In the winter of 2025, Vertex Pharmaceuticals presented results from the first major study (Phase I/II) of zimislecel (formerly VX-880), a stem cell-based drug. This experimental treatment aims to restore islet Langerhans cells in patients’ livers.
The trial involved 14 patients with severe type 1 diabetes and hypoglycaemia detection disorders. All participants received a single infusion of zimislecel into a hepatic vein and starter immunosuppressive therapy without glucocorticoids. Based on one-year data, 10 of 12 stopped insulin injections completely, becoming insulin-independent; the remaining two patients reduced their insulin dose by 92% on average. All participants had normalised HbA1c levels (<7%) and spent more than 70% of the time in the glycemic range of 70-180 mg/dl.
Side effects:
– neutropenia was observed in 3 patients;
– two fatalities were recorded: one from cryptococcal meningitis (off protocol), the other due to severe cognitive impairment unrelated to treatment.
The cessation of insulin therapy in 83% of participants is a very major achievement, signifying that endogenous insulin secretion can be restored. The American Diabetes Association (ADA) called the data “unprecedented” after three rounds of submissions at the ADA-2025 conference in Chicago.
However, it should be kept in mind that the study was small (12-14 participants) and short (12 months); extensive follow-up experience is required. Data on long-term efficacy, safety, and commercial affordability are not yet known.
Phase III has now been initiated, with approximately 50 patients planned to participate. Further results are expected later in the year, after which filing with the FDA will commence.
The drug is positioned as a breakthrough “functional remission” for a group of patients with severe diabetes and a propensity for hypoglycaemic events. If efficacy is fully confirmed, it will be a global revolution in type 1 diabetes therapy.