Pfizer's maraviroc has received support from an FDA advisory panel. It will be the first drug of the new CCR5 inhibitor class on the market, offering a welcome alternative to patients with limited therapeutic options. However, its initial positioning in the salvage market means that its commercial potential will remain limited for now.  An FDA advisory panel voted unanimously to recommend approval for Pfizer's investigational HIV entry inhibitor maraviroc. Since maraviroc, expected to be marketed as Celsentri, may be the first CCR5 inhibitor on the market it will provide an alternative for patients who have failed all other therapies and have limited or no remaining treatment options.

CCR5 is a type of co-receptor required by most HIV viruses to attach to and infect human cells. However, particularly at advanced stages of the disease, the virus may switch to using another receptor called CXCR4. Since maraviroc only blocks CCR5, a so-called tropism assay is required to confirm which co-receptor the patient's virus uses.

Results from the pivotal MOTIVATE trials demonstrated that nearly twice as many treatment-experienced CCR5-tropic HIV-1 infected patients treated with maraviroc plus optimized background therapy (OBT) achieved undetectable viral loads at 24 weeks compared to those receiving placebo plus OBT. In addition, there were no significant increases in hepatotoxicity, malignancy or mortality in maraviroc's treatment arms, while there were slight increases in upper respiratory and herpes simplex virus infections as well as with ischemic events, consistent with the rate observed in treatment experienced HIV/AIDs patients.

However, the committee has recommended further studies for the product, including testing in patients with liver disease as well as investigating potential interactions with erectile dysfunction treatments.

If successfully launched, maraviroc's use is most likely to be initially limited to treatment-experienced patients, a market that is currently dominated by Roche's Fuzeon. However, maraviroc's label could eventually be extended to newly-diagnosed patients.

Another new drug in late stage development, Merck & Co.'s integrase inhibitor raltegravir, is expected to be filed with the FDA within the next two months. With an anticipated launch towards the end of the year, it is also most likely to be used in treatment experienced patients.

Since both drugs offer a novel mechanism of action, Datamonitor expects considerable competition between the two. Nonetheless, their availability will extend treatment options for patients with more advanced HIV and those with AIDS, making them significant contributors to the growth in the HIV market.
 

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