Treatment-naive
Patients with Confirmed CCR5-tropic HIV Continue to Respond Well to Maraviroc
(Selzentry) at 96 Weeks in the MERIT Study
 | The
CCR5 antagonist maraviroc
(Selzentry) continued to work as well as efavirenz
(Sustiva), but with better tolerability, among treatment-naive patients in
the MERIT study whose viral tropism was determined using a new, more sensitive
assay, researchers reported at the 5th International AIDS Society Conference on
HIV Pathogenesis, Treatment, and Prevention (IAS 2009) last month in Cape Town,
South Africa. |
By
Liz Highleyman Individuals
with exclusively CCR5-tropic HIV -- that is, virus that uses only the CCR5 co-receptor
to enter cells -- are considered eligible to use maraviroc,
which blocks the virus from using this co-receptor. Patients considering the drug
are screened with a tropism assay called Trofile. 
The
MERIT study included more than 700 previously untreated participants with a median
CD4 cell count of about 250 cells/mm3 and a mean viral load of about 700,000 copies/mL,
who were determined to have CCR5-tropic virus. Participants were randomly assigned
to receive either 300 mg twice-daily maraviroc or 600 mg once-daily efavirenz,
both in combination with zidovudine/lamivudine
(Combivir). As
previously reported, at 48 weeks, patients taking maraviroc were overall slightly
less likely than those taking efavirenz to achieve HIV RNA below 50 copies/mL
(65% vs 69%). This was attributable to the subgroup of patients with high baseline
viral load (> 100,000 copies/mL), in which the response rate was significantly
lower in the maraviroc arm (60% vs 67%, respectively). However,
as
reported at last year's ICAAC, when tested using a new more sensitive Trofile
assay, about 15% of the original MERIT participants were found to actually have
CXCR4-tropic or dual/mixed-tropic HIV. An ad hoc retrospective analysis of the
48-week data excluding these patients found that maraviroc and efavirenz worked
equally well, with 68% in both arms achieving HIV RNA < 50 copies/mL, and response
rates were similar in the 2 arms regardless of baseline viral load. At
the IAS meeting Michael Saag from the University of
Alabama at Birmingham presented 96-week results from the amended study population,
dubbed MERIT-ES. Overall, demographic characteristics, baseline viral load, and
CD4 count were similar in the original MERIT and MERIT-ES groups. Results
 | At
96 weeks, similar proportions of patients in the maraviroc (59%) and efavirenz
(62%) arms achieved HIV RNA < 50 copies/mL. | | In
a TLOVR (time to loss of virological response) analysis, results were even closer,
with response rates of 61% in both arms. | | TLOVR
results were similar among participants with both low baseline viral load (64%
in the maraviroc arm vs 63% in the efavirenz arm) and high viral load (56% vs
57% respectively). | | The
mean CD4 cell gain was larger in the maraviroc compared with the efavirenz arm,
212 vs 171 cells/mm3. | | About
one-third of participants in both arms discontinued the study by week 96 (up from
about 25% in both arms by week 48). | | More
patients in the efavirenz arm withdrew due to adverse events (6% vs 16%), while
more in the maraviroc arm did so due to inadequate clinical response (13% vs 6%). | | Total
and LDL cholesterol and triglyceride levels were lower, on average, in the maraviroc
arm. |
"A
similar percentage of patients on maraviroc and efavirenz achieved HIV-1 RNA <
50 copies/mL at week 96," the investigators concluded. "Analysis of
percentage of patients with undetectable viremia over time continues to show only
small differences between efavirenz and maraviroc through week 96 without further
separation between the two treatment groups.""The
difference in CD4+ cell count increases favoring maraviroc was maintained through
week 96," they continued. "Fewer patients experienced malignancies in
the maraviroc arm than in the efavirenz arm. Maraviroc had a more favorable impact
on lipids than efavirenz." Pfizer
Global Research and Development, New London, CT; University of Pretoria and Tshwane
Academic Division, National Health Laboratory Service, Pretoria, South Africa;
Orlando Immunology Center, Orlando, FL; Saint-Pierre University Hospital, Brussels,
Belgium; University of New South Wales, Sydney, Australia; University of Toronto,
Toronto, Canada; Pfizer Global Research and Development, Sandwich, UK; Monogram
Biosciences, South San Francisco, CA; University of Alabama at Birmingham Medical
Center, Birmingham, AL. 8/4/09 Reference
J
Heera, P Ive, M Botes, and others. The MERIT study of maraviroc in antiretroviral-naive
patients with R5 HIV-1: 96-week results. 5th International AIDS Society Conference
on HIV Pathogenesis, Treatment, and Prevention (IAS 2009). July 19-22, 2009. Cape
Town, South Africa. Abstract
TuAb103.
Other
Source
Pfizer. 96-Week MERIT ES Analysis Shows Efficacy of Pfizer's HIV/AIDS
Treatment Celsentri/Selzentry (Maraviroc) in Treatment-Naive HIV Patients; Results
Consistent with 48-Week Analysis. Press release. July 21, 2009.
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