There are several chronic diseases that guarantee a pharmaceutical company a blockbuster drug, if it can develop a first-line treatment. Alzheimer's, multiple sclerosis, a variety of heart ailments, and diabetes are a few, and new drugs for them come on the market all the time. What makes one drug a frontline treatment and another a second-line treatment can include improved effectiveness, safety, or ease of use. MannKind (NASDAQ:MNKD) is pursuing this last route in trying to get its inhaled insulin compound, Technosphere, through clinical testing to regulatory approval.

Like competitor NektarTherapeutics (NASDAQ:NKTR), MannKind is trying to at least fill a niche by giving diabetics the option of using an inhaled insulin product rather than multiple daily injections.

Compared with injected insulin, MannKind's Technosphere could be simpler to use and require less dosing while also making compliance easier for those diabetics who are afraid of or dislike using needles.

Monday, MannKind released results from a small 24-week, phase 3 trial showing that Technosphere was as effective as injected insulin in controlling blood sugar levels in patients with type 2 diabetes.

Also, MannKind tried to answer critics' worries about the effects of inhaled insulin on lung functioning by stating that lung functioning didn't differ between Technosphere patients and those on a placebo over the six months.

This first trial is just the introduction to Technosphere's pivotal trials. The company is set to run another four phase 3 trials, which will be much larger and longer than this one, so Technosphere wouldn't be on the market until 2010 at the earliest.

Until Technosphere reaches the market, investors in MannKind would be smart to watch how fast Nektar's similar product, Exubera, ramps up sales. Exubera already has approval in the U.S. and the European Union and is being promoted by Nektar's partner, Pfizer (NYSE:PFE).

If Exubera fails to take hold among diabetics, it would be hard to justify MannKind's nearly $1 billion market cap with a product so far away from potential approval and only one phase 3 trial behind it.

Diabetics in the U.S. spend $12 billion every year to control their blood sugar levels, so there's plenty of room for Exubera and Technosphere in the market. Until there's more data from Technosphere's phase 3 trials, MannKind investors are in the unusual position of having to root for a brisk uptake in sales for a competitor's product.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy .