Selzentry taken without tropism test
Jun 23, 2011
I have been taking Selzentry for over a year now, and according to guidelines a tropism test should have been done. My provider said it wasn't necessary and so my question is what is the harm and risk in not first doing a tropism test? Background: I have been undetectable on Trizivir and Sustiva since 2002. We added Selzentry last year, so that I could drop AZT to coutneract lipoatrophy, which I have done this month. Thank you so much!
Response from Dr. Young
Hello and thank you for your post.
HIV viruses are either use CCR5 or the X4 co-receptor to get into CD4+ cells. Maraviroc (SELZENTRY) is the a CCR5 receptor inhibitor. A specialized test is required to see if your virus uses the R5 or X4 receptor. If your virus can use the X4 co-receptor, maraviroc will have no benefit. People with more advanced HIV disease/AIDS or a history of HIV drug resistance are at greater risk of having X4-utilizing virus.
In the past, one needed a blood sample with at least 1000 copies/ml of virus to run the tropism test; now there is an alternative test (called Trofile DNA) that can determine viral tropism from human cells, even if the viral load is undetectable.
With regards to your treatment regimen of AZT, abacavir, 3TC (Trizivir), efavirenz (Sustiva) and maraviroc, a number of simplifications schemes could be entertained. First, since you mentioned dropping AZT, abacavir+3TC (a combination called Epzicom here in the US) and efavirenz would be anticipated to be a very potent regimen (well studied)- and eliminate AZT and maraviroc. A much less studied option (though one that should work) would be to use Epzicom with maraviroc. I would not consider using the later regimen without the tropism test.
I hope that helps. BY
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