Stopping Leukemia

A tiny tweak to the DNA code just bought some of the sickest leukemia patients something they were told they’d never get.

Remission.

In an early trial from London, a gene‑edited CAR‑T therapy sent 82% of patients with aggressive, “incurable” T‑cell leukemia into deep remission, long enough to bridge most of them to curative stem cell transplants.

Instead of using the patient’s own immune cells, researchers at UCL and Great Ormond Street Hospital built “off‑the‑shelf” CAR‑T cells from healthy donors and then rewired them with base‑editing tools. The product, called BE‑CAR7, was given to 11 people with relapsed or refractory T‑cell acute lymphoblastic leukemia (T‑ALL), nine children and two adults who had essentially run out of options.

By day 28 after infusion, every single patient hit a complete morphologic remission, even if their blood counts hadn’t fully bounced back yet—a huge deal in a cancer that usually laughs at salvage therapy.

Here’s where that “82% remission” headline comes from. When doctors zoomed in with ultra‑sensitive tests (flow cytometry or PCR), 9 of the 11 patients (82%) reached deep, minimal-residual-disease-negative remission, meaning they couldn’t detect leukemia cells at all.

That clean window gave most of them the chance to go on to an allogeneic stem cell transplant, which is still the main route to long‑term cure in this setting. With 3 to 36 months of follow‑up so far, about 64% of the treated group (7 of 11) are still in remission post‑transplant, which far exceeds historical survival rates for multiply relapsed T‑ALL.

Classic CAR‑T therapies have a big problem in T‑cell leukemias. The engineered T cells want to kill each other and can also attack the host’s normal T cells. To get around that, the team used base editing—a gentler form of gene editing that swaps single DNA “letters” without slicing the double helix—to make several precise changes in the donor T cells.

The edits:

  • They removed the normal T‑cell receptor to lower graft‑versus‑host disease risk.

  • They knocked out CD7, so the CAR‑T cells don’t commit “friendly fire” on themselves while still targeting CD7 on cancerous T cells.

  • They deleted CD52 to enable survival with the lymphodepleting drug alemtuzumab, which is used to clear the patient’s own immune cells.

All of that is layered onto a CD7‑targeting CAR, so the final product is basically a smart, zombie‑resistant T cell designed to hunt down malignant T cells and stay functional through the pre‑treatment blitz.

Before we get too excited, there are a couple things to note:

This is still phase 1 territory, so it is more “proof of concept” than a ready‑for‑prime‑time cure. Patients saw the usual intense CAR‑T‑style toxicities such as cytokine release syndrome, long‑lasting low blood counts, skin rashes, and a lot of viral reactivations while their immune systems were rebuilding, especially after transplant.

Also, the trial-numbers are tiny.

11 people, hand‑picked and treated at expert centers, with follow‑up that tops out at three years so far, so no one can promise how durable these remissions will be or how scalable the therapy is. But the leap from “no options” to “two‑thirds alive and disease‑free a year or more after transplant” is a powerful signal that demands larger, more diverse trials.

On a larger scale, this is the first time base‑edited immune cells have shown this level of clinical punch in humans, and that opens multiple doors. If gene‑edited, “ready‑made” CAR‑T products like BE‑CAR7 can be mass‑manufactured, it could eventually mean:

  • Faster treatment. No weeks‑long wait to engineer each patient’s own cells.

  • Broader access. In theory, one donor batch could treat many patients, including those whose T cells are too beaten up for standard CAR‑T manufacturing.

  • More complex cancers. Similar multi‑edit strategies could be adapted for other leukemias or lymphomas that don’t respond to today’s tools.

For now, “82% remission” sits in the exciting‑but‑early stage. It is a truly hopeful and stunning result for a tiny group of people who had run out of options, and a glimpse of how quietly swapping a single DNA letter in the right immune cell might rewrite the story for some of the hardest-to-treat leukemias.

Sources:

https://www.mayoclinic.org/diseases-conditions/leukemia/symptoms-causes/syc-20374373

https://www.medpagetoday.com/hematologyoncology/leukemia/119346

https://www.nature.com/articles/s41591-025-03813-5

 

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