Emtricitabine is a nucleoside analogue of cytidine. Tenofovir disoproxil is converted in vivo to tenofovir, a nucleoside monophosphate (nucleotide) analogue of adenosine monophosphate. Both emtricitabine and tenofovir have activity that is specific to HIV-1, HIV-2 and, HBV.
Rilpivirine is a diarylpyrimidine NNRTI of HIV-1. Rilpivirine activity is mediated by non-competitive inhibition of HIV-1 reverse transcriptase (RT).
Emtricitabine and tenofovir are phosphorylated by cellular enzymes to form emtricitabine triphosphate and tenofovir diphosphate, respectively. In vitro studies have shown that both emtricitabine and tenofovir can be fully phosphorylated when combined together in cells. Emtricitabine triphosphate and tenofovir diphosphate competitively inhibit HIV-1 RT, resulting in DNA chain termination.
Both emtricitabine triphosphate and tenofovir diphosphate are weak inhibitors of mammalian DNA polymerases and there was no evidence of toxicity to mitochondria in vitro and in vivo. Rilpivirine does not inhibit the human cellular DNA polymerases α, β and mitochondrial DNA polymerase γ.
The triple combination of emtricitabine, rilpivirine, and tenofovir demonstrated synergistic antiviral activity in cell culture.
The antiviral activity of emtricitabine against laboratory and clinical isolates of HIV-1 was assessed in lymphoblastoid cell lines, the MAGI-CCR5 cell line, and peripheral blood mononuclear cells. The 50% effective concentration (EC50) values for emtricitabine were in the range of 0.0013 to 0.64 µM.
Emtricitabine displayed antiviral activity in cell culture against HIV-1 subtype A, B, C, D, E, F, and G (EC50 values ranged from 0.007 to 0.075 µM) and showed strain specific activity against HIV-2 (EC50 values ranged from 0.007 to 1.5 µM).
In combination studies of emtricitabine with NRTIs (abacavir, didanosine, lamivudine, stavudine, tenofovir, and zidovudine), NNRTIs (delavirdine, efavirenz, nevirapine, and rilpivirine), and PIs (amprenavir, nelfinavir, ritonavir, and saquinavir), additive to synergistic effects were observed.
Rilpivirine exhibited activity against laboratory strains of wild-type HIV-1 in an acutely infected T-cell line with a median EC50 value for HIV-1/IIIB of 0.73 nM (0.27 ng/mL). Although rilpivirine demonstrated limited in vitro activity against HIV-2 with EC50 values ranging from 2,510 to 10,830 nM (920 to 3,970 ng/mL), treatment of HIV-2 infection with rilpivirine hydrochloride is not recommended in the absence of clinical data.
Rilpivirine also demonstrated antiviral activity against a broad panel of HIV-1 group M (subtype A, B, C, D, F, G, H) primary isolates with EC50 values ranging from 0.07 to 1.01 nM (0.03 to 0.37 ng/mL) and group O primary isolates with EC50 values ranging from 2.88 to 8.45 nM (1.06 to 3.10 ng/mL).
The antiviral activity of tenofovir against laboratory and clinical isolates of HIV-1 was assessed in lymphoblastoid cell lines, primary monocyte/macrophage cells and peripheral blood lymphocytes. The EC50 values for tenofovir were in the range of 0.04 to 8.5 µM.
Tenofovir displayed antiviral activity in cell culture against HIV-1 subtype A, B, C, D, E, F, G, and O (EC50 values ranged from 0.5 to 2.2 µM) and strain specific activity against HIV-2 (EC50 values ranged from 1.6 to 5.5 µM).
In combination studies of tenofovir with NRTIs (abacavir, didanosine, emtricitabine, lamivudine, stavudine, and zidovudine), NNRTIs (delavirdine, efavirenz, nevirapine, and rilpivirine), and PIs (amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir), additive to synergistic effects were observed.
Considering all of the available in vitro data and data generated in previously untreated patients, the following resistance-associated mutations in HIV-1 RT, when present at baseline, may affect the activity of emtricitabine/rilpivirine/tenofovir disoproxil: K65R, K70E, K101E, K101P, E138A, E138G, E138K, E138Q, E138R, V179L, Y181C, Y181I, Y181V, M184I, M184V, Y188L, H221Y, F227C, M230I, M230L and the combination of L100I and K103N.
A negative impact by NNRTI mutations other than those listed above (e.g. mutations K103N or L100I as single mutations) cannot be excluded, since this was not studied in vivo in a sufficient number of patients.
As with other antiretroviral medicinal products, resistance testing and/or historical resistance data should guide the use of emtricitabine/rilpivirine/tenofovir disoproxil.
Resistance to emtricitabine or tenofovir has been seen in vitro and in some HIV-1 infected patients due to the development of the M184V or M184I substitution in RT with emtricitabine, or the K65R substitution in RT with tenofovir. In addition, a K70E substitution in HIV-1 RT has been selected by tenofovir and results in low-level reduced susceptibility to abacavir, emtricitabine, tenofovir and lamivudine. No other pathways of resistance to emtricitabine or tenofovir have been identified. Emtricitabine-resistant viruses with the M184V/I mutation were cross-resistant to lamivudine, but retained sensitivity to didanosine, stavudine, tenofovir, zalcitabine and zidovudine. The K65R mutation can also be selected by abacavir or didanosine and results in reduced susceptibility to these agents plus to lamivudine, emtricitabine, and tenofovir. Tenofovir disoproxil should be avoided in patients with HIV-1 harbouring the K65R mutation. The K65R, M184V, and K65R+M184V mutants of HIV-1 remain fully susceptible to rilpivirine.
Rilpivirine-resistant strains were selected in cell culture starting from wild-type HIV-1 of different origins and subtypes as well as NNRTI-resistant HIV-1. The most commonly observed resistanceassociated mutations that emerged included L100I, K101E, V108I, E138K, V179F, Y181C, H221Y, F227C and M230I.
The bioequivalence of one emtricitabine/rilpivirine/tenofovir disoproxil film-coated tablet with one emtricitabine 200 mg hard capsule, one rilpivirine (as hydrochloride) 25 mg film-coated tablet and one tenofovir disoproxil 245 mg film-coated tablet was established following single dose administration to fed, healthy subjects. Following oral administration of emtricitabine/rilpivirine/tenofovir disoproxil with food emtricitabine is rapidly and extensively absorbed with maximum plasma concentrations occurring within 2.5 hours post-dose. Maximum tenofovir concentrations are observed in plasma within 2 hours and maximum plasma concentrations of rilpivirine are generally achieved within 4-5 hours. Following oral administration of tenofovir disoproxil to HIV infected patients, tenofovir disoproxil is rapidly absorbed and converted to tenofovir. The absolute bioavailability of emtricitabine from 200 mg hard capsules was estimated to be 93%. The oral bioavailability of tenofovir from tenofovir disoproxil tablets in fasted patients was approximately 25%. The absolute bioavailability of rilpivirine is unknown. The administration of emtricitabine/rilpivirine/tenofovir disoproxil to healthy adult subjects with either a light meal (390 kcal) or a standard meal (540 kcal) resulted in increased exposures of rilpivirine and tenofovir relative to fasting conditions. The Cmax and AUC of rilpivirine increased by 34% and 9% (light meal) and 26% and 16% (standard meal), respectively. The Cmax and AUC for tenofovir increased by 12% and 28% (light meal) and 32% and 38% (standard meal), respectively. Emtricitabine exposures were not affected by food. Emtricitabine/rilpivirine/tenofovir disoproxil must be administered with food to ensure optimal absorption.
Following intravenous administration the volume of distribution of the single components emtricitabine and tenofovir was approximately 1,400 mL/kg and 800 mL/kg, respectively. After oral administration of the single components emtricitabine and tenofovir disoproxil, emtricitabine and tenofovir are widely distributed throughout the body. In vitro binding of emtricitabine to human plasma proteins was <4% and independent of concentration over the range of 0.02 to 200 µg/mL. In vitro binding of rilpivirine to human plasma proteins is approximately 99.7%, primarily to albumin. In vitro binding of tenofovir to plasma or serum protein was less than 0.7% and 7.2%, respectively, over the tenofovir concentration range 0.01 to 25 µg/mL.
There is limited metabolism of emtricitabine. The biotransformation of emtricitabine includes oxidation of the thiol moiety to form the 3'-sulphoxide diastereomers (approximately 9% of dose) and conjugation with glucuronic acid to form 2'-O-glucuronide (approximately 4% of dose). In vitro experiments indicate that rilpivirine hydrochloride primarily undergoes oxidative metabolism mediated by the CYP3A system. In vitro studies have determined that neither tenofovir disoproxil nor tenofovir are substrates for the CYP450 enzymes. Neither emtricitabine nor tenofovir inhibited in vitro drug metabolism mediated by any of the major human CYP450 isoforms involved in drug biotransformation. Also, emtricitabine did not inhibit uridine-5'-diphosphoglucuronyl transferase, the enzyme responsible for glucuronidation.
Emtricitabine is primarily excreted by the kidneys with complete recovery of the dose achieved in urine (approximately 86%) and faeces (approximately 14%). Thirteen percent of the emtricitabine dose was recovered in urine as three metabolites. The systemic clearance of emtricitabine averaged 307 mL/min. Following oral administration, the elimination half-life of emtricitabine is approximately 10 hours.
The terminal elimination half-life of rilpivirine is approximately 45 hours. After single dose oral administration of [14C]-rilpivirine, on average 85% and 6.1% of the radioactivity could be retrieved in faeces and urine, respectively. In faeces, unchanged rilpivirine accounted for on average 25% of the administered dose. Only trace amounts of unchanged rilpivirine (<1% of dose) were detected in urine.
Tenofovir is primarily excreted by the kidney by both filtration and an active tubular transport system (human organic anion transporter 1 [hOAT1]) with approximately 70-80% of the dose excreted unchanged in urine following intravenous administration. The apparent clearance of tenofovir averaged approximately 307 mL/min. Renal clearance has been estimated to be approximately 210 mL/min, which is in excess of the glomerular filtration rate. This indicates that active tubular secretion is an important part of the elimination of tenofovir. Following oral administration, the elimination half-life of tenofovir is approximately 12 to 18 hours.
Population pharmacokinetic analysis in HIV infected patients showed that rilpivirine pharmacokinetics is not different across the age range (18 to 78 years) evaluated, with only 2 patients aged 65 years of age or older.
Emtricitabine and tenofovir pharmacokinetics are similar in male and female patients. No clinically relevant differences in pharmacokinetics of rilpivirine have been observed between men and women.
No clinically important pharmacokinetic differences due to ethnicity have been identified.
In general, the pharmacokinetics of emtricitabine in infants, children and adolescents (aged 4 months up to 18 years) is similar to those seen in adults. The pharmacokinetics of rilpivirine and tenofovir disoproxil in children and adolescents are under investigation. Dosing recommendations for paediatric patients cannot be made due to insufficient data.
Limited data from clinical studies support once daily dosing of emtricitabine/rilpivirine/tenofovir disoproxil in patients with mild renal impairment (CrCl 50-80 mL/min). However, long-term safety data for the emtricitabine and tenofovir disoproxil components of emtricitabine/rilpivirine/tenofovir disoproxil have not been evaluated in patients with mild renal impairment. Therefore, in patients with mild renal impairment emtricitabine/rilpivirine/tenofovir disoproxil should only be used if the potential benefits of treatment are considered to outweigh the potential risks.
Emtricitabine/rilpivirine/tenofovir disoproxil combination is not recommended for patients with moderate or severe renal impairment (CrCl <50 mL/min). Patients with moderate or severe renal impairment require a dose interval adjustment of emtricitabine and tenofovir disoproxil that cannot be achieved with the combination tablet.
Pharmacokinetic parameters were mainly determined following administration of single doses of emtricitabine 200 mg or tenofovir disoproxil 245 mg to non-HIV infected patients with varying degrees of renal impairment. The degree of renal impairment was defined according to baseline CrCl (normal renal function when CrCl >80 mL/min; mild impairment with CrCl = 50-79 mL/min; moderate impairment with CrCl = 30-49 mL/min and severe impairment with CrCl = 10-29 mL/min).
The mean (CV) emtricitabine drug exposure increased from 12 (25) µg•h/mL in patients with normal renal function, to 20 (6%) µg•h/mL, 25 (23%) µg•h/mL and 34 (6%) µg•h/mL, in patients with mild, moderate and severe renal impairment, respectively.
The mean (CV) tenofovir drug exposure increased from 2,185 (12) ng•h/mL in patients with normal renal function, to 3,064 (30%) ng•h/mL, 6,009 (42%) ng•h/mL and 15,985 (45%) ng•h/mL, in patients with mild, moderate and severe renal impairment, respectively.
In patients with end-stage renal disease (ESRD) requiring haemodialysis, between dialysis drug exposures substantially increased over 72 hours to 53 µg•h/mL (19%) of emtricitabine, and over 48 hours to 42,857 ng•h/mL (29%) of tenofovir.
A small clinical study was conducted to evaluate the safety, antiviral activity and pharmacokinetics of tenofovir disoproxil in combination with emtricitabine in HIV infected patients with renal impairment. A subgroup of patients with baseline CrCl between 50 and 60 mL/min, receiving once daily dosing, had a 2- to 4-fold increase in tenofovir exposure and worsening renal function.
The pharmacokinetics of rilpivirine has not been studied in patients with renal insufficiency. Renal elimination of rilpivirine is negligible. In patients with severe renal impairment or ESRD, plasma concentrations may be increased due to alteration of drug absorption, distribution and/or metabolism secondary to renal dysfunction. As rilpivirine is highly bound to plasma proteins, it is unlikely that it will be significantly removed by haemodialysis or peritoneal dialysis.
No dose adjustment of emtricitabine/rilpivirine/tenofovir disoproxil is suggested but caution is advised in patients with moderate hepatic impairment. Emtricitabine/rilpivirine/tenofovir disoproxil combination has not been studied in patients with severe hepatic impairment (CPT Score C). Therefore, emtricitabine/rilpivirine/tenofovir disoproxil is not recommended in patients with severe hepatic impairment.
The pharmacokinetics of emtricitabine has not been studied in patients with varying degrees of hepatic insufficiency.
Rilpivirine hydrochloride is primarily metabolised and eliminated by the liver. In a study comparing 8 patients with mild hepatic impairment (CPT Score A) to 8 matched controls and 8 patients with moderate hepatic impairment (CPT Score B) to 8 matched controls, the multiple dose exposure of rilpivirine was 47% higher in patients with mild hepatic impairment and 5% higher in patients with moderate hepatic impairment. Rilpivirine has not been studied in patients with severe hepatic impairment (CPT Score C). However, it may not be excluded that the pharmacologically active, unbound, rilpivirine exposure is significantly increased in moderate impairment.
A single 245 mg dose of tenofovir disoproxil was administered to non-HIV infected subjects with varying degrees of hepatic impairment defined according to CPT classification. Tenofovir pharmacokinetics was not substantially altered in subjects with hepatic impairment suggesting that no dose adjustment is required in these subjects. The mean (CV) tenofovir Cmax and AUC0-∞ values were 223 (34.8) ng/mL and 2,050 (50.8%) ng•h/mL, respectively, in normal subjects compared with 289 (46.0%) ng/mL and 2,310 (43.5%) ng•h/mL in subjects with moderate hepatic impairment, and 305 (24.8%) ng/mL and 2,740 (44.0%) ng•h/mL in subjects with severe hepatic impairment.
In general, emtricitabine pharmacokinetics in HBV infected patients was similar to those in healthy subjects and in HIV infected patients.
Population pharmacokinetic analysis indicated that hepatitis B and/or C virus co-infection had no clinically relevant effect on the exposure to rilpivirine.
The efficacy data from study GS-US-264-0111 indicates that the brief period of lower rilpivirine exposure does not impact antiviral efficacy of emtricitabine/rilpivirine/tenofovir disoproxil. Due to the decline in efavirenz plasma levels, the inductive effect decreased and rilpivirine concentrations started to normalise. During the time period of declining efavirenz plasma levels and increasing rilpivirine plasma levels after switching, none of the patients had efavirenz or rilpivirine levels below their respective IC90 levels at the same time. No dose adjustment is required following the switch from an efavirenz-containing regimen.
After taking rilpivirine 25 mg once daily as part of an antiretroviral regimen, the total exposure of rilpivirine was lower during pregnancy (similar for the 2nd and 3rd trimester) compared with postpartum. The decrease in the unbound free fraction of rilpivirine exposure (i.e. active) during pregnancy compared to postpartum was less pronounced than for total exposure of rilpivirine.
In women receiving rilpivirine 25 mg once daily during the 2nd trimester of pregnancy, mean intraindividual values for total rilpivirine Cmax, AUC24h and Cmin values were 21%, 29% and 35% lower, respectively, as compared to postpartum; during the 3rd trimester of pregnancy, Cmax, AUC24h and Cmin values were 20%, 31% and 42% lower, respectively, as compared to postpartum.
Non-clinical data on emtricitabine reveal no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity, carcinogenic potential, and toxicity to reproduction and development.
Non-clinical data on rilpivirine hydrochloride reveal no special hazard for humans based on studies of safety pharmacology, drug disposition, genotoxicity, carcinogenic potential, and toxicity to reproduction and development. Liver toxicity associated with liver enzyme induction was observed in rodents. In dogs cholestasis-like effects were noted.
Carcinogenicity studies with rilpivirine in mice and rats revealed tumorigenic potential specific for these species, but are regarded as of no relevance for humans.
Studies in animals have shown limited placenta passage of rilpivirine. It is not known whether placental transfer of rilpivirine occurs in pregnant women. There was no teratogenicity with rilpivirine in rats and rabbits.
Non-clinical data on tenofovir disoproxil reveal no special hazard for humans based on conventional studies of safety pharmacology, genotoxicity, carcinogenic potential, and toxicity to reproduction and development. Findings in repeated dose toxicity studies in rats, dogs and monkeys at exposure levels greater than or equal to clinical exposure levels and with possible relevance to clinical use included kidney and bone changes and a decrease in serum phosphate concentration. Bone toxicity was diagnosed as osteomalacia (monkeys) and reduced BMD (rats and dogs).
Genotoxicity and repeated dose toxicity studies of one month or less with the combination of emtricitabine and tenofovir disproxil found no exacerbation of toxicological effects compared to studies with the separate components.
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