For many patients with aggressive blood cancer, a stem cell transplant is the last chance of cure. But even after a successful transplant, leukaemia returns in a share of patients, and the situation then is often hopeless. Researchers at University Medicine Frankfurt, led by Professor Eva Rettinger, have now shown in a phase I/II clinical trial that a new cell therapy can prevent exactly this relapse, and with significantly fewer side effects than previous approaches.
What Are CIK Cells and How Do They Work?
At the centre of the trial are cytokine-induced killer cells, or CIK cells. These are immune cells obtained from the blood of the stem cell donor, activated in the lab with interleukin-15 (IL-15), and then transferred to the patient. IL-15 is a natural signalling molecule that stimulates immune cells and helps them recognize and destroy cancer cells.
Until now, so-called donor lymphocytes were used after stem cell transplantation to prevent relapse. This method works but carries a significant risk. The donor cells can also attack healthy tissue of the patient, a feared complication known as graft-versus-host disease. In this trial, the CIK cells caused this effect significantly less often and less severely.
What the Trial Showed
In the multicentre trial, conducted at five research centres, 53 patients received the CIK cell therapy, including children and adolescents with multiple transplantations. The result: the therapy stabilized the success of the stem cell transplant over a longer period and prevented the return of leukaemia in a meaningful share of cases. The data were published in the Journal of Clinical Oncology, one of the world's most respected cancer medicine journals.
Professor Rettinger emphasized that the therapy builds on existing donor cells and therefore avoids the complex and costly procedure required for newer CAR-T cell therapies. This makes it easier to deploy in clinical practice.
A Step in a Larger Shift
In parallel, researchers elsewhere are working on even more ambitious approaches. Rather than modifying immune cells in the lab and then transferring them, lipid nanoparticles carrying mRNA and the CRISPR-Cas9 gene editor are being tested to reprogramme T cells directly inside the patient's body. That method is at an earlier stage but shows promising results in animal models.
The Frankfurt trial is thus one step in a series of advances that have fundamentally changed blood cancer treatment in recent years. Where a decade ago many patients had no options left after relapse, several approaches are now available. CIK therapy is now one of the best-documented of them.
What Comes Next
The Frankfurt group is planning a follow-up trial combining CIK therapy with an additional antibody treatment. Other teams are already working on combinations of CAR-T cells and bispecific antibodies designed to further boost the expansion of therapy cells. Initial results from these combination therapies are expected by 2028.