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.² 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.³ In this configuration the glucagon is dasiglucagon, a 29-amino-acid glucagon analog engineered by Zealand Pharma described as a stable, ready-to-use aqueous solution — solving the old problem that natural glucagon clumps and degrades within hours in water and must be reconstituted fresh.⁴

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.⁵ 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%).⁵ This echoed earlier bionic-pancreas trials: a 2014 outpatient study reached a mean of 138 mg/dL,² and a 2016 home-use trial (using reconstituted human glucagon) lowered mean glucose to ~140 mg/dL with less hypoglycemia and no carb counting.³

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.⁵ The chief complication was insulin leakage at the cartridge connector.⁵

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) and commercially sold.⁶ The bihormonal configuration is not approved or available anywhere in the regulator, registry, and filing sources read — 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.⁴ 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.⁴ 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 and reported a glucagon pharmacokinetic study in Canada.⁷ The dasiglucagon iLet is therefore best understood as the foundational research that proved a two-hormone closed loop works; the live commercial path now runs through the Xeris glucagon formulation.⁷

That path has restarted in the clinic, but it has also encountered development work. Beta Bionics reported completing a first-in-human Phase 2a feasibility trial in New Zealand in the fourth quarter of 2025 (per the cited Q4-2025 company release, whose body was unread in this review) and initiated a second Phase 2a trial in the first quarter of 2026.⁸⁹ Its August 2026 10-Q says those feasibility results identified opportunities to improve both the glucagon asset's excipient profile and the dosing algorithms.¹ In the filing sources read, no Phase 2b, pivotal, submission, or launch date was found. One honest caveat remains: the clinical disclosures call it only “the glucagon asset.” The Xeris formulation is a reasonable inference from the collaboration and supply agreement, not a formulation name used in the trial disclosure itself.