Paradigm leap

End of insulin? Stem cell therapy rekindles hope

The experimental treatment zimislecel restored insulin production. In 10 out of 12 patients, no more injections after 12 months

by Francesca Cerati

23 June 2025

2' min read

Key points

How the therapy works
A 'functional cure' on the horizon?
What happens now?

2' min read

It may sound like science fiction, but it is experimental medicine with a very real basis: 10 people with type 1 diabetes no longer need to inject themselves with insulin for over a year after receiving a cell therapy called zimislecel, developed by Vertex Pharmaceuticals.

The data, presented at the annual meeting of the American diabetes association and published simultaneously in the New England Journal of Medicine, confirm the revolutionary potential of this therapy. Zimislecel is the first treatment derived from stem cells that are fully differentiated into pancreatic insular cells, capable of producing insulin in response to glucose. A solution that aims not only to control symptoms, but to restore the very physiology of insulin production.

How the therapy works

Zimislecel is an allogeneic, i.e. universal, therapy obtained from pluripotent stem cells that are transformed into pancreatic beta cells and then infused directly into the patient's liver via the portal vein. To promote engraftment, patients receive immunosuppressive therapy without glucocorticoids.

In the phase 1/2 clinical trial, 12 patients with type 1 diabetes received a full dose of 0.8 billion cells. All patients showed endogenous insulin production measurable by C-peptide, no severe hypoglycaemic episodes and glycated haemoglobin (HbA1c) levels below the recommended threshold of 7%. But the most surprising finding was that 10 out of 12 (83%) were able to completely discontinue the use of exogenous insulin, maintaining glycaemic control.

'The magnitude, consistency and duration of the results are unprecedented for a cell therapy in type 1 diabetes,' commented Carmen Bozic, Chief Medical Officer of Vertex. - This study reinforces the transformative potential of zimislecel'.

A 'functional cure' on the horizon?

Type 1 diabetes is an autoimmune disease in which the immune system attacks the beta cells of the pancreas, making the patient completely dependent on exogenous insulin. Current therapies do not act on the causes, but on the daily management of blood glucose. Transplantation of pancreatic islets is possible, but limited by donor availability and complications related to immunosuppression.

Zimislecel is proposed as a standardised, ready-to-use and potentially scalable alternative, overcoming the limitations of traditional transplantation and according to Vertex s was 'generally well tolerated' and no serious adverse events were attributed to the treatment.

What happens now?

Zimislecel is currently in phase 3 clinical trials in North America and Europe, and Vertex aims to apply for approval by 2026. "We have completed enrolment and administration for phase 1/2/3 and look forward to submitting applications for approval," Bozic announced.

The programme became even more important after Vertex halted development of the VX-264 therapy, an implantable insular cell variant that failed to achieve its goals. Now, all attention is focused on zimislecel, the only candidate left in the pipeline for type 1 diabetes, alongside the already approved Casgevy for sickle cell anaemia.

The success of zimislecel could represent not only a therapeutic paradigm shift, but also a new standard in regenerative medicine applied to autoimmune diseases. 'This could be the first step towards a functional treatment of type 1 diabetes,' said one of the study authors.