The drug: Quad
The disease: HIV
The developer: Gilead
Peak projections: $1 billion-$2.5 billion

In September, Gilead took one look at some head-to-head data pitting Quad against Truvada with atazanavir (from Bristol-Myers Squibb) and boosted by ritonavir and decided they could shave some time off their prospective launch schedule. Atotal of 90% of the patients taking the treatment-a four-in-one pill-saw their viral loads drop to the target level, just barely edging out the standard therapy. And that, says Gilead, should warrant an approval in time for a mid-2012 launch.

Quad combines the experimental integrase inhibitor elvitegravir and a boosting agent-cobicistat--with Truvada, which combines the older drugs Emtriva and Viread.

Gilead has long been the dominant trendsetter in HIV therapies. Atripla--$3 billion in sales--has been a consistent blockbuster, and with that drug coming off patent protection, it's time for a better treatment to take its place. Its chances of getting an approval are actually quite good. What has analysts frowning is Gilead's ability to prove clear superiority over established therapies, both in efficacy and safety, to physicians and patients. This is all happening as some see the market maturing to the point at which there are limited new opportunities for expanding the market.

Those concerns have conspired to blunt sales projections, which once reached upward of $4 billion and now top out at about $1.5 billion a year, sliding all the way down to a few hundred million among some analysts. Decision Resources expects Gilead's Quad will earn peak income of up to $2.5 billion through 2018. Stifel Nicolaus analyst Maged Shenouda estimates that if Quad is approved by next year, the drug's sales will peak at $800 million by 2015.

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