Tenofovir Alafenamide (TAF) is a nucleotide reverse transcriptase inhibitor and a phosphoramidate prodrug of tenofovir. It is an important antiviral active pharmaceutical ingredient used in pharmaceutical formulations for HIV-1 infection and chronic hepatitis B virus (HBV) infection, depending on the approved finished-product formulation.
Tenofovir alafenamide is also known by the development code GS-7340. FDA's substance database identifies Tenofovir Alafenamide with the UNII EL9943AG5J, while PubChem identifies its CAS number as 379270-37-8, molecular formula as C21H29N6O5P, and molecular weight as 476.5 g/mol.
TAF is designed to deliver the active tenofovir moiety efficiently inside cells. Following intracellular activation, it forms tenofovir diphosphate, which inhibits viral reverse transcriptase and HBV polymerase and interferes with viral DNA synthesis.
| Parameter | Value |
|---|---|
| Product Name | Tenofovir Alafenamide |
| Abbreviation | TAF |
| Development Code | GS-7340 |
| CAS No. | 379270-37-8 |
| FDA UNII | EL9943AG5J |
| Molecular Formula | C21H29N6O5P |
| Molecular Weight | 476.5 g/mol |
| Exact Mass | 476.19370504 Da |
| Therapeutic Class | Antiviral |
| Drug Class | Nucleotide Reverse Transcriptase Inhibitor |
| API Type | Small-Molecule Antiviral Prodrug |
The identity and numerical chemical data above are supported by FDA GSRS and PubChem.
This distinction is very important for your product page and CMS.
Tenofovir Alafenamide is the active-moiety/free-form substance with molecular weight 476.5 g/mol.
The pharmaceutical material used in products such as Vemlidy is Tenofovir Alafenamide Fumarate, which the FDA labeling describes as a hemifumarate with empirical formula:
C21H29N6O5P · ½(C4H4O4)
and formula weight 534.50. The FDA label describes the fumarate material as a white to off-white or tan powder with water solubility of 4.7 mg/mL at 20°C.
Therefore, 476.5 g/mol should not be entered as the molecular weight of Tenofovir Alafenamide Fumarate.
PubChem also separately records Tenofovir Alafenamide monofumarate, CAS 379270-38-9, molecular weight 592.5 g/mol, illustrating why the exact salt/stoichiometric representation needs to be confirmed for regulatory documentation.
For your website, if the actual commercial API you offer is Tenofovir Alafenamide Fumarate, the product should ideally have a separate page titled Tenofovir Alafenamide Fumarate API.
Tenofovir Alafenamide is an L-alanine derivative containing a phosphoramidate group and an adenine-containing nucleotide structure. It is chemically designed as a prodrug that improves intracellular delivery of tenofovir.
PubChem reports the molecular formula as C21H29N6O5P, molecular weight 476.5 g/mol, exact mass 476.19370504 Da, XLogP3-AA 1.9, and topological polar surface area 143 Ų. These physicochemical descriptors are useful for chemical identification but are not pharmaceutical release specifications.
TAF's prodrug structure contributes to its pharmacological properties and enables efficient delivery of the active nucleotide analogue into target cells.
Tenofovir Alafenamide itself is a prodrug. After entering cells, it is metabolically converted to tenofovir and subsequently phosphorylated to tenofovir diphosphate.
Tenofovir diphosphate competes with natural nucleotides during viral DNA synthesis. Incorporation into viral DNA results in termination of the growing DNA chain and inhibits viral replication.
This mechanism provides activity against HIV-1 and HBV, depending on the finished pharmaceutical formulation and approved indication.
Tenofovir Alafenamide API is used in the development and manufacture of antiviral pharmaceutical products.
Major applications include:
TAF is used in several fixed-dose combination products, where it is combined with other antiretroviral agents.
PubChem identifies TAF as an antiviral drug, prodrug and HIV-1 reverse transcriptase inhibitor and notes its use as the fumarate salt in combination therapy.
Tenofovir Alafenamide API requires comprehensive pharmaceutical quality control.
Typical analytical controls include:
A regulatory assessment of Tenofovir Alafenamide Fumarate reports API controls covering description, solubility, IR/HPLC/PXRD identification, loss on drying, residue on ignition, heavy metals, chiral purity, residual solvents, HPLC assay, related impurities and water content. The assessment states that the API specifications were established as in-house specifications under ICH Q3A rather than presenting them as a universal pharmacopoeial specification.
A separate regulatory assessment also identifies control of TAF fumarate particle size and reports a D(v,0.9) NMT 350 µm in-process control for the evaluated material.
Tenofovir Alafenamide is a chemically synthesized small-molecule API.
A pharmaceutical manufacturing process requires appropriate control of starting materials, reaction conditions, stereochemistry, purification, crystallization, residual solvents, related substances and final product quality.
For Tenofovir Alafenamide Fumarate, regulatory documentation confirms manufacture through conventional chemical synthesis and quality control according to in-house specifications and ICH Q3A principles.
Particular attention should be given to:
| Property | Value |
|---|---|
| Molecular Formula | C21H29N6O5P |
| Molecular Weight | 476.5 g/mol |
| Exact Mass | 476.19370504 Da |
| XLogP3-AA | 1.9 |
| Topological Polar Surface Area | 143 Ų |
| API Type | Small-molecule antiviral prodrug |
| Therapeutic Class | Antiviral |
These values refer to Tenofovir Alafenamide free form, not the fumarate salt.
For Tenofovir Alafenamide Fumarate, FDA documentation reports formula weight 534.50 and water solubility 4.7 mg/mL at 20°C.
Solubility should be stated according to the exact API form.
For Tenofovir Alafenamide Fumarate, the FDA reports:
Water solubility: 4.7 mg/mL at 20°C.
This value should not be transferred to the free-form Tenofovir Alafenamide without qualification.
Tenofovir Alafenamide should be stored and packaged according to the validated pharmaceutical API stability program.
TAF fumarate is sensitive to moisture, and regulatory documentation specifically identifies moisture sensitivity as an important material attribute.
A regulatory assessment reports a 24-month retest period for the evaluated Tenofovir Alafenamide Fumarate API when packed in a heat-sealed HMLDPE bag under nitrogen and stored in tight, light-resistant containers at below 25°C. This is a specific evaluated manufacturer's storage condition and should not automatically be presented as a universal requirement for every TAF API manufacturer.
A professional Tenofovir Alafenamide API manufacturer should provide appropriate documentation, including:
Tenofovir Alafenamide is an important antiviral API requiring careful control of chemical purity, stereochemical purity, related substances, moisture, solid-state characteristics and particle size.
A qualified Tenofovir Alafenamide API manufacturing program should combine validated analytical methods, controlled chemical synthesis, appropriate impurity control and consistent batch quality.
For pharmaceutical companies sourcing TAF API from India, it is particularly important to verify the exact chemical form, because Tenofovir Alafenamide and Tenofovir Alafenamide Fumarate do not have the same molecular formula, molecular weight or salt composition.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | NLT 99.0% |
| Loss on Drying | NMT 0.3% |
| Heavy Metals | NMT 10 ppm |
| Water Content | NMT 0.3% |
| Solubility | Form-dependent; TAF fumarate: 4.7 mg/mL in water at 20°C |