Several clinical trial results of diabetics taking an inhaled version of insulin from


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showed the product was effective and well-tolerated over two years, the company said Tuesday.

The results for the experimental drug Exubera were presented Tuesday at an American Diabetes Association conference in San Diego, underlining Pfizer's efforts to show that inhaled insulin can be an alternative to injectable insulin.

Inhaled insulin is being promoted by Pfizer and its partners as a way to increase patients' compliance. Tests show inhaled insulin is as effective as injectable insulin. Pfizer is collaborating with


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Nektar Therapeutics

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to develop the product, which has been submitted for review to the Food and Drug Administration. The FDA is expected to act on the application by the end of October.

Exubera is

one of several inhaled insulin products in clinical trials, but it has at least a 24-month lead in the regulatory race among other products.

On Tuesday, Pfizer said that a pooled analysis of two clinical trials involving 304 adults showed that people who added Exubera to their regular treatment for diabetes were able to control blood sugar levels for two years. These patients "experienced no clinically important effects" on their lungs vs. patients taking other medications to control blood sugar, Pfizer said.

Long-term impact on the lungs is a key factor for the FDA in evaluating Exubera and other types of inhaled insulin. If the drugs impair lung function, the FDA would be less inclined to approve the drug -- or it might approve the drug with severe restrictions.

The pooled analysis covered late-stage clinical trials of people with Type 2 diabetes, the most common form of the disease. For these diabetics, the body doesn't make enough of the hormone insulin, which converts sugar into a fuel for the body. In other Type 2 diabetics, their bodies' cells don't absorb the sugar. Too much sugar in the blood can, over time, damage the heart, kidneys, nerves and eyes.

The companies say Exubera should be inhaled by patients before mealtime. They are seeking FDA approval of Exubera for both Type 2 diabetes and Type 1 diabetes in which patients can't make any insulin. Pfizer said on Tuesday that a study of 226 adults with Type 1 diabetes showed Exubera was as effective and as safe as injectable insulin over a 12-week period.