Researchers at Karolinska Institutet have explored natural killer (NK) cell-based immunotherapy on patients with treatment-resistant leukemia. The study, which is published in the scientific journal Clinical Cancer Research, shows that the new therapy is effective against several types of leukemia.

NK cells are a special type of white blood cell discovered at Karolinska Institutet in the 1970s that can recognize and kill cancer cells. In recent years, much knowledge has been generated on the biology of the cells and their ability to recognize tumor cells. Research into immunotherapy, in which the immune system is stimulated to attack cancer cells, has also made great strides forward. The potential of NK cells as a form of immunotherapy has not, however, been fully explored.

Researchers at Karolinska Institutet have now tested an NK cell-based immunotherapy on 16 patients with treatment-resistant leukemia of the types myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), or transitional MDS/AML phases. The patients were treated with activated NK cells from related donors.

Some patients became symptom-free

Six of the patients displayed objective responses to the treatment, some even attaining complete remission and thus becoming symptom-free. Five of these six patients became healthy enough to undergo curative stem cell transplantation, an intervention that was not possible before the NK cell treatment. Three of them have now survived for over 3 years, one for over 5. The infusion of NK cells produced no serious adverse effects.

“Our study shows that patients with MDS, AML, and MDS/AML can be treated with NK cell-based immunotherapy and that the therapy can be highly efficacious,” says Professor Hans-Gustaf Ljunggren at Karolinska Institutet’s Department of Medicine in Huddinge, who initiated and led the study with departmental colleague Professor Karl-Johan Malmberg.

Open the way for new clinical studies

“The results open the way for new clinical studies, where there is potential for further improvements to study design that includes producing the next generation of NK cell-based immunotherapy,” says Andreas Björklund, specialist doctor at Karolinska University Hospital, who had clinical responsibility for the patients treated using the new therapy.