Amylin Pharmaceuticals (NASDAQ:AMLN) is putting the cart before the horse, but for a good reason. It's got a Mack truck down the street ready to push both the cart and the horse past the finish line.

Yesterday, the company announced results of a phase 3 trial testing the ability of its diabetes drug BYETTA to lower glucose levels without the help of other drugs. The results weren't stellar, but 60% of patients taking the BYETTA were able to reduce their glucose levels below the target level.

The drug is currently only approved for use in combination with other oral medications, since the FDA rejected its request to be used as a stand-alone treatment in 2005.

Amylin and marketing partner Eli Lilly (NYSE:LLY) plan to submit the data to the FDA in the first half of next year. While the data is probably good enough to get a label expansion -- depending on how stringent the FDA is feeling -- I'm not sure the expansion will do much for BYETTA's sales. Why would patients inject themselves twice a day when oral compounds such as Bristol-Myers Squibb's (NYSE:BMY) Glucophage work just as well, if not better, as a monotherapy?

BYETTA does have the advantage of contributing to weight loss in patients, but I'm not sure that the added benefit will justify the patients' anxiety of having to inject themselves twice a day.

The real benefit of getting an expanded label now is that the company can use that label when it applies for a marketing application for Exenatide once weekly, its extended release version of BYETTA. The drug, developed using Alkermes' (NASDAQ:ALKS) microsphere technology, showed promising results in a recent phase 3 trial, but the New Drug Application won't be submitted until 2009 because Amylin is in the process of building the plant to manufacture it.

While 730 injections per year -- 732 in leap years -- will probably keep most patients from using the drug as a first choice, 52 injections of Exenatide per year might be a decent trade-off for not having to remember to take a pill twice a day.

It looks like the Mack truck is gassed up and ready to grab on to the label-expanding cart when Amylin steps on the gas.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Eli Lilly is a selection of the Income Investor newsletter. The Fool's disclosure policy is as slim as a piece of paper.