Gilead Sciences announced yesterday that it has submitted its investigational once-daily combination “Quad” pill for approval from the United States Food and Drug Administration.

The Quad regimen is a fixed-dose, single tablet consisting of the investigational booster drug cobicistat, the investigational integrase inhibitor elvitegravir, and Truvada (emtricitabine/tenofovir).

According to a representative from Gilead, the company is seeking approval only for previously untreated HIV-positive adults at this time.

The submission is based on results from two Phase 3 studies showing that the Quad pill is as safe and effective as Atripla (efavirenz/emtricitabine/tenofovir) and as Reyataz (atazanavir) plus Truvada, respectively (see related AIDS Beacon news articles for the Atripla and Reyataz studies).

“Based on data from our pivotal studies, we believe that the Quad has the potential to be an important new treatment option for people living with HIV, and we are pleased to have reached this significant milestone less than six weeks after the unblinding of the second pivotal Phase 3 study,” said Norbert Bischofberger, executive vice president of Research and Development and chief scientific officer of Gilead Sciences, in a press release.

If approved, the Quad pill would be the third all-in-one regimen for treatment of HIV. The first, Gilead’s Atripla, was approved in 2006; the second, Gilead’s Complera (rilpivirine/emtricitabine/tenofovir), was approved in August.

Gilead also noted that if the regimen is approved, the Quad pill would be the first all-in-one combination regimen that is integrase-inhibitor based; currently, the only approved integrase inhibitor is Isentress (raltegravir).

The two Phase 3 clinical trials, on which the submission is based, showed that 88 percent and 90 percent of participants, respectively, successfully achieved and maintained undetectable viral loads (amount of HIV in the blood) after 48 weeks of the Quad regimen.

By comparison, 84 percent of participants taking Atripla and 87 percent taking Norvir (ritonavir)-boosted Reyataz plus Truvada achieved and maintained undetectable viral loads after 48 weeks.

Gilead had previously stated, based on results of a Phase 2 clinical trial, that the side effects for the Quad pill were similar to those of Atripla. In both cases, the common side effects were abnormal dreams or nightmares, fatigue, dizziness, diarrhea, drowsiness, headaches, anxiety, nausea, bloating, and rash. However, fewer participants in the Quad treatment group experienced abnormal dreams or nightmares, dizziness, or anxiety.

Gilead indicated that it would present the full results from the Atripla and Reyataz Phase 3 clinical trials at scientific conferences in 2012.

For more information, please see the Gilead Sciences press release.