Targeting B-cell malignancies with specific T cells can lead to complete clinical responses

However, clinical success may require T cells to remain present in the body for prolonged periods of time, which results in sustained attack against B cells, an important branch of the immune response, and a substantial reduction in their total number.

The corresponding author of this work, Dr. Carlos A. Ramos, associate professor in the Center for Cell and Gene Therapy at Baylor College of Medicine, Houston Methodist Hospital and Texas Children's Hospital, and his colleagues from Baylor College of Medicine have designed and tested a variation of the above treatment. They armed T cells with the means to specifically target a subpopulation of B cells that encompasses the malignant ones, instead of all malignant and healthy B cells. The promising results of their phase I clinical trial appear in the Journal of Clinical Investigation.

B cells can be members of two mutually exclusive populations, each having either a κ- or a λ-light chain on their surface. Ultimately, each B-cell population will produce κ-type or λ-type antibodies. B cell malignancies, such as non-Hodgkin lymphoma, chronic lymphocytic leukemia or multiple myeloma, express on their surface either κ- or λ-light chains, but not both. "We reasoned that targeting the light chain expressed by malignant B cells should efficiently kill tumor cells while sparing normal B cells expressing the other type of light chain," said Ramos.

The researchers isolated T cells, members of the immune system that identify and destroy abnormal cells, from patients with B cell malignancies expressing the κ-light chain on their surface. Then, they modified each patients' T cells so they could target the κ-light chain on the surface of malignant B cells. The modified T cells were infused back into the patient, and each patient monitored for progression of the disease and side effects.

The main goal of phase I clinical trials is to determine the safety of a new medical treatment in human patients. "We found the treatment to be feasible and safe at all the dose levels studied," said Ramos. "In two of the nine patients with non-Hodgkin lymphoma or chronic lymphocytic leukemia, our treatment resulted in complete remission, and a third patient had a partial response. Four of the seven patients with multiple myeloma had a stable disease lasting two to 17 months after the treatment."

The potential advantages of this new approach to treating B cell malignancies include less toxicity and temporary side effects and preservation of a part of the B cell responses; that is, the body's ability to produce normal, λ-type antibodies. "Our approach, although we are still optimizing it, offers a new possibility for patients in whom other treatments have not been successful," said Ramos.