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Merck Stops Isentress Trial after Once a day Dosing Fails

Kathleen Blanchard's picture
Isentress RX

Merck has announced they have discontinued a Phase III trial for once a day dosing of the antiretroviral drug Isentress (raltegravir). The decision is the result of failure to find more benefit for HIV infected patients compared to twice a day dosing with the drug, even though the medication reduced viral load in 83.2 percent of patients to undetectable levels.

Slideshow: How Isentress tablets look like

Given twice a day, 88.9 percent of patients achieved HIV-RNA Isentress to be superior. Merck explained, “The difference did not meet the pre-defined statistical criteria for non-inferiority.”

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Isentress is approved for HIV treatment twice a day. The company recognized the pill burden for patients infected with HIV. The Phase III trial looked at the effectiveness of 800 mg once a day versus 400 mg twice a day in 775 patients receiving other standard treatment in an effort to expand its use.

HIV Drug Trial Halted per Monitoring Committee Recommendation

Merck says it discontinued the Phase III trial that initially looked promising, after receiving the recommendation from an independent Data Monitoring Committee. The patients in the study were evaluated after 48 weeks of treatment.

In the trial, the overall impact of Isentress, 800 mg once a day, was reportedly among patients with a high viral load of HIV - 100,000 copies/mL of HIV-RNA. The drug suppressed DNA replication in 74.3 percent at once daily dosing, compared to 84.2 percent in the twice a day study arm.

The drug works by preventing HIV replication in the body, and is an HIV integrase strand transfer inhibitor. Keeping the AIDS virus in check is important to prevent immune system dysfunction.

Merck plans to notify clinical investigators they have stopped the Isentress trial so patients in the once a day arm of the trial can return to twice daily dosing.