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Gilead Sciences Extends Phase 3 Elvitegravir Clinical Trial
Gilead Sciences announced in an SEC filing on Monday that it has extended the Phase 3 clinical trial for its investigational integrase inhibitor elvitegravir. The trial, which was supposed to last 48 weeks, will now last 96 weeks. Gilead stated that it extended the trial based on a recommendation from the U.S. Food and Drug Administration.
"The change allows for collection of more safety and efficacy data from a longer controlled and blinded study, the first head-to-head comparison of two integrase inhibitors," said a Gilead representative in correspondence with The AIDS Beacon. "Gilead has not been informed of any issues with the ongoing study that would cause us to halt or otherwise amend the study design."
Gilead has said the trial extension does not affect its investigational once-daily combination "Quad" regimen, which contains elvitegravir, cobicistat, emtricitabine, and tenofovir and is also in Phase 3 clinical trials (see related AIDS Beacon news).
Gilead has also stated that it expects its clinical trials for elvitegravir to be completed by the end of the year. Assuming positive results from the trials, Gilead said that the extension should not affect its timeline for submission of elvitegravir or the "Quad" pill for approval by the U.S. Food and Drug Administration (FDA).
Elvitegravir belongs to a class of drugs called integrase inhibitors, which is a relatively new class of antiretrovirals. The only currently approved integrase inhibitor is Isentress (raltegravir), produced by the U.S. pharmaceutical company Merck.
Dr. Derrick Butler, an HIV specialist and Associate Medical Director of the To Help Everyone Clinic in Los Angeles who is not affiliated with the clinical trial, told The AIDS Beacon that as a physician he is not particularly concerned about the extension. He speculated that the FDA was simply being cautious.
"From the FDA's perspective, based on the performance of Isentress in terms of having a lower threshold for resistance and issues around that, they probably wanted to extend this second integrase inhibitor study to get a better look at it. Probably more for durability and efficacy," he said.
Isentress was approved in 2007 after a 48 week clinical trial. Its use in a clinical setting has since shown that HIV resistance to Isentress can develop quickly. Additionally, results from a recent clinical trial failed to show that once-daily Isentress was as effective as twice-daily dosing (see related AIDS Beacon news).
Dr. Bill Owen, an HIV specialist in San Francisco who is not affiliated with the clinical trial, expressed some disappointment over the clinical trial extension, particularly if it affects when elvitegravir will become available.
"One advantage of elvitegravir (boosted by cobicistat or Norvir) is that the only currently FDA-approved member of the integrase inhibitor class, Merck & Company's Isentress, must be taken twice a day, whereas boosted elvitegravir need only be taken once daily," said Dr. Owen.
"I believe that any regimen which is effective, well-tolerated, and simple can greatly assist patients who have issues with compliance," he said.
However, he pointed out that there are a variety of other promising antiretrovirals and combination treatments under development. In particular, two Phase 3 trials for GSK1349572, an investigational integrase inhibitor from ViiV Healthcare, are currently recruiting participants. GSK1349572 will also be taken once daily.
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