Clinical Pharmacology for Symtuza
Mechanism Of Action
SYMTUZA is a fixed-dose combination of antiretroviral drugs darunavir (plus the CYP3A inhibitor cobicistat), emtricitabine, and tenofovir alafenamide [see Microbiology (12.4)].
Pharmacodynamics
Cardiac Electrophysiology
Thorough QT trials have been conducted for darunavir, cobicistat, and tenofovir alafenamide. The effect of emtricitabine or the combination regimen SYMTUZA on the QT interval has not been evaluated.
Darunavir
In a thorough QT/QTc study in 40 healthy subjects, darunavir doses (co-administered with 100 mg ritonavir) of approximately 2 times the recommended darunavir dose did not affect the QT/QTc interval.
Cobicistat
In a thorough QT/QTc study in 48 healthy subjects, a single dose of cobicistat 250 mg and 400 mg (1.67 and 2.67 times the dose in SYMTUZA) did not affect the QT/QTc interval. Prolongation of the PR interval was noted in subjects receiving cobicistat. The maximum mean (95% upper confidence bound) difference in PR from placebo after baseline-correction was 9.5 (12.1) msec for the 250 mg cobicistat dose and 20.2 (22.8) for the 400 mg cobicistat dose. Because the 150 mg cobicistat dose used in the SYMTUZA fixed-dose combination tablet is lower than the lowest dose studied in the thorough QT study, it is unlikely that treatment with SYMTUZA will result in clinically relevant PR prolongation.
Tenofovir Alafenamide
In a thorough QT/QTc study in 48 healthy subjects, tenofovir alafenamide at the recommended dose or at a dose approximately 5 times the recommended dose did not affect the QT/QTc interval and did not prolong the PR interval.
Effects On Serum Creatinine
The effect of cobicistat on serum creatinine was investigated in a trial in subjects with normal renal function (eGFRCG ≥80 mL/min, N=12) and mild-to-moderate renal impairment (eGFRCG 50-79 mL/min, N=18). A statistically significant decrease from baseline in the estimated glomerular filtration rate calculated by Cockcroft-Gault method (eGFRCG) was observed after 7 days of treatment with cobicistat 150 mg among subjects with normal renal function (-9.9 ± 13.1 mL/min) and mild-to-moderate renal impairment (-11.9 ± 7.0 mL/min). No statistically significant changes in eGFRCG were observed compared to baseline for subjects with normal renal function or mild-to-moderate renal impairment 7 days after cobicistat was discontinued. The actual glomerular filtration rate, as determined by the clearance of probe drug iohexol, was not altered from baseline during treatment with cobicistat among subjects with normal renal function and mild-to-moderate renal impairment, indicating that cobicistat inhibits tubular secretion of creatinine, reflected as a reduction in eGFRCG, without affecting the actual glomerular filtration rate.
Pharmacokinetics
Absorption, Distribution, Metabolism, And Excretion
The bioavailability of the components of SYMTUZA was not affected when administered orally as a split tablet compared to administration as a tablet swallowed whole.
Pharmacokinetic (PK) properties and PK parameters of the components of SYMTUZA are provided in Table 5 and Table 6, respectively.
Table 5: Pharmacokinetic Properties of the Components of SYMTUZA
|
Darunavir |
Cobicistat |
Emtricitabine |
TAF |
| Absorption |
| Tmax (h) |
3.0 |
3.0 |
1.5 |
0.5 |
| Effect of high-fat meala (compared to fasting) |
| AUClast LS mean ratio, 90% CI |
1.52
(1.32-1.76) |
1.41
(1.02-1.96) |
1.00
(0.96-1.04) |
1.12
(1.01-1.23) |
| Cmax LS mean ratio, 90% CI |
1.82
(1.55-2.14) |
1.30
(0.94-1.80) |
0.79
(0.71-0.89) |
0.55
(0.42-0.71) |
| Distribution |
| % bound to human plasma proteins |
95b |
97-98 |
<4 |
~80 |
| Source of protein binding data |
In vitro |
In vitro |
In vitro |
Ex vivo |
| Blood-to-plasma ratio |
0.64 |
0.5 |
0.6 |
1.0 |
| Metabolism |
| Metabolism |
CYP3A |
CYP3A
(major)
CYP2D6
(minor) |
Not significantly metabolized |
Cathepsin Ac
(PBMCs)
CES1
(hepatocytes)
CYP3A
(minimal) |
| Elimination |
| t1/2 (h) |
9.4 |
3.2 |
7.5 |
0.5d |
| Major route of elimination |
Metabolism |
Metabolism |
Glomerular filtration and active tubular secretion |
Metabolism
(>80% of oral dose) |
| % of dose excreted in fecese |
79.5f |
86.2 |
13.7 |
31.7 |
| % of dose excreted in urinee |
13.9f |
8.2 |
70 |
<1 |
PBMCs = peripheral blood mononuclear cells; CES-1 = carboxylesterase-1
a Approximately 928 kcal; 504 kcal from fat
(56 g), 260 kcal from carbohydrates, and 164 kcal from protein.
b Primarily alpha-1-acid glycoprotein
c 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. Upon co-administration with the moderate CYP3A inducer probe efavirenz, TAF exposure was unaffected.
d Note that the pharmacologically active metabolite tenofovir diphosphate has a half-life of 150-180 hours within PBMCs. Tenofovir in plasma has a median elimination half-life of approximately 44 hours.
e Dosing in mass balance studies: darunavir
(single dose administration of [14C] darunavir co-administered with multiple dose ritonavir 100 mg); cobicistat
(single dose administration of [14C] cobicistat after multiple dosing of cobicistat for six days); emtricitabine
(single dose administration of [14C] emtricitabine after multiple dosing of emtricitabine for ten days); TAF
(single dose administration of [14C] TAF).
f Unchanged darunavir accounted for approximately 41.2% and 7.7% of the administered dose in feces and urine, respectively. |
Table 6: Steady State Pharmacokinetic Parameters of Darunavir, Cobicistat, Emtricitabine, Tenofovir Alafenamide (TAF) and its Metabolite Tenofovir Following Oral Administration of SYMTUZA with Food in HIV-Infected Adults
| Parameter Mean (SD) |
Darunavir |
Cobicistata |
Emtricitabinea |
TAF |
Tenofovira |
| Cmax, ng/mL |
8826 (33.3)a |
1129 (35.3) |
2056 (25.3) |
163
(51.9) a |
18.8 (37.6) |
| AUC24h, ng.h/mL |
87909 (20232)b |
85972 (22413)c |
8745 (43.9) |
11918.0 (35.9) |
132 (41)b |
339 (37.1) |
| C0h, ng/mL |
1899 (759)b |
1813 (859)c |
31 (135) |
93.1 (58.3) |
NA |
11.7 (39.3) |
a From Phase 2 PK substudy (N=21)
b From population PK analysis in SYMTUZA Phase 3 study TMC114FD2HTX3001 in ARV naïve subjects (N=355)
c From population PK analysis in SYMTUZA Phase 3 study TMC114IFD3013 in ARV experienced subjects (N=750) |
Specific Populations
Geriatric Patients
Darunavir
Pharmacokinetic analysis in HIV-infected subjects taking darunavir co-administered with cobicistat, emtricitabine, and tenofovir alafenamide showed no considerable differences in darunavir pharmacokinetics for ages below or equal to 65 years compared to ages greater than 65 years (N=25).
Cobicistat and Emtricitabine
The pharmacokinetics of cobicistat and emtricitabine have not been fully evaluated in the elderly (65 years of age and older).
Tenofovir alafenamide Population pharmacokinetics analysis of HIV-infected subjects in Phase 2 and Phase 3 trials of TAF combined with emtricitabine, elvitegravir, and cobicistat showed that age did not have a clinically relevant effect on exposures of TAF up to 75 years of age.
Pediatric Patients Weighing At Least 40 Kg
Available pharmacokinetic data for the different components of SYMTUZA indicate that there were no clinically relevant differences in exposure between adults and pediatric subjects weighing at least 40 kg.
Darunavir and Cobicistat
In pediatric subjects aged 12 to less than 18 years, weighing at least 40 kg who received darunavir 800 mg co-administered with cobicistat 150 mg (N=7), geometric mean darunavir Cmax values were similar between adults and pediatric subjects. Geometric mean darunavir AUC24h and C24h values were 15% and 32% lower, with geometric mean ratios of 0.85 (90% CI: 0.64, 1.13) and 0.68 (90% CI: 0.30, 1.55) in pediatric subjects relative to adults, respectively. These differences were not considered clinically significant. Geometric mean cobicistat AUC24h, Cmax, and C24h values were comparable in pediatric subjects and adults (Table 7).
Table 7: Multiple-Dose PK Parameters of Darunavir and Cobicistat Following Administration of Darunavir with Cobicistat in HIV 1 Infected Adults and Pediatric Subjects Weighing at least 40 kga
| Parameter Geometric mean (CV%) |
Darunavir |
Cobicistat |
| Pediatric Subjectsa |
N=7 |
N=7 |
| AUC24h (mcg.hr/mL) |
77.22 (29.5) |
8.33 (34.9) |
| Cmax (mcg/mL) |
7.32 (21.7) |
1.10 (20.0) |
| C24h (mcg/mL) |
0.68 (91.6) |
0.02 (123.9)b |
| Adultsc |
N=21 |
N=21 |
| AUC24h (mcg.hr/mL) |
90.56 (45.3) |
7.69 (43.9) |
| Cmax (mcg/mL) |
8.34 (33.3) |
1.04 (35.3) |
| C24h (mcg/mL) |
1.00 (108.0) |
0.02 (135.1)d |
CV = Coefficient of Variation; mcg = microgram
a From intensive PK analysis of trial GS-US-216-0128, where HIV-infected subjects were administered darunavir 800 mg and cobicistat 150 mg once daily with 2 NRTIs
b N=5; Data from two subjects who had undetectable cobicistat C24h concentrations were excluded from summary statistics
c From intensive PK analysis of trial GS-US-299-0102 where HIV-infected subjects were administered SYMTUZA once daily
d N=18 |
Emtricitabine and Tenofovir Alafenamide
In 24 pediatric subjects aged 12 to less than 18 years, who received emtricitabine + TAF with elvitegravir + cobicistat, geometric mean emtricitabine Cmax, and C24h values were comparable to adults, with geometric mean ratios of 1.10 (90% CI: 0.98, 1.23) and 1.07 (90% CI: 0.88, 1.29), respectively (Table 8). Geometric mean emtricitabine AUC24h was 21% higher, with a geometric mean ratio of 1.21 (90% CI: 1.09, 1.34) in pediatric subjects relative to adults. Geometric mean tenofovir alafenamide Cmax and AUClast values were 29% and 23% lower in pediatric subjects versus adults with geometric mean ratios of 0.71 (90% CI: 0.50, 1.00) and 0.77 (90% CI: 0.59, 1.02), respectively (Table 8). The observed differences were not considered clinically significant.
Table 8: Multiple-Dose PK Parameters of Emtricitabine and Tenofovir Alafenamide Following Oral Administration with Food in HIV 1 Infected Adults and Pediatric Subjects
| Parameter Geometric mean (CV%) |
Emtricitabine |
Tenofovir alafenamide |
| Pediatric Subjectsa |
N=24 |
N=24 |
| AUC24h (mcg.hr/mL)b |
14.0 (23.9) |
0.16 (55.8) |
| Cmax (mcg/mL) |
2.2 (22.5) |
0.14 (64.4) |
| C24h (mcg/mL) |
0.10 (38.9)c |
NA |
| Adultsd |
N=19 |
N=19 |
| AUC24h (mcg.hr/mL)b |
11.6 (16.6) |
0.21 (47.3) |
| Cmax (mcg/mL) |
2.0 (20.2) |
0.19 (64.6) |
| C24h (mcg/mL) |
0.09 (46.7) |
NA |
CV = Coefficient of Variation; mcg = microgram; NA = not applicable
a From intensive PK analysis in trial GS-US-292-0106 in treatment-naïve pediatric subjects with HIV-1 infection
b AUClast for tenofovir alafenamide
c N=23
d From intensive PK analysis in trial GS-US-292-0102 in HIV-infected adults treated with emtricitabine+tenofovir alafenamide and elvitegravir+cobicistat |
Gender And Race
There were no clinically relevant differences in the pharmacokinetics of darunavir, cobicistat, emtricitabine, or tenofovir alafenamide based on gender or race.
Patients With Renal Impairment
Darunavir
The pharmacokinetics of darunavir were not altered in HIV-1 infected subjects with moderate renal impairment taking darunavir co-administered with ritonavir (creatinine clearance between 30-60 mL/min, estimated by Cockcroft-Gault method, N=20). There are no pharmacokinetic data available in HIV-1 infected patients with severe renal impairment or end-stage renal disease taking darunavir co-administered with cobicistat [see Use In Specific Populations].
Cobicistat
There were no clinically relevant differences in cobicistat pharmacokinetics observed between subjects with severe renal impairment (creatinine clearance below 30 mL/min, estimated by Cockcroft-Gault method) and healthy subjects [see Use In Specific Populations]. Emtricitabine: Mean systemic emtricitabine exposure was higher in patients with severe renal impairment (creatinine clearance less than 30 mL/min, estimated by Cockcroft-Gault method) than in subjects with normal renal function [see Use In Specific Populations].
Tenofovir Alafenamide
In studies of TAF, no clinically relevant differences in the pharmacokinetics of TAF or its metabolite tenofovir were observed between subjects with severe renal impairment (creatinine clearance of 15-30 mL/min, estimated by Cockcroft-Gault method) and healthy subjects [see Use In Specific Populations].
Patients With Hepatic Impairment
Darunavir
There were no clinically relevant differences in the pharmacokinetics of darunavir (600 mg with ritonavir 100 mg twice daily) in subjects with mild hepatic impairment (Child-Pugh Class A, n=8), and moderate hepatic impairment (Child-Pugh Class B, n=8), compared to subjects with normal hepatic function (n=16). The effect of severe hepatic impairment on the pharmacokinetics of darunavir has not been evaluated [see Use In Specific Populations].
Cobicistat
There were no clinically relevant differences in the cobicistat pharmacokinetics between subjects with moderate hepatic impairment (Child-Pugh Class B) and healthy subjects. The effect of severe hepatic impairment on the pharmacokinetics of cobicistat has not been evaluated [see Use In Specific Populations].
Emtricitabine
The pharmacokinetics of emtricitabine have not been studied in subjects with hepatic impairment; however, emtricitabine is not significantly metabolized by liver enzymes, so the impact of hepatic impairment should be limited [see Use In Specific Populations]. Tenofovir Alafenamide: Clinically relevant changes in the pharmacokinetics of tenofovir alafenamide or its metabolite tenofovir were not observed in patients with mild, moderate (Child-Pugh Class A and B), or severe hepatic impairment (Child-Pugh Class C); [see Use In Specific Populations].
Patients With Hepatitis B And/Or Hepatitis C Virus Coinfection
Darunavir
In HIV-infected subjects taking darunavir co-administered with ritonavir, the 48-week analysis of the data from clinical trials indicated that hepatitis B and/or hepatitis C virus coinfection status had no apparent effect on the exposure of darunavir.
Cobicistat
There were insufficient pharmacokinetic data in the clinical trials to determine the effect of hepatitis B and/or C virus infection on the pharmacokinetics of cobicistat.
Emtricitabine and Tenofovir Alafenamide
The pharmacokinetics of emtricitabine and tenofovir alafenamide have not been fully evaluated in subjects coinfected with hepatitis B and/or C virus.
Pregnancy And Postpartum
The exposure to total and unbound darunavir boosted with cobicistat after intake of darunavir/cobicistat as part of an antiretroviral regimen was substantially lower during the second and third trimesters of pregnancy compared with 6-12 weeks postpartum (see Table 9 and Figure 1).
Table 9: Pharmacokinetic Results of Total Darunavir after Administration of Darunavir/Cobicistat Once Daily as Part of an Antiretroviral Regimen, During the 2nd Trimester of Pregnancy, the 3rd Trimester of Pregnancy, and Postpartum
Pharmacokinetics of total darunavir
(mean ± SD) |
2nd Trimester of pregnancy
N=7 |
3rd Trimester of pregnancy
N=6 |
Postpartum
(6-12 weeks)
N=6 |
| Cmax, ng/mL |
4340 ± 1616 |
4910 ± 970 |
7918 ± 2199 |
| AUC24h, ng.h/mL |
47293 ± 19058 |
47991 ± 9879 |
99613 ± 34862 |
| Cmin, ng/mL |
168 ± 149 |
184 ± 99 |
1538 ± 1344 |
Figure 1: Pharmacokinetic Results (Within-Subject Comparison) of Total and Unbound Darunavir and Total Cobicistat After Administration of Darunavir/Cobicistat at 800/150 mg Once Daily as Part of an Antiretroviral Regimen, During the 2nd and 3rd Trimester of Pregnancy Compared to Postpartum
Drug Interactions
Darunavir is metabolized by CYP3A. Cobicistat is metabolized by CYP3A and, to a minor extent, by CYP2D6. Darunavir co-administered with cobicistat is an inhibitor of CYP3A and CYP2D6. Cobicistat inhibits the following transporters: P-gp, BCRP, MATE1, OATP1B1, and OATP1B3. Based on in vitro data, cobicistat is not expected to induce CYP1A2 or CYP2B6 and based on in vivo data, cobicistat is not expected to induce MDR1 or, in general, CYP3A to a clinically significant extent. The induction effect of cobicistat on CYP2C9, CYP2C19, or UGT1A1 is unknown, but is expected to be low based on CYP3A in vitro induction data.
Emtricitabine is not an inhibitor of human CYP450 enzymes. In vitro and clinical drug interaction studies have shown that the potential for CYP-mediated interactions involving emtricitabine with other medicinal products is low. Tenofovir alafenamide is not an inhibitor of CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, or UGT1A. It is not an inhibitor or inducer of CYP3A in vivo.
A drug-drug interaction study between darunavir/cobicistat and dabigatran etexilate was conducted in healthy participants. The effects of darunavir on co-administration with dabigatran etexilate are summarized in Table 10.
Table 10: Drug Interactions: Pharmacokinetic Parameters for Co-Administered Drugs in the Presence of darunavir/cobicistat
| Co-administered drug |
Dose/Schedule |
N |
PK |
LS Mean ratio (90% CI) of co-administered drug pharmacokinetic parameters with/without darunavir
no effect =1.00 |
| Co-administered drug |
Darunavir/ cobicistat |
Cmax |
AUC |
Cmin |
| Dabigatran etexilate |
150 mg |
800/100 mg single dose |
14 |
↑ |
2.64
(2.29-3.05) |
2.64
(2.32-3.00) |
- |
|
|
800/100 mg q.d.a |
14 |
↑ |
1.99
(1.72-2.30) |
1.88
(1.65-2.13) |
- |
N = number of subjects with data
q.d. = once daily
a 800/100 mg q.d. for 14 days before co-administered with dabigatran etexilate. |
Microbiology
Mechanism Of Action
Darunavir
Darunavir is an inhibitor of the HIV-1 protease. It selectively inhibits the cleavage of HIV-1 encoded Gag-Pol polyproteins in infected cells, thereby preventing the formation of mature virus particles.
Cobicistat
Cobicistat is a selective, mechanism-based inhibitor of CYPP450 of the CYP3A subfamily. Inhibition of CYP3A-mediated metabolism by cobicistat enhances the systemic exposure of CYP3A substrates.
Emtricitabine
Emtricitabine, 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 reverse transcriptase (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
Darunavir
Darunavir exhibits activity against laboratory strains and clinical isolates of HIV-1 and laboratory strains of HIV-2 in acutely infected T-cell lines, human PBMCs, and human monocytes/macrophages with median EC50 values ranging from 1.2 to 8.5 nM (0.7 to 5.0 ng/mL). Darunavir demonstrates antiviral activity in cell culture against a broad panel of HIV-1 group M (A, B, C, D, E, F, G) and group O primary isolates with EC50 values ranging from less than 0.1 to 4.3 nM. The EC50 value of darunavir increases by a median factor of 5.4 in the presence of human serum.
Cobicistat
Cobicistat has no detectable antiviral activity in cell culture against HIV-1. Emtricitabine: The antiviral activity of emtricitabine against laboratory and clinical isolates of HIV-1 was assessed in T lymphoblastoid cell lines, the MAGI-CCR5 cell line, and primary PBMCs. The EC50 values for emtricitabine were in the range of 1.3–640 nM. Emtricitabine displayed antiviral activity in cell culture against HIV-1 clades A, B, C, D, E, F, and G (EC50 values ranged from 7–75 nM) and showed strain specific activity against HIV-2 (EC50 values ranged from 7–1,500 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 sub-types A, B, C, D, E, F, and G (EC50 values ranged from 0.10 to 12.0 nM) and strain specific activity against HIV-2 (EC50 values ranged from 0.91 to 2.63 nM).
The combination of darunavir, emtricitabine, and tenofovir alafenamide was not antagonistic in cell culture combination antiviral activity assays. In addition, darunavir, emtricitabine, and tenofovir alafenamide were not antagonistic with a panel of representative agents from the major classes of approved HIV antivirals (PIs, NRTIs, NNRTIs, and INSTIs). The antiviral activity of approved HIV antivirals was not antagonized by cobicistat.
Resistance
Cell Culture
Darunavir
In cell culture, HIV-1 isolates with a decreased susceptibility to darunavir have been selected and obtained from subjects treated with darunavir co-administered with ritonavir. Darunavir-resistant virus derived in cell culture from wild-type HIV-1 had 21- to 88-fold decreased susceptibility to darunavir and developed 2 to 4 of the following amino acid substitutions S37D, R41E/T, K55Q, H69Q, K70E, T74S, V77I, or I85V in the protease. Selection in cell culture of darunavir-resistant HIV-1 from nine HIV-1 strains harboring multiple PI resistance-associated substitutions resulted in the overall emergence of 22 mutations in the protease gene, coding for amino acid substitutions L10F, V11I, I13V, I15V, G16E, L23I, V32I, L33F, S37N, M46I, I47V, I50V, F53L, L63P, A71V, G73S, L76V, V82I, I84V, T91A/S, and Q92R, of which L10F, V32I, L33F, S37N, M46I, I47V, I50V, L63P, A71V, and I84V were the most prevalent. These darunavir-resistant viruses had at least eight protease substitutions and exhibited 50- to 641-fold decreases in darunavir susceptibility with final EC50 values ranging from 125 nM to 3461 nM.
Emtricitabine
HIV-1 isolates with reduced susceptibility to emtricitabine were selected in cell culture and in subjects treated with emtricitabine. Reduced susceptibility to emtricitabine 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.
Clinical Trials
Darunavir resistance-associated substitutions (V11I, V32I, L33F, I47V, I50V, I54L or M, T74P, L76V, I84V, and L89V) in HIV-1 protease were derived from clinical trial data of antiretroviral therapy experienced patients, which were all protease inhibitor-experienced patients. Baseline International AIDS Society-USA (IAS-USA)-defined PI resistance substitutions confer reduced virologic response to darunavir.
In the AMBER clinical trial of subjects with no prior antiretroviral treatment history, there were 7 subjects with protocol-defined virologic failure and with HIV-1 RNA ≥400 copies/mL at failure or later timepoints who had post-baseline resistance data in the SYMTUZA arm. None of the subjects had detectable emergent darunavir resistance-associated substitutions or other primary protease inhibitor resistance-associated substitutions and only one subject had emergent M184M/I/V, which confers resistance to emtricitabine and lamivudine. In the comparative PREZCOBIX + emtricitabine/tenofovir disoproxil fumarate arm, there were 2 protocol-defined virologic failures with post-baseline resistance data and neither had detectable resistance emergence.
In the EMERALD clinical trial of virologically-suppressed subjects who switched to SYMTUZA, 1 subject who rebounded and 2 subjects who discontinued early from the study had post-baseline resistance genotypes. None of the subjects had darunavir, primary protease inhibitor, emtricitabine, or tenofovir resistance-associated substitutions. In the control arm, there were 3 subjects who rebounded with post-baseline genotypes and no resistance-associated substitutions were observed.
Cross-Resistance
Darunavir
Cross-resistance among PIs has been observed. Darunavir has a less than 10-fold decreased susceptibility in cell culture against 90% of 3309 clinical isolates resistant to amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, and/or tipranavir showing that viruses resistant to these PIs remain susceptible to darunavir. A less than 10-fold decreased susceptibility was observed for the other PIs in 26% to 96% of these PI resistant clinical isolates [nelfinavir (26%), ritonavir (34%), lopinavir (46%), indinavir (57%), atazanavir (59%), saquinavir (64%), amprenavir (70%), and tipranavir (96%)].
Cross-resistance between darunavir and nucleoside/nucleotide reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, gp41 fusion inhibitors, CCR5 co-receptor antagonists, or integrase strand transfer inhibitors is unlikely because the viral targets are different.
Emtricitabine
Emtricitabine-resistant viruses with the M184V or I substitution were cross-resistant to lamivudine, but retained sensitivity to didanosine, stavudine, tenofovir, and zidovudine.
Tenofovir Alafenamide
Tenofovir resistance-associated 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 3 and 9 month administration of tenofovir alafenamide; reversibility was seen after a 3-month recovery period. No eye toxicity was observed in the dog at systemic exposures of 3.5 (TAF) and 0.62 (tenofovir) times the exposure seen in humans with the recommended daily dose of TAF in SYMTUZA.
Clinical Studies
Clinical Trial Results In Subjects With HIV-1 Infection With No Prior Antiretroviral Treatment History
The efficacy of SYMTUZA in HIV-1 subjects with no prior antiretroviral treatment history was evaluated in the Phase 3 trial TMC114FD2HTX3001 [NCT02431247, (AMBER)] in which subjects were randomized in a 1:1 ratio to receive either SYMTUZA (N=362) or a combination of PREZCOBIX and FTC/TDF (N=363) once daily. The median age was 34.0 years (range 18-71), 88.3% were male, 83% White, 11% Black, and 2% Asian. The mean baseline plasma HIV-1 RNA was 4.5 log10 copies/mL (range 1.3-6.7), and 18% had a baseline viral load ≥100,000 copies/mL. The median baseline CD4+ cell count was 453 cells/mm3 (range 38 to 1456 cells/mm3).
Virologic outcomes at 48 weeks of treatment are presented in Table 11.
Table 11: Virologic Outcomes in AMBER at Week 48 in HIV-1 Subjects with No Prior Antiretroviral Treatment History
|
SYMTUZA
N=362 |
PREZCOBIX
+
FTC/TDF
N=363 |
| Virologic Response |
| HIV-1 RNA <50 copies/mL |
91% |
88% |
| Treatment differencea |
2.7 (95% CI: -1.6; 7.1) |
| Virologic Failureb |
4% |
3% |
| No virologic data at Week 48 windowc |
4% |
8% |
| Reasons |
| Discontinued trial due to adverse event or death |
2% |
4% |
| Discontinued trial for other reasonsd |
1% |
3% |
| Missing data during window but on trial |
1% |
1% |
a Based on stratum adjusted MH test where stratification factors are HIV-1 RNA level (≤100,000 or > 100,000 copies/mL) and CD4+ cell count (< 200 or ≥200 cells/μL).
b Included 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 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 Day 295 – Day 378
d Other includes reasons such as withdrew consent, loss to follow-up, and non-compliance. |
The mean increase from baseline in CD4+ cell count at Week 48 was 189 and 174 cells/mm3 in the SYMTUZA and PREZCOBIX + FTC/TDF groups, respectively.
Clinical Trial Results In Virologically-Suppressed Subjects With HIV-1 Infection Who Switched To SYMTUZA
Phase 3 trial TMC114IFD3013 [NCT02269917, (EMERALD)] evaluated the efficacy of SYMTUZA in virologically-suppressed (HIV-1 RNA less than 50 copies/mL) subjects with HIV-1 infection. Subjects were virologically suppressed for at least 2 months and no more than once had a viral load elevation above 50 HIV-1 RNA copies/mL during the year prior to enrollment. Subjects were on a stable antiretroviral regimen (for at least 6 months), consisting of a bPI [either darunavir once daily or atazanavir (both boosted with ritonavir or cobicistat), or lopinavir with ritonavir] combined with emtricitabine and TDF. Subjects had no history of failure on darunavir treatment and no known or suspected darunavir resistance-associated substitutions. Emtricitabine or tenofovir resistance-associated substitutions were not specifically excluded by the protocol. They either switched to SYMTUZA (N=763) or continued their treatment regimen (N=378) (randomized 2:1). Subjects had a median age of 46 years (range 19-78), 82% were male, 75% White, 21% Black, and 2% Asian. The median baseline CD4+ cell count was 628 cells/mm3 (range 111-1921 cells/mm3). Overall, 15% (N=169) of subjects had prior virologic failure. Five subjects had archived tenofovir resistance-associated substitutions and 53 subjects had archived emtricitabine resistance-associated substitutions, mainly at RT position M184. All of these subjects with emtricitabine resistance-associated substitutions had HIV-1 RNA<50 copies/mL at Week 48 (N=50) or at the last on-treatment viral load (N=3). Virologic outcomes are presented in Table 12. Prior virologic failure did not impact treatment outcomes.
Table 12: Virologic Outcomes in EMERALD at Week 48 in HIV-1 Virologically-Suppressed Subjects Who Switched to SYMTUZA
|
SYMTUZA
N=763 |
bPI+FTC/TDF
N=378 |
| Virologic Failurea |
1% |
1% |
| Treatment differenceb |
0.3 (95% CI: -0.7; 1.2) |
| HIV-1 RNA <50 copies/mL |
95% |
94% |
| No virologic data at Week 48 windowc |
4% |
6% |
| Reasons |
|
|
| Discontinued trial due to adverse event or death |
1% |
1% |
| Discontinued trial for other reasonsd |
3% |
4% |
| Missing data during windowc but on trial |
<1% |
1% |
a Included 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 an adverse event (AE), death, or lack or loss of efficacy and at the time of discontinuation had a viral value ≥ 50 copies/mL.
b Based on MH test adjusting for bPI at screening (ATV with rtv or COBI, DRV with rtv or COBI, LPV with rtv).
c Day 295 – Day 378
d Other includes reasons such as withdrew consent, loss to follow-up, and non-compliance |
The mean increase from baseline in CD4+ cell count at Week 48 was 20 cells/mm3 in subjects who switched to SYMTUZA and 8 cells/mm3 in subjects who stayed on their baseline PI + FTC/TDF.
Clinical Trial Results In Pediatric Subjects With HIV-1 Infection
The pharmacokinetic profile, safety, and antiviral activity of the components of SYMTUZA were evaluated in open-label clinical trials in pediatric subjects with HIV-1 infection aged 12 to less than 18 years: GS-US-216-0128 (N=7) and GS-US-292-0106 (N=50).
In the Phase 2/3 trial GS-US-216-0128, darunavir 800 mg and cobicistat 150 mg once daily with 2 NRTIs were evaluated in 7 virologically suppressed pediatric subjects aged 12 to less than 18 years and weighing at least 40 kg. Subjects had a median (range) age of 14 (12-16) years and a median (range) weight of 57 (45-78) kg. At baseline, plasma HIV-1 RNA was <50 copies/mL in all subjects, and the median (range) CD4+ cell count was 1,117 (658-2,416) cells/mm3. At Week 48, the proportion of subjects who maintained HIV-1 RNA <50 copies/mL was 86%, and the median change in CD4+ cell count from baseline was -342 cells/mm3 (range -1,389 to 210 cells/mm3). All 6 subjects with available data had CD4+ cell counts above 800 cells/mm3 at Week 48.
In the Phase 2/3 trial GS-US-292-0106, cobicistat 150 mg, emtricitabine 200 mg, and tenofovir alafenamide 10 mg, as part of a fixed-dose combination regimen together with elvitegravir 150 mg, were evaluated in 50 treatment-naïve pediatric subjects with HIV-1 aged 12 to less than 18 years and weighing at least 35 kg. Subjects had a median (range) age of 15 (12-17) years. At baseline, median (range) plasma HIV-1 RNA was 4.7 (3.3-6.5) log10 copies/mL, median (range) CD4+ cell count was 456 (95-1,110) cells/mm3, and 22% had baseline plasma HIV-1 RNA >100,000 copies/mL). At Week 48, the proportion of subjects who had HIV-1 RNA <50 copies/mL was 92%, and the median increase in CD4+ cell count from baseline was 220 cells/mm3.
The use of SYMTUZA in pediatric patients weighing less than 40 kg has not been established [see Use In Specific Populations].