Clinical Pharmacology for Vemlidy Tablets
Mechanism Of Action
Tenofovir alafenamide is an antiviral drug against the hepatitis B virus [see Microbiology].
Pharmacodynamics
Cardiac Electrophysiology
In a thorough QT/QTc study in 48 healthy subjects, tenofovir alafenamide at the recommended dose or at a dose 5 times the recommended dose did not affect the QT/QTc interval and did not prolong the PR interval.
Pharmacokinetics
The pharmacokinetic properties of VEMLIDY are provided in Table 5. The multiple dose PK parameters of tenofovir alafenamide and its metabolite tenofovir are provided in Table 6.
Table 5 : Pharmacokinetic Properties of VEMLIDY
|
Tenofovir Alafenamide |
| Absorption |
| Tmax (h) |
0.48 |
| Effect of high fat meal (relative to fasting): AUClast Ratioa |
1.65 (1.51, 1.81) |
| Distribution |
| % Bound to human plasma proteins |
80% |
| Source of protein binding data |
Ex vivo |
| Blood-to-plasma ratio |
1.0 |
| Metabolism |
| Metabolismb |
CES1 (hepatocytes) Cathepsin A (PBMCs) CYP3A (minimal) |
| Elimination |
| Major route of elimination |
Metabolism (>80% of oral dose) |
| t½ (h)c |
0.51 |
| % Of dose excreted in urined |
<1 |
| % Of dose excreted in fecesd |
31.7 |
CES1 = carboxylesterase 1; PBMCs = peripheral blood mononuclear cells.
a Values refer to geometric mean ratio in AUClast [fed/fasted] and (90% confidence interval). High fat meal = ~800 kcal, 50% fat.
b In vivo, TAF is hydrolyzed within cells to form tenofovir (major metabolite), which is phosphorylated to the active metabolite, tenofovir diphosphate. In vitro studies have shown that TAF is metabolized to tenofovir by CES1 in hepatocytes, and by cathepsin A in PBMCs and macrophages.
c t½ values refer to median terminal plasma half-life.
d Dosing in mass balance study: TAF 25 mg (single dose administration of [14C] TAF). |
Table 6 : Multiple Dose PK Parameters of Tenofovir Alafenamide and its Metabolite Tenofovir Following Oral Administration in Adults with Chronic Hepatitis B
| Parameter Mean (CV%) |
Tenofovir Alafenamidea |
Tenofovira |
| Cmax (mcg per mL) |
0.27 (63.3) |
0.03 (24.6) |
| AUCtau (mcg•hour per mL) |
0.27 (47.8) |
0.40 (35.2) |
| Ctrough (mcg per mL) |
NA |
0.01 (39.6) |
CV = coefficient of variation; NA = not applicable
a From Intensive PK analyses in Trial 108 and Trial 110; N = 8. |
Specific Populations
Geriatric Patients, Race, And Gender
Limited data in subjects aged 65 years and over suggest a lack of clinically relevant differences in tenofovir alafenamide or tenofovir pharmacokinetics. No clinically relevant differences in tenofovir alafenamide or tenofovir pharmacokinetics due to race or gender have been identified [see Use In Specific Populations].
Pediatric Patients
Steady-state pharmacokinetics of tenofovir alafenamide and its metabolite tenofovir were evaluated in HBV-infected pediatric subjects aged 6 to less than 18 years (Table 7).
Table 7 : Multiple Dose PK Parameters of Tenofovir Alafenamide and Tenofovir Following Oral Administration of VEMLIDY 25 mg in HBV-Infected Pediatric Subjects Aged 6 to less than 18 Years
| Age Group |
Parameter Mean (CV%) |
Tenofovir Alafenamidea |
Tenofovirb |
| 12 to <18 Years weighing ≥35 kg |
Cmax (mcg per mL) |
0.188 (45.0) |
0.015 (23.5) |
| AUCtau (mcg•hour per mL) |
0.254 (36.4) |
0.244 (28.3) |
| Ctrough (mcg per mL) |
NA |
0.0079 (35.0) |
| 6 to <12 Years weighing ≥25 kg |
Cmax (mcg per mL) |
0.388 (96.9) |
0.017 (19.6) |
| AUCtau (mcg•hour per mL) |
0.313 (64.8) |
0.272 (17.5) |
| Ctrough (mcg per mL) |
NA |
0.0089 (10.2) |
CV = coefficient of variation; NA = not applicable
a From Intensive PK analyses in Trial 1092: Cohort 1, N=13 except N=11 for AUCtau; Cohort 2, Group 1, N=5.
b From Intensive PK analyses in Trial 1092: Cohort 1, N=13; Cohort 2, Group 1, N=5. |
Patients With Renal Impairment
In a Phase 1, open-label study, tenofovir alafenamide and tenofovir systemic exposures (AUCinf) were evaluated in subjects with severe renal impairment and in subjects with normal renal function (Table 8). In an open-label trial of elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide 150/150/200/10 mg, tenofovir alafenamide and tenofovir AUC were evaluated in a subset of virologically suppressed HIV-1 infected subjects with ESRD receiving chronic hemodialysis (Table 8). In a Phase 2, open-label trial, tenofovir alafenamide and tenofovir AUC were evaluated in a subset of virologically suppressed HBV-infected subjects with ESRD receiving chronic hemodialysis (Table 8) [see Use In Specific Populations]. The pharmacokinetics of tenofovir alafenamide were similar among subjects with normal renal function, subjects with severe renal impairment, and subjects with ESRD receiving chronic hemodialysis. Relative to those with normal renal function, increased tenofovir exposures were observed in subjects with severe renal impairment and subjects with ESRD receiving chronic hemodialysis. Within the chronic hemodialysis population, increased tenofovir exposures were observed in subjects with HBV relative to those with HIV.
Table 8 : Pharmacokinetics of Tenofovir Alafenamide and its Metabolite Tenofovir in Subjects with Renal Impairment as Compared to Subjects with Normal Renal Function
| Estimated Creatinine Clearancea Mean (CV%) |
≥90 mL per minute 25 mg TAF
(N=13)b |
15-29 mL per minute 25 mg TAF
(N=14)b |
<15 mL per minute 25 mg TAFc
(N=5) |
<15 mL per minute 10 mg TAFd
(N=12) |
| Tenofovir alafenamide |
| AUC (mcg•hour per mL) |
0.27 (49.2)e |
0.51 (47.3)e |
0.30 (26.7)f |
0.23 (53.2)f |
| Cmax (mcg per mL) |
0.20 (62.1) |
0.36 (65.7) |
0.23 (48.4) |
0.25 (75.4) |
| Tenofovir |
| AUC (mcg•hour per mL) |
0.34 (27.2)e |
2.07 (47.1)e |
18.8 (30.4)g |
8.72 (39.4)gh |
| Cmax (mcg per mL) |
0.01 (36.5) |
0.03 (32.4) |
0.89 (26.4) |
0.44 (40.9) |
| C24h (mcg per mL) |
0.004 (25.6) |
0.02 (41.9) |
0.89 (26.4) |
0.26 (73.2)h |
CV = coefficient of variation
a By Cockcroft-Gault method.
b PK assessed on a single dose of TAF 25 mg in subjects with normal renal function and in subjects with severe renal impairment.
c PK assessed on the day prior to hemodialysis of TAF 25 mg. These subjects from Trial 4035 had a median baseline eGFR by Cockcroft-Gault of 7.2 mL/min (range, 4.8 to 12.0).
d Exposures from TAF 25 mg = exposures from TAF 10 mg as part of elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide. PK assessed on the day prior to hemodialysis following 3 consecutive daily doses of elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide. These subjects from Trial 1825 had a median baseline eGFR by Cockcroft-Gault of 10.2 mL/min (range, 6.8 to 19.2) .
e AUCinf.
f AUClast.
g AUCtau.
h N=10. |
Patients With Hepatic Impairment
Tenofovir alafenamide and tenofovir pharmacokinetics are similar in subjects with mild (Child-Pugh Class A) hepatic impairment and in subjects with normal hepatic function.
HIV And/Or Hepatitis C Virus Coinfection
The pharmacokinetics of tenofovir alafenamide have not been fully evaluated in subjects coinfected with HIV and/or hepatitis C virus.
Drug Interaction Studies
[see DRUG INTERACTIONS]
The effects of coadministered drugs on the exposure of tenofovir alafenamide are shown in Table 9. The effects of tenofovir alafenamide on the exposure of coadministered drugs are shown in Table 10 [For information regarding clinical recommendations, see DRUG INTERACTIONS]. Information regarding potential drug-drug interactions with HIV antiretrovirals is not provided (see the prescribing information for emtricitabine/tenofovir alafenamide for interactions with HIV antiretrovirals).
Table 9 : Drug Interactions: Changes in Pharmacokinetic Parameters for Tenofovir Alafenamide in the Presence of the Coadministered Druga
| Coadministered Drug |
Dose of Coadministered Drug (mg) |
Tenofovir Alafenamide (mg) |
N |
Geometric Mean Ratio of TAF Pharmacokinetic Parameters (90% CI)b; No effect = 1.00 |
| Cmax |
AUC |
Cmin |
| Carbamazepine |
300 twice daily |
25 once dailyc |
26 |
0.43
(0.36, 0.51) |
0.45
(0.40, 0.51) |
NC |
| Cobicistatd |
150 once daily |
8 once daily |
12 |
2.83
(2.20, 3.65) |
2.65
(2.29, 3.07) |
NC |
| Ledipasvir/ Sofosbuvir |
90/400 once daily |
25 once dailye |
42 |
1.03
(0.94, 1.14) |
1.32
(1.25, 1.40) |
NC |
| Sertraline |
50 single dose |
10 once dailyf |
19 |
1.00
(0.86, 1.16) |
0.96
(0.89, 1.03) |
NC |
| Sofosbuvir/ Velpatasvir/ Voxilaprevir |
400/100/100+ 100 voxilaprevirg once daily |
25 once dailye |
30 |
1.32
(1.17, 1.48) |
1.52
(1.43, 1.61) |
NC |
NC = not calculated
a All interaction studies conducted in healthy subjects.
b All no effect boundaries are 70%–143%.
c Study conducted with emtricitabine/tenofovir alafenamide.
d A representative inhibitor of P-glycoprotein.
e Study conducted with emtricitabine/rilpivirine/tenofovir alafenamide.
f Study conducted with elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide.
g Study conducted with additional voxilaprevir 100 mg to achieve voxilaprevir exposures expected in HCV-infected patients. |
Table 10 : Drug Interactions: Changes in Pharmacokinetic Parameters for Coadministered Drug in the Presence of Tenofovir Alafenamidea
| Coadministered Drug |
Dose of Coadministered Drug (mg) |
Tenofovir Alafenamide (mg) |
N |
Geometric Mean Ratio of Coadministered Drug Pharmacokinetic Parameters (90% CI)b; No effect = 1.00 |
| Cmax |
AUC |
Cmin |
| Ledipasvir |
90 ledipasvir / 400 sofosbuvir once daily |
25 once dailyd |
41 |
1.01
(0.97, 1.05) |
1.02
(0.97, 1.06) |
1.02
(0.98, 1.07) |
| Sofosbuvir |
0.96
(0.89, 1.04) |
1.05
(1.01, 1.09) |
NC |
| GS-331007c |
1.08
(1.05, 1.11) |
1.08
(1.06, 1.10) |
1.10
(1.07, 1.12) |
| Midazolame |
2.5 single dose orally |
25 once daily |
18 |
1.02
(0.92, 1.13) |
1.13
(1.04, 1.23) |
NC |
| 1 single dose IV |
0.99
(0.89, 1.11) |
1.08
(1.04, 1.14) |
NC |
| Norelgestromin |
norgestimate 0.180/0.215/0.250 once daily / ethinyl estradiol 0.025 once daily |
25 once dailyf |
29 |
1.17
(1.07, 1.26) |
1.12
(1.07, 1.17) |
1.16
(1.08, 1.24) |
| Norgestrel |
1.10
(1.02, 1.18) |
1.09
(1.01, 1.18) |
1.11
(1.03, 1.20) |
| Ethinyl estradiol |
1.22
(1.15, 1.29) |
1.11
(1.07, 1.16) |
1.02
(0.93, 1.12) |
| Sertraline |
50 single dose |
10 once dailyg |
19 |
1.14
(0.94, 1.38) |
0.93
(0.77, 1.13) |
NC |
| Sofosbuvir |
400 once daily |
25 once dailyh |
30 |
0.95
(0.86, 1.05) |
1.01
(0.97, 1.06) |
NC |
| GS-331007c |
1.02
(0.98, 1.06) |
1.04
(1.01, 1.06) |
NC |
| Velpatasvir |
100 once daily |
1.05
(0.96, 1.16) |
1.01
(0.94, 1.07) |
1.01
(0.95, 1.09) |
| Voxilaprevir |
100+100i once daily |
0.96
(0.84, 1.11) |
0.94
(0.84, 1.05) |
1.02
(0.92, 1.12) |
NC = not calculated
a All interaction studies conducted in healthy subjects.
b All no effect boundaries are 70%–143%.
c The predominant circulating nucleoside metabolite of sofosbuvir.
d Study conducted with emtricitabine/rilpivirine/tenofovir alafenamide.
e A sensitive CYP3A4 substrate.
f Study conducted with emtricitabine/tenofovir alafenamide.
g Study conducted with elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide.
h Study conducted with emtricitabine/rilpivirine/tenofovir alafenamide.
i Study conducted with additional voxilaprevir 100 mg to achieve voxilaprevir exposures expected in HCV-infected patients. |
Microbiology
Mechanism Of Action
Tenofovir alafenamide is a phosphonamidate prodrug of tenofovir (2’-deoxyadenosine monophosphate analog). Tenofovir alafenamide as a lipophilic cell-permeant compound enters primary hepatocytes by passive diffusion and by the hepatic uptake transporters OATP1B1 and OATP1B3. Tenofovir alafenamide is then converted to tenofovir through hydrolysis primarily by carboxylesterase 1 (CES1) in primary hepatocytes. Intracellular tenofovir is subsequently phosphorylated by cellular kinases to the pharmacologically active metabolite tenofovir diphosphate. Tenofovir diphosphate inhibits HBV replication through incorporation into viral DNA by the HBV reverse transcriptase, which results in DNA chain-termination.
Tenofovir diphosphate is a weak inhibitor of mammalian DNA polymerases that include mitochondrial DNA polymerase γ and there is no evidence of toxicity to mitochondria in cell culture.
Antiviral Activity In Cell Culture
The antiviral activity of tenofovir alafenamide was assessed in a transient transfection assay using HepG2 cells against a panel of HBV clinical isolates representing genotypes A-H. The EC50 (50% effective concentration) values for tenofovir alafenamide ranged from 34.7 to 134.4 nM, with an overall mean EC50 value of 86.6 nM. The CC50 (50% cytotoxicity concentration) values in HepG2 cells were greater than 44,400 nM. In cell culture combination antiviral activity studies of tenofovir with the HBV nucleoside reverse transcriptase inhibitors entecavir, lamivudine, and telbivudine, no antagonistic activity was observed.
Resistance In Clinical Trials
Genotypic resistance analysis was performed on paired baseline and on-treatment HBV isolates for subjects who either experienced virologic breakthrough (2 consecutive visits with HBV DNA greater than or equal to 69 IU/mL [400 copies/mL] after having been less than 69 IU/mL, or 1.0-log10 or greater increase in HBV DNA from nadir) through Week 48, or had HBV DNA greater than or equal to 69 IU/mL at early discontinuation at or after Week 24.
In a pooled analysis of treatment-naïve and treatment-experienced subjects receiving VEMLIDY in Trials 108 and 110 [see Clinical Studies], treatment-emergent amino acid substitutions in the HBV reverse transcriptase domain, all occurring at polymorphic positions, were observed in some HBV isolates evaluated (5/20); however, no specific substitutions occurred at a sufficient frequency to be associated with resistance to VEMLIDY.
In virologically suppressed subjects receiving VEMLIDY in Trial 4018 [see Clinical Studies], no subjects qualified for resistance analysis through 48 weeks of VEMLIDY treatment.
In pediatric Trial 1092, 17/70 subjects in Cohort 1 (aged 12 to less than 18 years) and 7/18 subjects in Cohort 2, Group 1 (aged 6 to less than 12 years) receiving VEMLIDY qualified for resistance analysis at Week 96. Results were obtained from 19/24 qualified subjects. No HBV amino acid substitutions known to be associated with resistance to tenofovir alafenamide were detected through 96 weeks of treatment [see Clinical Studies].
Cross-Resistance
The antiviral activity of tenofovir alafenamide was evaluated against a panel of isolates containing substitutions associated with HBV nucleoside reverse transcriptase inhibitor resistance in a transient transfection assay using HepG2 cells. HBV isolates expressing the lamivudine resistance-associated substitutions rtM204V/I (±rtL180M±rtV173L) and expressing the entecavir resistance-associated substitutions rtT184G, rtS202G, or rtM250V in the presence of rtL180M and rtM204V showed less than 2-fold reduced susceptibility (within the inter-assay variability) to tenofovir alafenamide. HBV isolates expressing the rtA181T, rtA181V, or rtN236T single substitutions associated with resistance to adefovir also had less than 2-fold changes in EC50 values; however, the HBV isolate expressing the rtA181V plus rtN236T double substitutions exhibited reduced susceptibility (3.7-fold) to tenofovir alafenamide. The clinical relevance of these substitutions is not known.
Animal Toxicology And/Or Pharmacology
Minimal to slight infiltration of mononuclear cells in the posterior uvea was observed in dogs with similar severity after three- and nine-month administration of tenofovir alafenamide; reversibility was seen after a three-month recovery period. At the NOAEL for eye toxicity, the systemic exposure in dogs was 5 (tenofovir alafenamide) and 14 (tenofovir) times the exposure seen in humans at the recommended daily VEMLIDY dosage.
Clinical Studies
Description Of Clinical Trials
The efficacy and safety of VEMLIDY were evaluated in the trials summarized in Table 11.
Table 11 : Trials Conducted with VEMLIDY in Subjects with Chronic HBV Infection
| Trial |
Population |
Trial Arms (N) |
Primary Endpoint (Week) |
| Trial 108a (NCT01940341) |
HBeAg-negative TN and TE adults with compensated liver disease |
VEMLIDY (285) TDF (140) |
48 |
| Trial 110a (NCT01940471) |
HBeAg-positive TN and TE adults with compensated liver disease |
VEMLIDY (581) TDF (292) |
48 |
| Trial 4018a (NCT02979613) |
HBeAg-negative and HBeAg-positive virologically suppressedb adults with compensated liver disease |
VEMLIDY (243) TDF (245) |
48 |
| Trial 4035 (Part A, Cohort 1)c (NCT03180619) |
Virologically suppressedb adults with moderate to severe renal impairment01 |
VEMLIDY (78) |
24 |
| Trial 4035 (Part A, Cohort 2)c (NCT03180619) |
Virologically suppressedb adults with ESRDe receiving chronic hemodialysis |
VEMLIDY (15) |
24 |
| Trial 1092f (NCT02932150) |
Pediatric subjects between the ages of 6 to less than 18 years (at least 25 kg) with compensated liver disease |
VEMLIDY (59) Placebo (29) |
24 |
TE = treatment-experienced, TN = treatment-naive
a Randomized, double-blind, active controlled trial.
b HBV DNA <20 IU/mL at screening.
c Open-label trial.
d Estimated creatinine clearance between 15 and 59 mL per minute by Cockcroft-Gault method.
e End stage renal disease (estimated creatinine clearance of below 15 mL per minute by Cockcroft-Gault method).
f Randomized, double-blind, placebo-controlled trial. |
Clinical Trials In Adults With Chronic Hepatitis B Virus Infection And Compensated Liver Disease
The efficacy and safety of VEMLIDY in the treatment of adults with chronic hepatitis B virus infection with compensated liver disease are based on 48-week data from two randomized, double-blind, active-controlled trials, Trial 108 (N=425) and Trial 110 (N=873). In both trials, besides trial treatment, subjects were not allowed to receive other nucleosides, nucleotides, or interferon.
In Trial 108, HBeAg-negative treatment-naïve and treatment-experienced subjects with compensated liver disease (no evidence of ascites, hepatic encephalopathy, variceal bleeding, INR <1.5x ULN, total bilirubin <2.5x ULN, and albumin >3.0 mg/dL) were randomized in a 2:1 ratio to receive VEMLIDY 25 mg (N=285) once daily or TDF 300 mg (N=140) once daily for 48 weeks. The mean age was 46 years, 61% were male, 72% were Asian, 25% were White, 2% were Black, and 1% were other races. 24%, 38%, and 31% had HBV genotype B, C, and D, respectively. 21% were treatment experienced [previous treatment with oral antivirals, including entecavir (N=41), lamivudine (N=42), TDF (N=21), or other (N=18)]. At baseline, mean plasma HBV DNA was 5.8 log10 IU/mL, mean serum ALT was 94 U/L, and 9% of subjects had a history of cirrhosis.
In Trial 110, HBeAg-positive treatment-naïve and treatment-experienced subjects with compensated liver disease were randomized in a 2:1 ratio to receive VEMLIDY 25 mg (N=581) once daily or TDF 300 mg (N=292) once daily for 48 weeks. The mean age was 38 years, 64% were male, 82% were Asian, 17% were White, and 1% were Black or other races. 17%, 52%, and 23% had HBV genotype B, C, and D, respectively. 26% were treatment experienced [previous treatment with oral antivirals, including adefovir (N=42), entecavir (N=117), lamivudine (N=84), telbivudine (N=25), TDF (N=70), or other (n=17)]. At baseline, mean plasma HBV DNA was 7.6 log10 IU/mL, mean serum ALT was 120 U/L, and 7% of subjects had a history of cirrhosis.
In both trials, randomization was stratified on prior treatment history (nucleoside naïve or experienced) and baseline HBV DNA (<7, ≥7 to <8, and ≥8 log10 IU/mL in Trial 108; and <8 and ≥8 log10 IU/mL in Trial 110). The efficacy endpoint in both trials was the proportion of subjects with plasma HBV DNA levels below 29 IU/mL at Week 48. Additional efficacy endpoints include the proportion of subjects with ALT normalization, HBsAg loss and seroconversion, and HBeAg loss and seroconversion in Trial 110.
Treatment outcomes of Trials 108 and 110 at Week 48 are presented in Table 12 and Table 13.
Table 12 : Trials 108 and 110: HBV DNA Virologic Outcome at Week 48a in Subjects with Chronic HBV Infection and Compensated Liver Disease
|
Trial 108 (HBeAg-Negative) |
Trial 110 (HBeAg-Positive) |
VEMLIDY
(N=285) |
TDF
(N=140) |
VEMLIDY
(N=581) |
TDF
(N=292) |
| HBV DNA <29 lU/mL |
94% |
93% |
64% |
67% |
| Treatment Differenceb |
1.8% (95% Cl = -3.6% to 7.2%) |
-3.6% (95% Cl = -9.8% to 2.6%) |
| HBV DNA ≥29 lU/mL |
2% |
3% |
31% |
30% |
| Baseline HBV DNA |
| <7 log10 lU/mL |
96% (221/230) |
92% (107/116) |
N/A |
N/A |
| ≥7 log10 lU/mL |
85% (47/55) |
96% (23/24) |
|
|
| Baseline HBV DNA |
| <8 log10 lU/mL |
N/A |
N/A |
82% (254/309) |
82% (123/150) |
| ≥8 log10 lU/mL |
|
|
43% (117/272) |
51% (72/142) |
| Nucleoside Naivec |
94% (212/225) |
93% (102/110) |
68% (302/444) |
70% (156/223) |
| Nucleoside Experienced |
93% (56/60) |
93% (28/30) |
50% (69/137) |
57% (39/69) |
| No Virologic Data at Week 48d |
4% |
4% |
5% |
3% |
a Missing = failure analysis.
b Adjusted by baseline plasma HBV DNA categories and oral antiviral treatment status strata.
c Treatment-naïve subjects received <12 weeks of oral antiviral treatment with any nucleoside or nucleotide analog including TDF or VEMLIDY.
d Includes subjects who discontinued due to lack of efficacy, adverse event or death, for reasons other than an AE, death or lack or loss of efficacy, e.g., withdrew consent, loss to follow-up, etc., or missing data during Week 48 window but still on study drug. |
In Trial 108, the proportion of subjects with cirrhosis who achieved HBV DNA <29 IU/mL at Week 48 was 92% (22/24) in the VEMLIDY group and 93% (13/14) in the TDF group. The corresponding proportions in Trial 110 were 63% (26/41) and 67% (16/24) in the VEMLIDY and TDF groups, respectively.
Table 13 : Additional Efficacy Parameters at Week 48a
|
Trial 108 (HBeAg-Negative) |
Trial 110 (HBeAg-Positive) |
VEMLIDY
(N=285) |
TDF
(N=140) |
VEMLIDY
(N=581) |
TDF
(N=292) |
| ALT |
| Normalized ALT (Central Lab)b |
83% |
75% |
72% |
67% |
| Normalized ALT (AASLD)c |
50% |
32% |
45% |
36% |
| Serology |
| HBeAg Loss / Seroconversiond |
N/A |
N/A |
14% / 10% |
12% / 8% |
| HBsAg Loss / Seroconversion |
0 / 0 |
0 / 0 |
1% / 1% |
<1% / 0 |
N/A = not applicable
a Missing = failure analysis.
b The population used for analysis of ALT normalization included only subjects with ALT above upper limit of normal (ULN) of the central laboratory range (>43 U/L for males aged 18 to <69 years and >35 U/L for males ≥69 years; >34 U/L for females 18 to <69 years and >32 U/L for females ≥69 years) at baseline.
c The population used for analysis of ALT normalization included only subjects with ALT above ULN of the 2016 American Association of the Study of Liver Diseases (AASLD) criteria (>30 U/L males and >19 U/L females) at baseline.
d The population used for serology analysis included only subjects with antigen (HBeAg) positive and anti-body (HBeAb) negative or missing at baseline. |
Clinical Trials In Virologically Suppressed Adults With Chronic Hepatitis B Virus Infection Who Switched To VEMLIDY
The efficacy and safety of switching from TDF to VEMLIDY in virologically suppressed adults with chronic hepatitis B virus infection is based on 48-week data from a randomized, double-blind, active-controlled trial, Trial 4018 (N=488). Subjects must have been taking TDF 300 mg once daily for at least 12 months, with HBV DNA less than the Lower Limit of Quantitation by local laboratory assessment for at least 12 weeks prior to screening and HBV DNA <20 IU/mL at screening. Subjects were stratified by HBeAg status (HBeAg-positive or HBeAg-negative) and age (≥50 or <50 years) and randomized in a 1:1 ratio to either switch to VEMLIDY 25 mg once daily (N=243) or stay on TDF 300 mg once daily (N=245). The mean age was 51 years (22% were ≥60 years), 71% were male, 82% were Asian, 14% were White, and 68% were HBeAg-negative. At baseline, median duration of prior TDF treatment was 220 and 224 weeks in the VEMLIDY and TDF groups, respectively. At baseline, mean serum ALT was 27 U/L, and 16% of subjects had a history of cirrhosis.
The primary efficacy endpoint was the proportion of subjects with plasma HBV DNA levels ≥20 IU/mL at Week 48. Additional efficacy endpoints in Trial 4018 included the proportion of subjects with HBV DNA <20 IU/mL, ALT normal and normalization, HBsAg loss and seroconversion, and HBeAg loss and seroconversion.
Treatment outcomes of Trial 4018 at Week 48 are presented in Table 14 and Table 15.
Table 14 : Trial 4018: HBV DNA Virologic Outcome at Week 48a in Virologically Suppressed Subjects with Chronic HBV Infection
|
VEMLIDY
(N=243) |
TDF
(N=245) |
| HBV DNA ≥20 IU/mLb |
<1% |
<1% |
| Treatment Differencec |
0.0% (95% CI = -1.9% to 2.0%) |
| HBV DNA <20 IU/mL |
96% |
96% |
| Treatment Differencec |
0.0% (95% CI = -3.7% to 3.7%) |
| No Virologic Data at Week 48 |
3% |
3% |
| Discontinued Study Drug Due to AE or Death and Last Available HBV DNA <20 IU/mL |
1% |
0 |
| Discontinued Study Drug Due to Other Reasonsd and Last Available HBV DNA <20 IU/mL |
2% |
3% |
a Week 48 window was between Day 295 and Day 378 (inclusive).
b No subject discontinued treatment due to lack of efficacy.
c Adjusted by baseline age groups (< 50, ≥ 50 years) and baseline HBeAg status strata.
d Includes subjects who discontinued for reasons other than an AE, death, or lack of efficacy, e.g., withdrew consent, loss to follow-up, etc. |
Table 15 : Additional Efficacy Parameters at Week 48a (Trial 4018)
|
VEMLIDY
(N=243) |
TDF
(N=245) |
| ALT |
| Normal ALT (Central Lab) |
89% |
85% |
| Normal ALT (AASLD) |
79% |
75% |
| Normalized ALT (Central Lab)bc |
50% |
37% |
| Normalized ALT (AASLD)de |
50% |
26% |
| Serology |
| HBeAg Loss / Seroconversionf |
8% / 3% |
6% / 0 |
| HBsAg Loss / Seroconversion |
0 / 0 |
2% / 0 |
a Missing = failure analysis.
b The population used for analysis of ALT normalization included only subjects with ALT above upper limit of normal (ULN) of the central laboratory range (>43 U/L for males 18 to <69 years and >35 U/L for males ≥69 years; >34 U/L for females 18 to <69 years and >32 U/L for females ≥69 years) at baseline.
c Proportion of subjects at Week 48: VEMLIDY, 16/32; TDF, 7/19.
d The population used for analysis of ALT normalization included only subjects with ALT above ULN of the 2018 American Association of the Study of Liver Diseases (AASLD) criteria (35 U/L males and 25 U/L females) at baseline.
e Proportion of subjects at Week 48: VEMLIDY, 26/52; TDF, 14/53.
f The population used for serology analysis included only subjects with antigen (HBeAg) positive and anti-body (HBeAb) negative or missing at baseline. |
Clinical Trial In Adults With Chronic Hepatitis B Virus Infection And Renal Impairment
In Trial 4035, Part A, the efficacy and safety of switching from TDF and/or other antivirals to VEMLIDY were evaluated in an open-label clinical trial of virologically suppressed chronic hepatitis B infected adults with moderate to severe renal impairment (estimated creatinine clearance between 15 and 59 mL per minute by Cockcroft-Gault method) (Cohort 1, N=78) or ESRD (estimated creatinine clearance below 15 mL per minute by Cockcroft-Gault method) on hemodialysis (Cohort 2, N=15). At baseline, 98% of subjects in Part A had baseline HBV DNA <20 IU/mL. Median age was 65 years, 74% were male, 77% were Asian, 16% were White, and 83% were HBeAg-negative. Previous treatment with oral antivirals included TDF (Cohort 1, N=57; Cohort 2, N=1), lamivudine (N=46), adefovir dipivoxil (N=46), and entecavir (N=43). At baseline, 97% and 95% of subjects had ALT ≤ULN based on central laboratory criteria and 2018 AASLD criteria, respectively; median estimated creatinine clearance by Cockcroft-Gault was 43 mL per minute (45 mL per minute in Cohort 1 and 7 mL per minute in Cohort 2); and 34% of subjects had a history of cirrhosis.
Overall, 98% of subjects achieved HBV DNA <20 IU/mL at Week 24 (Cohort 1, 97%; Cohort 2, 100%). Two subjects in Cohort 1 discontinued treatment early (due to subject decision); last available HBV DNA for both of these subjects was <20 IU/mL. The overall mean (SD) change from baseline in ALT values was +1 (11.3) U/L (Cohort 1, +1 [11.9] U/L; Cohort 2, +3 [7.9] U/L) at Week 24. No subject had HBeAg or HBsAg loss at Week 24. The mean (SD) changes in HBsAg level from baseline were -0.05 (0.122) log10 IU/mL (-0.05 [0.124] log10 IU/mL for Cohort 1 and -0.07 [0.115] log10 IU/mL for Cohort 2) at Week 24.
Clinical Trial In Pediatric Subjects 6 Years Of Age And Older With Chronic Hepatitis B Virus Infection
In Trial 1092, the efficacy and safety of VEMLIDY in chronic HBV-infected subjects were evaluated in a randomized, double-blind, placebo-controlled clinical trial of treatment-naïve and treatment-experienced subjects between the ages of 12 to less than 18 years weighing at least 35 kg (Cohort 1; N=70) and 6 to less than 12 years weighing at least 25 kg (Cohort 2, Group 1; N=18). Subjects were randomized to receive VEMLIDY (N=59) or placebo (N=29) once daily. Baseline demographics and HBV disease characteristics were comparable between the VEMLIDY treatment arm and the placebo arm: in the VEMLIDY group, 58% were male, 63% were Asian, and 27% were White; 9%, 24%, 22%, and 44% had HBV genotype A, B, C, and D, respectively; 98% percent were HBeAg positive. At baseline, overall median HBV DNA was 8.1 log10 IU/mL, mean ALT was 107 U/L, median HBsAg was 4.5 log10 IU/mL. Previous treatment included oral antivirals (N=20 [23%]), including entecavir (N=10 [11%]), lamivudine (N=10 [11%]), and TDF (N=2 [2%]), and/or interferons (N=13 [15%]).
The results for each treatment group and cohort for HBV DNA < 20 IU/mL at Weeks 24, 48 and 96 are presented in Table 16 below.
Table 16 : Trial 1092: HBV DNA Virologic Outcome in Pediatric Subjects 6 Years of Age and Older with Chronic HBV
|
TAF
(N=59) |
PBO-TAF
(N=29) |
| HBV DNA <20 IU/mL at Week 24 (total) |
11/59 (19%) |
0/29 |
| - Cohort 1 (12- <18 and at least 35 kg) |
10/47 (21%) |
0/23 |
| - Cohort 2 Group 1 (6- <12 and at least 25 kg) |
1/12 (8%) |
0/6 |
| HBV DNA <20 IU/mL at Week 48 (total) |
22/59 (37%) |
6/29 (21%)a |
| - Cohort 1 (12- <18 and at least 35 kg) |
19/47 (40%) |
5/23 (22) |
| - Cohort 2 Group 1 (6- <12 and at least 25 kg) |
3/12 (25%) |
1/6 (17%) |
| HBV DNA <20 IU/mL at Week 96 (total) |
36/59 (61%) |
14/29 (48%)b |
| - Cohort 1 (12- <18 and at least 35 kg) |
30/47 (64%) |
12/23 (52%) |
| - Cohort 2 Group 1 (6- <12 and at least 25 kg) |
6/12 (50%) |
2/6 (33%) |
a Week 24 on TAF
b Week 72 on TAF |
At Week 96, the overall mean (SD) change from baseline in HBV DNA for VEMLIDY-treated subjects and subjects who switched from placebo to VEMLIDY, respectively, was -6.18 (1.495) log10 IU/mL and -5.92 (1.775) log10 IU/mL. The overall median change from baseline in ALT values for the VEMLIDY and placebo-VEMLIDY treatment groups, respectively, was -39.5 U/L and -46.5 U/L at Week 96. ALT normalization (AASLD criteria) was achieved for 54% of VEMLIDY-treated subjects and 57% of subjects who switched from placebo to VEMLIDY.
At Week 96, 14/58 (24%) VEMLIDY-treated subjects and 5/29 (17%) subjects who switched from placebo to VEMLIDY experienced HBeAg loss with anti-HBe seroconversion. One of 47 (2%) subjects in the Cohort 1 VEMLIDY group achieved HBsAg loss at Week 96.