Once-daily arm in maraviroc treatment-naive study terminated

30 January 2006

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Phase IIB/III clinical trials into Pfizer’s investigational CCR5 inhibitor, maraviroc, should be allowed to continue, the study’s independent Data Safety Monitoring Board (DSMB) has concluded.

Clinical studies examining the safety and efficacy of once- and twice-daily doses of maraviroc in combination with AZT (zidovudine, Retrovir) and 3TC (lamivudine, Epivir) involving individuals with previous experience of HIV treatment are to be allowed to continue as originally designed.

However, the trial into once-daily maraviroc treatment involving people who had never taken HIV therapy before, is to be stopped early. An analysis of the first 205 patients given 300mg of maraviroc once daily in combination with AZT and 3TC found that, after 16 weeks of treatment, the combination did not prove itself to be “non-inferior” to efavirenz, AZT and 3TC, a recognised standard of HIV care.

Glossary

treatment-naive

A person who has never taken treatment for a condition.

naive

In HIV, an individual who is ‘treatment naive’ has never taken anti-HIV treatment before.

data safety monitoring board (DSMB)

An independent committee of clinical research experts that reviews data not available to the study team while a clinical trial is in progress to ensure that participants are not exposed to undue risks. A DSMB can recommend that the study be stopped if the intervention is not effective, is causing harm to participants or the study is not likely to serve its scientific purpose. Also known as an Independent Data Monitoring Committee (IDMC).

phase II

The second stage in the clinical evaluation of a new drug or intervention, in which preliminary data on effectiveness and additional information about safety is collected among a few hundred people with the disease or condition.

CCR5

A protein on the surface of certain immune system cells, including CD4 cells. CCR5 can act as a co-receptor (a second receptor binding site) for HIV when the virus enters a host cell. A CCR5 inhibitor is an antiretroviral medication that blocks the CCR5 co-receptor and prevents HIV from entering the cell.

A study comparing twice-daily maraviroc and AZT with 3TC against efavirenz (Sustiva) with AZT and 3TC is to be allowed to continue, and individuals randomised to the once-daily treatment arm are to be offered the option of switching to the twice-daily dose of maraviroc.

So far over 1,400 patients have been enrolled in maraviroc studies. Late in 2005, a treatment-naïve patient enrolled in the maraviroc study experienced severe liver toxicities. The DSMB concluded that these were probably due to other medications she was taking that are known to cause liver problems, but they did not rule out the possible involvement of maraviroc. In September 2005, GlaxoSmithKline terminated a Phase IIB study involving treatment-naïve patients into its CCR5 inhibitor aplaviroc after reports of severe liver toxicities. Last year Schering Plough terminated a study of its chemokine antagonist, vircriviroc, in treatment-naive patients because of a higher failure rate in the vicriviroc group when compared to the AZT/3TC/efavirenz control group.

Once-daily arm in maraviroc treatment-naive study terminated