The microneedle pill has hollow needles, and when it reaches the desired location in the digestive tract, the pH-sensitive coating surrounding the capsule dissolves, allowing the drug to be released through the microneedles.
Image credit: Christine Daniloff/MIT, based on images by Carol Schoellhammer and Giovanni Traverso
The researchers, from the Massachusetts Institute of Technology (MIT) and Massachusetts General Hospital (MGH), have published the results of their study - which tested the microneedle pill in the gastrointestinal (GI) tracts of pigs - in the Journal of Pharmaceutical Sciences.
Though most of us would probably prefer swallowing a pill over having an injection, many drugs cannot be given in pill form because they are broken down in the stomach before being absorbed.
Biopharmaceuticals made from large proteins, such as antibodies - known as "biologics" - are used to treat cancer and autoimmune disorders such as arthritis and Crohn's disease, and they also include vaccines, recombinant DNA and RNA.
"The large size of these biologic drugs makes them nonabsorbable," explains lead author MIT graduate student Carl Schoellhammer. "And before they even would be absorbed, they're degraded in your GI tract by acids and enzymes that just eat up the molecules and make them inactive."
In an effort to design a capsule that is capable of delivering a wide range of drugs - while preventing degradation and effectively injecting the medicine into the GI tract - Schoellhammer and colleagues constructed the capsule from acrylic, including a reservoir for the drug that is coated with hollow, 5 mm long needles made of stainless steel.
The capsule measures 2 cm long and 1 cm in diameter.
Needle capsule worked safely and effectively in pigs
The team notes that previous studies involving humans who have accidentally swallowed sharp objects have suggested swallowing a capsule coated with short needles could be safe. They explain that there are no pain receptors in the GI tract and that, as a result, patients would not feel any pain.
But to assess whether their capsule could safely and effectively deliver the drugs, the researchers tested the pill in pigs, using insulin in the drug reservoir.
The capsules took more than a week to move through the whole digestive tract, and there were no traces of tissue damage, the researchers say. Additionally, the microneedles effectively injected insulin into the lining of the pigs' stomachs, small intestines and colons, which resulted in their blood glucose levels dropping.
The video below explains in more detail how the capsule works:
Co-lead author Giovanni Traverso, a research fellow at MIT's Koch Institute for Integrative Cancer Research and gastroenterologist at MGH, notes that the pigs' reduction in blood glucose was faster and larger than the drop observed from insulin injection.
"The kinetics are much better and much faster-onset than those seen with traditional under-the-skin administration," he says. "For molecules that are particularly difficult to absorb, this would be a way of actually administering them at much higher efficiency."
'Oral delivery of drugs is a major challenge'
Though they used insulin for their tests in pigs, the researchers say they envision their capsule being used to deliver biologics to humans.
"This could be a way that the patient can circumvent the need to have an infusion or subcutaneous administration of a drug," says Traverso.
Prof. Samir Mitragotri, a professor at the University of California-Santa Barbara - who was not involved in the research - says:
"This is a very interesting approach. Oral delivery of drugs is a major challenge, especially for protein drugs. There is tremendous motivation on various fronts for finding other ways to deliver drugs without using the standard needle and syringe."
In terms of future modifications, the team plans to alter the capsule so that contractions of the digestive tract slowly squeeze the drug out of the capsule as it travels through the body, and they also want to make the needles out of degradable polymers and sugar that break off, becoming embedded in the gut lining and slowly disintegrating.