CCR5
entry inhibitors (aka CCR5 antagonists) are a novel class of antiretroviral drugs that interfere with
HIV binding to the CCR5 co-receptor, which most strains of the virus use to enter
host cells.
Pfizer,
Inc., the developer of the experimental CCR5 antagonist maraviroc (Celsentri), announced this week that the U.S. Food and Drug
Administration (FDA) has issued an “approvable letter” for the drug.
Maraviroc
is the first CCR5 entry antagonist to be considered for FDA approval. The drug
is under review as a therapy for treatment-experienced patients with CCR5-tropic
HIV-1. Vicriviroc,another experimental CCR5 entry antagonist (from
Schering Plough), is in Phase II development for use as therapy in treatment-experienced
HIV patients.
FDA
issuance of an “approvable letter” for maraviroc is one of several intermediate
steps that the agency can take during the drug review process. It does not mean that the drug is approved
for marketing in the United States
at this time. Rather, the approvable letter suggests that the FDA has determined
that the submitted clinical data demonstrate that the benefits of maraviroc appear
to outweigh the known risks in treatment-experienced HIV patients when the drug
is used under appropriate medical supervision.
However, before a final approval is granted, additional
information, including the wording of the final drug labeling, must be submitted
by Pfizer and reviewed and agreed upon by FDA. The agency previously indicated
that it wanted more data on the use of maraviroc in women and people of color,
since most of the initial study subjects were white men.
As announced by Pfizer, the company
and the FDA are in discussions about these issues. Following is the text of Pfizer’s
recent announcement:
“We
continue our discussions with the FDA to address outstanding questions and finalize
the product labeling [for maraviroc] as soon as possible. Pfizer is committed to making maraviroc available to the thousands
of patients with HIV whose virus has become
resistant to one or more currently available treatment options.
“To
date, more than 2,000 patients worldwide have received or are currently receiving
treatment with maraviroc through clinical trials. Pfizer has also established
an expanded access program (EAP) in 30 countries. The EAP is a clinical study
that provides maraviroc in countries to patients who have limited treatment options
prior to approval.
“Pfizer
is currently in the process of submitting marketing applications around the world
to make maraviroc available globally.
Selected HIV and Hepatitis.com
Articles on Maraviroc
