New drug profile: Maraviroc: it's different, it's strong, and it's almost here.
Maraviroc (or Celsentri) is an HIV medication, the first of its kind. Maraviroc doesn't block HIV directly; instead, maraviroc binds to a human protein known as CCR5. This is one of the proteins HIV uses to enter human T cells. By binding to CCR5, maraviroc keeps HIV from infecting T cells.
Who's it for?
Maraviroc, in combination with other HIV meds, is indicated for treatment-experienced adults infected with CCR5-tropic (attracted to something specified) HIV.
What does that mean?
In order for HIV to infect a T cell, the virus must first latch onto a receptor (nerve ending), called CD4, on the cell's surface. Researchers have known for a long time that HIV needs a second receptor on the CD4 receptor to enter the T cell. The others receptors that it uses are CCR5 and CXCR4, with CCR5 being the most common. The new drug, maraviroc, has the ability to block HIV that uses CCR5, but not HIV that uses CXCR4. This is the first time that a treatment for HIV is targeting a function of the cells in the body, not the virus itself.
How do I know what kind of virus I have?
Your doctor can order a test called Trofile to see whether you have virus that uses CCR5, CXCR4 or both. This test is expensive and may take more than a month to complete. Some providers may not offer it. Also, if you have a low level of CXCR4 virus, the test can't detect it.
What's the dose?
The recommended initial dose is 300 mg twice daily. But your dose might be decreased to 150 mg twice daily, or increased to 600 mg twice daily, depending on the other medications you're taking.
Do I have to take maraviroc with food?
You can take it with or without food, as you prefer. (Of course, this might not be true of all your other medications.)
When does maraviroc become available?
The Food and Drug Administration's Antiviral Advisory (FDA) Committee voted 12 to 0 on April 24, 2007 to approve maraviroc. The drug will probably be available in June 2007.
What did the studies show?
The two registrational studies were known as MOTIVATE I and MOTIVATE II. (MOTIVATE stands for Maraviroc + Optimized Therapy In Viremic Antiretroviral Treatment Experienced Patients.) The studies were also known by their numbers, 1027 and 1028.
In both studies, nearly twice as many patients treated with maraviroc reached undetectable viral loads (less than 50 copies) compared to those receiving placebo. Patients treated with maraviroc also bad greater increases in their T-cell counts than patients receiving placebo.
What are the risks?
In the studies, thrush, herpes simplex infections, and upper respiratory tract infections were more common among those receiving maraviroc than among those receiving placebo.
As noted above, maraviroc doesn't block the virus; it blocks a natural human protein, CCR5. Some worry about the long-term effects of blocking a natural protein, one that may play an important role in the immune system. That's a reasonable concern. But keep this in mind: some people are born without the ability to make CCR5, and they live healthy, normal lives.
Others worry that by blocking CCR5, CXCR4-using virus will emerge. CXCR4-using virus has been associated with rapid HIV disease progression. But in the MOTIVATE studies, when CXCR4-using virus emerged in people taking maraviroc, it did not appear to damage their immune systems. In fact, some of these people had increases in their T-cell counts even though their viral loads did not decline.
Who makes maraviroc?
Does Pfizer have any plans to study maraviroc in treatment-naive patients?
Yes. In fact, that study is already underway.
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|Publication:||HIV Treatment: ALERTS!|
|Article Type:||Drug overview|
|Date:||Jun 1, 2007|
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