Entecavir

12.1 Mechanism of Action Entecavir is an antiviral drug against the hepatitis B virus [see Microbiology (12.4) ] .

1 INDICATIONS AND USAGE Entecavir tablets are indicated for the treatment of chronic hepatitis B virus infection in adults and pediatric patients 2 years of age and older with evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases (ALT or AST) or histologically active disease. Entecavir tablets are a hepatitis B virus nucleoside analogue reverse transcriptase inhibitor indicated for the treatment of chronic hepatitis B virus infection in adults and children at least 2 years of age with evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases (ALT or AST) or histologically active disease. ( 1 )

2 DOSAGE AND ADMINISTRATION Nucleoside-inhibitor-treatment-naïve with compensated liver disease (greater than or equal to 16 years old): 0.5 mg once daily. ( 2.2 ) Nucleoside-inhibitor-treatment-naïve and lamivudine-experienced pediatric patients at least 2 years of age and weighing at least 10 kg: dosing is based on weight. ( 2.3 ) Lamivudine-refractory or known lamivudine or telbivudine resistance substitutions (greater than or equal to 16 years old): 1 mg once daily. ( 2.2 ) Decompensated liver disease (adults): 1 mg once daily. ( 2.2 ) Renal impairment: Dosage adjustment is recommended if creatinine clearance is less than 50 mL/min. ( 2.4 ) Entecavir tablets should be administered on an empty stomach. ( 2.1 ) 2.1 Timing of Administration Entecavir tablets should be administered on an empty stomach (at least 2 hours after a meal and 2 hours before the next meal). 2.2 Recommended Dosage in Adults Compensated Liver Disease The recommended dose of entecavir tablets for chronic hepatitis B virus infection in nucleoside-inhibitor-treatment-naïve adults and adolescents 16 years of age and older is 0.5 mg once daily. The recommended dose of entecavir tablets in adults and adolescents (at least 16 years of age) with a history of hepatitis B viremia while receiving lamivudine or known lamivudine or telbivudine resistance substitutions rtM204I/V with or without rtL180M, rtL80I/V, or rtV173L is 1 mg once daily. Decompensated Liver Disease The recommended dose of entecavir tablets for chronic hepatitis B virus infection in adults with decompensated liver disease is 1 mg once daily. 2.3 Recommended Dosage in Pediatric Patients Table 1 describes the recommended dose of entecavir tablets for pediatric patients 2 years of age or older and weighing at least 10 kg. The oral solution should be used for patients with body weight up to 30 kg. Table 1: Dosing Schedule for Pediatric Patients Recommended Once-Daily Dose of Oral Solution (mL) Body Weight (kg) Treatment-Naïve Patients a Lamivudine-Experienced Patients b 10 to 11 3 6 greater than 11 to 14 4 8 greater than 14 to 17 5 10 greater than 17 to 20 6 12 greater than 20 to 23 7 14 greater than 23 to 26 8 16 greater than 26 to 30 9 18 greater than 30 10 20 a Children with body weight greater than 30 kg should receive 10 mL (0.5 mg) of oral solution or one 0.5 mg tablet once daily. b Children with body weight greater than 30 kg should receive 20 mL (1 mg) of oral solution or one 1 mg tablet once daily. 2.4 Renal Impairment In adult subjects with renal impairment, the apparent oral clearance of entecavir decreased as creatinine clearance decreased [see Clinical Pharmacology (12.3) ] . Dosage adjustment is recommended for patients with creatinine clearance less than 50 mL/min, including patients on hemodialysis or continuous ambulatory peritoneal dialysis (CAPD), as shown in Table 2. The once-daily dosing regimens are preferred. Table 2: Recommended Dosage of Entecavir Tablets in Adult Patients with Renal Impairment Creatinine Clearance (mL/min) Usual Dose (0.5 mg) Lamivudine-Refractory or Decompensated Liver Disease (1 mg) 50 or greater 0.5 mg once daily 1 mg once daily 30 to less than 50 0.5 mg every 48 hours 0.5 mg once daily OR 1 mg every 48 hours 10 to less than 30 0.5 mg every 72 hours 1 mg every 72 hours Less than 10 Hemodialysis * or CAPD 0.5 mg every 7 days 1 mg every 7 days * If administered on a hemodialysis day, administer entecavir tablets after the hemodialysis session. Although there are insufficient data to recommend a specific dose adjustment of entecavir tablets in pediatric patients with renal impairment, a reduction in the dose or an increase in the dosing interval similar to adjustments for adults should be considered. 2.5 Hepatic Impairment No dosage adjustment is necessary for patients with hepatic impairment. 2.6 Duration of Therapy The optimal duration of treatment with entecavir tablets for patients with chronic hepatitis B virus infection and the relationship between treatment and long-term outcomes such as cirrhosis and hepatocellular carcinoma are unknown.

6 ADVERSE REACTIONS The following adverse reactions are discussed in other sections of the labeling: Exacerbations of hepatitis after discontinuation of treatment [see Boxed Warning , Warnings and Precautions (5.1) ] . Lactic acidosis and severe hepatomegaly with steatosis [see Boxed Warning , Warnings and Precautions (5.3) ] . In adults, the most common adverse reactions (≥3%, all severity grades) are headache, fatigue, dizziness, and nausea. The adverse reactions observed in pediatric patients were consistent with those observed in adults. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Amneal Pharmaceuticals at 1-877-835-5472 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trial 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. Clinical Trial Experience in Adults Compensated Liver Disease Assessment of adverse reactions is based on four studies (AI463014, AI463022, AI463026, and AI463027) in which 1,720 subjects with chronic hepatitis B virus infection and compensated liver disease received double-blind treatment with entecavir 0.5 mg/day (n=679), entecavir 1 mg/day (n=183), or lamivudine (n=858) for up to 2 years. Median duration of therapy was 69 weeks for entecavir-treated subjects and 63 weeks for lamivudine-treated subjects in Studies AI463022 and AI463027 and 73 weeks for entecavir-treated subjects and 51 weeks for lamivudine-treated subjects in Studies AI463026 and AI463014. The safety profiles of entecavir and lamivudine were comparable in these studies. The most common adverse reactions of any severity (≥3%) with at least a possible relation to study drug for entecavir-treated subjects were headache, fatigue, dizziness, and nausea. The most common adverse reactions among lamivudine-treated subjects were headache, fatigue, and dizziness. One percent of entecavir-treated subjects in these four studies compared with 4% of lamivudine-treated subjects discontinued for adverse events or abnormal laboratory test results. Clinical adverse reactions of moderate-severe intensity and considered at least possibly related to treatment occurring during therapy in four clinical studies in which entecavir was compared with lamivudine are presented in Table 3. Table 3: Clinical Adverse Reactions a of Moderate-Severe Intensity (Grades 2 to 4) Reported in Four Entecavir Clinical Trials Through 2 Years Nucleoside-Inhibitor-Naïve b Lamivudine-Refractory c Entecavir Lamivudine Entecavir Lamivudine Body System/ Adverse Reaction 0.5 mg 100 mg 1 mg 100 mg n=679 n=668 n=183 n=190 Any Grade 2 to 4 adverse reaction a 15% 18% 22% 23% Gastrointestinal Diarrhea <1% 0 1% 0 Dyspepsia <1% <1% 1% 0 Nausea <1% <1% <1% 2% Vomiting <1% <1% <1% 0 General Fatigue 1% 1% 3% 3% Nervous System Headache 2% 2% 4% 1% Dizziness <1% <1% 0 1% Somnolence <1% <1% 0 0 Psychiatric Insomnia <1% <1% 0 <1% a Includes events of possible, probable, certain, or unknown relationship to treatment regimen. b Studies AI463022 and AI463027. c Includes Study AI463026 and the entecavir 1 mg and lamivudine treatment arms of Study AI463014, a Phase 2 multinational, randomized, double-blind study of three doses of entecavir (0.1, 0.5, and 1 mg) once daily versus continued lamivudine 100 mg once daily for up to 52 weeks in subjects who experienced recurrent viremia on lamivudine therapy. Laboratory Abnormalities Frequencies of selected treatment-emergent laboratory abnormalities reported during therapy in four clinical trials of entecavir compared with lamivudine are listed in Table 4. Table 4: Selected Treatment-Emergent a Laboratory Abnormalities Reported in Four Entecavir Clinical Trials Through 2 Years Nucleoside-Inhibitor-Naïve b Lamivudine-Refractory c Entecavir Lamivudine Entecavir Lamivudine 0.5 mg 100 mg 1 mg 100 mg Test n=679 n=668 n=183 n=190 Any Grade 3 to 4 laboratory abnormality d 35% 36% 37% 45% ALT >10 x ULN and >2 x baseline 2% 4% 2% 11% ALT >5 x ULN 11% 16% 12% 24% Albumin <2.5 g/dL <1% <1% 0 2% Total bilirubin >2.5 x ULN 2% 2% 3% 2% Lipase ≥2.1 x ULN 7% 6% 7% 7% Creatinine >3 x ULN 0 0 0 0 Confirmed creatinine increase ≥0.5 mg/dL 1% 1% 2% 1% Hyperglycemia, fasting >250 mg/dL 2% 1% 3% 1% Glycosuria e 4% 3% 4% 6% Hematuria f 9% 10% 9% 6% Platelets <50,000/mm 3 <1% <1% <1% <1% a On-treatment value worsened from baseline to Grade 3 or Grade 4 for all parameters except albumin (any on-treatment value <2.5 g/dL), confirmed creatinine increase ≥0.5 mg/dL, and ALT >10 x ULN and >2 x baseline. b Studies AI463022 and AI463027. c Includes Study AI463026 and the entecavir 1 mg and lamivudine treatment arms of Study AI463014, a Phase 2 multinational, randomized, double-blind study of three doses of entecavir (0.1, 0.5, and 1 mg) once daily versus continued lamivudine 100 mg once daily for up to 52 weeks in subjects

7 DRUG INTERACTIONS Since entecavir is primarily eliminated by the kidneys [see Clinical Pharmacology (12.3) ] , co-administration of entecavir with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either entecavir or the co-administered drug. Co-administration of entecavir with lamivudine, adefovir dipivoxil, or tenofovir disoproxil fumarate did not result in significant drug interactions. The effects of co-administration of entecavir with other drugs that are renally eliminated or are known to affect renal function have not been evaluated, and patients should be monitored closely for adverse events when entecavir is co-administered with such drugs.