With little fanfare, Novo Nordisk (NYSE: NVO) on Monday settled its 2006 patent-infringement lawsuit against Pfizer (NYSE: PFE) over inhalable insulin and then dropped development of the treatment.

Novo Nordisk's inhalable insulin system, dubbed AERx, was in phase 3 testing as a potential short-acting diabetes treatment. Like other inhalable insulins, including Nektar Therapeutics' (Nasdaq: NKTR) Exubera and Eli Lilly's (NYSE: LLY) AIR insulin system, Novo's pulmonary insulin system basically changed the delivery of short-acting insulin from a simple injection to less painful -- but potentially more inconvenient -- inhalation.

In the press release, Novo stated that it was halting development of its inhaled insulin compound because the drug was "unlikely to offer significant clinical or convenience benefits" versus current diabetes treatments. That's also why Pfizer could garner only $12 million in sales of the short-acting Exubera in last year's first nine months, before it handed the product back to Nektar.

Interestingly, Novo didn't say that it was giving up on inhalable insulins, only that it was raising the white flag on its current late-stage AERx program. The company did announce plans to pursue a GLP-1 inhalable diabetes treatment, pitting it against a similar MannKind (Nasdaq: MNKD) project in phase 1 testing.

Novo also announced plans this week to work on developing a long-acting inhaled insulin product -- a first for any drugmaker, as far as I know. Long-acting insulins sound even less ideal for inhalation than their short-acting counterparts; they're already injected less frequently, giving needle-phobic patients fewer qualms about their use.

Eli Lilly and partner Alkermes (Nasdaq: ALKS) haven't given any indication that they'll give up on their short-acting inhaled insulin compound. A New Drug Application for their compound is expected in 2009, while MannKind is guiding for a 2008 filing for its Technosphere inhalable insulin.

Lilly and Alkermes will probably avoid some of the problems that Exubera faced, such as its confusing dosage quantities and an unwieldy device size, but they probably won't escape all Exubera's woes. This puts MannKind and its completely different Technosphere as the next great rapid-acting inhalable insulin hope. Unless MannKind can prove otherwise, Sanofi-Aventis (NYSE: SNY) still seems to be the only big winner from drugmakers' adventures with short-acting inhaled insulin.

More Foolishness on diabetes drug makers:

Eli Lilly is an active Income Investor pick, Pfizer was selected by Inside Value, and MannKind is a Motley Fool Hidden Gems Pay Dirt recommendation. Need new ideas for your money? Give any of our newsletters a try free for 30 days.

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