New & experimental HIV treatments

Fosamprenavir: US approves once-daily dose with less ritonavir boosting

Keith Alcorn
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A new once-daily dose of the protease inhibitor fosamprenavir, marketed in the United States as Lexiva, has been approved by the US Food and Drug Administration.

The new indication offers patients new to HIV treatment the option of taking fosamprenavir as a once daily dose of two 700mg tablets with a single booster dose of 100mg of ritonavir. This represents a halving of the ritonavir booster dose, and says manufacturer GlaxoSmithKline, it should result in better toleration of fosamprenavir treatment.

A study in healthy volunteers showed that while the lower ritonavir dose did not result in significantly lower fosamprenavir levels, volunteers who received the 100mg ritonavir dose experienced fewer side-effects.

Glossary

boosting agent

Booster drugs are used to ‘boost’ the effects of protease inhibitors and some other antiretrovirals. Adding a small dose of a booster drug to an antiretroviral makes the liver break down the primary drug more slowly, which means that it stays in the body for longer times or at higher levels. Without the boosting agent, the prescribed dose of the primary drug would be ineffective.

treatment-naive

A person who has never taken treatment for a condition.

naive

In HIV, an individual who is ‘treatment naive’ has never taken anti-HIV treatment before.

Food and Drug Administration (FDA)

Regulatory agency that evaluates and approves medicines and medical devices for safety and efficacy in the United States. The FDA regulates over-the-counter and prescription drugs, including generic drugs. The European Medicines Agency performs a similar role in the European Union.

Once-daily dosing of fosamprenavir is not recommended for protease inhibitor-experienced patients, because of a concern that lower trough levels that occur with once-daily dosing will not be enough to overcome any existing resistance to protease inhibitors. Instead a twice daily dose of one 700mg tablet and 100mg of ritonavir is recommended.

In Europe fosamprenavir is marketed as Telzir and is licensed for use in both treatment-naïve and tretament-experienced patients at a dose of 700mg twice daily plus 100mg of ritonavir twice daily.

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