2.1 Testing Prior to the Initiation of Therapy

Test all patients for evidence of current or prior HBV infection by measuring hepatitis B surface antigen (HBsAg) and hepatitis B core antibody (anti-HBc) before initiating HCV treatment with EPCLUSA [see Warnings and Precautions (5.1)] .

2.2 Recommended Treatment Regimen and Duration in Patients 6 Years of Age and Older or Weighing at Least 17 kg

Table 1 shows the recommended treatment regimen and duration based on patient population .

For patients with HCV/HIV-1 coinfection, follow the dosage recommendations in Table 1 Refer to for dosage recommendations for concomitant HIV-1 antiviral drugs. For patients with HCV/HIV-1 coinfection, follow the dosage recommendations in Table 1 [see Clinical Studies (14.3)]. Refer to Drug Interactions (7) for dosage recommendations for concomitant HIV-1 antiviral drugs.

2.3 Recommended Dosage in Adults

The recommended dosage of EPCLUSA in adults is one tablet (400 mg sofosbuvir and 100 mg velpatasvir) taken orally once daily with or without food [see Clinical Pharmacology (12.3)] .

When administered with EPCLUSA, the recommended dosage of ribavirin is based on weight (administered with food): 1,000 mg per day for patients less than 75 kg and 1,200 mg for those weighing at least 75 kg, divided and administered twice daily. The starting dosage and on-treatment dosage of ribavirin can be decreased based on hemoglobin and creatinine clearance. For ribavirin dosage modifications refer to the ribavirin prescribing information When administered with EPCLUSA, the recommended dosage of ribavirin is based on weight (administered with food): 1,000 mg per day for patients less than 75 kg and 1,200 mg for those weighing at least 75 kg, divided and administered twice daily. The starting dosage and on-treatment dosage of ribavirin can be decreased based on hemoglobin and creatinine clearance. For ribavirin dosage modifications refer to the ribavirin prescribing information [see Use in Specific Populations (8.6) and Clinical Studies (14.4)].

2.4 Recommended Dosage in Pediatric Patients 6 Years of Age and Older or Weighing at Least 17 kg

The recommended dosage of EPCLUSA in pediatric patients 6 years of age and older or weighing at least 17 kg is based on weight and provided in Table 2. Table 3 provides the weight-based dosage of ribavirin when used in combination with EPCLUSA for pediatric patients. Take EPCLUSA once daily with or without food [see Use in Specific Populations (8.4), Clinical Pharmacology (12.3), and Clinical Studies (14.6)] .

2.5 Renal Impairment

No dosage adjustment of EPCLUSA is recommended in patients with any degree of renal impairment, including patients requiring dialysis. Administer EPCLUSA with or without ribavirin according to the recommendations in Table 1 [see Adverse Reactions (6.1), Use in Specific Populations (8.6), and Clinical Studies (14.5)]. Refer to ribavirin tablet prescribing information for ribavirin dosage modification for patients with CrCl less than or equal to 50 mL per minute.

5.1 Risk of Hepatitis B Virus Reactivation in Patients Coinfected with HCV and HBV

Hepatitis B virus (HBV) reactivation has been reported in HCV/HBV coinfected patients who were undergoing or had completed treatment with HCV direct acting antivirals, and who were not receiving HBV antiviral therapy. Some cases have resulted in fulminant hepatitis, hepatic failure, and death. Cases have been reported in patients who are HBsAg positive and also in patients with serologic evidence of resolved HBV infection (i.e., HBsAg negative and anti-HBc positive). HBV reactivation has also been reported in patients receiving certain immunosuppressants or chemotherapeutic agents; the risk of HBV reactivation associated with treatment with HCV direct-acting antivirals may be increased in these patients.

HBV reactivation is characterized as an abrupt increase in HBV replication manifesting as a rapid increase in serum HBV DNA level. In patients with resolved HBV infection, reappearance of HBsAg can occur. Reactivation of HBV replication may be accompanied by hepatitis, i.e., increases in aminotransferase levels and, in severe cases, increases in bilirubin levels, liver failure, and death can occur.

Test all patients for evidence of current or prior HBV infection by measuring HBsAg and anti-HBc before initiating HCV treatment with EPCLUSA. In patients with serologic evidence of HBV infection, monitor for clinical and laboratory signs of hepatitis flare or HBV reactivation during HCV treatment with EPCLUSA and during post-treatment follow-up. Initiate appropriate patient management for HBV infection as clinically indicated.

5.2 Serious Symptomatic Bradycardia When Coadministered with Amiodarone

Postmarketing cases of symptomatic bradycardia and cases requiring pacemaker intervention have been reported when amiodarone is coadministered with a sofosbuvir-containing regimen. A fatal cardiac arrest was reported in a patient taking amiodarone who was coadministered a sofosbuvir-containing regimen (HARVONI™ [ledipasvir/sofosbuvir]). Bradycardia has generally occurred within hours to days, but cases have been observed up to 2 weeks after initiating HCV treatment. Patients also taking beta blockers, or those with underlying cardiac comorbidities and/or advanced liver disease may be at increased risk for symptomatic bradycardia with coadministration of amiodarone. Bradycardia generally resolved after discontinuation of HCV treatment. The mechanism for this effect is unknown.

Coadministration of amiodarone with EPCLUSA is not recommended. For patients taking amiodarone who have no other alternative viable treatment options and who will be coadministered EPCLUSA:

• Counsel patients about the risk of symptomatic bradycardia.
• Cardiac monitoring in an in-patient setting for the first 48 hours of coadministration is recommended, after which outpatient or self-monitoring of the heart rate should occur on a daily basis through at least the first 2 weeks of treatment.

Patients who are taking EPCLUSA who need to start amiodarone therapy due to no other alternative viable treatment options should undergo similar cardiac monitoring as outlined above.

Due to amiodarone's long half-life, patients discontinuing amiodarone just prior to starting EPCLUSA should also undergo similar cardiac monitoring as outlined above.

Patients who develop signs or symptoms of bradycardia should seek medical evaluation immediately. Symptoms may include near-fainting or fainting, dizziness or lightheadedness, malaise, weakness, excessive tiredness, shortness of breath, chest pains, confusion, or memory problems [see Adverse Reactions (6.2) and Drug Interactions (7.3)] .

5.3 Risk of Reduced Therapeutic Effect Due to Concomitant Use of EPCLUSA with Inducers of P-gp and/or Moderate to Strong Inducers of CYP

Drugs that are inducers of P-gp and/or moderate to strong inducers of CYP2B6, CYP2C8, or CYP3A4 (e.g., rifampin, St. John's wort, carbamazepine) may significantly decrease plasma concentrations of sofosbuvir and/or velpatasvir, leading to potentially reduced therapeutic effect of EPCLUSA. The use of these agents with EPCLUSA is not recommended [see Drug Interactions (7.3)] .

5.4 Risks Associated with Ribavirin and EPCLUSA Combination Treatment

If EPCLUSA is administered with ribavirin, the warnings and precautions for ribavirin apply to this combination regimen. Refer to the ribavirin prescribing information for a full list of the warnings and precautions for ribavirin [see Dosage and Administration (2.2)].

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.

If EPCLUSA is administered with ribavirin, refer to the prescribing information for ribavirin for a description of ribavirin-associated adverse reactions.

6.2 Postmarketing Experience

The following adverse reactions have been identified during post approval use of sofosbuvir. Because postmarketing 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 drug exposure.

7.1 Potential for Other Drugs to Affect EPCLUSA

Sofosbuvir and velpatasvir are substrates of drug transporters P-gp and BCRP while GS-331007 (the predominant circulating metabolite of sofosbuvir) is not. In vitro, slow metabolic turnover of velpatasvir by CYP2B6, CYP2C8, and CYP3A4 was observed.

Drugs that are inducers of P-gp and/or moderate to strong inducers of CYP2B6, CYP2C8, or CYP3A4 (e.g., rifampin, St. John's wort, carbamazepine) may decrease plasma concentrations of sofosbuvir and/or velpatasvir, leading to reduced therapeutic effect of EPCLUSA. The use of these agents with EPCLUSA is not recommended [see Warnings and Precautions (5.3) and Clinical Pharmacology (12.3)] . EPCLUSA may be coadministered with P-gp, BCRP, and CYP inhibitors.

7.2 Potential for EPCLUSA to Affect Other Drugs

Velpatasvir is an inhibitor of drug transporters P-gp, breast cancer resistance protein (BCRP), OATP1B1, OATP1B3, and OATP2B1. Coadministration of EPCLUSA with drugs that are substrates of these transporters may increase the exposure of such drugs.

7.3 Established and Potentially Significant Drug Interactions

Clearance of HCV infection with direct acting antivirals may lead to changes in hepatic function, which may impact the safe and effective use of concomitant medications. For example, altered blood glucose control resulting in serious symptomatic hypoglycemia has been reported in diabetic patients in postmarketing case reports and published epidemiological studies. Management of hypoglycemia in these cases required either discontinuation or dose modification of concomitant medications used for diabetes treatment.

Frequent monitoring of relevant laboratory parameters (e.g., International Normalized Ratio [INR] in patients taking warfarin, blood glucose levels in diabetic patients) or drug concentrations of concomitant medications such as cytochrome P450 substrates with a narrow therapeutic index (e.g., certain immunosuppressants) is recommended to ensure safe and effective use. Dose adjustments of concomitant medications may be necessary.

Table 4 provides a listing of established or potentially clinically significant drug interactions. The drug interactions described are based on studies conducted with either EPCLUSA, the components of EPCLUSA (sofosbuvir and velpatasvir) as individual agents, or are predicted drug interactions that may occur with EPCLUSA [see Warnings and Precautions (5.2, 5.3) and Clinical Pharmacology (12.3)] .

7.4 Drugs without Clinically Significant Interactions with EPCLUSA

Based on drug interaction studies conducted with the components of EPCLUSA (sofosbuvir or velpatasvir) or EPCLUSA, no clinically significant drug interactions have been observed with the following drugs [see Clinical Pharmacology (12.3)]:

• EPCLUSA: atazanavir/ritonavir, cyclosporine, darunavir/ritonavir, dolutegravir, elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide, emtricitabine, raltegravir, or rilpivirine.
• Sofosbuvir: ethinyl estradiol/norgestimate, methadone, or tacrolimus.
• Velpatasvir: ethinyl estradiol/norgestimate, ketoconazole, or pravastatin. See Table 4 for use of EPCLUSA with certain HIV antiretroviral regimens [see Drug Interactions (7.3)] .

8.1 Pregnancy

8.2 Lactation

8.3 Females and Males of Reproductive Potential

If EPCLUSA is administered with ribavirin, the information for ribavirin with regard to pregnancy testing, contraception, and infertility also applies to this combination regimen. Refer to ribavirin prescribing information for additional information.

8.4 Pediatric Use

The pharmacokinetics, safety, and effectiveness of EPCLUSA for treatment of HCV genotype 1, 2, 3, 4, or 6 infection in treatment-naïve and treatment-experienced pediatric patients 6 years of age and older or weighing at least 17 kg without cirrhosis or with compensated cirrhosis have been established in an open-label, multicenter clinical trial (Study 1143, N=175; 149 treatment-naïve, 26 treatment-experienced). No clinically meaningful differences in pharmacokinetics were observed in comparison to those observed in adults. The safety and effectiveness were comparable with those observed in adults [see Dosage and Administration (2.4), Adverse Reactions (6.1), Clinical Pharmacology (12.3), and Clinical Studies (14.6)].

The safety and effectiveness of EPCLUSA for treatment of HCV genotype 5 in pediatric patients 6 years of age and older or weighing at least 17 kg without cirrhosis or with compensated cirrhosis are supported by sofosbuvir, GS-331007, and velpatasvir exposures in adults and pediatric patients [see Dosage and Administration (2.2 and 2.4), Adverse Reactions (6.1), Clinical Pharmacology (12.3), and Clinical Studies (14.6)] . Similar rationale is used to support dosing recommendations for pediatric patients with HCV genotype 1, 2, 3, 4, 5, or 6 infection who have decompensated cirrhosis (Child-Pugh B or C).

In patients with severe renal impairment, including those requiring dialysis, exposures of GS-331007, the inactive metabolite of sofosbuvir, are increased [see Clinical Pharmacology (12.3)] . No data are available regarding the safety of EPCLUSA in pediatric patients with renal impairment [see Use in Specific Populations (8.6)].

The safety and effectiveness of EPCLUSA have not been established in pediatric patients less than 6 years of age.

8.5 Geriatric Use

Clinical trials of EPCLUSA included 156 subjects aged 65 and over (12% of total number of subjects in the Phase 3 clinical trials). No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out. No dosage adjustment of EPCLUSA is warranted in geriatric patients [see Clinical Pharmacology (12.3)] .

8.6 Renal Impairment

No dosage adjustment of EPCLUSA is recommended for patients with mild, moderate, or severe renal impairment, including ESRD requiring dialysis [see Dosage and Administration (2.5), Adverse Reactions (6.1), Clinical Pharmacology (12.3), and Clinical Studies (14.5)]. No safety data are available in subjects with both decompensated cirrhosis and severe renal impairment, including ESRD requiring dialysis. Additionally, no safety data are available in pediatric patients with renal impairment [see Use in Specific Populations (8.4)]. Refer to ribavirin tablet prescribing information regarding use of ribavirin in patients with renal impairment.

8.7 Hepatic Impairment

No dosage adjustment of EPCLUSA is recommended for patients with mild, moderate, or severe hepatic impairment (Child-Pugh Class A, B, or C) [see Adverse Reactions (6.1), Clinical Pharmacology (12.3), and Clinical Studies (14)].

Clinical and hepatic laboratory monitoring (including direct bilirubin), as clinically indicated, is recommended for patients with decompensated cirrhosis receiving treatment with EPCLUSA and ribavirin [see Adverse Reactions (6.1)].

Sofosbuvir: The IUPAC name for sofosbuvir is ( S)-isopropyl 2-(( S)-(((2 R,3 R,4 R,5 R)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2 H)-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)-(phenoxy)phosphorylamino)propanoate. It has a molecular formula of C 22H 29FN 3O 9P and a molecular weight of 529.45. It has the following structural formula:

Sofosbuvir is a white to off-white crystalline solid with a solubility of at least 2 mg/mL across the pH range of 2–7.7 at 37 °C and is slightly soluble in water.

Velpatasvir: The IUPAC name for velpatasvir is methyl {(1 R)-2-[(2 S,4 S)-2-(5-{2-[(2 S,5 S)-1-{(2 S)-2-[(methoxycarbonyl)amino]-3-methylbutanoyl}-5-methylpyrrolidin-2-yl]-1,11-dihydro[2]benzopyrano[4',3':6,7]naphtho[1,2- d]imidazol-9-yl}-1 H-imidazol-2-yl)-4-(methoxymethyl)pyrrolidin-1-yl]-2-oxo-1-phenylethyl}carbamate. It has a molecular formula of C 49H 54N 8O 8 and a molecular weight of 883.0. It has the following structural formula:

Velpatasvir is practically insoluble (less than 0.1 mg/mL) above pH 5, slightly soluble (3.6 mg/mL) at pH 2, and soluble (greater than 36 mg/mL) at pH 1.2.

12.1 Mechanism of Action

EPCLUSA is a fixed-dose combination of sofosbuvir and velpatasvir, which are direct-acting antiviral agents against the hepatitis C virus [see Microbiology (12.4)].

12.2 Pharmacodynamics

12.3 Pharmacokinetics

The pharmacokinetic properties of the components of EPCLUSA are provided in Table 5. The multiple dose pharmacokinetic parameters of sofosbuvir and its metabolite, GS-331007, and velpatasvir are provided in Table 6.

Sofosbuvir and GS-331007 AUC 0–24 and C max were similar in healthy adult subjects and subjects with HCV infection. Relative to healthy subjects (N=331), velpatasvir AUC 0–24 and C max were 37% lower and 42% lower, respectively, in HCV-infected subjects.

Velpatasvir AUC increases in a greater than proportional manner from 5 to 50 mg and in a less than proportional manner from 50 to 450 mg in healthy volunteers. However, velpatasvir exhibited more than or near dose-proportional increase in exposures 25 mg to 150 mg in HCV-infected patients when coadministered with sofosbuvir. Sofosbuvir and GS-331007 AUCs are near dose-proportional over the dose range of 200 mg to 1200 mg.

12.4 Microbiology

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

14.1 Description of Clinical Trials

Table 12 presents the clinical trial design including different treatment groups that were conducted with EPCLUSA with and without ribavirin in subjects with chronic hepatitis C (HCV) genotype 1, 2, 3, 4, 5, and 6 infection. For detailed description of trial design and recommended regimen and duration [see Dosage and Administration (2.2, 2.3, and 2.4) and Clinical Studies (14.2, 14.3, 14.4, 14.5, and 14.6)] .

The ribavirin dosage was weight-based (1000 mg daily administered in two divided doses for subjects less than 75 kg and 1200 mg for those greater than or equal to 75 kg) and administered in two divided doses when used in combination with sofosbuvir in the ASTRAL-2 and ASTRAL-3 trials or in combination with EPCLUSA in the ASTRAL-4 trial. Ribavirin dosage adjustments were performed according to the ribavirin prescribing information. Serum HCV RNA values were measured during the clinical trials using the COBAS AmpliPrep/COBAS Taqman HCV test (version 2.0) with a lower limit of quantification (LLOQ) of 15 IU/mL. SVR12, defined as HCV RNA less than LLOQ at 12 weeks after the cessation of treatment, was the primary endpoint in all the trials. Relapse is defined as HCV RNA greater than or equal to LLOQ during the post-treatment period after having achieved HCV RNA less than LLOQ at the end of treatment. On-treatment virologic failure is defined as breakthrough, rebound, or non-response.

14.2 Clinical Trials in Subjects without Cirrhosis and Subjects with Compensated Cirrhosis

14.3 Clinical Trial in Subjects Coinfected with HCV and HIV-1

ASTRAL-5 was an open-label trial that evaluated 12 weeks of treatment with EPCLUSA in subjects with genotype 1, 2, 3, 4, 5, or 6 HCV infection who were coinfected with HIV-1. Subjects were on a stable HIV-1 antiretroviral therapy that included emtricitabine/tenofovir disoproxil fumarate or abacavir/lamivudine administered with atazanavir/ritonavir, darunavir/ritonavir, lopinavir/ritonavir, rilpivirine, raltegravir or elvitegravir/cobicistat.

Of the 106 treated subjects, the median age was 57 years (range: 25 to 72); 86% of the subjects were male; 51% were White; 45% were Black; 22% had a baseline body mass index at least 30 kg/m 2; the proportions of patients with genotype 1, 2, 3, or 4 HCV infection were 74%, 10%, 11%, and 5%, respectively; no subjects with genotype 5 or 6 HCV were treated with EPCLUSA; 77% had non-CC IL28B alleles (CT or TT); 74% had baseline HCV RNA levels of at least 800,000 IU/mL; 18% had compensated cirrhosis; and 29% were treatment experienced. The overall mean CD4+ count was 598 cells/μL (range: 183−1513 cells/μL) and 57% of subjects had CD4+ counts > 500 cells/μL.

Table 17 presents the SVR12 for the ASTRAL-5 trial by HCV genotype.

No subject had HIV-1 rebound during treatment and CD4+ counts were stable during treatment.

14.4 Clinical Trials in Subjects with Decompensated Cirrhosis

ASTRAL-4 was a randomized, open-label trial in subjects with genotype 1, 2, 3, 4, 5, or 6 HCV infection and Child-Pugh B cirrhosis at screening. Subjects were randomized in a 1:1:1 ratio to treatment with EPCLUSA for 12 weeks (N=90), EPCLUSA with ribavirin for 12 weeks (N=87), or EPCLUSA for 24 weeks (N=90). Randomization was stratified by HCV genotype (1, 2, 3, 4, 5, 6, and indeterminate).

Demographics and baseline characteristics were balanced across the treatment groups. Of the 267 treated subjects, the median age was 59 years (range: 40 to 73); 70% of the subjects were male; 90% were White; 6% were Black; 42% had a baseline body mass index at least 30 kg/m 2. The proportions of subjects with genotype 1, 2, 3, 4, or 6 HCV were 78%, 4%, 15%, 3%, and less than 1% (1 subject), respectively. No subjects with genotype 5 HCV infection were enrolled. 76% had non-CC IL28B alleles (CT or TT); 56% had baseline HCV RNA levels at least 800,000 IU/mL; 55% were treatment-experienced; and 95% of subjects had Model for End Stage Liver Disease (MELD) score less than or equal to 15 at baseline. Although all subjects had Child-Pugh B cirrhosis at screening, 6% and 4% of subjects were assessed to have Child-Pugh A and Child-Pugh C cirrhosis, respectively, on the first day of treatment.

Treatment with EPCLUSA with ribavirin for 12 weeks resulted in numerically higher SVR12 rates than treatment with EPCLUSA for 12 weeks or 24 weeks. Because EPCLUSA with ribavirin for 12 weeks is the recommended dosage regimen, the results of the 12- and 24-week EPCLUSA treatment groups are not presented.

Table 18 presents the SVR12 for subjects treated with EPCLUSA with ribavirin for 12 weeks in the ASTRAL-4 trial by HCV genotype. No subjects with genotype 5 or 6 HCV were treated with EPCLUSA with ribavirin for 12 weeks.

All subjects with genotype 2 (N=4) and genotype 4 (N=2) HCV infection treated with EPCLUSA and ribavirin achieved SVR12.

14.5 Clinical Trial in Subjects with Severe Renal Impairment Requiring Dialysis

Trial 4062 was an open-label clinical trial that evaluated 12 weeks of treatment with EPCLUSA in 59 HCV-infected adults with ESRD requiring dialysis. The proportions of subjects with genotype 1, 2, 3, 4, 6 or indeterminate HCV infection were 42%,12%, 27%, 7%, 3%, and 8%, respectively. At baseline, 29% of subjects had cirrhosis, 22% were treatment-experienced (subjects with prior exposure to any HCV NS5A inhibitor were excluded), 92% were on hemodialysis, and 8% were on peritoneal dialysis; mean duration on dialysis was 7 years (range: 0 to 40 years). The overall SVR rate was 95% (56/59). Of the subjects completing 12 weeks of EPCLUSA, 1 subject experienced virologic relapse.

14.6 Clinical Trial in Pediatric Subjects

The efficacy of EPCLUSA once daily for 12 weeks was evaluated in an open-label trial (Study 1143) in 173 genotype 1, 2, 3, 4, or 6 HCV treatment-naïve (N=147) or treatment-experienced (N=26) pediatric subjects 6 years of age and older without cirrhosis or with compensated cirrhosis.

Store below 30 °C (86 °F). Dispense only in original container.

Risk of Hepatitis B Virus Reactivation in Patients Coinfected with HCV and HBV

Inform patients that HBV reactivation can occur in patients coinfected with HBV during or after treatment of HCV infection. Advise patients to tell their healthcare provider if they have a history of HBV infection [see Warnings and Precautions (5.1)] .

Serious Symptomatic Bradycardia When Coadministered with Amiodarone

Advise patients to seek medical evaluation immediately for symptoms of bradycardia such as near-fainting or fainting, dizziness or lightheadedness, malaise, weakness, excessive tiredness, shortness of breath, chest pain, confusion, or memory problems [see Warnings and Precautions (5.2), Adverse Reactions (6.2), and Drug Interactions (7.3)].

Drug Interactions

Inform patients that EPCLUSA may interact with other drugs. Advise patients to report to their healthcare provider the use of any other prescription or nonprescription medication or herbal products including St. John's wort [see Warnings and Precautions (5.2, 5.3) and Drug Interactions (7)].

Administration

Advise patients to take EPCLUSA once daily on a regular dosing schedule with or without food. Inform patients that it is important not to miss or skip doses and to take EPCLUSA for the duration that is recommended by the physician.

Pregnancy

Advise patients to avoid pregnancy during combination treatment with EPCLUSA and ribavirin and for 6 months after completion of treatment. Inform patients to notify their healthcare provider immediately in the event of a pregnancy [see Use in Specific Populations (8.1)] .