icon-folder.gif   Conference Reports for NATAP  
  International HIV and Hepatitis Drug Resistance Workshop
June 8-12, 2010,
Dubrovnik Croatia
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Long-Term Outcome of Individuals Experiencing a Phenotypic Switch in HIV-1 Co-receptor Use in the Merit Study
  Reported by Jules Levin
Intl HIV/Hepatitis Drug Resistance Wkp, Croatia June 8-12 2010
SD Portmouth1, M Lewis2, C Criaig2, D Chapman1, LC Swenson3, J Heera4 1Pfizer Inc, NY, NY USA, 2Pfizer Global Research and Development, Sandwich, UK, 3 BC Centre for Excellence in HIV/AIDS, Vamcouver BC, Canada, 4Pfizer PGRD, New London, CT USA
There were no observed adverse clinical or immunological consequences related to the emergence of CXCR4-using virus associated with virologic failure on maraviroc therapy
Individuals switching tropism during maraviroc-containing terapy had good immunological outcomes and responded to subsequent therapy
Tropism change is often reversible on stopping maraviroc, if viremia persists or no further therapy is instituted
5 of the 15 treatment failures would have been excluded from the study had population genotyping been used at screening


- Figure 1 shows follow-up HIV-1 RNA data, CD4 coiunts, treatment changes, and tropism test results for the 8 individuals with 192-week data
- Five individuals were lost to followup before week 48, and 2 individuals between weeks 48 & 96
- Tropism test results are indicated as R5 (CCR5-tropic), X4 (CXCR4-tropic), DM (dual/mixed tropic), or NR (not reportable), MVC with a red-crosout indicates when maraviroc therapy was stopped
- At sreening, DM virus was detected by ESTA in 5 of these 8 individuals, and X4 virus was detected in 4 of these individuals (all were R5 at screening by original profile)