Beta Bionics iLet — bihormonal (insulin + dasiglucagon)

The bihormonal iLet is the dual-hormone version of Beta Bionics' bionic pancreas, descended from the Boston University and Massachusetts General Hospital "bionic pancreas" research program.¹ It delivers two hormones: insulin to bring glucose down, and glucagon — the body's natural counter-hormone — in tiny automated microdoses to push glucose back up before a low becomes dangerous. That second hormone is what lets a closed loop run more aggressively without trading tight control for hypoglycemia.² In this configuration the glucagon is dasiglucagon, a 29-amino-acid glucagon analog engineered by Zealand Pharma with seven substitutions so it stays stable as a ready-to-use liquid at neutral pH — solving the old problem that natural glucagon clumps and degrades within hours in water and must be reconstituted fresh.³

The defining evidence is a 2021 home-use study, the first human test of the bihormonal iLet and the first multi-day use of dasiglucagon. Ten adults with type 1 diabetes used each configuration for 7 days with no diet or exercise restrictions, the device initialized only with body weight.⁴ In the bihormonal arm, mean sensor glucose was 139 mg/dL with 79% time in range (70-180 mg/dL), versus 149 mg/dL and 72% on insulin alone. Median time below 54 mg/dL — the dangerous-low threshold — fell to just 0.2% (from 0.6%).⁴ This echoed earlier bionic-pancreas trials: a 2014 outpatient study reached a mean of 138 mg/dL,¹ and a 2016 home-use trial (using reconstituted human glucagon) lowered mean glucose to ~140 mg/dL with less hypoglycemia and no carb counting.²

Device burden is the honest trade-off. A two-hormone pump means a second reservoir and a second consumable, but the 2021 study was encouraging on practicality: a single prefilled dasiglucagon cartridge lasted the entire 7 days (average dose 0.35 mg/day), with no occlusions or infusion-site reactions. The main side effect was mild nausea (0.47 on a 0-10 scale), with one episode of vomiting.⁴ The chief complication was insulin leakage at the cartridge connector — a hardware issue the team redesigned for future devices.⁴

Maturity and access — read this carefully. Only the insulin-only iLet is FDA-cleared (May 2023, for people 6 and older with type 1 diabetes, paired with a compatible CGM) and commercially sold.⁵ The bihormonal configuration is not approved or available anywhere — it remains investigational, evaluated only in small feasibility studies. Beta Bionics holds FDA Breakthrough Device Designation across its insulin-only, glucagon-only, and bihormonal configurations.³ We classify this record as research and historical lineage, not a shipping product.

What's coming. The original path to market was the Zealand dasiglucagon program.³ In May 2024, however, Beta Bionics signed an exclusive worldwide agreement with Xeris Biopharma to supply a pump-compatible glucagon using Xeris's XeriSol stable-glucagon technology for the bihormonal iLet — and by 2025 had completed pump-compatibility milestones with Xeris.⁶ In 2025 the company reported a glucagon pharmacokinetic study in Canada and planned a fresh bihormonal feasibility trial.⁶ So the "dasiglucagon iLet" specifically is best understood as the foundational research that proved a two-hormone closed loop works; the live commercial path now runs through a next-generation glucagon formulation and a registration program that has not yet reached approval.

References

1. Russell SJ, El-Khatib FH, Sinha M, et al. Outpatient glycemic control with a bionic pancreas in type 1 diabetes. N Engl J Med (2014). https://doi.org/10.1056/NEJMoa1314474 ↩ ↩²

2. El-Khatib FH, Balliro C, Hillard MA, et al. Home use of a bihormonal bionic pancreas versus insulin pump therapy in adults with type 1 diabetes: a multicentre randomised crossover trial. Lancet (2016). https://doi.org/10.1016/S0140-6736%2816%2932567-3 ↩ ↩²

3. Zealand Pharma / Beta Bionics. Beta Bionics receives FDA Breakthrough Device Designation for the iLet Bionic Pancreas System (describes dasiglucagon as a stable, ready-to-use aqueous glucagon analog for the bihormonal iLet). GlobeNewswire (2019). https://www.globenewswire.com/news-release/2019/12/10/1958323/0/en/Zealand-Pharma-partner-Beta-Bionics-receives-FDA-Breakthrough-Device-Designation-for-the-iLet-Bionic-Pancreas-System.html ↩ ↩² ↩³

4. Castellanos LE, Balliro CA, Sherwood JS, et al. Performance of the insulin-only iLet bionic pancreas and the bihormonal iLet using dasiglucagon in adults with type 1 diabetes in a home-use setting. Diabetes Care (2021); NCT03840278. https://doi.org/10.2337/dc20-1086 ↩ ↩² ↩³ ↩⁴

5. U.S. Food and Drug Administration. FDA clears new insulin pump and algorithm-based software to support enhanced automatic insulin delivery (iLet ACE Pump and iLet Dosing Decision Software, insulin-only, ages 6+, May 2023). FDA (2023). https://www.fda.gov/news-events/press-announcements/fda-clears-new-insulin-pump-and-algorithm-based-software-support-enhanced-automatic-insulin-delivery ↩

6. Beta Bionics. Fourth Quarter and Full Year 2024 Financial Results (completion and delivery by Xeris of a pump-compatible XeriSol glucagon formulation for the bihormonal pump; bihormonal pipeline advancement). GlobeNewswire (2025). https://www.globenewswire.com/news-release/2025/03/25/3049143/0/en/Beta-Bionics-Announces-Fourth-Quarter-and-Full-Year-2024-Financial-Results-and-Introduces-Annual-Guidance-for-Full-Year-2025.html ↩ ↩²