ENTECAVIR: 4,487 Adverse Event Reports & Safety Profile

BARACLUDE ® is the tradename for entecavir, a guanosine nucleoside analogue with selective activity against HBV. The chemical name for entecavir is 2-amino-1,9-dihydro-9-[( 1S,3R,4S )-4-hydroxy-3-(hydroxymethyl)-2-methylenecyclopentyl]-6 H -purin-6-one, monohydrate. Its molecular formula is C 12 H 15 N 5 O 3

• H 2 O, which corresponds to a molecular weight of 295.3. Entecavir has the following structural formula: Entecavir is a white to off-white powder. It is slightly soluble in water (2.4 mg/mL), and the pH of the saturated solution in water is 7.9 at 25° C ± 0.5° C. BARACLUDE film-coated tablets are available for oral administration in strengths of 0.5 mg and 1 mg of entecavir. BARACLUDE 0.5 mg and 1 mg film-coated tablets contain the following inactive ingredients: lactose monohydrate, microcrystalline cellulose, crospovidone, povidone, and magnesium stearate. The tablet coating contains titanium dioxide, hypromellose, polyethylene glycol 400, polysorbate 80 (0.5 mg tablet only), and iron oxide red (1 mg tablet only).

Baraclude

Oral Solution is available for oral administration as a ready-to-use solution containing 0.05 mg of entecavir per milliliter.

Baraclude

Oral Solution contains the following inactive ingredients: maltitol, sodium citrate, citric acid, methylparaben, propylparaben, and orange flavor. entecavir structure.jpg

AND USAGE Entecavir tablet is 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 ) Entecavir tablet is 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. The following points should be considered when initiating therapy with entecavir tablet: In adult patients, this indication is based on clinical trial data in nucleoside-inhibitor-treatment-naïve and lamivudine-resistant subjects with HBeAg-positive and HBeAg-negative HBV infection and compensated liver disease and a more limited number of subjects with decompensated liver disease [see Clinical Studies ( 14.1 ) ]. In pediatric patients 2 years of age and older and weighing greater than 30 kg, this indication is based on clinical trial data in nucleoside-inhibitor-treatment-naïve and in a limited number of lamivudine-experienced subjects with HBeAg-positive chronic HBV infection and compensated liver disease [see Clinical Studies ( 14.2 )].

AND ADMINISTRATION

2.1 Timing of Administration

2.4 Renal Impairment

2.2 Recommended Dosage in Adults

2.5 Hepatic Impairment

2.3 Recommended Dosage in Pediatric Patients

2.6 Duration of Therapy

• 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 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 Peditric Patients Recommended Once-Daily Dose of Oral Solution (mL)

Body

Weight (kg)

Treatment Naive

Patients a Lamuvidine-Experienced Patients b 10 o 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 <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.3)]</span>. 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) Lamividune-Refractory or Decompensated Liver Disease (1 mg) 50 or greater 0.5 mg once daily 1 mg once daily 30 to less than 50 0.25 mg once dailya OR 0.5 mg every 48 hours 0.5 mg once daily OR 1 mg every 48 hours 10 to less than 30 0.15 mg once dailya OR 0.5 mg every 72 hours 0.3 mg once dailya OR 1 mg every 72 hours Less than 10 Hemodialysisb or CAPD 0.05 mg once dailya OR 0.5 mg every 7 days 0.1 mg once dailya OR 1 mg every 7 day a For doses less than 0.5 mg, entecavir oral solution is recommended. b 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 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.

None.

• None. (4)

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 Yaopharma at 1-609-285-5783 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 1720 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 2–4) Reported in Four Entecavir Clinical Trials Through 2 Years Nucleoside-Inhibitor-Naïve b Lamivudine-Refractory c Body System/ Adverse Reaction Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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.

Any Grade

2–4 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% 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 Test Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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 × ULN and >2 × 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 who experienced recurrent viremia on lamivudine therapy. d Includes hematology, routine chemistries, renal and liver function tests, pancreatic enzymes, and urinalysis. e Grade 3 = 3+, large, ≥500 mg/dL; Grade 4 = 4+, marked, severe. f Grade 3 = 3+, large; Grade 4 = ≥4+, marked, severe, many. ULN=upper limit of normal.

Any Grade

3–4 laboratory abnormality d 35% 36% 37% 45% ALT >10 × ULN and >2 × baseline 2% 4% 2% 11% ALT >5 × ULN 11% 16% 12% 24% Albumin <2.5 g/dL <1% <1% 0 2% Total bilirubin >2.5 × ULN 2% 2% 3% 2% Lipase ≥2.1 × ULN 7% 6% 7% 7% Creatinine >3 × 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% Among entecavir-treated subjects in these studies, on-treatment ALT elevations greater than 10 times the upper limit of normal (ULN) and greater than 2 times baseline generally resolved with continued treatment. A majority of these exacerbations were associated with a ≥ 2 log 10 /mL reduction in viral load that preceded or coincided with the ALT elevation. Periodic monitoring of hepatic function is recommended during treatment. Exacerbations of Hepatitis after Discontinuation of Treatment An exacerbation of hepatitis or ALT flare was defined as ALT greater than 10 times ULN and greater than 2 times the subject’s reference level (minimum of the baseline or last measurement at end of dosing). For all subjects who discontinued treatment (regardless of reason), Table 5 presents the proportion of subjects in each study who experienced post-treatment ALT flares. In these studies, a subset of subjects was allowed to discontinue treatment at or after 52 weeks if they achieved a protocol-defined response to therapy. If entecavir is discontinued without regard to treatment response, the rate of post-treatment flares could be higher. [See Warnings and Precautions (5.1) .]

Table

5: Exacerbations of Hepatitis During Off-Treatment Follow-up, Subjects in Studies AI463022, AI463027, and AI463026 Subjects with ALT Elevations >10 × ULN and >2 × Reference a Entecavir Lamivudine a Reference is the minimum of the baseline or last measurement at end of dosing. Median time to off-treatment exacerbation was 23 weeks for entecavir-treated subjects and 10 weeks for lamivudine-treated subjects. Nucleoside-inhibitor-naïve HBeAg-positive 4/174 (2%) 13/147 (9%) HBeAg-negative 24/302 (8%) 30/270 (11%) Lamivudine-refractory 6/52 (12%) 0/16 Decompensated Liver Disease Study AI463048 was a randomized, open-label study of entecavir 1 mg once daily versus adefovir dipivoxil 10 mg once daily given for up to 48 weeks in adult subjects with chronic HBV infection and evidence of hepatic decompensation, defined as a Child-Turcotte-Pugh (CTP) score of 7 or higher [see Clinical Studies (14.1) ] . Among the 102 subjects receiving entecavir, the most common treatment-emergent adverse events of any severity, regardless of causality, occurring through Week 48 were peripheral edema (16%), ascites (15%), pyrexia (14%), hepatic encephalopathy (10%), and upper respiratory infection (10%). Clinical adverse reactions not listed in Table 3 that were observed through Week 48 include blood bicarbonate decreased (2%) and renal failure (< 1%). Eighteen of 102 (18%) subjects treated with entecavir and 18/89 (20%) subjects treated with adefovir dipivoxil died during the first 48 weeks of therapy. The majority of deaths (11 in the entecavir group and 16 in the adefovir dipivoxil group) were due to liver-related causes such as hepatic failure, hepatic encephalopathy, hepatorenal syndrome, and upper gastrointestinal hemorrhage. The rate of hepatocellular carcinoma (HCC) through Week 48 was 6% (6/102) for subjects treated with entecavir and 8% (7/89) for subjects treated with adefovir dipivoxil. Five percent of subjects in either treatment arm discontinued therapy due to an adverse event through Week 48. No subject in either treatment arm experienced an on-treatment hepatic flare (ALT >2 × baseline and >10 × ULN) through Week 48. Eleven of 102 (11%) subjects treated with entecavir and 11/89 (13%) subjects treated with adefovir dipivoxil had a confirmed increase in serum creatinine of 0.5 mg/dL through Week 48. HIV/HBV Co-infected The safety profile of entecavir 1 mg (n = 51) in HIV/HBV co-infected subjects enrolled in Study AI463038 was similar to that of placebo (n = 17) through 24 weeks of blinded treatment and similar to that seen in non-HIV infected subjects [see Warnings and Precautions (5.2) ] .

Liver Transplant Recipients Among

65 subjects receiving entecavir in an open-label, post-liver transplant trial [see Use in Specific Populations (8.8) ] , the frequency and nature of adverse events were consistent with those expected in patients who have received a liver transplant and the known safety profile of entecavir.

Clinical Trial

Experience in Pediatric Subjects The safety of entecavir in pediatric subjects 2 to less than 18 years of age is based on two ongoing clinical trials in subjects with chronic HBV infection (one Phase 2 pharmacokinetic trial [AI463028] and one Phase 3 trial [AI463189]). These trials provide experience in 168 HBeAg-positive subjects treated with entecavir for a median duration of 72 weeks. The adverse reactions observed in pediatric subjects who received treatment with entecavir were consistent with those observed in clinical trials of entecavir in adults. Adverse drug reactions reported in greater than 1% of pediatric subjects included abdominal pain, rash events, poor palatability (“product taste abnormal”), nausea, diarrhea, and vomiting.

6.2 Postmarketing Experience The following adverse reactions have been reported during postmarketing use of entecavir. Because these reactions were reported voluntarily from a population of unknown size, it is not possible to reliably estimate their frequency or establish a causal relationship to entecavir exposure. Immune system disorders: Anaphylactoid reaction. Metabolism and nutrition disorders: Lactic acidosis. Hepatobiliary disorders: Increased transaminases. Skin and subcutaneous tissue disorders: Alopecia, rash.

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 1720 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 2–4) Reported in Four Entecavir Clinical Trials Through 2 Years Nucleoside-Inhibitor-Naïve b Lamivudine-Refractory c Body System/ Adverse Reaction Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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.

Any Grade

2–4 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% 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 Test Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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 × ULN and >2 × 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 who experienced recurrent viremia on lamivudine therapy. d Includes hematology, routine chemistries, renal and liver function tests, pancreatic enzymes, and urinalysis. e Grade 3 = 3+, large, ≥500 mg/dL; Grade 4 = 4+, marked, severe. f Grade 3 = 3+, large; Grade 4 = ≥4+, marked, severe, many. ULN=upper limit of normal.

Any Grade

3–4 laboratory abnormality d 35% 36% 37% 45% ALT >10 × ULN and >2 × baseline 2% 4% 2% 11% ALT >5 × ULN 11% 16% 12% 24% Albumin <2.5 g/dL <1% <1% 0 2% Total bilirubin >2.5 × ULN 2% 2% 3% 2% Lipase ≥2.1 × ULN 7% 6% 7% 7% Creatinine >3 × 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% Among entecavir-treated subjects in these studies, on-treatment ALT elevations greater than 10 times the upper limit of normal (ULN) and greater than 2 times baseline generally resolved with continued treatment. A majority of these exacerbations were associated with a ≥ 2 log 10 /mL reduction in viral load that preceded or coincided with the ALT elevation. Periodic monitoring of hepatic function is recommended during treatment. Exacerbations of Hepatitis after Discontinuation of Treatment An exacerbation of hepatitis or ALT flare was defined as ALT greater than 10 times ULN and greater than 2 times the subject’s reference level (minimum of the baseline or last measurement at end of dosing). For all subjects who discontinued treatment (regardless of reason), Table 5 presents the proportion of subjects in each study who experienced post-treatment ALT flares. In these studies, a subset of subjects was allowed to discontinue treatment at or after 52 weeks if they achieved a protocol-defined response to therapy. If entecavir is discontinued without regard to treatment response, the rate of post-treatment flares could be higher. [See Warnings and Precautions (5.1) .]

Table

5: Exacerbations of Hepatitis During Off-Treatment Follow-up, Subjects in Studies AI463022, AI463027, and AI463026 Subjects with ALT Elevations >10 × ULN and >2 × Reference a Entecavir Lamivudine a Reference is the minimum of the baseline or last measurement at end of dosing. Median time to off-treatment exacerbation was 23 weeks for entecavir-treated subjects and 10 weeks for lamivudine-treated subjects. Nucleoside-inhibitor-naïve HBeAg-positive 4/174 (2%) 13/147 (9%) HBeAg-negative 24/302 (8%) 30/270 (11%) Lamivudine-refractory 6/52 (12%) 0/16 Decompensated Liver Disease Study AI463048 was a randomized, open-label study of entecavir 1 mg once daily versus adefovir dipivoxil 10 mg once daily given for up to 48 weeks in adult subjects with chronic HBV infection and evidence of hepatic decompensation, defined as a Child-Turcotte-Pugh (CTP) score of 7 or higher [see Clinical Studies (14.1) ] . Among the 102 subjects receiving entecavir, the most common treatment-emergent adverse events of any severity, regardless of causality, occurring through Week 48 were peripheral edema (16%), ascites (15%), pyrexia (14%), hepatic encephalopathy (10%), and upper respiratory infection (10%). Clinical adverse reactions not listed in Table 3 that were observed through Week 48 include blood bicarbonate decreased (2%) and renal failure (< 1%). Eighteen of 102 (18%) subjects treated with entecavir and 18/89 (20%) subjects treated with adefovir dipivoxil died during the first 48 weeks of therapy. The majority of deaths (11 in the entecavir group and 16 in the adefovir dipivoxil group) were due to liver-related causes such as hepatic failure, hepatic encephalopathy, hepatorenal syndrome, and upper gastrointestinal hemorrhage. The rate of hepatocellular carcinoma (HCC) through Week 48 was 6% (6/102) for subjects treated with entecavir and 8% (7/89) for subjects treated with adefovir dipivoxil. Five percent of subjects in either treatment arm discontinued therapy due to an adverse event through Week 48. No subject in either treatment arm experienced an on-treatment hepatic flare (ALT >2 × baseline and >10 × ULN) through Week 48. Eleven of 102 (11%) subjects treated with entecavir and 11/89 (13%) subjects treated with adefovir dipivoxil had a confirmed increase in serum creatinine of 0.5 mg/dL through Week 48. HIV/HBV Co-infected The safety profile of entecavir 1 mg (n = 51) in HIV/HBV co-infected subjects enrolled in Study AI463038 was similar to that of placebo (n = 17) through 24 weeks of blinded treatment and similar to that seen in non-HIV infected subjects [see Warnings and Precautions (5.2) ] .

Liver Transplant Recipients Among

65 subjects receiving entecavir in an open-label, post-liver transplant trial [see Use in Specific Populations (8.8) ] , the frequency and nature of adverse events were consistent with those expected in patients who have received a liver transplant and the known safety profile of entecavir.

Clinical Trial

Experience in Pediatric Subjects The safety of entecavir in pediatric subjects 2 to less than 18 years of age is based on two ongoing clinical trials in subjects with chronic HBV infection (one Phase 2 pharmacokinetic trial [AI463028] and one Phase 3 trial [AI463189]). These trials provide experience in 168 HBeAg-positive subjects treated with entecavir for a median duration of 72 weeks. The adverse reactions observed in pediatric subjects who received treatment with entecavir were consistent with those observed in clinical trials of entecavir in adults. Adverse drug reactions reported in greater than 1% of pediatric subjects included abdominal pain, rash events, poor palatability (“product taste abnormal”), nausea, diarrhea, and vomiting.

Clinical Trial

Experience in Adults Compensated Liver Disease Assessment of adverse reactions is based on four studies (AI463014, AI463022, AI463026, and AI463027) in which 1720 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 2–4) Reported in Four Entecavir Clinical Trials Through 2 Years Nucleoside-Inhibitor-Naïve b Lamivudine-Refractory c Body System/ Adverse Reaction Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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.

Any Grade

2–4 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% 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 Test Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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 × ULN and >2 × 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 who experienced recurrent viremia on lamivudine therapy. d Includes hematology, routine chemistries, renal and liver function tests, pancreatic enzymes, and urinalysis. e Grade 3 = 3+, large, ≥500 mg/dL; Grade 4 = 4+, marked, severe. f Grade 3 = 3+, large; Grade 4 = ≥4+, marked, severe, many. ULN=upper limit of normal.

Any Grade

3–4 laboratory abnormality d 35% 36% 37% 45% ALT >10 × ULN and >2 × baseline 2% 4% 2% 11% ALT >5 × ULN 11% 16% 12% 24% Albumin <2.5 g/dL <1% <1% 0 2% Total bilirubin >2.5 × ULN 2% 2% 3% 2% Lipase ≥2.1 × ULN 7% 6% 7% 7% Creatinine >3 × 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% Among entecavir-treated subjects in these studies, on-treatment ALT elevations greater than 10 times the upper limit of normal (ULN) and greater than 2 times baseline generally resolved with continued treatment. A majority of these exacerbations were associated with a ≥ 2 log 10 /mL reduction in viral load that preceded or coincided with the ALT elevation. Periodic monitoring of hepatic function is recommended during treatment. Exacerbations of Hepatitis after Discontinuation of Treatment An exacerbation of hepatitis or ALT flare was defined as ALT greater than 10 times ULN and greater than 2 times the subject’s reference level (minimum of the baseline or last measurement at end of dosing). For all subjects who discontinued treatment (regardless of reason), Table 5 presents the proportion of subjects in each study who experienced post-treatment ALT flares. In these studies, a subset of subjects was allowed to discontinue treatment at or after 52 weeks if they achieved a protocol-defined response to therapy. If entecavir is discontinued without regard to treatment response, the rate of post-treatment flares could be higher. [See Warnings and Precautions (5.1) .]

Table

5: Exacerbations of Hepatitis During Off-Treatment Follow-up, Subjects in Studies AI463022, AI463027, and AI463026 Subjects with ALT Elevations >10 × ULN and >2 × Reference a Entecavir Lamivudine a Reference is the minimum of the baseline or last measurement at end of dosing. Median time to off-treatment exacerbation was 23 weeks for entecavir-treated subjects and 10 weeks for lamivudine-treated subjects. Nucleoside-inhibitor-naïve HBeAg-positive 4/174 (2%) 13/147 (9%) HBeAg-negative 24/302 (8%) 30/270 (11%) Lamivudine-refractory 6/52 (12%) 0/16

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 Test Entecavir 0.5 mg n=679 Lamivudine 100 mg n = 668 Entecavir 1 mg n = 183 Lamivudine 100 mg n = 190 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 × ULN and >2 × 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 who experienced recurrent viremia on lamivudine therapy. d Includes hematology, routine chemistries, renal and liver function tests, pancreatic enzymes, and urinalysis. e Grade 3 = 3+, large, ≥500 mg/dL; Grade 4 = 4+, marked, severe. f Grade 3 = 3+, large; Grade 4 = ≥4+, marked, severe, many. ULN=upper limit of normal.

Any Grade

3–4 laboratory abnormality d 35% 36% 37% 45% ALT >10 × ULN and >2 × baseline 2% 4% 2% 11% ALT >5 × ULN 11% 16% 12% 24% Albumin <2.5 g/dL <1% <1% 0 2% Total bilirubin >2.5 × ULN 2% 2% 3% 2% Lipase ≥2.1 × ULN 7% 6% 7% 7% Creatinine >3 × 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% Among entecavir-treated subjects in these studies, on-treatment ALT elevations greater than 10 times the upper limit of normal (ULN) and greater than 2 times baseline generally resolved with continued treatment. A majority of these exacerbations were associated with a ≥ 2 log 10 /mL reduction in viral load that preceded or coincided with the ALT elevation. Periodic monitoring of hepatic function is recommended during treatment.

Exacerbations of Hepatitis after Discontinuation of Treatment An exacerbation of hepatitis or ALT flare was defined as ALT greater than 10 times ULN and greater than 2 times the subject’s reference level (minimum of the baseline or last measurement at end of dosing). For all subjects who discontinued treatment (regardless of reason), Table 5 presents the proportion of subjects in each study who experienced post-treatment ALT flares. In these studies, a subset of subjects was allowed to discontinue treatment at or after 52 weeks if they achieved a protocol-defined response to therapy. If entecavir is discontinued without regard to treatment response, the rate of post-treatment flares could be higher. [See Warnings and Precautions (5.1) .]

Table

5: Exacerbations of Hepatitis During Off-Treatment Follow-up, Subjects in Studies AI463022, AI463027, and AI463026 Subjects with ALT Elevations >10 × ULN and >2 × Reference a Entecavir Lamivudine a Reference is the minimum of the baseline or last measurement at end of dosing. Median time to off-treatment exacerbation was 23 weeks for entecavir-treated subjects and 10 weeks for lamivudine-treated subjects. Nucleoside-inhibitor-naïve HBeAg-positive 4/174 (2%) 13/147 (9%) HBeAg-negative 24/302 (8%) 30/270 (11%) Lamivudine-refractory 6/52 (12%) 0/16

Decompensated Liver Disease Study AI463048 was a randomized, open-label study of entecavir 1 mg once daily versus adefovir dipivoxil 10 mg once daily given for up to 48 weeks in adult subjects with chronic HBV infection and evidence of hepatic decompensation, defined as a Child-Turcotte-Pugh (CTP) score of 7 or higher [see Clinical Studies (14.1) ] . Among the 102 subjects receiving entecavir, the most common treatment-emergent adverse events of any severity, regardless of causality, occurring through Week 48 were peripheral edema (16%), ascites (15%), pyrexia (14%), hepatic encephalopathy (10%), and upper respiratory infection (10%). Clinical adverse reactions not listed in Table 3 that were observed through Week 48 include blood bicarbonate decreased (2%) and renal failure (< 1%). Eighteen of 102 (18%) subjects treated with entecavir and 18/89 (20%) subjects treated with adefovir dipivoxil died during the first 48 weeks of therapy. The majority of deaths (11 in the entecavir group and 16 in the adefovir dipivoxil group) were due to liver-related causes such as hepatic failure, hepatic encephalopathy, hepatorenal syndrome, and upper gastrointestinal hemorrhage. The rate of hepatocellular carcinoma (HCC) through Week 48 was 6% (6/102) for subjects treated with entecavir and 8% (7/89) for subjects treated with adefovir dipivoxil. Five percent of subjects in either treatment arm discontinued therapy due to an adverse event through Week 48. No subject in either treatment arm experienced an on-treatment hepatic flare (ALT >2 × baseline and >10 × ULN) through Week 48. Eleven of 102 (11%) subjects treated with entecavir and 11/89 (13%) subjects treated with adefovir dipivoxil had a confirmed increase in serum creatinine of 0.5 mg/dL through Week 48.

HIV/HBV Co-infected The safety profile of entecavir 1 mg (n = 51) in HIV/HBV co-infected subjects enrolled in Study AI463038 was similar to that of placebo (n = 17) through 24 weeks of blinded treatment and similar to that seen in non-HIV infected subjects [see Warnings and Precautions (5.2) ] .

Liver Transplant Recipients Among

65 subjects receiving entecavir in an open-label, post-liver transplant trial [see Use in Specific Populations (8.8) ] , the frequency and nature of adverse events were consistent with those expected in patients who have received a liver transplant and the known safety profile of entecavir.

Clinical Trial

Experience in Pediatric Subjects The safety of entecavir in pediatric subjects 2 to less than 18 years of age is based on two ongoing clinical trials in subjects with chronic HBV infection (one Phase 2 pharmacokinetic trial [AI463028] and one Phase 3 trial [AI463189]). These trials provide experience in 168 HBeAg-positive subjects treated with entecavir for a median duration of 72 weeks. The adverse reactions observed in pediatric subjects who received treatment with entecavir were consistent with those observed in clinical trials of entecavir in adults. Adverse drug reactions reported in greater than 1% of pediatric subjects included abdominal pain, rash events, poor palatability (“product taste abnormal”), nausea, diarrhea, and vomiting.

6.2 Postmarketing Experience The following adverse reactions have been reported during postmarketing use of entecavir. Because these reactions were reported voluntarily from a population of unknown size, it is not possible to reliably estimate their frequency or establish a causal relationship to entecavir exposure. Immune system disorders: Anaphylactoid reaction. Metabolism and nutrition disorders: Lactic acidosis. Hepatobiliary disorders: Increased transaminases. Skin and subcutaneous tissue disorders: Alopecia, rash.

AND PRECAUTIONS Severe acute exacerbations of hepatitis B virus infection after discontinuation: Monitor hepatic function closely for at least several months. (5.1 , 6.1) Co-infection with HIV: Entecavir is not recommended unless the patient is also receiving HAART. (5.2) Lactic acidosis and severe hepatomegaly with steatosis: If suspected, treatment should be suspended. (5.3)

5.1 Severe Acute Exacerbations of Hepatitis B Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued anti-hepatitis B therapy, including entecavir <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue anti-hepatitis B therapy. If appropriate, initiation of anti-hepatitis B therapy may be warranted.

5.2 Patients Co-infected with HIV and HBV Entecavir has not been evaluated in HIV/HBV co-infected patients who were not simultaneously receiving effective HIV treatment. Limited clinical experience suggests there is a potential for the development of resistance to HIV nucleoside reverse transcriptase inhibitors if entecavir is used to treat chronic hepatitis B virus infection in patients with HIV infection that is not being treated <span class="opacity-50 text-xs">[see Microbiology (12.4) ]</span> . Therefore, therapy with entecavir is not recommended for HIV/HBV co-infected patients who are not also receiving HAART. Before initiating entecavir therapy, HIV antibody testing should be offered to all patients. Entecavir has not been studied as a treatment for HIV infection and is not recommended for this use.

5.3 Lactic Acidosis and Severe Hepatomegaly with Steatosis Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogue inhibitors, including entecavir, alone or in combination with antiretrovirals. A majority of these cases have been in women. Obesity and prolonged nucleoside inhibitor exposure may be risk factors. Particular caution should be exercised when administering nucleoside analogue inhibitors to any patient with known risk factors for liver disease; however, cases have also been reported in patients with no known risk factors. Lactic acidosis with entecavir use has been reported, often in association with hepatic decompensation, other serious medical conditions, or drug exposures. Patients with decompensated liver disease may be at higher risk for lactic acidosis. Treatment with entecavir should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

5.1 Severe Acute Exacerbations of Hepatitis B Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued anti-hepatitis B therapy, including entecavir <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue anti-hepatitis B therapy. If appropriate, initiation of anti-hepatitis B therapy may be warranted.

5.2 Patients Co-infected with HIV and HBV Entecavir has not been evaluated in HIV/HBV co-infected patients who were not simultaneously receiving effective HIV treatment. Limited clinical experience suggests there is a potential for the development of resistance to HIV nucleoside reverse transcriptase inhibitors if entecavir is used to treat chronic hepatitis B virus infection in patients with HIV infection that is not being treated <span class="opacity-50 text-xs">[see Microbiology (12.4) ]</span> . Therefore, therapy with entecavir is not recommended for HIV/HBV co-infected patients who are not also receiving HAART. Before initiating entecavir therapy, HIV antibody testing should be offered to all patients. Entecavir has not been studied as a treatment for HIV infection and is not recommended for this use.

5.3 Lactic Acidosis and Severe Hepatomegaly with Steatosis Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogue inhibitors, including entecavir, alone or in combination with antiretrovirals. A majority of these cases have been in women. Obesity and prolonged nucleoside inhibitor exposure may be risk factors. Particular caution should be exercised when administering nucleoside analogue inhibitors to any patient with known risk factors for liver disease; however, cases have also been reported in patients with no known risk factors. Lactic acidosis with entecavir use has been reported, often in association with hepatic decompensation, other serious medical conditions, or drug exposures. Patients with decompensated liver disease may be at higher risk for lactic acidosis. Treatment with entecavir should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

INTERACTIONS Since entecavir is primarily eliminated by the kidneys [see Clinical Pharmacology (12.3) ] , coadministration of BARACLUDE with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either entecavir or the coadministered drug. Coadministration of entecavir with lamivudine, adefovir dipivoxil, or tenofovir disoproxil fumarate did not result in significant drug interactions. The effects of coadministration of BARACLUDE 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 BARACLUDE is coadministered with such drugs.

Drug Interactions

The metabolism of entecavir was evaluated in in vitro and in vivo studies. Entecavir is not a substrate, inhibitor, or inducer of the cytochrome P450 (CYP450) enzyme system. At concentrations up to approximately 10,000-fold higher than those obtained in humans, entecavir inhibited none of the major human CYP450 enzymes 1A2, 2C9, 2C19, 2D6, 3A4, 2B6, and 2E1. At concentrations up to approximately 340-fold higher than those observed in humans, entecavir did not induce the human CYP450 enzymes 1A2, 2C9, 2C19, 3A4, 3A5, and 2B6. The pharmacokinetics of entecavir are unlikely to be affected by coadministration with agents that are either metabolized by, inhibit, or induce the CYP450 system. Likewise, the pharmacokinetics of known CYP substrates are unlikely to be affected by coadministration of entecavir. The steady-state pharmacokinetics of entecavir and coadministered drug were not altered in interaction studies of entecavir with lamivudine, adefovir dipivoxil, and tenofovir disoproxil fumarate [see Drug Interactions (7) ].