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new drugs that block the ccr5 receptor?

Jun 27, 2008

Hi Dr. Bob,

You are the most amazing expert on this site -not only sexy but by far- the most compassionate. i wish i could see you in person to squeeze you tightly and thank you. now, on to my question darling. My dearest doctor Bob -do you think with David Ho announcing how some people cant get hiv due them not having ccr5 receptors - this might present a new line of hiv medications to treat us treatment experienced patients. Please make me fabulous with your words of wisdom. MUAAAH!!!

Davi ... Wondering the streets of NYC looking for you to come visit :-))))

Response from Dr. Frascino

Hi Davi,

Actually we are one step ahead of you. A novel new anti-HIV drug therapy that inhibits CCR5 receptors has already been developed and FDA approved. It's called maraviroc. (See below.) However, before you start doing naked cartwheels around Times Square, I also need to point out, even though we may be one step ahead of you, the virus is still one step ahead of us! As it turns out, CCR5 receptors aren't the only way all HIV virus gets into our cells. Some virus uses an alternative receptor called CXCR4. Consequently, even if your CCR5 receptors are blocked (or not there), you are not immune to the dangers of HIV! Tricky little bastard, isn't it??!?

As for wandering the streets of NYC looking for me, I'm there quite frequently. Generally you can find me at Lincoln Center, Carnegie Hall, Broadway or Chelsea. Thanks for the warning about the tight squeeze! I'll look forward to it and try to remember not to carry anything breakable in my pockets.

Dr. Bob

Approval of Maraviroc

August 6, 2007

On August 6, 2007, the Food and Drug Administration (FDA) approved Selzentry (maraviroc) 150 mg and 300 mg tablets, a CCR5 co-receptor antagonist used in combination with other antiretroviral products for the treatment of adults infected with CCR5-tropic HIV-1.

Maraviroc received a priority review by the FDA and is the first drug approved in the new class of anti-HIV medications called CCR-5 co-receptor antagonist.

Rather than fighting HIV inside white blood cells, like most antiretrovirals used to treat infection with HIV, maraviroc prevents the virus from entering uninfected cells by blocking the predominant route of entry, the CCR5 co-receptor, a protein on the surface of immune cells affected by HIV. Among patients who have previously received HIV medications, approximately 50 percent to 60 percent have circulating CCR5-tropic HIV.

Maraviroc, in combination with other antiretroviral agents, is indicated for treatment-experienced adult patients infected with only CCR5-tropic HIV-1 detectable virus, who have evidence of viral replication and HIV-1 strains resistant to multiple antiretroviral agents.

The approval of maraviroc is based on analyses of plasma HIV-1 RNA levels in two controlled studies each of 24 weeks duration with over 1000 clinical trial participants of which 840 received maraviroc. Both studies were conducted in clinically advanced, 3-class antiretroviral (nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitor, protease inhibitors or fusion inhibitor, specifically enfuvirtide) treatment-experienced adults with evidence of HIV-1 replication despite ongoing antiretroviral therapy.

The following points should be considered when initiating therapy with maraviroc:

Tropism testing and treatment history should guide the use of maraviroc. Use of maraviroc is not recommended in patients with dual/mixed or CXCR4-tropic HIV-1 as efficacy was not demonstrated in a phase 2 study of this patient group. The safety and efficacy of maraviroc have not been established in treatment-naive adult patients or pediatric patients. The recommended dose of maraviroc differs based on concomitant medications due to drug interactions (See attached PDF label, Section 2, Dosage and Administration). Maraviroc can be taken with or without food.

The product label includes a boxed warning about liver toxicity (hepatoxicity) and a statement in the Warnings/Precautions section about the possibility of increased risk for cardiovascular events such as heart attack or symptomatic postural hypotension (dizziness upon quickly standing). The most common adverse events reported with maraviroc were cough, fever, upper respiratory tract infections, rash, musculoskeletal symptoms, abdominal pain, and dizziness.

Maraviroc has not been tested or studied in pregnant women. The FDA recommends HIV positive women should not breast feed, whether or not they are on antiretroviral medications.

Maraviroc is distributed by Pfizer Inc., of New York and is available as 150 mg or 300 mg tablets.

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