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Active Substance: fosamprenavir calcium
Common Name: fosamprenavir
ATC Code: J05AE07
Marketing Authorisation Holder: ViiV Healthcare UK Limited  
Active Substance: fosamprenavir calcium
Status: Authorised
Authorisation Date: 2004-07-12
Therapeutic Area: HIV Infections
Pharmacotherapeutic Group: Antivirals for systemic use

Therapeutic Indication

Telzir in combination with low-dose ritonavir is indicated for the treatment of human-immunodeficiency-virus-type-1-infected adults, adolescents and children of six years and above in combination with other antiretroviral medicinal products.

In moderately antiretroviral-experienced adults, Telzir in combination with low-dose ritonavir has not been shown to be as effective as lopinavir / ritonavir. No comparative studies have been undertaken in children or adolescents.

In heavily pretreated patients, the use of Telzir in combination with low-dose ritonavir has not been sufficiently studied.

In protease-inhibitor-experienced patients, the choice of Telzir should be based on individual viral resistance testing and treatment history.

What is Telzir?

Telzir is a medicine that contains the active substance fosamprenavir. It is available as pink, capsule-shaped tablets (700 mg) and as an oral suspension (50 mg/ml).

What is Telzir used for?

Telzir is an antiviral medicine. It is used in combination with ritonavir (another antiviral medicine) and other antiviral medicines to treat patients aged six years or above who are infected with human immunodeficiency virus type 1 (HIV-1), a virus that causes acquired immune deficiency syndrome (AIDS). In patients who have already taken medicines belonging to the same class as Telzir (protease inhibitors), doctors should prescribe Telzir only after they have looked at the antiviral medicines the patient has taken before and the likelihood that the virus will respond to the medicine.

The medicine can only be obtained with a prescription.

How is Telzir used?

Treatment with Telzir should be started by a doctor who has experience in the management of HIV infection.

The recommended dose of Telzir for adults (aged 18 years and above) and for children (aged between six and 18 years) weighing more than 39 kg is 700 mg twice a day. In children who weigh between 25 and 39 kg, the dose depends on body weight. There is no recommended dose for children below 25 kg.

Telzir tablets can be taken with or without food. The oral suspension should be taken without food on an empty stomach in adults, but in children it should be taken with food in order to hide the taste and help them stick to treatment. In adults, each dose of Telzir must be given with 100 mg ritonavir, twice a day. In children, the ritonavir dose depends on body weight.

Adults with liver problems should take a reduced dose and be closely monitored for safety and the response to treatment. For more information, see the package leaflet.

How does Telzir work?

The active substance in Telzir, fosamprenavir, is a ‘prodrug’ of the protease inhibitor amprenavir, which means that it is converted into amprenavir in the body. 

Amprenavir has been approved in the European Union (EU) since October 2000 as Agenerase. Amprenavir blocks an enzyme called protease, which is involved in the reproduction of HIV. When the enzyme is blocked, the virus does not reproduce normally, slowing down the spread of infection.

Ritonavir is another protease inhibitor that is used as a ‘booster’. It slows down the rate at which amprenavir is broken down, increasing the levels of amprenavir in the blood. This allows a lower dose of Telzir to be used for the same antiviral effect. Telzir, taken in combination with other antiviral medicines, reduces the amount of HIV in the blood and keeps it at a low level. Telzir does not cure HIV infection or AIDS, but it may delay the damage to the immune system and the development of infections and diseases associated with AIDS.

How has Telzir been studied?

Telzir has been studied in three main studies involving 1,862 adults infected with HIV. The first compared ritonavir-boosted Telzir with nelfinavir (another protease inhibitor) in treatment-naïve adults (who had previously taken treatment for HIV infection for no longer than four weeks). The other two studies compared Telzir with lopinavir (another protease inhibitor), both of which were boosted with ritonavir. In one of these studies, the patients were treatment-naïve, but in the other study, they had taken HIV treatment including protease inhibitors before. In all three studies, the patients also took two reverse-transcriptase inhibitors (another type of antiviral medicine). The main measure of effectiveness was the level of HIV in the blood (viral load) in the first 48 weeks of treatment.

The effectiveness of Telzir, in combination with other antiviral medicines, has also been assessed in one main study including 57 HIV-infected children aged between two and 18 years.

What benefit has Telzir shown during the studies?

In the studies of treatment-naïve adults, ritonavir-boosted Telzir was as effective as the comparator medicines, but it was less effective in treatment-experienced adults. After 48 weeks, 69% of the treatment-naïve adults taking ritonavir-boosted Telzir (221 out of 322) and 68% of those taking nelfinavir (221 out of 322) had viral loads below 400 copies/ml. Similar results were seen in the study comparing Telzir with lopinavir, with around three-quarters of both groups of patients having viral loads below 400 copies/ml. In the study of treatment-experienced patients, the patients taking lopinavir had larger reductions in viral loads over the first 48 weeks.

A similar benefit has also been seen in children receiving Telzir. However, there were too few children aged below six years to support the use of Telzir in this age group.

What is the risk associated with Telzir?

The most common side effects in adults taking Telzir (seen in more than 1 patient in 10) are diarrhoea and increases in the levels of triglycerides (a type of fat) in the blood. Similar side effects are seen in children. For the full list of all side effects reported with Telzir, see the package leaflet.

Telzir should not be used in people who may be hypersensitive (allergic) to fosamprenavir, amprenavir, any of the other ingredients, or ritonavir. Telzir must not be used in patients who are taking rifampicin (used to treat tuberculosis), St John's wort (a herbal preparation used to treat depression), or medicines that are broken down in the same way as Telzir or ritonavir and are harmful at high levels in the blood. See the package leaflet for the full list of these medicines.

As Telzir is converted into amprenavir in the body, it must not be given at the same time as other medicines containing amprenavir. Caution is also needed by patients taking Telzir at the same time as other medicines. See the package leaflet for full details.

As with other anti-HIV medicines, patients taking Telzir may be at risk of lipodystrophy (changes in the distribution of body fat), osteonecrosis (death of bone tissue) or immune reactivation syndrome (symptoms of infection caused by the recovering immune system). Patients who have problems with their liver (including hepatitis-B or -C infection) may be at an elevated risk of liver damage when taking Telzir.

Why has Telzir been approved?

The Committee for Medicinal Products for Human Use (CHMP) concluded that Telzir, which contains a prodrug of amprenavir, provides an advantage for patients, as the number of tablets they need to take is reduced when compared to the number of Agenerase capsules that they would need to take for the same dose of amprenavir. The Committee decided that Telzir’s benefits are greater than its risks for the treatment of HIV-1-infected adults and children of six years and above in combination with other antiretroviral medicinal products. The Committee noted that, in adults with moderate levels of exposure to antiviral medicines for the treatment of HIV infection, ritonavir-boosted Telzir has not been shown to be as effective as ritonavir-boosted lopinavir. In heavily pretreated patients, the use of ritonavir-boosted Telzir has not been studied sufficiently. In addition, no comparative studies have been carried out in children. The Committee recommended that Telzir be given marketing authorisation.

Other information about Telzir

The European Commission granted a marketing authorisation valid throughout the EU for Telzir to Glaxo Group Ltd on 12 July 2004. The marketing authorisation was renewed on 12 July 2009.

Source: European Medicines Agency

Disclaimer: Every effort has been made to ensure that the information provided here is accurate, up-to-date and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This information has been compiled for use by healthcare practitioners and consumers in the United States. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate that the drug or combination is safe, effective or appropriate for any given patient. If you have questions about the substances you are taking, check with your doctor, nurse or pharmacist.