The U.S. Food and Drug Administration has placed a clinical hold on ZIOPHARM Oncology Inc.'s phase 1 study using CAR-T therapies to treat certain types of blood cancers.

Chimeric antigen receptor T-cell, or CAR-T cell, therapies involve infusing patients with lab-enhanced versions of their own cells to attack cancer cells.

The trial is being conducted by Ziopharm, Intrexon Corp.'s unit Precigen Inc. and the University of Texas MD Anderson Cancer Center in patients with CD19 positive leukemias and lymphomas that have returned or are resistant to treatment.

Leukemia is a type of cancer that usually begins in the bone marrow and results in high numbers of abnormal white blood cells. Lymphoma is a type of cancer that begins in cells of the immune system, called lymphocytes. These cells are in the lymph nodes, spleen, thymus, bone marrow and other parts of the body.

The FDA has requested additional information relating to chemistry, manufacturing and controls. The company, along with its partners, will address the FDA's requests, which may cause a delay in the initiation of this trial.

"We know what is needed to address the hold issues and are looking forward to responding to the agency in a timely manner," said Ziopharm CEO Laurence Cooper.

Boston-based Ziopharm Oncology is a biotechnology company focused on the development of next-generation immunotherapies utilizing gene- and cell-based therapies to treat patients with cancer.