 100 mg : The pink cap contains FD&C Blue #1, FD&C Red #3, FD&C Red #40, gelatin and titanium dioxide.
Temozolomide Capsules USP, 140 mg : The blue cap contains FD&C Blue #1, gelatin and titanium dioxide.
Temozolomide Capsules USP, 180 mg : The red cap contains FD&C Blue #1, FD&C Red #40, gelatin and titanium dioxide.
Temozolomide Capsules USP, 250 mg : The white cap contains gelatin and titanium dioxide.
12 CLINICAL PHARMACOLOGY
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 alkylation of DNA. Alkylation (methylation) occurs mainly at the O6 and N7 positions of guanine.
Following a single oral dose of 150 mg/m2 , the mean Cmax value for temozolomide was 7.5 mcg/mL and for MTIC was 282 ng/mL. The mean AUC value for temozolomide was 23.4 mcg·hr/mL and for MTIC was 864 ng·hr/mL.
Following a single 90-minute intravenous infusion of 150 mg/m2 , the mean Cmax value for temozolomide was 7.3 mcg/mL and for MTIC was 276 ng/mL. The mean AUC value for temozolomide was 24.6 mcg·hr/mL and for MTIC was 891 ng·hr/mL.
Temozolomide exhibits linear kinetics over the therapeutic dosing range of 75 mg/m2 /day to 250 mg/m2 /day.
The median Tmax is 1 hour.
Effect of Food
The mean Cmax and AUC decreased by 32% and 9%, respectively, and median Tmax increased by 2-fold (from 1 to 2.25 hours) when temozolomide capsules were administered after a modified high-fat breakfast (587 calories comprised of 1 fried egg, 2 strips of bacon, 2 slices of toast, 2 pats of butter, and 8 oz whole milk).
Temozolomide has a mean apparent volume of distribution of 0.4 L/kg (%CV=13%). The mean percent bound of drug-related total radioactivity is 15%.
Clearance of temozolomide is about 5.5 L/hr/m2 and the mean elimination half-life is 1.8 hours.
Temozolomide is spontaneously hydrolyzed at physiologic pH to the active species, MTIC and to temozolomide acid metabolite. MTIC is further hydrolyzed to 5-amino-imidazole-4-carboxamide (AIC), which is known to be an intermediate in purine and nucleic acid biosynthesis, and to methylhydrazine, which is believed to be the active alkylating species. Cytochrome P450 enzymes play only a minor role in the metabolism of temozolomide and MTIC. Relative to the AUC of temozolomide, the exposure to MTIC and AIC is 2.4% and 23%, respectively.
About 38% of the administered temozolomide total radioactive dose is recovered over 7 days: 38% in urine and 0.8% in feces. The majority of the recovery of radioactivity in urine is unchanged temozolomide (6%), AIC (12%), temozolomide acid metabolite (2.3%), and unidentified polar metabolite(s) (17%).
No clinically meaningful differences in the pharmacokinetics of temozolomide were observed based on age (range: 19 to 78 years), gender, smoking status (smoker vs. non-smoker), creatinine clearance (CLcr) of 36 to 130 mL/min/m2 , or mild to moderate hepatic impairment (Child Pugh class A and B). The pharmacokinetics of temozolomide has not been studied in patients with CLcr < 36 mL/min/m2 , end-stage renal disease on dialysis, or severe hepatic impairment (Child-Pugh class C).
Drug Interaction Studies
Effect of Other Drugs on Temozolomide Pharmacokinetics:
In a multiple-dose study, administration of temozolomide capsules with ranitidine did not change the Cmax or AUC values for temozolomide or MTIC.
A population analysis indicated that administration of valproic acid decreases the clearance of temozolomide by about 5%.
A population analysis did not demonstrate any influence of coadministered dexamethasone, prochlorperazine, phenytoin, carbamazepine, ondansetron, histamine-2-receptor antagonists, or phenobarbital on the clearance of orally administered temozolomide.
13 NONCLINICAL TOXICOLOGY
13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
Temozolomide is carcinogenic in rats at doses less than the maximum recommended human dose. Temozolomide induced mammary carcinomas in both males and females at doses 0.13 to 0.63 times the maximum human dose (25-125 mg/m2) when administered orally on 5 consecutive days every 28 days for 6 cycles. Temozolomide also induced fibrosarcomas of the heart, eye, seminal vesicles, salivary glands, abdominal cavity, uterus, and prostate, carcinomas of the seminal vesicles, schwannomas of the heart, optic nerve, and harderian gland, and adenomas of the skin, lung, pituitary, and thyroid at doses 0.5 times the maximum daily dose. Mammary tumors were also induced following 3 cycles of temozolomide at the maximum recommended daily dose.
Temozolomide is a mutagen and a clastogen. In a reverse bacterial mutagenesis assay (Ames assay), temozolomide increased revertant frequency in the absence and presence of metabolic activation. Temozolomide was clastogenic in human lymphocytes in the presence and absence of metabolic activation.
Temozolomide impairs male fertility. Temozolomide caused syncytial cells/immature sperm formation at doses of 50 and 125 mg/m2 (0.25 and 0.63 times the human dose of 200 mg/m2) in rats and dogs, respectively, and testicular atrophy in dogs at 125 mg/m2.
13.2 Animal Toxicology and/or Pharmacology
Toxicology studies in rats and dogs identified a low incidence of hemorrhage, degeneration, and necrosis of the retina at temozolomide doses equal to or greater than 125 mg/m2 (0.63 times the human dose of 200 mg/m2). These changes were most commonly seen at doses where mortality was observed.
14 CLINICAL STUDIES
14.1 Newly Diagnosed Glioblastoma
The efficacy of temozolomide was evaluated in Study MK-7365-051, a randomized (1:1), multicenter, open-label trial. Eligible patients were required to have newly diagnosed glioblastoma. Patients were randomized to receive either radiation therapy alone or concomitant temozolomide 75 mg/m2 once daily starting the first day of radiation therapy and continuing until the last day of radiation therapy for 42 days (with a maximum of 49 days), followed by temozolomide 150 mg/m2 or 200 mg/m2 once daily on Days 1 to 5 of each 28-day cycle, starting 4 weeks after the end of radiation therapy and continuing for 6 cycles. In both arms, focal radiation therapy was delivered as 60 Gy/30 fractions and included radiation to the tumor bed or resection site with a 2- to 3-cm margin. PCP prophylaxis was required during the concomitant phase regardless of lymphocyte count and continued until recovery of lymphocyte count to Grade 1 or less. The major efficacy outcome measure was overall survival.
A total of 573 patients were randomized, 287 to temozolomide and radiation therapy and 286 to radiation therapy alone. At the time of disease progression, temozolomide was administered as salvage therapy in 161 patients of the 282 (57%) in the radiation therapy alone arm and 62 patients of the 277 (22%) in the temozolomide and radiation therapy arm.
The addition of concomitant and maintenance temozolomide to radiation therapy for the treatment of patients with newly diagnosed glioblastoma showed a statistically significant improvement in overall survival compared to radiotherapy alone (Figure 1). The hazard ratio (HR) for overall survival was 0.63 (95% CI: 0.52, 0.75) with a log-rank P < 0.0001 in favor of the temozolomide arm. The median survival was increased by 2.5 months in the temozolomide arm.
FIGURE 1: Kaplan-Meier Curves for Overall Survival (ITT Population) in Newly Diagnosed Glioblastoma Trial
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