Treatment options for people with HIV have increased now that two new classes of drugs--integrase inhibitors and chemokine receptor blockers--have come to market. Medications in both of these new classes are available now, but you need to be careful in how you use them. The first integrase inhibitor, raltegravir (Isentress), works by blocking the 'integration' of HIV into the DNA of our CD4 cells. By doing this, it prevents HIV from taking over our immune cells and making more copies of itself. So far, studies show that this drug is powerful at reducing viral loads and increasing CD4 counts. Additionally, studies indicate that this drug is metabolically 'friendly,' meaning that it does not cause increases in 'bad' cholesterol or blood-sugar levels. This is very important, since people with HIV are at increased risk for heart disease, diabetes, and body changes caused by lipodystrophy.
Other good features of this drug are that it can be safely combined with other medications and its potential for drug interactions is very low. Although raltegravir has these promising characteristics, it cannot be used alone. Other antiretrovirals need to be combined with it to make it effective and to prevent the development of resistance against this powerful new medication class.
The second new drug to come to market is the entry inhibitor maraviroc (Selzentry), which works by blocking the CCR5, or R5, receptor, one of two on the CD4 cell that HIV uses to make its entry. When blocked by maraviroc, HIV is left hanging until it is destroyed by our immune cells. The other receptor that HIV can use to enter our CD4 cells is the CXCR4, or X4, receptor. Maraviroc will only work if your virus is R5--it cannot block X4 virus. Therefore, before you can use this new medication you will need to have your blood screened to verify which receptor (also called a tropism) your virus uses. A test called the trofile assay requires a simple blood draw and returns results in about two weeks. Your chances of having a virus with only an R5 receptor are greater if you are not heavily treatment-experienced--meaning that you have not been on a lot of anti-HIV meds--and have never had a CD4 count of less than 200 cells.
If properly used, maraviroc is potent at lowering viral loads and raising CD4 counts. Unlike raltegravir, this drug's concentration is affected by other drugs, so you and your health care provider will need to review all your other medications to ensure that this drug is properly dosed. And finally, similar to raltegravir, this drug is well-tolerated and is not likely to worsen cholesterol or blood-sugar levels.
