HIV-1/2 nucleotide reverse transcriptase

According to the MTT experiment, tenofovir has a deleterious effect on HK-2 cell viability, with IC50 values of 2.77 μM and 9.21 μM at 48 and 72 hours, respectively. ATP levels in HK-2 cells are lowered by tenofovir. In HK-2 cells, tenofovir (3.0 to 28.8 μM) elevates protein carbonylation and oxidative stress. Furthermore, tenofovir has the ability to cause HK-2 cells to undergo apoptosis, which is brought on by damage to the mitochondria [1]. The replication of R5-tropic HIV-1BaL and X4-tropic HIV-1IIIb in activated PBMC was suppressed by tenofovir and M48U1, which were compounded in 0.25% HEC. Additionally, several laboratory strains and patient-derived HIV-1 isolates were inhibited. In addition to being non-toxic to PBMC, the combination formulation of M48U1 and tenofovir in 0.25% HEC demonstrated synergistic antiretroviral efficacy against R5-tropic HIV-1BaL infection [2].

In BLT humanized mice, tenofovir disoproxil fumarate (20, 50, 140, or 300 mg/kg) administration resulted in dose-dependent activity during vaginal HIV challenge. HIV transmission in BLT mice is dramatically decreased by tenofovir disoproxil fumarate (50, 140, or 300 mg/kg) [3]. In woodchucks that are chronically infected with WHV, tenofovir disoproxil fumarate (0.5, 1.5, or 5.0 mg/kg/day) causes a dose-dependent decrease in serum viremia. For treating a persistent HBV infection in woodchucks, tenofovir disoproxil fumarate is both safe and efficacious [4].

Cells are plated into 48-well tissue culture plates (39,000 cells/mL) and allowed to grow for 48 h followed by treatment with vehicle or Tenofovir. Following the treatment period, cell viability is assessed using the MTT assay. The MTT assay relies on the conversion of tetrazolium dye 3-(4,5-dimethlthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to formazan by NAD(P)H-dependent oxidoreductases[1].

Tenofovir disoproxil fumarate (TDF) is a nucleotide analogue approved for treatment of human immunodeficiency virus (HIV) infection. TDF also has been shown in vitro to inhibit replication of wild-type hepatitis B virus (HBV) and lamivudine-resistant HBV mutants and to inhibit lamivudine-resistant HBV in patients and HBV in patients coinfected with the HIV. Data on the in vivo efficacy of TDF against wild-type virus in non-HIV-coinfected or lamivudine-naïve chronic HBV-infected patients are lacking in the published literature. The antiviral effect of oral administration of TDF against chronic woodchuck hepatitis virus (WHV) infection, an established and predictive animal model for antiviral therapy, was evaluated in a placebo-controlled, dose-ranging study (doses, 0.5 to 15.0 mg/kg of body weight/day). Four weeks of once-daily treatment with TDF doses of 0.5, 1.5, or 5.0 mg/kg/day reduced serum WHV viremia significantly (0.2 to 1.5 log reduction from pretreatment level). No effects on the levels of anti-WHV core and anti-WHV surface antibodies in serum or on the concentrations of WHV RNA or WHV antigens in the liver of treated woodchucks were observed. Individual TDF-treated woodchucks demonstrated transient declines in WHV surface antigen serum antigenemia and, characteristically, these woodchucks also had transient declines in serum WHV viremia, intrahepatic WHV replication, and hepatic expression of WHV antigens. No evidence of toxicity was observed in any of the TDF-treated woodchucks. Following drug withdrawal there was prompt recrudescence of WHV viremia to pretreatment levels. It was concluded that oral administration of TDF for 4 weeks was safe and effective in the woodchuck model of chronic HBV infection.[5]

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Twenty adult chronic WHV carrier woodchucks are stratified equally by age, sex, body weight, and serum GGT activity into five treatment groups consisting of four animals each: (i) Tenofovir Disoproxil Fumarate at 15.0 mg/kg once per day, (ii) Tenofovir Disoproxil Fumarate at 5.0 mg/kg/day, (iii) Tenofovir Disoproxil Fumarate at 1.5 mg/kg/day, (iv) Tenofovir Disoproxil Fumarate at 0.5 mg/kg/day, and (v) a placebo control. The woodchucks are treated daily for 4 weeks and observed for an additional 12 weeks following cessation of drug treatment.

Absorption, Distribution and Excretion
After oral administration of tenofovir disoproxil to patients with HIV infection, tenofovir disoproxil is quickly absorbed and metabolized to tenofovir. Administration of tenofovir disoproxil 300 mg tablets after a high-fat meal increases the oral bioavailability of this drug, as demonstrated by an increase in tenofovir AUC0-∞ of about 40% as well as an increase in Cmax of about 14%. On the contrary, the administration of tenofovir disoproxil with a light meal did not exert a relevant effect on the pharmacokinetics of tenofovir when compared to administration under fasting conditions. The presence of ingested food slows the time to tenofovir Cmax by approximately 1 hour. Cmax and AUC of tenofovir are 0.33 ± 0.12 μg/mL and 3.32 ± 1.37 μg•hr/mL after several doses of tenofovir disoproxil 300 mg once daily in the fed state when meal content is not controlled.
Following IV administration of tenofovir, approximately 70–80% of the dose is recovered in the urine as unchanged tenofovir within 72 hours of dosing. Tenofovir is eliminated by a combination of glomerular filtration and active tubular secretion. There may be competition for elimination with other compounds that are also eliminated by the kidneys.
The volume of distribution at steady-state is 1.3 ± 0.6 L/kg and 1.2 ± 0.4 L/kg, following intravenous administration of tenofovir 1.0 mg/kg and 3.0 mg/kg. After oral administration of tenofovir disoproxil, tenofovir is distributed to the majority tissues with the highest concentrations measured in the kidney, liver and the intestinal contents (based on data from preclinical studies).
The clearance of tenofovir is highly dependent on renal function and may vary greatly. Total clearance has been estimated to be approximately 230 ml/h/kg (approximately 300 ml/min). On average, renal clearance has been estimated to be approximately 160 ml/h/kg (approximately 210 ml/min), which is in excess of the glomerular filtration rate. This shows that active tubular secretion is an essential part of the elimination of tenofovir. The FDA label provides specific guidelines for dosing according to renal function. It is important to consult product labeling before administering tenofovir to individuals with renal dysfunction, as the clearance of this drug may vary greatly among these patients.
Following IV administration of tenofovir, approximately 70-80% of the dose is recovered in the urine as unchanged tenofovir within 72 hours of dosing. Following single dose, oral administration of tenofovir, the terminal elimination half-life of tenofovir is approximately 17 hours. After multiple oral doses of tenofovir 300 mg once daily (under fed conditions), 32 + or - 10% of the administered dose is recovered in urine over 24 hours. Tenofovir is eliminated by a combination of glomerular filtration and active tubular secretion. There may be competition for elimination with other compounds that are also renally eliminated.
In vitro binding of tenofovir to human plasma or serum proteins is less than 0.7 and 7.2%, respectively, over the tenofovir concentration range 0.01 to 25 ug/mL. The volume of distribution at steady-state is 1.3 + or - 0.6 L/kg and 1.2 + or - 0.4 L/kg, following intravenous administration of tenofovir 1.0 mg/kg and 3.0 mg/kg.
Viread is a water soluble diester prodrug of the active ingredient tenofovir. The oral bioavailability of tenofovir from Viread in fasted subjects is approximately 25%. Following oral administration of a single dose of Viread 300 mg to HIV-1 infected subjects in the fasted state, maximum serum concentrations (Cmax) are achieved in 1.0 + or - 0.4 hr. Cmax and AUC values are 0.30 + or - 0.09 ug/mL and 2.29 + or - 0.69 ug hr/mL, respectively.
Administration of Viread 300 mg tablets following a high-fat meal (approximately 700 to 1000 kcal containing 40 to 50% fat) increases the oral bioavailability, with an increase in tenofovir AUC of approximately 40% and an increase in Cmax of approximately 14%. However, administration of Viread with a light meal did not have a significant effect on the pharmacokinetics of tenofovir when compared to fasted administration of the drug. Food delays the time to tenofovir Cmax by approximately 1 hour. Cmax and AUC of tenofovir are 0.33 + or - 0.12 ug/mL and 3.32 + or - 1.37 ug hr/mL following multiple doses of Viread 300 mg once daily in the fed state, when meal content was not controlled.
For more Absorption, Distribution and Excretion (Complete) data for TENOFOVIR DISOPROXIL FUMARATE (6 total), please visit the HSDB record page.

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Metabolism / Metabolites
Tenofovir disoproxil fumarate is the fumarate salt of the prodrug _tenofovir disoproxil_. Tenofovir disoproxil is absorbed and converted to its active form, _tenofovir_, a nucleoside monophosphate (nucleotide) analog. Tenofovir is then converted to the active metabolite, _tenofovir diphosphate_, a chain terminator, by constitutively expressed enzymes in the cell. Two phosphorylation steps are required to convert tenofovir disoproxil to the active drug form. The cytochrome P450 enzyme system is not involved with the metabolism of tenofovir disoproxil or tenofovir.
Tenofovir disoproxil fumarate is a prodrug and is not active until it undergoes diester hydrolysis in vivo to tenofovir and subsequently is metabolized to the active metabolite (tenofovir diphosphate).

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Biological Half-Life
When a single oral dose is given, the terminal elimination half-life is approximately 17 hours.
Following single dose, oral administration of Viread, the terminal elimination half-life of tenofovir is approximately 17 hours.

Protein Binding
_In vitro_ binding of tenofovir to human plasma or serum proteins is <0.7 and <7.2%, respectively, over the tenofovir concentration range 0.01 to 25 μg/mL.

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Interactions
Potential pharmacokinetic interaction with drugs that reduce renal function or that may compete with tenofovir for active renal tubular secretion (i.e., acyclovir, cidofovir, ganciclovir, valacyclovir, valganciclovir); increased plasma concentrations of tenofovir or the concomitantly administered drug may occur.
The manufacturer of tenofovir states that tenofovir should not be used with adefovir for the treatment of hepatitis B virus (HBV) infection.
Pharmacokinetic interaction with atazanavir sulfate (decrease plasma concentrations and AUC of atazanavir (minimum concentration decreased 40%) and increased plasma concentrations and AUC of tenofovir when atazanavir 400 mg and tenofovir disoproxil fumarate 300 mg given once daily). Pharmacokinetic interaction with ritonavir-boosted atazanavir sulfate (decrease plasma concentrations and AUC of atazanavir (minimum concentration decreased 23%) and increased plasma concentrations and AUC of tenofovir when atazanavir 300 mg, ritonavir 100 mg, and tenofovir disoproxil fumarate 300 mg given once daily). If used concomitantly, a dosage regimen of atazanavir 300 mg, ritonavir 100 mg, and tenofovir disoproxil fumarate 300 mg given once daily with food is recommended; atazanavir should not be used with tenofovir unless low-dose ritonavir is a component of the regimen. Monitor for tenofovir toxicity and discontinue the drug if tenofovir-associated adverse effects occur. If atazanavir is used concomitantly with tenofovir and a histamine H2-receptor antagonist, the recommended dosage for treatment-experienced patients is atazanavir 400 mg, ritonavir 100 mg, and tenofovir disoproxil fumarate 300 mg given once daily with food.
Pharmacokinetic interaction with the buffered didanosine preparation (pediatric oral solution admixed with antacid; Videx) or delayed-release capsules containing enteric-coated pellets of didanosine (Videx EC) resulting in increased plasma concentrations and AUC of didanosine; no change in tenofovir pharmacokinetics. Potential for early virologic failure, rapid selection of resistant mutations, immunologic nonresponse (e.g., decline in CD4+ T-cell count), and increased risk of didanosine-associated adverse effects (e.g., pancreatitis, neuropathy). Caution is advised if didanosine and tenofovir are used concomitantly and patients should be monitored closely for didanosine-associated adverse effects; didanosine should be discontinued if such effects occur. If didanosine delayed-release capsules are used with tenofovir disoproxil fumarate, the recommended dosage of didanosine is 250 mg once daily for those weighing 60 kg or more with creatinine clearances of 60 mL/minute or greater and 200 mg once daily for those weighing less than 60 kg with creatinine clearances of 60 mL/minute or greater. Didanosine delayed-release capsules and tenofovir may be taken at the same time with a light meal (no more than 400 kcal, no more than 20% fat) or in the fasted state.
For more Interactions (Complete) data for TENOFOVIR DISOPROXIL FUMARATE (10 total), please visit the HSDB record page.

[1]. Establishment of HK-2 Cells as a Relevant Model to Study Tenofovir-Induced Cytotoxicity. Int J Mol Sci. 2017 Mar 1;18(3).

[2]. M48U1 and Tenofovir combination synergistically inhibits HIV infection in activated PBMCs and human cervicovaginal histocultures. Sci Rep. 2017 Feb 1;7:41018.

[3]. Predicting HIV Pre-exposure Prophylaxis Efficacy for Women using a Preclinical Pharmacokinetic-Pharmacodynamic In Vivo Model. Sci Rep. 2017 Feb 1;7:41098.

[4]. Menne S, Cote PJ, Korba BE, Antiviral effect of oral administration of tenofovir disoproxil fumarate in woodchucks with chronic woodchuck hepatitis virus infection. Antimicrob Agents Chemother. 2005 Jul;49(7):2720-8.

Therapeutic Uses
Anti-HIV Agents, Reverse Transcriptase Inhibitors
Tenofovir disoproxil fumarate is used in conjunction with other antiretroviral agents for the treatment of human immunodeficiency virus type 1 (HIV-1) infections in adults. /Included in US product labeling/
Tenofovir is used for the management of chronic hepatitis B virus (HBV) infection in adults. This indication is based on histologic, virologic, biochemical, and serologic responses in adults with hepatitis B e antigen (HBeAg)-positive or -negative chronic HBV with compensated liver function.
Tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and efavirenz (EFV) are the three components of the once-daily, single tablet regimen (Atripla) for treatment of HIV-1 infection. Previous cell culture studies have demonstrated that the double combination of tenofovir (TFV), the parent drug of TDF, and FTC were additive to synergistic in their anti-HIV activity, which correlated with increased levels of intracellular phosphorylation of both compounds. In this study, /researchers/ demonstrated the combinations of TFV+FTC, TFV+EFV, FTC+EFV, and TFV+FTC+EFV synergistically inhibit HIV replication in cell culture and synergistically inhibit HIV-1 reverse transcriptase (RT) catalyzed DNA synthesis in biochemical assays. Several different methods were applied to define synergy including median-effect analysis, MacSynergyII and quantitative isobologram analysis. We demonstrated that the enhanced formation of dead-end complexes (DEC) by HIV-1 RT and TFV-terminated DNA in the presence of FTC-triphosphate (TP) could contribute to the synergy observed for the combination of TFV+FTC, possibly through reduced terminal NRTI excision. Furthermore, /researchers/ showed that EFV facilitated efficient formation of stable, DEC-like complexes by TFV- or FTC-monophosphate (MP)-terminated DNA and this can contribute to the synergistic inhibition of HIV-1 RT by TFV-diphosphate (DP)+EFV and FTC-TP+EFV combinations. This study demonstrated a clear correlation between the synergistic antiviral activities of TFV+FTC, TFV+EFV, FTC+EFV, and TFV+FTC+EFV combinations and synergistic HIV-1 RT inhibition at the enzymatic level. /Researchers/ propose the molecular mechanisms for the TFV+FTC+EFV synergy to be a combination of increased levels of the active metabolites TFV-DP and FTC-TP and enhanced DEC formation by a chain-terminated DNA and HIV-1 RT in the presence of the second and the third drug in the combination. This study furthers the understanding of the longstanding observations of synergistic anti-HIV-1 effects of many NRTI+NNRTI and certain NRTI+NRTI combinations in cell culture, and provides biochemical evidence that combinations of anti-HIV agents can increase the intracellular drug efficacy, without increasing the extracellular drug concentrations.

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Drug Warnings
/BOXED WARNING/ WARNING: LACTIC ACIDOSIS/SEVERE HEPATOMEGALY WITH STEATOSIS and POST TREATMENT EXACERBATION OF HEPATITIS. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs, including Viread, in combination with other antiretrovirals. Severe acute exacerbations of hepatitis have been reported in HBV-infected patients who have discontinued anti-hepatitis B therapy, including Viread. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue anti-hepatitis B therapy, including Viread. If appropriate, resumption of anti-hepatitis B therapy may be warranted.
Lactic acidosis and severe hepatomegaly with steatosis (sometimes fatal) have been reported rarely in patients receiving nucleoside reverse transcriptase inhibitors alone or in conjunction with other antiretroviral agents. Most reported cases have involved women; obesity and long-term therapy with a nucleoside reverse transcriptase inhibitor also may be risk factors. Caution should be observed when nucleoside analogs are used in patients with known risk factors for liver disease; however, lactic acidosis and severe hepatomegaly with steatosis have been reported in patients with no known risk factors. Tenofovir therapy should be interrupted in any patient with clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (signs of hepatotoxicity include hepatomegaly and steatosis even in the absence of marked increases in serum aminotransferase concentrations).
Redistribution or accumulation of body fat, including central obesity, dorsocervical fat enlargement (buffalo hump), peripheral wasting, facial wasting, breast enlargement, and general cushingoid appearance, has been reported with antiretroviral therapy.
The most common adverse effects in HIV-infected patients receiving tenofovir disoproxil fumarate are rash, diarrhea, headache, pain, depression, asthenia, and nausea. The most common adverse effect in HIV-infected patients receiving tenofovir disoproxil fumarate is nausea.
For more Drug Warnings (Complete) data for TENOFOVIR DISOPROXIL FUMARATE (14 total), please visit the HSDB record page.

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Pharmacodynamics
This drug prevents viral DNA chain elongation through inhibition of enzymes necessary for host cell infection viral replication in HIV-1 and Hepatitis B infections,. **In vitro effects** The antiviral activity of tenofovir against in laboratory and clinical isolates of HIV-1 was studied in lymphoblastoid cell lines, primary monocyte/macrophage cells, in addition to peripheral blood lymphocytes. The EC50 (50% effective concentration) values of tenofovir against HIV-1 virus ranged between 0.04 μM to 8.5 μM. **Combination of tenofovir disoproxil with other drugs** In drug combination studies of tenofovir with nucleoside reverse transcriptase inhibitors (abacavir, didanosine, lamivudine, stavudine, zalcitabine, zidovudine), non-nucleoside reverse transcriptase inhibitors (delavirdine, efavirenz, nevirapine), and protease inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, saquinavir), additive and synergistic effects were seen. Tenofovir demonstrated antiviral activities in cell cultures against HIV-1.

C19H30N5O10P

519.4478

519.173

C, 43.93; H, 5.82; N, 13.48; O, 30.80; P, 5.96

201341-05-1

Tenofovir Disoproxil fumarate;202138-50-9; 201341-05-1 (free) ; 147127-20-6 (Tenofovir); 206184-49-8 (hydrate); 379270-37-8 (alafenamide); 1571075-19-8 (aspartate)

5481350

White to off-white solid powder

1.5±0.1 g/cm3

642.7±65.0 °C at 760 mmHg

113-115

342.5±34.3 °C

0.0±1.9 mmHg at 25°C

1.578

2.04

1

14

17

35

698

1

P(C([H])([H])O[C@]([H])(C([H])([H])[H])C([H])([H])N1C([H])=NC2=C(N([H])[H])N=C([H])N=C12)(=O)(OC([H])([H])OC(=O)OC([H])(C([H])([H])[H])C([H])([H])[H])OC([H])([H])OC(=O)OC([H])(C([H])([H])[H])C([H])([H])[H]

JFVZFKDSXNQEJW-CQSZACIVSA-N

InChI=1S/C19H30N5O10P/c1-12(2)33-18(25)28-9-31-35(27,32-10-29-19(26)34-13(3)4)11-30-14(5)6-24-8-23-15-16(20)21-7-22-17(15)24/h7-8,12-14H,6,9-11H2,1-5H3,(H2,20,21,22)/t14-/m1/s1

[[(2R)-1-(6-aminopurin-9-yl)propan-2-yl]oxymethyl-(propan-2-yloxycarbonyloxymethoxy)phosphoryl]oxymethyl propan-2-yl carbonate

GS 4331; GS-4331; GS4331; Bis(POC)PMPA; PMPA prodrug; 9-((R)-2-((Bis(((isopropoxycarbonyl)oxy)methoxy)phosphinyl)methoxy)propyl)adenine; (r)-bis(poc)pmpa; bis-POC-PMPA; tenofovir bis(isopropyloxycarbonyloxymethyl) ester; Viread.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 38 mg/mL (~73.16 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.00 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (4.00 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (4.00 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)