Fostemsavir
HIV entry inhibitors
HIV entry inhibitors
An oral HIV attachment inhibitor for heavily treated adults with multidrug-resistant HIV. Its active form, temsavir, binds the viral gp120.
Quick facts
- Group
- HIV entry inhibitors
- Target
- HIV-1 envelope glycoprotein gp120
- Used for
- HIV-1 infection
- Key effects
- Nausea
- Monitor
- HIV viral load · ECG when QT risk factors exist
- ATC
- J05AX29
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows temsavir (BMS-626529), the active form of fostemsavir, bound to the HIV-1 envelope trimer.
Fostemsavir is a phosphate prodrug that is quickly converted to temsavir. Temsavir binds gp120 on the viral envelope, so the virus cannot attach to the CD4 receptor and enter the cell. Because the target is new, it keeps activity against virus resistant to other classes. Natural gp120 polymorphisms can reduce susceptibility.
- Fostemsavir is converted to temsavir
- Temsavir binds viral gp120
- gp120 cannot attach to CD4
- HIV cannot enter the T cell
Indications
- HIV-1 infection in heavily treatment-experienced adults with multidrug resistance, with other antiretrovirals HIV infection and AIDS →
Adverse effects
Common
- Nausea
Contraindications
- Strong CYP3A inducers such as rifampicin
- Hypersensitivity to fostemsavir
Key interactions
- Rifampicin and other strong CYP3A inducers
- Lower temsavir and cause treatment failure; not combined
- Statins carried by OATP1B1/3
- Temsavir inhibits these transporters and raises statin levels; avoided or chosen carefully
- QT-prolonging drugs
- Added QT risk
What is monitored
- HIV viral load
- ECG when QT risk factors exist
- Liver enzymes, especially with viral hepatitis
Administration and safety
- Oral, twice a day, with or without food
- Tablets are swallowed whole, not split, chewed or crushed
Pregnancy and breastfeeding
Human data are limited; benefit and risk are weighed with the HIV team.
Nursing care
- Check heart history and other QT-prolonging drugs
- Teach to report fainting, palpitations or dizziness
- Teach to report new signs of infection after starting
- Reinforce adherence: options are few in multidrug resistance
Pharmacokinetics
- Absorption
- Oral tablet; food and stomach pH have little effect
- Metabolism
- Temsavir is cleared by esterases and CYP3A4; a substrate of P-gp
- Elimination
- Partly unchanged in the urine; no adjustment for kidney or liver disease
- Half-life
- Short, so it is taken twice a day
Test yourself
Think of the answer, then tap the question to see it.
What is the active form of fostemsavir?
Temsavir.
Which viral protein does temsavir bind?
gp120, preventing attachment to CD4.
Which antimycobacterial must not be combined with fostemsavir?
Rifampicin, a strong CYP3A inducer.
Connections
← Back to the class: HIV entry inhibitors
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Fostemsavir: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Crystal Structure of HIV-1 BG505 SOSIP.664 Prefusion Env Trimer Bound to Small Molecule HIV-1 Entry Inhibitor BMS-626529 in Complex with Human Antibodies PGT122 and 35O22 at 3.8 Angstrom (RCSB Protein Data Bank, 2017); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.