CAR-T cell therapy has offered new hope to children and adults with certain types of blood cancers who have no other remaining treatment options.

The treatment, a personalized cancer immunotherapy, turns a patient’s T cells, a type of white blood cell, into cancer-cell fighters. CAR-T cell therapy is not a drug a pharmacist can provide. The process of adding chimeric antigen receptors (CARs) to the patient’s T cells must be done in a special laboratory and can take several weeks. Some patients don’t have enough T cells, or the T cells they have are not the right quality needed to manufacture the treatment. And it’s expensive. The therapy, which is typically given one time, can cost $373,000 or more.

To get around these obstacles, Katy Rezvani, an immunology researcher at the University of Texas MD Anderson Cancer Center in Houston, developed a CAR treatment that uses a donor’s natural killer (NK) cells instead of the patient’s T cells. NK cells are another type of white blood cell. They can be harvested from the blood of a baby’s umbilical cord and then stored in a blood bank to be used for other medical purposes. If using NK cells from cord blood works as well as using a patient’s white blood cells, Rezvani says it may be possible to develop an equivalent to CAR-T cell therapy that is readily available.

Rezvani launched the first U.S. trial in humans of her CAR-NK cell treatment in June 2017. To date, nine patients have been treated in the phase I trial, which is evaluating the treatment’s safety and the type of immune response it generates.

Beatriz Martín-Antonio, a biologist at the Josep Carreras Leukaemia Research Institute in Barcelona, Spain, says the big unknown is whether CAR-NK treatments will have side effects not seen with CAR-T therapy. She says that researchers are also trying to develop CAR-T cells made from the T cells of people without cancer. These CAR-T treatments are starting to be tested in clinical trials.