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Pfizer's Pending HIV Drug Maraviroc May Require Patients to Confirm CCR5-Tropism Status

BOSTON (GenomeWeb News) — Pfizer yesterday said that the label for its impending HIV drug Maraviroc will likely include information requiring patients to confirm their CCR5-tropism status before being prescribed the drug.
Pfizer expects to file the CCR5-antagonist for US Food and Drug Administration approval in treatment-experienced patients by the end of the year, according to Andy Schmeltz, senior director of Pfizer’s worldwide virology and vaccines division. Additional information about the label will likely be known when the drug is approved.
Schmeltz made his remarks at the Harvard-Partners Center for Genetics and Genomics conference on personalized medicine, held here this week.
“The reality is we need to make sure this assay is going to be available everywhere we want to market Maraviroc because every patient in our clinical development program was screened with this assay for CCR5-tropism,” said Schmeltz. “We knew that it was going to be in our label and would be required for eligibility to benefit from Maraviroc.” 
Pfizer’s plans will have significant implications for Monogram Biosciences, which makes the CCR5 co-receptor tropism assay, currently the only one of its kind. Pfizer and Monogram in May announced a non-exclusive collaboration to make Monogram’s Trofile assay available for patient use on a global basis. Pfizer at the time also invested $25 million in Monogram.
Monogram has been providing its test as a CLIA-lab service for Pfizer, which has been using it in its Maraviroc trials since 2002. Pfizer will market the Trofile assay to Maraviroc prescribers. Monogram has not announced any plans to apply the test for FDA clearance.
Monogram’s test confirms whether an individual’s virus is exclusively R5-tropic and thus will respond to Maraviroc, or non-R5 tropic, Schmeltz explained in his presentation.
“If this assay is not available in every country we wanted to market Maraviroc in, then the medicine couldn’t be used,” Schmeltz said. “So, the bottom line at Pfizer is the recognition that if there was no assay then there was not going to be any sales of this medicines in which we had already invested hundreds of millions of dollars in.”
Monogram Senior Vice President William Welch said the Trofile is “a first in HIV where drugs are designed in conjunction with a molecular assay.” Pfizer held up Maraviroc, currently in Phase III clinical trials, as the first oral entry inhibitor that works against HIV resistance to all other drug classes.
“What started out as a technical enabler really became a need for a commercial enabler,” Schmeltz added during the HPCGG conference, describing the evolution of Pfizer and Monogram’s relationship with the Trofile assay.
According to Pfizer, about 80 to 85 percent of treatment-naive HIV patients and about half of the treatment-experienced population may be eligible for Maraviroc treatment.
Maraviroc and other CCR5 antagonists block the cell-surface receptor CCR5, which binds to proteins that can enter white blood cells. However, for 15-20 percent of treatment-naive patients the HIV virus can use the CXCR4 co-receptor to infect white blood cells.
Monogram also provides its CCR5-tropism assay for Schering-Plough’s CCR5-antagonist vicriviroc, for which two Phase III clinical trials are planned but have not begun recruiting. Human Genome Sciences is currently recruiting patients for a phase 1 clinical trial for its anti-CCR5 antibody CCR5mAb004.

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