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CXCR4 ansd CCR5 HIV Drugs in Development
  AMD11070 is an experimental drug (not approved by the U.S. Food and Drug Administration), and in early research studies. It is a member of a new class of drugs, called CXCR4 receptor blockers, that block one of the ways HIV enters T cells. HIV needs to get into the T cells to make more copies of itself. Whether or not thisdrug is successfully developed the explanation of the difference between drugs targeting CCR5 and CXCR4 is of interest. Several drugs targeting CCR5 are in development and in studies in HIV-infected patients. These drugs had updates at the 11th Retrovirus Conference, and the new information about them can be read on the NATAP website in the Retrovirus Conference Update reports.
To enter a T cell, HIV needs to grab onto two parts of the cell (like doors) at the same time. One "door" is called CD4. The other "door" is either CXCR4 or CCR5. Viruses that use the CXCR4 "door" are called X4 HIV, and viruses that use the CCR5 "door" are called R5 HIV.
Most people with HIV have mostly R5 HIV. People with mostly X4 HIV sometimes have faster disease progression. AMD11070 is made to block the CXCR4 "door" so X4 virus cannot get into the T cells. AMD11070 cannot stop R5 HIV from entering the T cell.
A virus that is X4 tropic HIV = X4 HIV -- means it uses the CXCR4 "door". (Tropism means having an affinity for, or being attracted to.)
If the "door" is blocked, the virus cannot get into the T cell. CCR5 is the more commonly used "door".
People with X4-tropic virus sometimes have disease that progresses faster. Eventually, if these new drugs work, they may be combined so that both the X4 and R5 receptors are blocked.
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