According to a Regeneron statement to NBC News, the company based its tests for its anti-COVID-19 treatment on a cell line called HEK293T. They come from fetal kidney tissue that was donated in the 1970s. Research laboratories use these cells because they can replicate indefinitely, and are therefore considered “immortalized.”

“293T cells were used to test the ability of antibodies to neutralize the virus. HEK293T was not used otherwise, and fetal tissue was not used in this research. We do not use human stem cells or embryonic stem cells in the development of the monoclonal antibody cocktail, “said Alexandra Bowie, Regeneron’s spokeswoman.

The properties of HEK293T cells are very useful in scientific research. They can be trained to generate virus proteins like small factories, said Arnold Kriegstein, director of the stem cell program at the University of California, San Francisco.

The researcher, who is not involved in Regeneron’s research, says scientists can exploit these properties in the development of treatments and vaccines for COVID-19, as cells can be taught to produce the so-called spike protein of the virus. It is a unique protein of the SARS-CoV-2 virus, which causes COVID-19 disease, so it is an excellent target for drugs and vaccines.

It is also the mode of action of Regeneron’s monoclonal antibody-based treatment that binds to this spike protein through which the virus infects cells. HEK293T cell lines played a role in the early development of the drug: the researchers used cells trained to produce the virus protein to test the drug’s effectiveness against the virus.

“The antibodies themselves are not made up of these fetal cells. But the role of these cells has been critical in testing the effectiveness of their method, “said Kriegstein.

Fetal tissue cells have been used over the years in studies of birth defects, Alzheimer’s disease and AIDS.

“I think it’s very important to know that the public understands that this tissue has been important in a number of discoveries over time and will continue to be an important resource,” he said.

Three of the vaccine candidates who received federal funding in the White House’s Warp Speed ​​operation to develop a vaccine also used fetal tissue-derived cells in their preliminary research. AstraZeneca and Moderna used the HEK293T cell lines, while Johnson & Johnson used the PER.C6 cell line derived from retinal cells of an aborted fetus in 1985.