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  49th ICAAC
San Francisco, CA
September 12-15, 2009
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MERIT: Week 96 Virologic Response and
Tropism at Virologic Failure by Baseline CD4+ Cell Count

  Reported by ICAAC Sept 15 2009 San Francisco
B Trottier1, DA Cooper2, R Wood3, G Carosi4, E van der Ryst5, J Heera6, H Fan6, H Valdez7, J Goodrich6, C Craig5, H Mayer7
1 Clinique Medicale l'Actuel, Montreal, Canada; 2 University of New South Wales, Sydney, Australia; 3 UCT Lung Institute, Cape Town, South Africa; 4 Spedali Civili di Brescia, Brescia, Italy; 5 Pfizer Global Research and Development, Sandwich, UK; 6 Pfizer Global Research and Development, New London, CT, USA; 7 Pfizer Inc, New York, NY, USA
For further information, please contact: Jayvant R Heera, Pfizer Global R&D, New London, CT, 860-732-2248, jayvant.heera@pfizer.com
The 96-week MERIT-ES analysis showed similar virologic responses (TLOVR) between MVC and EFV across baseline CD4+ cell count and screening viral load strata
Emergence of DM/X4 virus at virologic failure occurred in 38% of MVC recipients with a valid tropism result at failure
- Emergence of DM/X4 virus at virologic failure occurred in patients with baseline CD4+ cell counts ≤ 350 cells/mm3
- DM/X4 virus was detected at baseline in three patients who experienced virologic failure
Eighteen (53%) MVC recipients had emergence of DM/X4 virus at the time of virologic failure in the original MERIT analysis
- About 50% of these subjects had DM/X4 virus detected at screening with the enhanced sensitivity Trofile assay
MERIT is an ongoing non-inferiority study of maraviroc (MVC) 300 mg BID + Combivir (CBV; zidovudine/lamivudine) and efavirenz (EFV) 600 mg QD + CBV for the treatment of antiretroviral-na´ve subjects infected with CCR5-tropic HIV-1
- The primary analysis of MERIT occurred at Week 481
The original MERIT analysis contained subjects whose viral tropism at screening was determined by the original Trofile assay (Monogram Biosciences)
An enhanced sensitivity tropism assay, Trofile-ES, has since been developed that has been shown to detect X4 variants 100% of the time when they comprise 0.3% of the total viral population as opposed to 5% with the original Trofile assay2
The results of MERIT have been reanalyzed to omit patients who had a screening tropism of DM/X4 according to Trofile-ES and thus would not have been eligible for the study (MERIT-ES)3
- Only MERIT-ES data are presented in this poster
To investigate the proportion of responders through week 96 for the MVC+CBV arm vs EFV+CBV arm by screening viral load and baseline CD4+ cell count
To assess HIV-1 tropism at baseline and at the time of failure by baseline CD4+ cell count