New HIV Drug Will Benefit Those with Resistant Virus

Currently there are 27 HIV medications used in various combinations to treat HIV and AIDS. While it has been proven that these HIV medications are very effective there is a growing concern that as time goes by more and more people are becoming resistant to the drugs currently on the market. Drug manufacturer Pfizer is about to ask for FDA approval for its new HIV medication Maraviroc that will greatly benefit those patients currently resistant to medications, giving them another viable choice in the fight against their disease.

What is Resistance?
Simply put, resistance means that certain medicines lose their ability to fight HIV. Some drugs become less effective while others can become completely ineffective. As cells reproduce, they make copy after copy of themselves, growing in number with each replication. Sometimes, small errors in one cell will be passed on to the next copy. After time, cells that contain these small errors become larger in number. These small changes in the cell's genetic make-up are called mutations. It's these mutations that cause resistance to HIV medications.

A Complete Guide to Resistance and Resistance Testing

Will Maraviroc Help with Resistance?
The troubling thing about resistance is that often, resistance to one medication means resistance to an entire class of medications. The new drug Maraviroc is the first drug from the new class of HIV medications called CCR5 entry inhibitors. Because it is a new class, people living with HIV will not have resistance to that class because they have not been exposed to any drugs from the class previously.

The 5 Classes of HIV Medications

What are CCR5 Entry Inhibitors?
HIV medications classes are named for the step in the HIV life cycle that they interrupt. For instance, protease inhibitors got their name because they stop HIV replication by preventing the enzyme protease from cutting the virus into the shorter pieces that it needs to make copies of itself in newly infected cells. CCR5 is a receptor site on the human T-cell that HIV uses to bind to the cell allowing it to enter and begin replication. Think of CCR5 as the lock and the receptor on HIV as the key. CCR5 entry inhibitors change the molecular shape of CCR5 (the lock) meaning the HIV binding site (gp120 - the key) no longer can bind to the T-cell. In other words the key no longer fits the lock. When the key doesn't fit it won't open the lock. Being unable to bind with the T-cell means that HIV life cycle can't continue.

The Steps of the HIV Life Cycle

Step-by-Step Illustrations of the HIV Life Cycle

What Makes CCR5 Entry Inhibitors so Different?
Unlike currently available HIV medications which act on HIV directly, CCR5 entry inhibitors are the first class of drugs that act on the human T-cell, changing it in such a way that HIV is unable to bind and therefore continue the replication process. Simply put, CCR5 entry inhibitors work directly on the body's immune system, a novel approach but one that does carry some risk.

Parts of Your Immune System

What is a T-cell (CD4 cell)?

The Problem With CCR5 Entry Inhibitors
Because CCR5 entry inhibitors work on human T-cells the possibility of side effects still exists. In fact, two other companies developing their own CCR5 drugs have stopped trials because of safety issues, specifically liver toxicity and rebounding viral load values. Thankfully Maraviroc in extensive clinical trials has shown no such problems and in fact has a very encouraging drug safety profile.

The Three Phases of Clinical Trials

When Will Maraviroc Be Available?
Pfizer, the maker of Maraviroc will seek FDA approval sometime toward the end of 2006. Depending on the approval process, Maraviroc could be in your local pharmacies by mid 2007.