The Latest on Inhaled Insulin
Researchers revisit possible diabetes therapy
As a medical writer with type 1 diabetes, I love learning about developments in diabetes care that might help myself and others with diabetes – this is one of the best parts about dLife, for me, seeing news on the show about new diabetes products! I attend 30-40 conferences per year in which I learn about new developments in diabetes, and dLife has asked me, in this column, to write about some of my most interesting learnings each month. Hurrah – it is a great time in diabetes and I'm excited to share my learnings.
So first up, in mid-April, 2005, I heard Jay Skyler, M.D., of the University of Miami, Florida, speak at the Clinical Diabetes Technology Meeting in San Francisco, California. Dr. Skyler's distinguished career has spanned a wide spectrum of topics in diabetes, including diabetes prevention, diagnosis and management of complications, psychological aspects of living with diabetes, and the use of new technologies and drugs to improve the health of people with diabetes. I was privileged to attend his presentation, "Update on Inhaled Insulin."
The prospect of inhaled insulin was first discussed in a German medical journal in 1925, only four years after the discovery of insulin. According to Dr. Skyler, inhaled insulin has resurfaced as a possible therapy for diabetes approximately every ten years since then. As they say, everything old is new again! Today, questions are swirling about inhaled insulin - whether it works as well as insulin taken by shots or in a pump, whether it is safe, whether it will be approved, how it will be priced, who should take it, etc.
There has been progress on the development front, and earlier this year, the companies making one formulation, Exubera (made by a small biotechnology company, Nektar, with Big Pharma partners Sanofi-Aventis and Pfizer), submitted the drug to the FDA – that means they are now waiting for the FDA to say yes or no as to whether it should be made available to individuals with diabetes. Dr. Skyler's presentation covered both the potential benefits and drawbacks of inhaled insulin – fascinating!
• PRINCIPLES: Dr. Skyler began his presentation by explaining the principles underlying the development of inhaled insulin. If the tissues within an adult's lungs that can absorb an inhaled substance were spread on the ground, they would cover a tennis court! For this reason, inhaled insulin can be absorbed well into the body. Yet insulin delivered into the lungs has a bioavailability of 10–15% (this means only 10-15% is available for use in the body to manage blood glucose), so a pulmonary liquid or powder insulin formulation must be highly concentrated to be effective. All of the companies at work on inhaled insulin have designed proprietary delivery devices for their products, ranging from the size of two soft-drink cans stacked on top of each other down to the size of a common asthma inhaler (i.e., a deck of cards).
• STUDY FINDINGS: Dr. Skyler also discussed the findings of several recent scientific studies of inhaled insulin. Inhaled insulin can control blood glucose levels at mealtimes, but insulin-requiring patients (whether type 1 or type 2) must still take at least one long-acting basal insulin injection each day. Thus far, he noted, there is more improvement in patients not already on insulin than in patients who were already on injected insulin therapy before trying inhaled insulin. In particularly, it sounds like patients with type 2 diabetes who struggle to control their diabetes using oral medications might be the best candidates from inhaled insulin. Inhaled insulin does entail a risk for hypoglycemia, just like injected insulin. Most trial participants have preferred inhaled insulin to injections, Dr. Skyler said.
• VARIOUS FORMULATIONS: Some formulations of inhaled insulin begin to lower blood glucose as quickly as injected rapid-acting insulin analogs (Humalog or Novolog), but the inhaled insulin may take longer to wear off. However, inhaled insulin's action within the body can vary by 15–30%, about the same as injected human Regular insulin. If you ever thought that Regular insulin seemed to work differently from day to day, you were probably right! Smokers tend to experience better inhaled insulin absorption because inhaled insulin can better penetrate the surface of a damaged lung — but that is not a reason to smoke. Inhaled insulin works less well in the presence of an upper respiratory infection, but right now the impact of inhaled insulin on chronic obstructive pulmonary disease (COPD) is unclear. To date, inhaled insulin users with asthma have seen no deterioration in respiratory function from using inhaled insulin, but some non-asthmatic patients have developed a mild cough. Dr. Skyler emphasized the need for long-term safety studies as well as for more short-term investigations.
• FURTHER RESEARCH NEEDED: In the last part of his presentation, Dr. Skyler outlined some issues for further research regarding inhaled insulin. Inhaled insulin is very expensive; whether the extra cost is justified has not been conclusively demonstrated. There are still remaining major research needs – longer-term studies, more extensive study of inhaled insulin use in children (the diabetic population for whom reducing the number of injections per day might be most attractive), etc. Additionally, using inhaled insulin combined with exercise could be an issue: at this point, whether cardiovascular exercise affects the absorption of insulin in the lungs is an open question.
The bottom line? Inhaled insulin could be a significant advance in the treatment of diabetes, but it is not a magic bullet, it won't suit everyone with diabetes, and more research is needed to understand the effects of long-term inhaled insulin use. That said, it could well serve as a wonderful tool for people who need insulin but don't take it currently and the public health benefits may be quite meaningful – stay tuned!
Next Up: The annual American Diabetes Association meeting in June in San Diego. Close Concerns publishes a monthly newsletter, Diabetes Close Up, which focuses on the businesses of diabetes and obesity – sign up at www.diabetescloseup.com. All Diabetes Close Up writers have either diabetes themselves or are close to someone who does.
Kelly Close is editor in chief of diaTribe (www.diaTribe.us), a free online newsletter for patients looking for more information on products and research.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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