Sofosbuvir (Sovaldi)

Patients with Genotype 1 HCV Who are Ineligible to Receive an Interferon-Based Regimen

SOVALDI in combination with ribavirin for 24 weeks can be considered as a therapeutic option for patients with genotype 1 infection who are ineligible to receive an interferon-based regimen [see Clinical Studies (14.4)]. Treatment decision should be guided by an assessment of the potential benefits and risks for the individual patient.

Patients with Hepatocellular Carcinoma Awaiting Liver Transplantation

Administer SOVALDI in combination with ribavirin for up to 48 weeks or until the time of liver transplantation, whichever occurs first, to prevent post-transplant HCV reinfection [see Use in Specific Populations (8.8)].

Adverse Reactions in Adult Subjects

The safety assessment of SOVALDI was based on pooled Phase 3 clinical trial data (both controlled and uncontrolled) including:

• 650 subjects who received SOVALDI + ribavirin (RBV) combination therapy for 12 weeks,
• 98 subjects who received SOVALDI + ribavirin combination therapy for 16 weeks,
• 250 subjects who received SOVALDI + ribavirin combination therapy for 24 weeks,
• 327 subjects who received SOVALDI + peginterferon (Peg-IFN) alfa + ribavirin combination therapy for 12 weeks,
• 243 subjects who received peginterferon alfa + ribavirin for 24 weeks, and
• 71 subjects who received placebo (PBO) for 12 weeks [see Clinical Studies (14)].

The proportion of subjects who permanently discontinued treatment due to adverse events was 4% for subjects receiving placebo, 1% for subjects receiving SOVALDI + ribavirin for 12 weeks, less than 1% for subjects receiving SOVALDI + ribavirin for 24 weeks, 11% for subjects receiving peginterferon alfa + ribavirin for 24 weeks and 2% for subjects receiving SOVALDI + peginterferon alfa + ribavirin for 12 weeks.

Adverse events observed in at least 15% of subjects in the Phase 3 clinical trials outlined above are provided in Table 5. A side-by-side tabulation is displayed to simplify presentation; direct comparison across trials should not be made due to differing trial designs.

The most common adverse events (at least 20%) for SOVALDI + ribavirin combination therapy were fatigue and headache. The most common adverse events (at least 20%) for SOVALDI + peginterferon alfa + ribavirin combination therapy were fatigue, headache, nausea, insomnia and anemia.

With the exception of anemia and neutropenia, the majority of events presented in Table 5 occurred at severity of grade 1 in SOVALDI-containing regimens.

Bilirubin Elevations

Total bilirubin elevation of more than 2.5×ULN was observed in none of the subjects in the SOVALDI + peginterferon alfa + ribavirin 12 weeks group and in 1%, 3% and 3% of subjects in the peginterferon alfa + ribavirin 24 weeks, SOVALDI + ribavirin 12 weeks and SOVALDI + ribavirin 24 weeks groups, respectively. Bilirubin levels peaked during the first 1 to 2 weeks of treatment and subsequently decreased and returned to baseline levels by post-treatment Week 4. These bilirubin elevations were not associated with transaminase elevations.

Creatine Kinase Elevations

Creatine kinase was assessed in the FISSION and NEUTRINO trials. Isolated, asymptomatic creatine kinase elevation of greater than or equal to 10×ULN was observed in less than 1%, 1% and 2% of subjects in the peginterferon alfa + ribavirin 24 weeks, SOVALDI + peginterferon alfa + ribavirin 12 weeks and SOVALDI + ribavirin 12 weeks groups, respectively.

Lipase Elevations

Isolated, asymptomatic lipase elevation of greater than 3×ULN was observed in less than 1%, 2%, 2%, and 2% of subjects in the SOVALDI + peginterferon alfa + ribavirin 12 weeks, SOVALDI + ribavirin 12 weeks, SOVALDI + ribavirin 24 weeks and peginterferon alfa + ribavirin 24 weeks groups, respectively.

Patients with HCV/HIV-1 Coinfection

SOVALDI used in combination with ribavirin was assessed in 223 HCV/HIV-1 coinfected subjects [see Clinical Studies (14.4)]. The safety profile in HCV/HIV-1 coinfected subjects was similar to that observed in HCV mono-infected subjects. Elevated total bilirubin (grade 3 or 4) was observed in 30/32 (94%) subjects receiving atazanavir as part of the antiretroviral regimen. None of the subjects had concomitant transaminase increases. Among subjects not taking atazanavir, grade 3 or 4 elevated total bilirubin was observed in 2 (1.5%) subjects, similar to the rate observed with HCV mono-infected subjects receiving SOVALDI + ribavirin in Phase 3 trials.

Adverse Reactions in Pediatric Subjects 3 Years of Age and Older

The safety assessment of SOVALDI in pediatric subjects 3 years of age and older is based on data from 106 subjects who were treated with SOVALDI plus ribavirin for 12 weeks (genotype 2 subjects) or 24 weeks (genotype 3 subjects) in a Phase 2, open-label clinical trial. The adverse reactions observed were consistent with those observed in clinical studies of SOVALDI plus ribavirin in adults. Among pediatric subjects 3 years to < 12 years of age taking SOVALDI in combination with ribavirin oral solution, decreased appetite was observed in 13% (7/54) subjects [see Clinical Studies 14.5)].

Cardiac Disorders

Serious symptomatic bradycardia has been reported in patients taking amiodarone who initiate treatment with a sofosbuvir-containing regimen [see Warnings and Precautions (5.2), Drug Interactions (7.1)].

Skin and Subcutaneous Tissue Disorders

Skin rashes, sometimes with blisters or angioedema-like swelling Angioedema

Risk Summary

If SOVALDI is administered with ribavirin or peginterferon alfa and ribavirin, the combination regimen is contraindicated in pregnant women and in men whose female partners are pregnant. Refer to the ribavirin and/or peginterferon alfa prescribing information for more information on ribavirin- and peginterferon alfa-associated risks of use during pregnancy.

No adequate human data are available to establish whether or not SOVALDI poses a risk to pregnancy outcomes. In animal reproduction studies, no evidence of adverse developmental outcomes was observed with sofosbuvir at exposures greater than those in humans at the recommended human dose (RHD) [see Data]. During organogenesis in the rat and rabbit, systemic exposures (AUC) to the predominant circulating metabolite of sofosbuvir (GS-331007) were ≥5 (rats) and 12 (rabbits) times the exposure in humans at the RHD. In the rat pre/postnatal development study, maternal systemic exposure (AUC) to GS-331007 was ≥6 times the exposure in humans at the RHD.

The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2–4% and 15–20%, respectively.

Data

Risk Summary

It is not known whether sofosbuvir or its metabolites are present in human breast milk, affect human milk production or have effects on the breastfed infant. The predominant circulating metabolite of sofosbuvir (GS-331007) was the primary component observed in the milk of lactating rats, without effect on nursing pups [see Data].

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for SOVALDI and any potential adverse effects on the breastfed child from SOVALDI or from the underlying maternal condition.

If SOVALDI is administered with ribavirin, the nursing mother's information for ribavirin also applies to this combination regimen. Refer to the ribavirin prescribing information for more information on use during lactation.

Data

Cardiac Electrophysiology

The effect of sofosbuvir 400 and 1200 mg (three times the recommended dosage) on QTc interval was evaluated in a randomized, single-dose, placebo- and active-controlled (moxifloxacin 400 mg) four period crossover thorough QT trial in 59 healthy subjects. At a dosage three times the maximum recommended dosage, SOVALDI does not prolong QTc to any clinically relevant extent.

Absorption

The pharmacokinetic properties of sofosbuvir and the predominant circulating metabolite GS-331007 have been evaluated in healthy adult subjects and in subjects with chronic hepatitis C. Following oral administration of SOVALDI, sofosbuvir was absorbed with a peak plasma concentration observed at ~0.5–2 hour post-dose, regardless of dose level. Peak plasma concentration of GS-331007 was observed between 2 to 4 hours post-dose. Based on population pharmacokinetic analysis in subjects with genotype 1 to 6 HCV infection who were coadministered ribavirin (with or without pegylated interferon), geometric mean steady state AUC_0–24 was 969 ng∙hr/mL for sofosbuvir (N=838), and 6790 ng∙hr/mL for GS-331007 (N=1695). Relative to healthy subjects administered sofosbuvir alone (N=272), the sofosbuvir AUC_0–24 was 60% higher; and GS-331007 AUC_0–24 was 39% lower, respectively, in HCV-infected subjects. Sofosbuvir and GS-331007 AUCs are near dose proportional over the dose range of 200 mg to 1200 mg.

Effect of Food

Relative to fasting conditions, the administration of a single dose of SOVALDI with a standardized high fat meal did not substantially affect the sofosbuvir C_max or AUC_0–inf. The exposure of GS-331007 was not altered in the presence of a high-fat meal. Therefore, SOVALDI can be administered without regard to food.

Distribution

Sofosbuvir is approximately 61–65% bound to human plasma proteins and the binding is independent of drug concentration over the range of 1 microgram/mL to 20 microgram/mL. Protein binding of GS-331007 was minimal in human plasma. After a single 400 mg dose of [¹⁴C]-sofosbuvir in healthy subjects, the blood to plasma ratio of ¹⁴C-radioactivity was approximately 0.7.

Metabolism

Sofosbuvir is extensively metabolized in the liver to form the pharmacologically active nucleoside analog triphosphate GS-461203. The metabolic activation pathway involves sequential hydrolysis of the carboxyl ester moiety catalyzed by human cathepsin A (CatA) or carboxylesterase 1 (CES1) and phosphoramidate cleavage by histidine triad nucleotide-binding protein 1 (HINT1) followed by phosphorylation by the pyrimidine nucleotide biosynthesis pathway. Dephosphorylation results in the formation of nucleoside metabolite GS-331007 that cannot be efficiently rephosphorylated and lacks anti-HCV activity in vitro.

After a single 400 mg oral dose of [¹⁴C]-sofosbuvir, sofosbuvir and GS-331007 accounted for approximately 4% and greater than 90% of drug related material (sum of molecular weight-adjusted AUC of sofosbuvir and its metabolites) systemic exposure, respectively.

Elimination

Following a single 400 mg oral dose of [¹⁴C]-sofosbuvir, mean total recovery of the dose was greater than 92%, consisting of approximately 80%, 14%, and 2.5% recovered in urine, feces, and expired air, respectively. The majority of the sofosbuvir dose recovered in urine was GS-331007 (78%) while 3.5% was recovered as sofosbuvir. These data indicate that renal clearance is the major elimination pathway for GS-331007. The median terminal half-lives of sofosbuvir and GS-331007 were 0.4 and 27 hours, respectively.

Specific Populations

Mechanism of Action

Sofosbuvir is an inhibitor of the HCV NS5B RNA-dependent RNA polymerase, which is essential for viral replication. Sofosbuvir is a nucleotide prodrug that undergoes intracellular metabolism to form the pharmacologically active uridine analog triphosphate (GS-461203), which can be incorporated into HCV RNA by the NS5B polymerase and acts as a chain terminator. In a biochemical assay, GS-461203 inhibited the polymerase activity of the recombinant NS5B from HCV genotype 1b, 2a, 3a and 4a with IC₅₀ values ranging from 0.7 to 2.6 micromolar. GS-461203 is neither an inhibitor of human DNA and RNA polymerases nor an inhibitor of mitochondrial RNA polymerase.

Antiviral Activity

In HCV replicon assays, the EC₅₀ values of sofosbuvir against full-length replicons from genotype 1a, 1b, 2a, 3a and 4a, and chimeric 1b replicons encoding NS5B from genotype 2b, 5a or 6a ranged from 0.014 to 0.11 micromolar. The median EC₅₀ value of sofosbuvir against chimeric replicons encoding NS5B sequences from clinical isolates was 0.062 micromolar for genotype 1a (range 0.029–0.128 micromolar; N=67), 0.102 micromolar for genotype 1b (range 0.045–0.170 micromolar; N=29), 0.029 micromolar for genotype 2 (range 0.014–0.081 micromolar; N=15) and 0.081 micromolar for genotype 3a (range 0.024–0.181 micromolar; N=106). In infectious virus assays, the EC₅₀ values of sofosbuvir against genotype 1a and 2a were 0.03 and 0.02 micromolar, respectively. The presence of 40% human serum had no effect on the anti-HCV activity of sofosbuvir. Evaluation of sofosbuvir in combination with interferon alpha or ribavirin showed no antagonistic effect in reducing HCV RNA levels in replicon cells.

Resistance

Cross Resistance

HCV replicons expressing the sofosbuvir-associated resistance substitution S282T were susceptible to NS5A inhibitors and ribavirin. HCV replicons expressing the ribavirin-associated substitutions T390I and F415Y were susceptible to sofosbuvir. Sofosbuvir was active against HCV replicons with NS3/4A protease inhibitor, NS5B non-nucleoside inhibitor and NS5A inhibitor resistant variants.

Carcinogenesis and Mutagenesis

Impairment of Fertility

Treatment-Naïve Adults ─ NEUTRINO (Study 110)

NEUTRINO was an open-label, single-arm trial that evaluated 12 weeks of treatment with SOVALDI in combination with peginterferon alfa 2a and ribavirin in treatment-naïve subjects with genotype 1, 4, 5 or 6 HCV infection compared to pre-specified historical control.

Treated subjects (N=327) had a median age of 54 years (range: 19 to 70); 64% of the subjects were male; 79% were White, 17% were Black; 14% were Hispanic or Latino; mean body mass index was 29 kg/m² (range: 18 to 56 kg/m²); 78% had baseline HCV RNA greater than 6 log₁₀ IU per mL; 17% had cirrhosis; 89% had HCV genotype 1; 9% had HCV genotype 4 and 2% had HCV genotype 5 or 6. Table 12 presents the SVR12 for the treatment group of SOVALDI + peginterferon alfa + ribavirin in subjects with genotype 1 or 4 HCV. Available data on subjects with genotype 5 or 6 HCV treated with SOVALDI + peginterferon alfa + ribavirin for 12 weeks were insufficient for dosing recommendations; therefore these results are not presented in Table 12 [see Use in Specific Populations (8.10)].

SVR12 for selected subgroups are presented in Table 13.

SVR12 rates were 99% (89/90) in subjects with genotype 1 or 4 HCV and baseline IL28B C/C allele and 87% (200/230) in subjects with genotype 1 or 4 HCV and baseline IL28B non-C/C alleles.

It is estimated that the SVR12 in patients who previously failed pegylated interferon and ribavirin therapy will approximate the observed SVR12 in NEUTRINO subjects with multiple baseline factors traditionally associated with a lower response to interferon-based treatment (Table 13).

The SVR12 rate in the NEUTRINO trial in genotype 1 subjects with IL28B non-C/C alleles, HCV RNA greater than 800,000 IU/mL and Metavir F3/F4 fibrosis was 71% (37/52).

Treatment-Naïve Adults ─ FISSION (Study 1231)

FISSION was a randomized, open-label, active-controlled trial that evaluated 12 weeks of treatment with SOVALDI and ribavirin compared to 24 weeks of treatment with peginterferon alfa 2a and ribavirin in treatment-naïve subjects with genotype 2 and 3 HCV. The ribavirin dosage used in the SOVALDI + ribavirin and peginterferon alfa 2a + ribavirin arms were weight-based 1000–1200 mg per day and 800 mg per day regardless of weight, respectively. Subjects were randomized in a 1:1 ratio and stratified by cirrhosis (presence vs. absence), HCV genotype (2 vs. 3) and baseline HCV RNA level (less than 6 log₁₀ IU/mL vs. at least 6 log₁₀ IU/mL). Subjects with genotype 2 or 3 HCV were enrolled in an approximately 1:3 ratio.

Treated subjects (N=499) had a median age of 50 years (range: 19 to 77); 66% of the subjects were male; 87% were White, 3% were Black; 14% were Hispanic or Latino; mean body mass index was 28 kg/m² (range: 17 to 52 kg/m²); 57% had baseline HCV RNA levels greater than 6 log₁₀ IU per mL; 20% had cirrhosis; 72% had HCV genotype 3. Table 14 presents the SVR12 for the treatment groups of SOVALDI + ribavirin and peginterferon alfa + ribavirin in subjects with genotype 2 HCV. SVR12 for genotype 3 subjects treated with SOVALDI + ribavirin for 12 weeks was suboptimal; therefore these results are not presented in Table 14.

SVR12 for genotype 2 HCV-infected subjects with cirrhosis at baseline are presented in Table 15.

Interferon Intolerant, Ineligible or Unwilling Adults ─ POSITRON (Study 0107)

POSITRON was a randomized, double-blinded, placebo-controlled trial that evaluated 12 weeks of treatment with SOVALDI and ribavirin (N=207) compared to placebo (N=71) in subjects who are interferon intolerant, ineligible or unwilling. Subjects were randomized in 3:1 ratio and stratified by cirrhosis (presence vs. absence).

Treated subjects (N=278) had a median age of 54 years (range: 21 to 75); 54% of the subjects were male; 91% were White, 5% were Black; 11% were Hispanic or Latino; mean body mass index was 28 kg/m² (range: 18 to 53 kg/m²); 70% had baseline HCV RNA levels greater than 6 log₁₀ IU per mL; 16% had cirrhosis; 49% had HCV genotype 3. The proportions of subjects who were interferon intolerant, ineligible, or unwilling were 9%, 44%, and 47%, respectively. Most subjects had no prior HCV treatment (81%). Table 16 presents the SVR12 for the treatment groups of SOVALDI + ribavirin and placebo in subjects with genotype 2 HCV. SVR12 for genotype 3 subjects treated with SOVALDI + ribavirin for 12 weeks was suboptimal; therefore these results are not presented in Table 16.

Table 17 presents the subgroup analysis for cirrhosis and interferon classification in subjects with genotype 2 HCV.

Previously Treated Adults ─ FUSION (Study 0108)

FUSION was a randomized, double-blinded trial that evaluated 12 or 16 weeks of treatment with SOVALDI and ribavirin in subjects who did not achieve SVR with prior interferon-based treatment (relapsers and nonresponders). Subjects were randomized in a 1:1 ratio and stratified by cirrhosis (presence vs. absence) and HCV genotype (2 vs. 3).

Treated subjects (N=201) had a median age of 56 years (range: 24 to 70); 70% of the subjects were male; 87% were White; 3% were Black; 9% were Hispanic or Latino; mean body mass index was 29 kg/m² (range: 19 to 44 kg/m²); 73% had baseline HCV RNA levels greater than 6 log₁₀ IU per mL; 34% had cirrhosis; 63% had HCV genotype 3; 75% were prior relapsers. Table 18 presents the SVR12 for the treatment groups of SOVALDI + ribavirin for 12 weeks in subjects with genotype 2 HCV. Treatment of 16 weeks in subjects with genotype 2 HCV was not shown to increase the SVR12 observed with 12 weeks of treatment. SVR12 for genotype 3 subjects treated with SOVALDI + ribavirin for 12 or 16 weeks was suboptimal; therefore these results are not presented in Table 18.

Table 19 presents the subgroup analysis for cirrhosis and response to prior HCV treatment in subjects with genotype 2 HCV.

Treatment-Naïve and Previously Treated Adults ─ VALENCE (Study 0133)

The VALENCE trial evaluated SOVALDI in combination with weight-based ribavirin for the treatment of genotype 2 or 3 HCV infection in treatment-naïve subjects or subjects who did not achieve SVR with prior interferon-based treatment, including subjects with compensated cirrhosis. The original trial design was a 4 to 1 randomization to SOVALDI + ribavirin for 12 weeks or placebo. Based on emerging data, this trial was unblinded and all genotype 2 HCV-infected subjects continued the original planned treatment and received SOVALDI + ribavirin for 12 weeks, and duration of treatment with SOVALDI + ribavirin in genotype 3 HCV-infected subjects was extended to 24 weeks. Eleven genotype 3 subjects had already completed SOVALDI + ribavirin for 12 weeks at the time of the amendment.

Treated subjects (N=419) had a median age of 51 years (range: 19 to 74); 60% of the subjects were male; mean body mass index was 26 kg/m² (range: 17 to 44 kg/m²); the mean baseline HCV RNA level was 6.4 log₁₀ IU per mL; 78% had HCV genotype 3; 58% of the subjects were treatment-experienced and 65% of those subjects experienced relapse/breakthrough to prior HCV treatment.

Table 20 presents the SVR12 for the treatment groups of SOVALDI + ribavirin for 12 weeks and 24 weeks.

Table 21 presents the subgroup analysis by genotype for cirrhosis and prior HCV treatment experience.

Subjects 12 Years to <18 Years of Age: SOVALDI was evaluated in 52 subjects12 years to <18 years of age with HCV genotype 2 (N = 13) or genotype 3 (N = 39) infection. The median age was 15 years (range: 12 to 17); 40% of the subjects were female; 90% were White, 4% were Black, and 2% were Asian; 4% were Hispanic/Latino; mean body mass index was 22 kg/m² (range: 16 to 32 kg/m²);mean weight was 60 kg (range: 30 to 101 kg); 17% were treatment experienced; 65% had baseline HCV RNA levels greater than or equal to 800,000 IU/mL; and no subjects had known cirrhosis. The majority of subjects (71%) had been infected through vertical transmission.

The SVR12 rate was 100% [13/13] in genotype 2 subjects and 97% [38/39] in genotype 3 subjects. No subject experienced on-treatment virologic failure or relapse.

Subjects 6 Years to <12 Years of Age: SOVALDI was evaluated in 41 subjects 6 years to <12 years of age with HCV genotype 2 (N = 13) or genotype 3 (N = 28) infection. The median age was 9 years (range: 6 to 11); 73% of the subjects were female; 71% were White and 20% were Asian; 15% were Hispanic/Latino; mean body mass index was 19 kg/m² (range: 13 to 32 kg/m²); mean weight was 34 kg (range 15 to 80 kg); 98% were treatment naive; 46% had baseline HCV RNA levels greater than or equal to 800,000 IU/mL; and no subjects had known cirrhosis. The majority of subjects (98%) had been infected through vertical transmission.

The SVR12 rate was 100% (13/13) in genotype 2 and 100% (28/28) in genotype 3 subjects.). No subjects experienced on-treatment virologic failure or relapse.

Subjects 3 Years to <6 Years of Age: SOVALDI was evaluated in 13 subjects 3 years to <6 years of age with HCV genotype 2 (N = 5) or genotype 3 (N = 8) infection. The median age was 4 years (range: 3 to 5); 77% of the subjects were female; 69% were White, 8% were Black, and 8% were Asian; 8% were Hispanic/Latino; mean body mass index was 15 kg/m² (range: 13 to 17 kg/m²); mean weight was 17 kg (range 13 to 19 kg); 100% were treatment naive; 23% had baseline HCV RNA levels greater than or equal to 800,000 IU/mL; and no subjects had known cirrhosis. The majority of subjects (85%) had been infected through vertical transmission.

The SVR12 rate was 80% (4/5) in genotype 2 subjects and 100% (8/8) in genotype 3 subjects. No subjects experienced on-treatment virologic failure or relapse. One subject prematurely discontinued study treatment due to an adverse event.