Clinical Pharmacology for Biktarvy
Mechanism Of Action
BIKTARVY is a fixed dose combination of antiretroviral drugs bictegravir (BIC), emtricitabine (FTC), and tenofovir alafenamide (TAF) [see Microbiology].
Pharmacodynamics
Cardiac Electrophysiology
In a thorough QT/QTc trial in 48 healthy subjects, BIC at doses 1.5 and 6 times the recommended dose did not affect the QT/QTc interval and did not prolong the PR interval. In a thorough QT/QTc trial in 48 healthy subjects, TAF 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. The effect of FTC on the QT interval is not known.
Effects On Serum Creatinine
Mean change from baseline in serum creatinine in healthy subjects who received BIC 75 mg (1.5 times the approved recommended dosage) once daily with food for 14 days was 0.1 mg per dL on Days 7 and 14 compared to placebo. BIC did not have a significant effect on the estimated creatinine clearance or on the actual glomerular filtration rate (determined by the clearance of probe drug, iohexol).
Pharmacokinetics
The pharmacokinetic (PK) properties of BIKTARVY components are provided in Table 4.The multiple dose PK parameters of BIKTARVY components (based on population pharmacokinetic analysis) are provided in Table 5.
Table 4 Pharmacokinetic Properties of the Components of BIKTARVY
|
Bictegravir (BIC) |
Emtricitabine (FTC) |
Tenofovir Alafenamide (TAF) |
| Absorption |
| Tmax (h)a |
2.0–4.0 |
1.5–2.0 |
0.5–2.0 |
Effect of high-fat meal
(relative to fasting)b |
AUC ratio |
1.24
(1.16, 1.33) |
0.96
(0.93, 0.99) |
1.63
(1.43, 1.85) |
|
Cmax ratio |
1.13
(1.06, 1.20) |
0.86
(0.78, 0.93) |
0.92
(0.73, 1.14) |
| Distribution |
| % bound to human plasma proteins |
>99 |
<4 |
~80 |
| Blood-to-plasma ratio |
0.64 |
0.6 |
1.0 |
| Elimination |
| t1/2 (h)c |
17.3
(14.8, 20.7) |
10.4
(9.0, 12.0) |
0.51
(0.45, 0.62)c |
| Metabolism |
| Metabolic pathway(s) |
CYP3AUGT1A1 |
Not significantly metabolized |
Cathepsin Ad
(PBMCs)
CES1 (hepatocytes) |
| Excretion |
| Major route of elimination |
Metabolism |
Glomerular filtration and active tubular secretion |
Metabolism |
| % of dose excreted in urinee |
35 |
70 |
<1 |
| % of dose excreted in fecese |
60.3 |
13.7 |
31.7 |
PBMCs=peripheral blood mononuclear cells; CES1=carboxylesterase 1
a.Values reflect administration of BIKTARVY with or without food.
b.Values refer to geometric mean ratio [high-fat meal/ fasting] in PK parameters and (90% confidence interval). High fat meal is approximately 800 kcal, 50% fat.
c.t1/2 values refer to median (Q1, Q3) terminal plasma half-life. Note that the active metabolite of TAF, tenofovir diphosphate, has a half-life of 150-180 hours within PBMCs.
d.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 cathepsin A in PBMCs and macrophages; and by CES1 in hepatocytes.
e.Dosing in mass balance studies: single dose administration of [14C] BIC; single dose administration of [14C] FTC after multiple dosing of FTC for ten days; single dose administration of [14C] TAF. |
Table 5 Multiple Dose PK Parameters of BIC, FTC, and TAF Following OralAdministration of BIKTARVY in HIV-Infected Adults
| Parameter Mean (CV%) |
Bictegravir |
Emtricitabine |
Tenofovir Alafenamide |
Cmax
(microgram per mL) |
6.15 (22.9) |
2.13 (34.7) |
0.121 (15.4) |
AUCtau
(microgram•h per mL) |
102 (26.9) |
12.3 (29.2) |
0.142 (17.3) |
Ctrough
(microgram per mL) |
2.61 (35.2) |
0.096 (37.4) |
NA |
| CV=Coefficient of Variation; NA=Not Applicable |
Specific Populations
Patients With Renal Impairment
No clinically relevant differences in the pharmacokinetics of BIC, TAF, or its metabolite tenofovir were observed between subjects with severe renal impairment (estimated creatinine clearance of 15 to less than 30 mL/min, by Cockcroft-Gault method) and healthy subjects in Phase 1 studies. In a separate Phase 1 study of FTC alone, FTC exposures were increased in subjects with severe renal impairment.
The pharmacokinetics of BIC, FTC and TAF were evaluated in a subset of HIV-1 infected virologically-suppressed subjects with ESRD (estimated creatinine clearance less than 15 mL/min, by Cockcroft-Gault method) receiving chronic hemodialysis in Trial 1825. The pharmacokinetics of TAF were similar between healthy subjects and subjects with ESRD receiving chronic hemodialysis; increases in FTC and tenofovir exposures in subjects with ESRD were not considered clinically relevant. Median (minimum, maximum) BIC Ctrough values in subjects (n=7) with ESRD who received BIKTARVY were 846 ng/mL (288, 1810) compared to 2540 ng/mL (757, 6499) in subjects (N=584) with normal renal function. Despite significantly lower BIC Ctrough values in the virologically-suppressed ESRD population, virologic suppression was maintained [see Use In Specific Populations and Clinical Studies].
Patients With Hepatic Impairment
Bictegravir
Clinically relevant changes in the pharmacokinetics of BIC were not observed in subjects with moderate (Child-Pugh Class B) hepatic impairment.
Emtricitabine
The pharmacokinetics of FTC has not been studied in subjects with hepatic impairment; however, FTC is not significantly metabolized by liver enzymes, so the impact of hepatic impairment should be limited.
Tenofovir Alafenamide
Clinically relevant changes in the pharmacokinetics of TAF or its metabolite tenofovir were not observed in subjects with mild or moderate (Child-Pugh Class A and B) hepatic impairment [see Use In Specific Populations].
Hepatitis B And/Or Hepatitis C Virus Coinfection
The pharmacokinetics of BIC, FTC, and TAF have not been evaluated in subjects coinfected with hepatitis B and/or C virus.
Geriatric Patients
The pharmacokinetics of BIC, FTC, and TAF have not been fully evaluated in the elderly (65 years of age and older). Population pharmacokinetics analysis of HIV-infected subjects in Phase 3 trials of BIKTARVY showed that age did not have a clinically relevant effect on exposures of BIC and TAF up to 74 years of age [see Use In Specific Populations].
Pediatric Patients
Mean BIC Ctrough was lower in 50 pediatric patients aged 12 to less than 18 years and weighing at least 35 kg who received BIKTARVY in Trial 1474 relative to adults following administration of BIKTARVY, but was not considered clinically significant based on exposure-response relationships; exposures of FTC and TAF in these pediatric patients were similar to those in adults (Table 6).
Table 6 Multiple Dose PK Parameters of BIC, FTC, and TAF Following OralAdministration of BIKTARVY in HIV-Infected Pediatric Subjects Aged 12 to less than 18 years
| Parameter Mean (CV%) |
Bictegravira |
Emtricitabineb |
Tenofovir Alafenamidea |
Cmax
(microgram per mL) |
6.24 (27.1) |
2.69 (34.0) |
0.133 (70.2) |
AUCtau
(microgram•h per mL) |
89.1 (31.0) |
13.6 (21.7) |
0.196 (50.3) |
Ctrough
(microgram per mL) |
1.78 (44.4) |
0.064 (25.0) |
NA |
CV=Coefficient of Variation; NA=Not Applicable
a.From Population PK analysis of cohort 1 of Trial 1474 (n=50 for BIC; n=49 for TAF).
b.From Intensive PK analysis of cohort 1 of Trial 1474 (n=24). |
Mean BIC Cmax, and exposures of FTC and TAF (AUCtau and Cmax) achieved in 50 pediatric patients between the ages of 6 to less than 12 years and weighing at least 25 kg, and in 22 pediatric patients at least 2 years of age and weighing at least 14 to less than 25 kg who received BIKTARVY in Trial 1474 were higher than exposures in adults; however, the increases were not considered clinically significant as the safety profiles were similar in adult and pediatric patients (Tables 7 and 8) [see Use In Specific Populations].
Table 7 Multiple Dose PK Parameters of BIC, FTC, and TAF Following OralAdministration of BIKTARVY in HIV-Infected Pediatric Subjects Aged 6 to less than 12 years
| Parameter Mean (CV%) |
Bictegravira |
Emtricitabineb |
Tenofovir
Alafenamidea |
Cmax
(microgram per mL) |
9.46 (24.3) |
3.89 (31.0) |
0.205 (44.6) |
AUCtau
(microgram•h per mL) |
128 (27.8) |
17.6 (36.9) |
0.278 (40.3) |
Ctrough
(microgram per mL) |
2.36 (39.0) |
0.227 (323) |
NA |
CV=Coefficient of Variation; NA=Not Applicable
a.From Population PK analysis of cohort 2 of Trial 1474 (n=50 for BIC; n=47 for TAF).
b.From Intensive PK analysis of cohort 2 of Trial 1474 (n=25 except n=24 for Ctrough). |
Table 8 Multiple Dose PK Parameters of BIC, FTC, and TAF Following OralAdministration of BIKTARVY in HIV-Infected Pediatric Subjects at Least 2 Years of Agea and Weighing at Least 14 to Less than 25 kg
| Parameter Mean (CV%) |
Bictegravirb |
Emtricitabinec |
Tenofovir Alafenamidec |
Cmax
(microgram per mL) |
9.15 (44.8) |
3.85 (34.7) |
0.414 (31.0) |
AUCtau
(microgram•h per mL) |
126 (42.4) |
15.0 (21.9) |
0.305 (42.6) |
Ctrough
(microgram per mL) |
2.43 (40.1) |
0.210 (243) |
NA |
CV=Coefficient of Variation; NA=Not Applicable
a.Cohort 3 of Trial 1474 enrolled pediatric subjects from 3 to 9 years of age.
b.From Population PK analysis of cohort 3 of Trial 1474 (n=22).
c.From Intensive PK analysis of cohort 3 of Trial 1474 (n=12 except n=11 for Ctrough for FTC). |
Race And Gender
No clinically relevant changes in the pharmacokinetics of BIC, FTC, and TAF were observed based on gender or race.
Pregnancy
Plasma exposures (Ctrough and AUCtau) of BIC, FTC, and TAF after intake of BIKTARVY 50 mg/200 mg/25 mg were lower during pregnancy as compared to postpartum (Table 9). The exposure changes during pregnancy are not considered clinically significant in virologically suppressed pregnant individuals [see DRUG INTERACTIONS].
Table 9 Steady-state PK Parameters of BIC, FTC, and TAF Following OralAdministration of BIKTARVY in Virologically-Suppressed PregnantAdults with HIV-1 in the Second and Third Trimesters and Week 12 Postpartum
| Parameter Mean (%CV) |
Second Trimester (N=21) |
Third Trimester (N=30) |
Week 12 Postpartum (N=32) |
| Bictegravir |
Cmax
(microgram per mL) |
5.82 (30.1) |
5.37 (25.9) |
11.03 (24.9) |
AUCtau
(microgram•h per mL) |
62.8 (32.2) |
60.2 (29.1) |
148.3 (28.5) |
Unbound AUCtau a
(microgram•h per mL) |
0.224 (42.0) |
0.219 (33.9) |
0.374 (32.2) |
Ctrough
(microgram per mL) |
1.05 (45.2) |
1.07 (41.7) |
3.64 (34.1) |
| Emtricitabine |
Cmax
(microgram per mL) |
2.64 (36.6) |
2.59 (26.5) |
3.36 (26.9) |
AUCtau
(microgram•h per mL) |
10.3 (20.0) |
10.4 (20.3) |
15.3 (21.9) |
Ctrough
(microgram per mL) |
0.06 (103.9) |
0.05 (27.2) |
0.08 (33.7) |
| Tenofovir Alafenamide |
Cmax
(microgram per mL) |
0.33 (52.1) |
0.27 (42.1) |
0.49 (52.5) |
AUCtau
(microgram•h per mL) |
0.24 (45.6) |
0.21 (45.0) |
0.30 (31.8) |
Unbound AUCtau a
(microgram•h per mL) |
0.015 (28.2) |
0.016 (28.4) |
0.017 (23.4) |
CV = Coefficient of Variation; NA = Not Available
a. Calculated by correcting the individual AUCtau estimates by the % unbound fraction |
Drug Interaction Studies
As BIKTARVY is a complete regimen for the treatment of HIV-1 infection, comprehensive information regarding potential drug-drug interactions with other antiretroviral agents is not provided.
BIC Is A Substrate Of CYP3A And UGT1A1.
BIC is an inhibitor of OCT2 and MATE1. At clinically relevant concentrations, BIC is not an inhibitor of hepatic transporters OATP1B1, OATP1B3, OCT1, BSEP, renal transporters OAT1 and OAT3, or CYP (including CYP3A) or UGT1A1 enzymes.
TAF Is A Substrate Of P-Gp And BCRP.
At clinically relevant concentrations, TAF is not an inhibitor of drug transporters P-gp, BCRP, hepatic transporters OATP1B1, OATP1B3, OCT1, BSEP, renal transporters OAT1, OAT3, OCT2, MATE1, or CYP (including CYP3A) or UGT1A1 enzymes.
Drug interaction studies were conducted with BIKTARVY or its components. Tables 10 and 11 summarize the pharmacokinetic effects of other drugs on BIC and TAF, respectively. Table 12 summarizes the pharmacokinetic effects of BIKTARVY or its components on other drugs.
Effect Of Other Drugs On BIKTARVY Components
Table 10 Effect of Other Drugs on BICa
Coadministered
Drug |
Dose of Coadministered Drug (mg) |
BIC (mg) |
Mean Ratio of BIC Pharmacokinetic Parameters (90% CI); No effect = 1.00 |
| Cmax |
AUC |
Cmin |
| Ledipasvir/ Sofosbuvir (fed) |
90/400 once
daily |
75 once
daily |
0.98
(0.94, 1.03) |
1.00
(0.97, 1.03) |
1.04
(0.99, 1.09) |
| Rifabutin (fasted) |
300 once
daily |
75 once
daily |
0.80
(0.67, 0.97) |
0.62
(0.53, 0.72) |
0.44
(0.37, 0.52) |
| Rifampin (fed) |
600 once
daily |
75 single
dose |
0.72
(0.67, 0.78) |
0.25
(0.22, 0.27) |
NA |
| Sofosbuvir/ velpatasvir/ voxilaprevir (fed) |
400/100/100+100 voxilaprevirb
once daily |
50 once
daily |
0.98
(0.94, 1.01) |
1.07
(1.03, 1.10) |
1.10
(1.05, 1.17) |
| Voriconazole (fasted) |
300 twice daily |
75 single
dose |
1.09
(0.96, 1.23) |
1.61
(1.41, 1.84) |
NA |
Maximum strength antacid
(simultaneous administration, fasted) |
20 mLc single
dose (oral) |
50 single
dose |
0.20
(0.16, 0.24) |
0.21
(0.18, 0.26) |
NA |
| Maximum strength antacid (2 h afterBIKTARVYfasted) |
20 mLc single
dose (oral) |
50 single
dose |
0.93
(0.88, 1.00) |
0.87
(0.81, 0.93) |
NA |
Maximum strength antacid
(2 h before BIKTARVY fasted) |
20 mLc single
dose (oral) |
50 single
dose |
0.42
(0.33, 0.52) |
0.48
(0.38, 0.59) |
NA |
Maximum strength antacid
(simultaneous administration, fedd) |
20 mLc single
dose (oral) |
50 single
dose |
0.51
(0.43, 0.62) |
0.53
(0.44, 0.64) |
NA |
Calcium
carbonate
(simultaneous administration, fasted) |
1200 single dose |
50 single
dose |
0.58
(0.51, 0.67) |
0.67
(0.57, 0.78) |
NA |
Calcium
carbonate
(simultaneous administration, fedd) |
1200 single dose |
50 single
dose |
0.90
(0.78, 1.03) |
1.03
(0.89, 1.20) |
NA |
Ferrous
fumarate
(simultaneous administration, fasted) |
324 single dose |
50 single
dose |
0.29
(0.26, 0.33) |
0.37
(0.33, 0.42) |
NA |
Ferrous
fumarate
(simultaneous administration, fedd) |
324 single dose |
50 single
dose |
0.75
(0.65, 0.87) |
0.84
(0.74, 0.95) |
NA |
NA= Not Applicable
a. All interaction studies conducted in healthy volunteers.
b.Study conducted with additional voxilaprevir 100 mg to achieve voxilaprevir exposures expected in HCV-infected patients.
c.Maximum strength antacid contained 80 mg aluminum hydroxide, 80 mg magnesium hydroxide, and 8 mg simethicone, per mL.
d.Reference treatment administered under fasted conditions. |
Table 11 Effect of Other Drugs on TAFa
| Coadministered Drug |
Dose of Coadministered Drug (mg) |
Tenofovir Alafenamide (mg) |
Mean Ratio of Tenofovir
Alafenamide Pharmacokinetic
Parameters (90% CI);
No effect = 1.00 |
| Cmax |
AUC |
Cmin |
| Carbamazepine |
300 twice daily |
25 single
doseb |
0.43
(0.36, 0.51) |
0.46
(0.40, 0.54) |
NA |
| Ledipasvir/sofosbuvir |
90/400 once daily |
25 once
daily |
1.17
(1.00, 1.38) |
1.27
(1.19, 1.34) |
NA |
| Sofosbuvir/ velpatasvir/ voxilaprevir |
400/100/100 +100 voxilaprevirc once daily |
25 once
daily |
1.28
(1.09, 1.51) |
1.57
(1.44, 1.71) |
NA |
NA= Not Applicable
a.All interaction studies conducted in healthy volunteers.
b.Study conducted with emtricitabine/tenofovir alafenamide.
c.Study conducted with additional voxilaprevir 100 mg to achieve voxilaprevir exposures expected in HCV-infected patients. |
Effect Of BIKTARVY Components On Other Drugs
Table 12 Effect of Components of BIKTARVY on Other Drugsa
| Coadministered Drug |
Dose of Coadministered Drug (mg) |
BIC
(mg) |
TAF (mg) |
Mean Ratio of Coadministered Drug Pharmacokinetic Parameters
(90% CI); No effect = 1.00 |
| Cmax |
AUC |
Cmin |
| Ledipasvir |
90/400 once daily |
75 once daily |
25 once daily |
0.85
(0.81, 0.90) |
0.87
(0.83, 0.92) |
0.90
(0.84, 0.96) |
| Sofosbuvir |
1.11
(1.00, 1.24) |
1.07
(1.01, 1.13) |
NA |
| GS-331007b |
1.10
(1.07, 1.13) |
1.11
(1.08, 1.14) |
1.02
(0.99, 1.06) |
| Metformin |
500 twice daily |
50 once daily |
25 once daily |
1.28
(1.21, 1.36) |
1.39
(1.31, 1.48) |
1.36
(1.21, 1.53) |
| Midazolam |
2 single dose |
50 once daily |
25 once daily |
1.03
(0.87, 1.23) |
1.15
(1.00, 1.31) |
NA |
| Norelgestromin |
norgestimate 0.180/0.215/0.250 once daily /ethinyl estradiol 0.025 once daily |
75 once daily |
- |
1.23
(1.14, 1.32) |
1.08
(1.05, 1.10) |
1.10
(1.05, 1.15) |
| Norgestrel |
1.15
(1.10, 1.21) |
1.13
(1.07, 1.19) |
1.14
(1.06, 1.22) |
| Ethinyl estradiol |
1.15
(1.03, 1.27) |
1.04
(0.99, 1.10) |
1.05
(0.95, 1.14) |
| Norelgestromin |
norgestimate 0.180/0.215/0.250 once daily / ethinyl estradiol 0.025 once daily |
- |
25 once dailyc |
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
(0.92, 1.12) |
| Sertraline |
50 single dose |
- |
10 once dailyd |
1.14
(0.94, 1.38) |
0.93
(0.77, 1.13) |
NA |
| Sofosbuvir |
400/100/100+ 100e once daily |
50 once daily |
25 once daily |
1.14 (1.04,1.25) |
1.09
(1.02, 1.15) |
NA |
| GS-331007b |
1.03 (0.99,1.06) |
1.03 (1.00,1.06) |
1.01
(0.98, 1.05) |
| Velpatasvir |
0.96 (0.91,1.01) |
0.96
(0.90, 1.02) |
0.94
(0.88, 1.01) |
| Voxilaprevir |
0.90
(0.76, 1.06) |
0.91
(0.80, 1.03) |
0.97
(0.88, 1.06) |
NA= Not Applicable
a. All interaction studies conducted in healthy volunteers.
b. The predominant circulating nucleoside metabolite of sofosbuvir.
c. Study conducted with emtricitabine/tenofovir alafenamide.
d. Study conducted with elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide.
e. Study conducted with additional voxilaprevir 100 mg to achieve voxilaprevir exposures expected in HCV-infected patients. |
Microbiology
Mechanism Of Action
Bictegravir
BIC inhibits the strand transfer activity of HIV-1 integrase (integrase strand transfer inhibitor; INSTI), an HIV-1 encoded enzyme that is required for viral replication. Inhibition of integrase prevents the integration of linear HIV-1 DNA into host genomic DNA, blocking the formation of the HIV-1 provirus and propagation of the virus.
Emtricitabine
FTC, a synthetic nucleoside analog of cytidine, is phosphorylated by cellular enzymes to form emtricitabine 5'-triphosphate. Emtricitabine 5'-triphosphate inhibits the activity of the HIV-1 RT by competing with the natural substrate deoxycytidine 5'-triphosphate and by being incorporated into nascent viral DNA which results in chain termination. Emtricitabine 5′-triphosphate is a weak inhibitor of mammalian DNA polymerases α, β, ε, and mitochondrial DNA polymerase γ.
Tenofovir Alafenamide
TAF is a phosphonamidate prodrug of tenofovir (2′-deoxyadenosine monophosphate analog). Plasma exposure to TAF allows for permeation into cells and then TAF is intracellularly converted to tenofovir through hydrolysis by cathepsin A. Tenofovir is subsequently phosphorylated by cellular kinases to the active metabolite tenofovir diphosphate. Tenofovir diphosphate inhibits HIV-1 replication through incorporation into viral DNA by the HIV RT, 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 triple combination of BIC, FTC, and TAF was not antagonistic with respect to antiviral activity in cell culture.
Bictegravir
The antiviral activity of BIC against laboratory and clinical isolates of HIV-1 was assessed in lymphoblastoid cell lines, PBMCs, primary monocyte/macrophage cells, and CD4+ T-lymphocytes. In MT-4 cells (human lymphoblastoid T-cell line) acutely infected with HIV-1 IIIB, the mean 50% effective concentration (EC50) was 2.4±0.4 nM, and the protein-adjusted EC95 value was 361 nM (0.162 micrograms per mL). BIC displayed antiviral activity in activated PBMCs against clinical isolates of HIV-1 representing groups M, N, and O, including subtypes A, B, C, D, E, F, and G, with a median EC50 value of 0.55 nM (range <0.05 to 1.71 nM). The EC50 value against a single HIV-2 isolate was 1.1 nM.
Emtricitabine
The antiviral activity of FTC against laboratory and clinical isolates of HIV-1 was assessed in T lymphoblastoid cell lines, the MAGI-CCR5 cell line, and PBMCs. In PBMCs acutely infected with HIV-1 subtypes A, B, C, D, E, F, and G, the median EC50 value for FTC was 9.5 nM (range 1 to 30 nM) and against HIV-2 was 7 nM.
Tenofovir Alafenamide
The antiviral activity of TAF against laboratory and clinical isolates of HIV-1 subtype B was assessed in lymphoblastoid cell lines, PBMCs, primary monocyte/macrophage cells and CD4-T lymphocytes. The EC50 values for TAF ranged from 2.0 to 14.7 nM. TAF displayed antiviral activity in cell culture against all HIV-1 groups (M, N, O), including subtypes A, B, C, D, E, F, and G (EC50 values ranged from 0.1 to 12 nM) and strain specific activity against HIV-2 (EC50 values ranged from 0.9 to 2.6 nM).
Resistance
In Cell Culture
Bictegravir
HIV-1 isolates with reduced susceptibility to BIC have been selected in cell culture. In one selection with BIC, a virus pool emerged expressing amino acid substitutions M50I and R263K in the HIV-1 integrase. M50I, R263K, and M50I+R263K substitutions, when introduced into a wild-type virus by site-directed mutagenesis, conferred 1.3-, 2.2-, and 2.9-fold reduced susceptibility to BIC, respectively. In a second selection, emergence of amino acid substitutions T66I and S153F was detected, and 0.4-, 1.9-, and 0.5-fold reductions in BIC susceptibility were observed with T66I, S153F, and T66I+S153F, respectively. In addition, S24G and E157K substitutions emerged during the selection process.
Emtricitabine
HIV-1 isolates with reduced susceptibility to FTC were selected in cell culture and in subjects treated with FTC. Reduced susceptibility to FTC was associated with M184V or I substitutions in HIV-1 RT.
Tenofovir Alafenamide
HIV-1 isolates with reduced susceptibility to TAF were selected in cell culture. HIV-1 isolates selected by TAF expressed a K65R substitution in HIV-1 RT, sometimes in the presence of S68N or L429I substitutions; in addition, a K70E substitution in HIV-1 RT was observed.
In Clinical Trials
In Subjects with No Antiretroviral Treatment History
Pooled results of genotypic resistance analyses were performed on paired baseline and on-treatment HIV-1 isolates from subjects receiving BIKTARVY in Trials 1489 and 1490 through Week 144 of the double-blind phase (N=634) or Week 96 of the extension phase (n=1025) [see Clinical Studies] who had HIV-1 RNA greater than or equal to 200 copies/mL at the time of confirmed virologic failure or early study drug discontinuation. In the final resistance analysis population, no specific amino acid substitutions emerged consistently in the 11 treatment failure subjects with evaluable genotypic resistance data and failed to establish an association with genotypic BIC resistance. There were no treatment-emergent NRTI resistance-associated substitutions detected in the 11 evaluated treatment failure isolates. Phenotypic resistance analyses of failure isolates found fold-changes in drug susceptibility below the biological or clinical cutoffs for BIC, FTC, and TFV, compared to wild-type reference HIV-1.
In Virologically Suppressed Adult Subjects
In 2 of the switch trials, Trials 1844 and 1878, of virologically suppressed HIV-1 infected subjects (n=572), only one subject with virologic rebound in the resistance analysis population had IN genotypic and phenotypic data, and 2 rebounders had RT genotypic and phenotypic data. No subjects had HIV-1 with treatment-emergent genotypic or phenotypic resistance to BIC, FTC, or TAF. In Trial 4030, no subjects receiving BIKTARVY had treatment-emergent phenotypic resistance to BIC, FTC, or TAF.
In Virologically Suppressed Pediatric Subjects
In Trial 1474 [see Clinical Studies], two of 50 subjects in cohort 1 were evaluated for the development of resistance through Week 48; no amino acid substitutions known to be associated with resistance to BIC, FTC, or TFV were detected. No subjects in cohort 2 or 3 met the criteria for resistance analyses through Week 24.
Cross-Resistance
Bictegravir
Cross-resistance has been observed among INSTIs. The susceptibility of BIC was tested against 64 clinical isolates expressing known INSTI resistance-associated substitutions listed by IAS-USA (20 with single substitutions and 44 with 2 or more substitutions). Isolates with a single INSTI-resistance substitution including E92Q, T97A, Y143C/R, Q148R, and N155H showed less than 2-fold reduced susceptibility to BIC. All isolates (n=14) with more than 2.5-fold reduced susceptibility to BIC (above the biological cutoff for BIC) contained G140A/C/S and Q148H/R/K substitutions; the majority (64.3%, 9/14) had a complex INSTI resistance pattern with an additional INSTI-resistance substitution L74M, T97A, or E138A/K. Of those evaluated isolates containing G140A/C/S and Q148H/R/K substitutions in the absence of additional INSTI-resistance substitutions, 38.5% (5/13) showed more than 2.5-fold reduction. In addition, site-directed mutant viruses with G118R (dolutegravir and raltegravir treatment-emergent substitution) and G118R+T97A had 3.4-and 2.8-fold reduced susceptibility to BIC, respectively.
BIC demonstrated equivalent antiviral activity with less than 2-fold reductions in susceptibility against HIV-1 variants expressing substitutions associated with resistance to NNRTIs, NRTIs, and PIs, compared with the wild-type virus.
Emtricitabine
Cross-resistance has been observed among NRTIs. FTC-resistant viruses with an M184V/I substitution in HIV-1 RT were cross-resistant to lamivudine. HIV-1 isolates containing the K65R RT substitution, selected in vivo by abacavir, didanosine, and tenofovir, demonstrated reduced susceptibility to inhibition by FTC.
Tenofovir Alafenamide
Cross-resistance has been observed among NRTIs. Tenofovir resistance substitutions K65R and K70E result in reduced susceptibility to abacavir, didanosine, emtricitabine, lamivudine, and tenofovir. HIV-1 with multiple thymidine analog substitutions (M41L, D67N, K70R, L210W, T215F/Y, K219Q/E/N/R), or multinucleoside resistant HIV-1 with a T69S double insertion mutation or with a Q151M substitution complex including K65R, showed reduced susceptibility to TAF in cell culture.
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 TAF; reversibility was seen after a three month recovery period. No eye toxicity was observed in the dog at systemic exposures of 7 (TAF) and 14 (tenofovir) times the exposure seen in humans with the recommended daily dose of BIKTARVY.
Clinical Studies
Description Of Clinical Trials
The efficacy and safety of BIKTARVY were evaluated in the trials summarized in Table 13.
Table 13 Trials Conducted with BIKTARVY in Subjects with HIV-1 Infection
| Trial |
Population |
Trial Arms (N) |
Timepoint (Week) |
Trial 1489a
(NCT 02607930) |
Adults with no antiretroviral treatment history |
BIKTARVY (314)
ABC/DTG/3TC (315) |
144 + 96
(OLE)b |
Trial 1490a
(NCT 02607956) |
|
BIKTARVY (320)
DTG + FTC/TAF(325) |
144 + 96
(OLE)b |
Trial 1844a
(NCT 02603120) |
Virologically-suppressedd adults |
BIKTARVY (282)
ABC/DTG/3TC (281) |
48 |
Trial 1878c
(NCT 02603107) |
BIKTARVY (290)
ATV or DRV (with cobicistat or ritonavir) plus either FTC/TDF or ABC/3TC (287) |
48 |
Trial 4030a
(NCT 03110380) |
BIKTARVY (284 [47 with M184V/I])DTG plus FTC/TAF (281 [34 with M184V/I]) |
48 |
| Trial 1825e (NCT 02600819) |
Virologically-suppressedd adults with ESRDf receiving chronic hemodialysis |
FTC+TAF in combination with elvitegravir and cobicistat as a fixed-dose combination(55). In an extension phase of Trial 1825, 10 virologicallysuppressed subjects switched to BIKTARVY. |
48g |
Trial 4449e
(NCT 03405935) |
Virologically-suppressedd adults aged 65 years and over |
BIKTARVY (86) |
48 |
Trial 1474e
(cohort 1)(NCT 02881320) |
Virologically-suppressedd adolescents between the ages of 12 to less than 18 years (at least 35 kg) |
BIKTARVY (50) |
48 |
Trial 1474e
(cohort 2)(NCT 02881320) |
Virologically-suppressedd children between the ages of 6 to less than 12 years (at least 25 kg) |
BIKTARVY (50) |
24 |
Trial 1474e
(cohort 3)(NCT 02881320) |
Virologically- suppressedd children at least 2 years of age (at least 14 to less than 25 kg) |
BIKTARVY (22) |
24 |
OLE = open-label extension
a.Randomized, double blind, active controlled trial.
b.44-week double-blind active controlled phase followed by an extension phase in which 1025 subjects from Trials 1489 and 1490 received open-label BIKTARVY for 96 weeks.
c.Randomized, open-label, active controlled trial.
d.HIV-1 RNA less than 50 copies per mL.
e.Open-label trial.
f.End stage renal disease (estimated creatinine clearance of less than 15 mL/min by Cockcroft-Gault method).
g.Subjects received FTC+TAF in combination with elvitegravir and cobicistat for 96 weeks, followed by an extension phase in which 10 subjects received BIKTARVY for 48 weeks. |
Clinical Trial Results In Adults With HIV-1 And No Antiretroviral Treatment History
In Trial 1489, adults were randomized in a 1:1 ratio to receive either BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF) (N=314) or ABC/DTG/3TC (600 mg/50 mg/300 mg) (N=315) once daily. In Trial 1490, subjects were randomized in a 1:1 ratio to receive either BIKTARVY (N=320) or DTG + FTC/TAF (50 mg + 200 mg/25 mg) (N=325) once daily.
In Trial 1489, the mean age was 34 years (range 18–71), 90% were male, 57% were White, 36% were Black, and 3% were Asian. 22% of patients identified as Hispanic/Latino. The mean baseline plasma HIV-1 RNA was 4.4 log10 copies/mL (range 1.3–6.5). The mean baseline CD4+ cell count was 464 cells per mm3 (range 0–1424) and 11% had CD4+ cell counts less than 200 cells per mm3. 16% of subjects had baseline viral loads greater than 100,000 copies per mL.
In Trial 1490, the mean age was 37 years (range 18–77), 88% were male, 59% were White, 31% were Black, and 3% were Asian. 25% of patients identified as Hispanic/Latino. The mean baseline plasma HIV-1 RNA was 4.4 log10 copies/mL (range 2.3–6.6). The mean baseline CD4+ cell count was 456 cells per mm3 (range 2–1636) and 12% had CD4+ cell counts less than 200 cells per mm3. 19% of subjects had baseline viral loads greater than 100,000 copies per mL.
In both trials, subjects were stratified by baseline HIV-1 RNA (less than or equal to 100,000 copies per mL, greater than 100,000 copies per mL to less than or equal to 400,000 copies per mL, or greater than 400,000 copies per mL), by CD4 count (less than 50 cells per mm3, 50-199 cells per mm3, or greater than or equal to 200 cells per mm3), and by region (US or ex-US).
Treatment outcomes of Trials 1489 and 1490 through Week 144 are presented in Table 14.
Table 14 Virologic Outcomes of Randomized Treatment in Trials 1489 and 1490 at Week 144a in Adults with No Antiretroviral Treatment History
|
Trial 1489 |
Trial 1490 |
|
BIKTARVY
(N=314) |
ABC/DTG/3TC
(N=315) |
BIKTARVY
(N=320) |
DTG + FTC/TAF
(N=325) |
| HIV-1 RNA < 50 copies/mL |
82% |
84% |
82% |
84% |
| Treatment Difference (95% CI) BIKTARVY vs. Comparator |
-2.6% (-8.5% to 3.4%) |
-1.9% (-7.8% to 3.9%) |
| HIV-1 RNA ≥ 50 copies/mLb |
1% |
3% |
5% |
3% |
| No Virologic Data at Week 144 Window |
18% |
13% |
13% |
13% |
| Discontinued Study Drug Due to AE or Deathc |
1% |
2% |
3% |
3% |
| Discontinued Study Drug Due to Other Reasons and Last Available HIV-1 RNA <50 copies/mLd |
16% |
11% |
11% |
9% |
| Missing Data During Window but on Study Drug |
1% |
<1% |
0% |
1% |
a.Week 144 window was between Day 967 and 1050 (inclusive).
b.Includes subjects who had ≥ 50 copies/mL in the Week 144 window; subjects who discontinued early due to lack or loss of efficacy; subjects who discontinued for reasons other than an adverse event (AE), death or lack or loss of efficacy and at the time of discontinuation had a viral value of ≥ 50 copies/mL.
c.Includes subjects who discontinued due to AE or death at any time point from Day 1 through the time window if this resulted in no virologic data on treatment during the specified window.
d.Includes subjects who discontinued for reasons other than an AE, death, or lack or loss of efficacy, e.g., withdrew consent, loss to follow-up, etc. |
Treatment outcomes were similar across subgroups by age, sex, race, baseline viral load, and baseline CD4+ cell count.
In Trials 1489 and 1490, the mean increase from baseline in CD4+ count at Week 144 was 299 and 317 cells per mm3 in the BIKTARVY and ABC/DTG/3TC groups, respectively, and 278 and 289 cells per mm3 in the BIKTARVY and DTG + FTC/TAF groups, respectively.
Clinical Trial Results In Adults With Virologically-Suppressed HIV-1 Who Switched To BIKTARVY
In Trial 1844, the efficacy and safety of switching from a regimen of DTG + ABC/3TC or ABC/DTG/3TC to BIKTARVY were evaluated in a randomized, double-blind trial of virologically-suppressed (HIV-1 RNA less than 50 copies per mL) HIV-1 infected adults (N=563, randomized and dosed). Subjects must have been stably suppressed (HIV-1 RNA less than 50 copies per mL) on their baseline regimen for at least 3 months prior to trial entry and had no history of treatment failure. Subjects were randomized in a 1:1 ratio to either switch to BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF) at baseline (N=282), or stay on their baseline antiretroviral regimen (N=281). Subjects had a mean age of 45 years (range 20–71), 89% were male, 73% were White, and 22% were Black. 17% of subjects identified as Hispanic/Latino. The mean baseline CD4+ cell count was 723 cells per mm3 (range 124–2444).
In Trial 1878, the efficacy and safety of switching from either ABC/3TC or FTC/TDF (200/300 mg) plus ATV or DRV (given with either cobicistat or ritonavir) to BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF) were evaluated in a randomized, open-label study of virologically-suppressed HIV-1 infected adults (N=577, randomized and dosed). Subjects must have been stably suppressed on their baseline regimen for at least 6 months, must not have been previously treated with any INSTI, and had no history of treatment failure. Subjects were randomized in a 1:1 ratio to either switch to BIKTARVY (N=290) or stay on their baseline antiretroviral regimen (N=287). Subjects had a mean age of 46 years (range 20–79), 83% were male, 66% were White, and 26% were Black. 19% of subjects identified as Hispanic/Latino. The mean baseline CD4+ cell count was 663 cells per mm3 (range 62–2582). Subjects were stratified by prior treatment regimen. At screening, 15% of subjects were receiving ABC/3TC plus ATV or DRV (given with either cobicistat or ritonavir) and 85% of subjects were receiving FTC/TDF plus ATV or DRV (given with either cobicistat or ritonavir).
Treatment outcomes of Trials 1844 and 1878 through Week 48 are presented in Table 15.
Table 15 Virologic Outcomes of Trials 1844 and 1878 at Week 48a in Virologically-Suppressed Adults who Switched to BIKTARVY
|
Trial 1844 |
Trial 1878 |
|
BIKTARVY
(N=282) |
ABC/DTG/3TC
(N=281) |
BIKTARVY
(N=290) |
ATV- or DRV
based regimenb
(N=287) |
| HIV-1 RNA ≥ 50 copies/mLc |
1% |
<1% |
2% |
2% |
| Treatment Difference (95% CI) |
0.7% (-1.0% to 2.8%) |
0.0% (-2.5% to 2.5%) |
| HIV-1 RNA < 50 copies/mL |
94% |
95% |
92% |
89% |
| No Virologic Data at Week 48 Window |
5% |
5% |
6% |
9% |
| Discontinued Study Drug Due to AE or Death and Last Available HIV-1 RNA < 50 copies/mL |
2% |
1% |
1% |
1% |
| Discontinued Study Drug Due to Other Reasons and Last Available HIV-1 RNA < 50 copies/mLd |
2% |
3% |
3% |
7% |
| Missing Data During Window but on Study Drug |
2% |
1% |
2% |
2% |
a.Week 48 window was between Day 295 and 378 (inclusive).
b.ATV given with cobicistat or ritonavir or DRV given with cobicistat or ritonavir plus either FTC/TDF or ABC/3TC.
c.Includes subjects who had ≥ 50 copies/mL in the Week 48 window; subjects who discontinued early due to lack or loss of efficacy; subjects who discontinued for reasons other than lack or loss of efficacy and at the time of discontinuation had a viral value of ≥ 50 copies/mL.
d. Includes subjects who discontinued for reasons other than an AE, death, or lack or loss of efficacy, e.g., withdrew consent, loss to follow-up, etc. |
In Trial 1844, treatment outcomes between treatment groups were similar across subgroups by age, sex, race, and region. The mean change from baseline in CD4+ count at Week 48 was -31 cells per mm3 in subjects who switched to BIKTARVY and 4 cells per mm3 in subjects who stayed on ABC/DTG/3TC.
In Trial 1878, treatment outcomes between treatment groups were similar across subgroups by age, sex, race, and region. The mean change from baseline in CD4+ count at Week 48 was 25 cells per mm3 in patients who switched to BIKTARVY and 0 cells per mm3 in patients who stayed on their baseline regimen.
In Trial 4030, the efficacy and safety of switching from DTG plus either FTC/TAF or FTC/TDF to BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF) were evaluated in a randomized, double-blind study of virologically suppressed HIV-1 infected adults. Subjects must have been stably suppressed (HIV-1 RNA less than 50 copies/mL) on their baseline regimen for at least 6 months (if documented or suspected
NRTI resistance), or at least 3 months (if no documented or suspected NRTI resistance) prior to trial entry. Subjects were randomized to switch to BIKTARVY (N=284) or to continue their prior treatment regimen, DTG+ F/TAF (N=281). The primary endpoint was the proportion of subjects with HIV-1 RNA ≥ 50 copies/mL at Week 48. At Week 48 the proportion of subjects with HIV-1 RNA ≥50 copies/mL was 0.4% (1/284) in the BIKTARVY group and 1.1% (3/281) in the DTG+F/TAF group (difference -0.7% [95%CI: -2.8%, 1.0%]).
Of the subjects receiving BIKTARVY, 47 had HIV-1 with pre-existing M184V or I resistance substitutions (M184M/V, M184M/I, M184V/I, M184V) in HIV-1 RT. Eighty-nine percent (42/47) of subjects with M184V or I remained suppressed (HIV-1 RNA < 50 copies/mL) and 11% (5/47 subjects) did not have virologic data at the Week 48 timepoint due to study drug discontinuation.
In Trial 1825, an open-label single arm trial, the efficacy, safety, and pharmacokinetics of FTC and TAF (components of BIKTARVY) were evaluated in virologically-suppressed adults with ESRD (estimated creatinine clearance of less than 15 mL/min) on chronic hemodialysis treated with FTC+TAF in combination with elvitegravir and cobicistat as a fixed-dose combination tablet for 96 weeks (N=55). In an extension phase of Trial 1825, 10 virologically-suppressed subjects switched to BIKTARVY and all subjects remained virologically suppressed (HIV-1 RNA < 50 copies/mL) for 48 weeks.
In Trial 4449, the efficacy and safety of switching from a stable antiretroviral regimen to BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF) were evaluated in an open-label, single arm trial of virologically-suppressed (HIV-1 RNA less than 50 copies per mL) HIV-1 infected adults aged 65 years and over (N=86). Subjects treated with BIKTARVY had a mean age of 70 years (range: 65 to 80). The primary endpoint was the proportion of subjects with HIV RNA > 50 copies/mL at Week 48. No subjects had HIV RNA > 50 copies/mL. Ninety-one percent (78/86) of subjects remained suppressed (HIV-1 RNA < 50 copies/mL) at Week 48. Eight subjects did not have virologic data at the Week 48 timepoint due to discontinuation or missing data.
Clinical Trial Results In Pediatric Subjects With HIV-1
In Trial 1474, an open-label, single arm trial the efficacy, safety, and pharmacokinetics of BIKTARVY in HIV-1 infected pediatric subjects were evaluated in virologicallysuppressed adolescents between the ages of 12 to less than 18 years weighing at least 35 kg (N=50), in virologically-suppressed children between the ages of 6 to less than 12 years weighing at least 25 kg (N=50), and in virologically-suppressed children at least 2 years of age and weighing at least 14 to less than 25 kg (N=22).
Cohort 1: Virologically-Suppressed Adolescents (12 To Less Than 18 Years; At Least 35 kg)
Subjects in cohort 1 treated with BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF) once daily had a mean age of 14 years (range: 12 to 17) and a mean baseline weight of 51.7 kg (range: 35 to 123), 64% were female, 27% were Asian and 65% were black. At baseline, median CD4+ cell count was 750 cells per mm3 (range: 337 to 1207), and median CD4+% was 33% (range: 19% to 45%).
After switching to BIKTARVY, 98% (49/50) of subjects in cohort 1 remained suppressed (HIV-1 RNA < 50 copies/mL) at Week 48. The mean change from baseline in CD4+ cell count at Week 48 was -22 cells per mm3.
Cohort 2: Virologically-Suppressed Children (6 To Less Than 12 Years; At Least 25 kg)
Subjects in cohort 2 treated with BIKTARVY once daily had a mean age of 10 years (range: 6 to 11) and a mean baseline weight of 31.9 kg (range: 25 to 69), 54% were female, 22% were Asian and 72% were black. At baseline, median CD4+ cell count was 898 cells per mm3 (range 390 to 1991) and median CD4+% was 37% (range: 19% to 53%).
After switching to BIKTARVY (containing 50 mg of BIC, 200 mg of FTC, and 25 mg of TAF), 100% (50/50) of subjects in cohort 2 remained suppressed (HIV-1 RNA < 50 copies/mL) at Week 24. The mean change from baseline in CD4+ cell count at Week 24 was -24 cells per mm3.
Cohort 3: Virologically-Suppressed Children (At Least 2 Years; At Least 14 To Less Than 25 kg)
Subjects in cohort 3 treated with BIKTARVY (containing 30 mg of BIC, 120 mg of FTC, and 15 mg of TAF) once daily had a mean age of 5 years (range: 3 to 9) and a mean baseline weight of 18.8 kg (range: 14 to 24), 50% were female, 23% were Asian and 73% were black. At baseline, the mean CD4+ cell count (SD) was 1104 (440), and the mean CD4% (SD) was 33.4% (6.0%).
After switching to BIKTARVY, 91% (20/22) of subjects in cohort 3 remained suppressed (HIV-1 RNA < 50 copies/mL) at Week 24. HIV-1 RNA was not collected at Week 24 for 2 subjects because of COVID-19 pandemic-related study disruption. The mean change from baseline to Week 24 in CD4+ cell count (SD) was −126 (264.2) cells per mm3 ; and the mean change in CD4% (SD) from baseline to Week 24 was 0.2% (4.4%).