(Image: Felice Frankel)
For decades, scientists have been trying to develop an effective way to deliver insulin by mouth.
As we noted in an article a few months ago, a number of approaches are currently being tested by researchers at universities and pharmaceutical companies — and it’s possible that some of them may become commercially available within a few years.
But a slightly different approach to oral insulin delivery has recently received widespread attention — in part because it could be used to deliver not just insulin, but a number of other injectable drugs.
A needle inside a pill
Insulin can’t be taken orally because of the size and chemical makeup of its molecules. In most drugs that are taken by mouth, the molecules aren’t broken down by the digestive system and are small enough to pass through the wall of the intestine into the bloodstream.
But insulin is a hormone, or a very large protein. This means it can’t pass through the intestine into the blood before being broken down by digestive enzymes, rendering it ineffective.
Unlike competing approaches that seek to protect insulin molecules from stomach acid and digestive enzymes, a new pill developed by researchers at MIT and Brigham and Women’s Hospital in Boston doesn’t rely on absorption in the intestine.
Instead, the pill contains a microneedle that injects insulin right through the wall of the stomach, as outlined in a study published in February 2019 in the journal Science.
Each capsule is about the size of a blueberry, as noted in an MIT news release on the study. It’s designed to orient itself with the needle side down no matter how it lands in the stomach.
The needle, which is made of compressed freeze-dried insulin, is attached to a compressed spring that’s held in place by a disk made of sugar. When the sugar dissolves, the needle is ejected from the capsule and penetrates the stomach wall.
The insulin in the needle is then gradually absorbed into the blood stream, similar to the way that injected insulin is absorbed.
(Video: Diana Saville)
From pigs to humans?
The new microneedle pill has only been tested in pigs, not humans. But the latest study results show the promise of the technology.
When pigs swallowed the microneedle insulin capsules, their blood glucose levels dropped by roughly the same amount as in control animals that were injected with a similar amount of insulin.
Just as importantly, the pigs that swallowed the capsules showed no signs of digestive distress or tissue damage.
But the capsules were only shown to work in pigs that were fasting, with empty stomachs. It’s not clear how they might work in a pig, or person, that has recently eaten.
It’s also important to note that in the published study, the capsules delivered only 0.3 milligrams of insulin — a low dose of the drug. But the researchers announced that they had developed a version of the capsule that delivers 5 milligrams of insulin, which is a more practical dose for people with diabetes.
While much more research is needed before insulin microneedle pills are available to treat diabetes in humans, this approach is just one more reason to believe that in a few years, injecting insulin — or infusing it with a pump — won’t be the only way to take the drug.
Want to learn more about oral insulin? Read “Oral Insulin: Inching Closer to Reality.”