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New Drug Hope For HIV Patients For Whom Treatment No Longer Works

Article Date: 28 Feb 2007

The drug company Pfizer says that its latest HIV drug maraviroc doubles the number of people with undetectable levels of HIV compared to the current treatments.

The company revealed half-year results of two advanced trials of maraviroc on patients for whom treatment no longer works at the 14th Conference on Retroviruses and Opportunistic Infections (CROI 2007) in Los Angeles.

Maraviroc belongs to a class of drugs known as CCR5 inhibitors. They stop CCR5 receptors in the immune system's vital T-cells from letting in the HIV virus. If the virus can't get into T-cells it can't reproduce.

The CCR5 receptor is the first point of entry for the virus, which eventually tries to get in via another "keyhole", the CXCR4 receptor.

It is estimated that about 80 per cent of newly infected HIV carriers have the version of the virus that tries to gain entry via the CCR5 receptor. Also, 50 per cent of patients who have had treatment for some time also carry this version.

According to Pfizer's executive responsible for the drug trials, Dr Howard Mayer, patients treated with the drug are not showing increased infection risks or signs of the liver damage that occurs with other CCR5 inhibitors in development; there is no evidence of elevated risk of malignancies such as lymphoma.

One trial is testing the drug on 601 patients and the other is testing it on 475 patients.

In both cases maraviroc is showing similar effects, effectively to almost double the number of patients with a lower than 400 copies of HIV detectable per ml of blood compared to those on other drugs alone.

This level was achieved with a twice daily dose of maraviroc, but even a once daily dose had a much greater success rate than other drugs alone.

HIV is very good at mutating into forms that become drug resistant, and people who have been on HIV drugs for a while can stop responding to treatment.

However, CCR5 inhibitors are not strictly anti-HIV drugs, they do not attack the virus itself, but stop it gaining entry to its host cells. Mayer said that this means the HIV virus would be less likely to mutate in response to these kinds of drugs.

HIV/AIDS experts welcome this news because there are not many treatments available for people who have become unresponsive to the current HIV drugs.

According the US Centers for Disease Control and Prevention (CDC) there are over 1 million Americans living with HIV/AIDS, with 40,000 new infections occurring in the US every year.

Written by: Catharine Paddock
Writer: Medical News Today

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