Bloomberg has an article on Novo Nordisk (NVO) and their huge ongoing effort to come up with an orally available form of insulin. That's been a dream for a long time now, but it's always been thought to be very close to impossible. The reasons for this are well known: your gut will treat a big protein like insulin pretty much like it treats a hamburger. It'll get digested, chopped into its constituent amino acids, and absorbed as non-medicinally-active bits which are used as raw material once inside the body. That's what digestion is. The gut wall specifically guards against letting large biomolecules through intact.
So you're up against a lot of defenses when you try to make something like oral insulin. Modifying the protein itself to make it more permeable and stable will be a big part of it, and formulating the pill to escape the worst of the gut environments will be another. Even then, you have to wonder about patient-to-patient variability in digestion, intestinal flora, and so on. The dosing is probably going to have to be pretty strict with respect to meals (and the content of those meals).
But insulin dosing is always going to be strict, because there's a narrow window to work in. That's one of the factors that's helped to sink so many other alternative-dosing schemes for it, most famously Pfizer's (PFE) Exubera. The body's response to insulin is brittle in the extreme. If you take twice as much antihistamine as you should, you may feel funny. If you take twice as much insulin as you should, you're going to be on the floor, and you may stay there.
So I salute Novo Nordisk for trying this. The rewards will be huge if they get it to work, but it's a long way from working just yet.