Maraviroc approved in the US
On 6 August 2007, the US Food and Drug Administration (FDA) approved maraviroc for combination antiretroviral treatment of treatment-experienced adults with CCR5-tropic (R5) HIV.
The only currently approved tropism test is the Trofile test manufactured by Monogram, which was commercially launched in the US on the same day (see below).
The FDA approval is based on 24-week data from two ongoing double-blind, placebo-controlled clinical trials in treatment-experienced patients (Motivate 1 and 2). Longer-term data will be required before the FDA can consider traditional approval for maraviroc.
Approximately twice as many patients receiving maraviroc combined with an optimised background therapy (OBT) achieved undetectable viral load at 24 weeks compared with those receiving OBT alone.
In the trials, patients receiving maraviroc with OBT also experienced significantly greater viral load reductions and increases in CD4 cell counts compared with those receiving OBT alone.
Approximately 70% patients in the Motivate studies had two or fewer active drugs in their optimised background regimen.
Discontinuation due to adverse events (3.8%) was similar in the maraviroc and placebo arms (each 3.8%). The most common adverse reactions (>8% incidence and greater than placebo) are cough, pyrexia (fever), upper respiratory tract infections, rash, musculoskeletal symptoms, abdominal pain, and dizziness.
Maraviroc is the first in a class of drugs known as CCR5 antagonists which block the CCR5 co-receptor, and stop cell entry. Maraviroc is manufactured by Pfizer.
Maraviroc is expected to be available in the U.S. by the middle of September, where it will be sold under the brand name Selzentry. The brand name outside the US will be Celsentri.
Pfizer recently received a positive opinion from the CHMP in the EU and maraviroc is currently available in the UK in an expanded access program (EAP).
For full prescribing information, including boxed warning:
It is always important when a new drug reaches approval.
Maraviroc is produced in 150mg and 300mg tablets. US price is approximately USD $900 per month ($29/day), for either 150mg or 300mg BID dose. Patients using maraviroc with efavirenz need to use 600mg BID and will have to pay the double cost.
The only currently approved tropism test is the Trofile test manufactured by Monogram and costs approximately £900. Samples to be shipped to the US. Viral load needs to be >1,000 copies/mL for the test to work, and sensitivity drops from 100% at 10% dual/mixed tropism to around 80% when only 5% virus is X4.
Approximately half of patients screened for the Motivate studies were ineligible, having dual or mixed X4/R5 tropism. Additionally, some patients with R5 sensitive virus at screening developed detectable dual/mixed tropism within six weeks to baseline, and these patients were more likely to experience treatment failure.