Fostemsavir is an HIV-1 attachment inhibitor that provides a new treatment option for treatment-experienced adult patients with multidrug-resistant HIV-1 infection. The following briefly describes it from three aspects: mechanism of action, indicated population, and key points of medication.

I. Mechanism of Action

1.Prodrug and Active Component

Fostemsavir is a prodrug that is metabolized in the body to the active component Temsavir.

The active component acts directly on the virus rather than on host cells, with a unique target.

2.Blocking Viral Attachment

Temsavir binds to the HIV-1 envelope glycoprotein gp120, blocking viral attachment to receptors on the surface of host CD4+ T cells.

Once attachment is blocked, the virus cannot enter the cell, and the replication cycle is interrupted at an early stage.

3.Activity Against Resistant Strains

Its target differs from that of reverse transcriptase, protease, and integrase inhibitors, so it retains activity against multidrug-resistant strains.

Combined with drugs of other mechanisms, it can form effective regimens and reduce the risk of cross-resistance.

II. Indicated Population

1.Treatment-Experienced Patients with Multidrug Resistance

It is suitable for adult patients with prior failure of multiple treatment lines and resistance to multiple classes of antiretroviral drugs.

It must be used in combination with other effective antiretroviral drugs and must not be used as monotherapy.

2.Patients with Limited Treatment Options

It provides a new drug class option for patients with severe resistance and limited available regimens.

It helps construct combination regimens capable of suppressing viral replication.

III. Key Points of Medication and Precautions

1.Dosage and Administration

The recommended dose is one tablet twice daily, at an interval of approximately 12 hours.

It may be taken with or without food and should be swallowed whole, not chewed or crushed.

2.Management of Missed Doses

Take it as soon as remembered; if the next dose is near, skip it and do not double the dose.

3.Contraindications and Interactions

Concomitant use with strong CYP3A4 inducers (such as rifampin, carbamazepine, phenytoin, and St. John's wort) is prohibited to avoid loss of efficacy.

It is contraindicated in patients with severe hepatic impairment (Child-Pugh Class C).

4.Monitoring and Adherence

Regular twice-daily dosing is key to maintaining viral suppression; repeated missed doses increase the risk of resistance.

Viral load, CD4 cell count, and hepatic function should be monitored regularly during treatment.