As I write this, there's a continuous glucose monitoring sensor attached to my left arm. The little iPod-style receiver sits nearby on my desk, taking in blood sugar readings every few minutes and displaying those numbers on its color screen.
What if I could have that same minute-by-minute sensor implanted under my skin, where it could do its work without needing to be changed out for full year or more?
That's the dream a number of companies have been working on for years -- including GlySens in San Diego, CA. This company's actually been chipping away at this dream for more than a decade; we wrote about them back in 2011, and there was also this comprehensive report from Karmel Allison a year earlier.
The small 16-year-old startup is developing an implantable CGM dubbed ICGM, which in its second incarnation uses a sensor that looks like a fat thumb drive with a quarter-sized circle in the middle.
The sensor will be implanted under the skin, probably in the lower abdomen area, through a simple surgical procedure, and would last at least a year. Fingerstick calibrations would only be needed once or twice a month. The implanted sensor would communicate with a receiver a little thicker than an iPhone that you'd carry around with you.
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GlySens is now back in the news, as it gears up for late-stage clinical studies and a fresh round of investor-searching so it can conduct a larger human trial within the next year -- and hopefully move toward FDA regulatory filing by 2017.
"Our goal is to deliver a CGM product that let's person hopefully forget about the sensor itself and just have the information without the hassle you get from a traditional sensor," said Joe Lucisano, CEO and co-founder of GlySens. "We're trying to offer some new level of freedom, for people to take control in way they can't now."
Though cutting-edge, this certainly isn't a new idea, and GlySens itself has been around a while. Founded in 1998, the idea for the ICGM product came from Dr. David Gough, who studied at the University of Utah and then did post-doctoral research at the Joslin Clinic, before starting at the University of California, San Diego (UCSD) in the late 70s. He's been working on these glucose-monitoring biosensors since then. Lucisano was one of his grad students at UCSD, and after becoming an entrepreneur and working on some diabetes glucose monitoring projects on his own (including Minimed), the two teamed up in the late 90s and created the tech startup GlySens.
Early on, they were exploring a long-term implantable catheter CGM, but eventually determined it wasn't appealing because people seemed too concerned about the higher risk of infection. So, they changed the design and eventually settled on a model that more resembled a mini hockey puck, or maybe a thicker silver-colored milk cap. With a small six-person feasibility study finished about a year-and-a-half ago showing positive results, Lucisano says they decided to make the ICGM sensor even smaller, to its current size of about an inch-and-a-half long and one-third of an inch thick.
Patients eventually won't even think about the implanted sensor their day-to-day diabetes routine, he said -- aside from when they look at the color screen receiver.
Lucisano tells us that the ICGM system should be as accurate as any other CGM device, but unlike other devices it works by detecting oxygen, allowing the system to be more stable in that interstitial fluid environment than traditional CGMs. The sensor will have an outer membrane with electro-chemical detectors, and they'd be primed with enzymes to interact with the oxygen.
Basically, the ICGM will have multiple built-in checks to ensure the sensor is doing what it's supposed to.
"By measuring the amount of remaining oxygen from the enzyme reaction, the device can calculate the extent of the enzyme reaction and the concentration of glucose," Lucisano said.
Yes, it's true that competing CGM manufacturers Dexcom and Medtronic have turned their attention away from long-term implantable sensors... concepts may still be in development, but they aren't immediate priorities. When asked about this, Lucisano pointed to differences in business models.
"I personally, and we as a company, have nothing but admiration for the pioneering work Medtronic and Dexcom have done. They've chosen a path to get a product on the market, and that's worked out very well for them and the diabetes community. We think our approach is the next step."
— Joe Lucisano, CEO and co-founder of GlySens, on implantable CGM technology
He also says the ICGM would function in situations where conventional CGMs might not, like if a Dexcom or Medtronic sensor gets dislodged or gets thrown off by some other human-use factor.
"We certainly believe that it will deliver clinical accuracy that patients expect. but we don't have enough human clinical trials yet to show that conclusively," he said.
GlySens has research under its belt that it says proves the concept would work, and the company leaders hope for a larger human trial in the next year, using the second-gen design they have now. Chances are the design may change and get even smaller, Lucisano says, and they still need to determine things like whether the ICGM would need to be rotated under the skin or could be implanted in the same spot.
We asked how GlySens would respond to concerns about infection or allergy under the skin, and Lucisano really downplayed that as something that science shows wouldn't be much of an issue, if at all. He pointed to defibrillators and infusion port sites, and how those rarely present issues in the people they're implanted in.
Down the road, Lucisano says GlySens would ideally be able to be integrated with an insulin pump and other D-tech for easier use, but nothing is definite at this point.
The cost could also be something that might weigh people for or against a particular device, but Luciscano says their initial vision of ICGM will cost less than existing CGMs on the market (!).
As to Artificial Pancreas tech, Lucisano sees the ICGM as the next step in getting an AP device to the market.
"We see that a conventional CGM has played a role in enabling great research to be done, but we think our device would enable broader capability for an Artificial Pancreas," he said.
God knows the idea of an implantable CGM is a concept many of us patients are interested in seeing become a reality. Recently, I participated in a diaTribe survey saying exactly that: I'd be interested in seeing it and even trying it out, but my larger concerns about whether it's possible for an implanted sensor to function correctly over time without problems trump everything else. Just keeping it real...
And on that note, what stands out to me the most is the fact that we're 40 years into the research without any marketable product, and these feasibility trials seem to always be ongoing as companies search for investors...
Meanwhile, we cannot and should not give up hope for something better. And I trust that the existing CGM companies are working on implantable options that could someday present an "under the skin" option that we can trust.
And until then, I'll keep wearing this current CGM sensor on my skin, trusting and relying on it and most of the time when I'm not looking at the receiver, forgetting that it's even attached to me.