Fostemsavir is an HIV-1 gp120-directed attachment inhibitor indicated for the treatment of adult patients with HIV-1 infection that is resistant to multiple drugs.

How to Use Fostemsavir

Dosing Regimen

Dose: 600 mg (1 tablet) per dose, taken orally twice daily.

Administration method: The tablet must be swallowed whole; do not chew, crush, or split it.

Effect of food: The drug can be taken with food or on an empty stomach. However, a high-fat meal may increase drug absorption (with an approximate 81% increase in AUC). It is recommended to maintain consistent medication-taking habits (i.e., consistently with or without food) to avoid fluctuations in plasma drug concentration.

Precautions for Fostemsavir Dose Adjustment

Contraindicated Conditions

Contraindicated in patients with a known allergy to fostemsavir or any of its components.

Concomitant use with strong CYP3A inducers (e.g., rifampicin, carbamazepine, St. John’s wort, etc.) is strictly prohibited. Such combinations can significantly reduce the plasma concentration of temsavir (the active component of fostemsavir), leading to treatment failure.

Drugs Requiring Cautious Concomitant Use

Drugs that prolong the QT interval: Fostemsavir may prolong the QT interval at supratherapeutic doses (2400 mg). When used concomitantly with other drugs that cause QT prolongation, close monitoring of the electrocardiogram (ECG) is required.

Statins: Dose adjustments of statins (e.g., rosuvastatin, atorvastatin) may be necessary to avoid adverse reactions.

Oral contraceptives: The daily dose of contraceptives containing ethinyl estradiol should not exceed 30 mcg to reduce the risk of thrombosis.

Fostemsavir Use in Special Populations

Patients with Hepatic or Renal Impairment

Hepatic impairment: No dose adjustment is required for patients with mild to severe hepatic impairment (Child-Pugh Class A/B/C). However, monitoring of transaminases is necessary, especially in patients coinfected with hepatitis B virus (HBV) or hepatitis C virus (HCV).

Renal impairment: No dose adjustment is required, including for patients with end-stage renal disease undergoing hemodialysis. Hemodialysis only removes approximately 12.3% of the drug.

Pregnancy and Lactation

Pregnancy: Existing animal data do not show teratogenicity, but human data are limited.

Lactation: HIV-infected patients should avoid breastfeeding to prevent virus transmission and potential adverse effects of the drug on infants.

Elderly Patients

Elderly patients (≥ 65 years old) may be more prone to QT prolongation due to comorbidities or drug interactions, requiring individualized assessment.

Children and Adolescents

The efficacy of fostemsavir in patients under 18 years of age has not been established, and its use is not recommended in this population.