“In short: we did not use human stem cells or human embryonic stem cells in the development of REGN-COV2,” Bowie told Snopes in an email.

But it’s not quite that cut and dried.

In the research and development of pharmaceutical therapeutics, many companies turn to what is known as a cell line. These are cultures of human or animal cells that are derived from a living organism and cultured and propagated repeatedly, and, in some cases, used indefinitely. The development of REGN-COV2 utilized HEK293T — a cell line that is derived from human fetal embryonic kidney tissues — to create a “pseudovirus” that mimics a spike Protein found in SARS-CoV-2 in order to test the drug’s ability to neutralize — and ultimately treat — the novel coronavirus.

“HEK293s are considered ‘immortalized’ cells (not stem cells) and are a common and widespread tool in research labs. This cell line was originally derived by adenovirus transformation of human embryonic kidney cells in 1977,” explained Bowie, adding that HEK293 were further transformed at Stanford in the 1980s with SV40 large T antigen, a solution that is used by researchers to initiate and maintain DNA replication necessary for creating cell lines.

Fetal tissues were not directly used n the development of REGN-COV2, but cell lines from decades-old embryonic kidney tissues were. Fetal tissues are used to develop cell lines. Embryonic stem cells, on the other hand, are different than adult stem cells in that they are undifferentiated and regenerative cells, which means that they have not been assigned a key task in the human body. As such, researchers have uncovered ways to direct their use in creating human tissues that allow for a variety of uses, including testing new pharmaceuticals.

Opposition to the use of fetal tissue and embryonic stem cell research has been at the heart of the pro-life platform due to the way in which these cells are obtained and its association with using living fetuses either inside (in utero) or outside of the uterus (ex utero). Pro-life groups like March for Life have even gone so far as to pressure the Trump administration to halt “funding for research that requires aborted fetal organs and tissues.” In summer 2019, the president required any federally funded research using fetal tissue to undergo an ethics review, and has since stocked his cabinet with other similarly-minded officials.

REGN-COV2 is currently in late-stage clinical trials for various populations, including non-hospitalized and hospitalized patients as well as for the potential prevention in individuals who may have had close household exposure to COVID-19. According to a news release published on Sept. 29, the company announced that the antibody cocktail was shown to reduce the viral load and alleviate symptoms in non-hospitalized patients with COVID-19. REGN-COV2 also showed positive trends in reducing medical visits. However, it is important to note that the research included a relatively small sample size of just 275 patients.

“The greatest treatment benefit was in patients who had not mounted their own effective immune response, suggesting that REGN-COV2 could provide a therapeutic substitute for the naturally-occurring immune response. These patients were less likely to clear the virus on their own and were at greater risk for prolonged symptoms,” said Regeneron President and Chief Scientific Officer Dr. George D. Yancopoulos in a statement.

As of Oct. 12, Regeneron had submitted an emergency use authorization (EUA) to the U.S. Food and Drug Administration in early October, and noted REGN-COV2’s “early, promising clinical data — paired with the continued, pressing unmet need of COVID-19 — meets the FDA standard for emergency use authorization.”

Regeneron told Snopes that it “can’t speculate on potential timing for an EUA.” We will update when such is available.