NEW YORK: The U.S. Food and Drug Administration has been looking into 22 cases of T-cell cancers that occurred after treatment with CAR-T, two top FDA officials said on Wednesday, days after asking drugmakers to add a serious warning on the label of their cancer therapies that use the CAR-T technology.

In an article published in the New England Journal of Medicine, the officials – Dr. Peter Marks and Dr. Nicole Verdun – said that secondary malignancies have been reported in conjunction with five of the six available CAR-T products and that the cancers included T-cell lymphoma, T-cell large granular lymphocytosis, peripheral T-cell lymphoma, and cutaneous T-cell lymphoma.

CAR-T treatment generally involves extracting disease-fighting white blood cells known as T-cells from a patient, re-engineering them to attack cancer and infusing them back into the body.

The products in question include Bristol Myers Squibb’s Breyanzi as well as Abecma, which BMS developed with 2seventy bio.

J&J unit Janssen and Legend Biotech’s Carvykti, Novartis AG’s Kymriah, and Gilead’s Tecartus and Yescarta are also a part of the investigation.

Marks and Verdun said the FDA has enough data about 14 of the cancer cases to determine that those cancers had manifested within two years of treatment.

They said that in three cases for which genetic sequencing had been done they had found evidence that the CAR-T product was most likely involved in development of the cancer.

Still, “with more than 27,000 doses of the six approved products having been administered in the United States, the overall rate of T-cell cancers among people receiving CAR-T therapies appears to be quite low, even if all reported cases are assumed to be related to treatment,” the FDA officials wrote.