When Gilead Sciences' ($GILD) Truvada was approved as an HIV preventative last year, it was hailed as a historic event. It was the first time an HIV drug had been approved to stave off HIV infection, rather than treat those who had already contracted the virus. But at a reported cost of $13,000 a year for the daily pill, Truvada is a heavy load for patients and payers. A vaccine that prevented the infection would be an even greater breakthrough, but that looks unlikely anytime soon.
A little more than 18 months after expanding it, the National Institutes of Health (NIH) has halted what was the largest ongoing HIV vaccine trial. The decision was made after a look at interim data showed the vaccine neither prevented infection with HIV nor reduced viral load. After enrolling more than 2,500 people in the study--roughly half of whom received a placebo--the lack of efficacy carried enough weight to see the project canned. Researchers will now follow those already vaccinated to monitor long-term trends.
The regime trialed by NIH began with a DNA-based vaccine expressing antigens representing surface and internal HIV proteins to prime the immune system. A booster vaccine was given in Week 24. Researchers hoped the two-pronged approach could confer immunity. When the NIH began recruiting for an HIV vaccine trial in 2009, another team in Thailand was weeks away from reporting success in cutting the risk of viral infection. The news from Thailand raised hopes and prompted the NIH to expand the ambitions of its trial.
Cancellation of the Phase IIb trial is a blow to a sector that has already seen Merck ($MRK) and others fail in the clinic. IAVIReport lists 37 other ongoing HIV vaccine trials, but all but three of these are still in Phase I. The canned NIH clinical trial has more participants listed than all the other studies combined. Observers still hold out hope that a successful vaccine is out there, though. "While today's result is disappointing, we need to look at the bigger picture of AIDS vaccine science. It's not the answer we hoped for, but the search doesn't end here," Mitchell Warren, executive director of AVAC: Global Advocacy for AIDS Prevention, told Bloomberg.
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