After a bioengineered upgrade, cancer-fighting immune cells no longer cause severe side effects, but are still effective against an aggressive form of cancer.

B-cell lymphoma is a malignancy of the human immune system. Some cases are treated with non-cancerous immune cells that have been isolated from the patient and genetically modified. But these CAR T cells — shorthand for chimeric antigen receptor T cells — can cause serious side effects, including multi-organ failure.

Si-Yi Chen at the University of Southern California in Los Angeles and Jun Zhu at Peking University Cancer Hospital and Institute in Beijing and their colleagues tinkered with a portion of a receptor on the T cells. They used the cells they modified to treat people with B-cell lymphoma whose cancer either had not responded to treatment or had recurred.

The 25 study participants received a range of T-cell dosages, but none of the participants reported serious side effects. In a subset of 11 participants who received a particular dose of modified T cells, 6 went into complete remission.