An experimental stem cell therapy derived from human placentas will begin early testing in patients with the coronavirus, a New Jersey biotech company said Thursday.

The treatment, being developed by the company Celularity, has not yet been used on any patients with symptoms of Covid-19, but it has caught the attention of Rudy Giuliani, President Trump’s personal lawyer. Mr. Giuliani recently featured an interview with the company founder on his website and said on Twitter that the product has “real potential,” while also criticizing the Food and Drug Administration for not moving more quickly to approve potential remedies.

There is no proven treatment for the respiratory disease, but several experimental approaches, including old malaria drugs and H.I.V. antivirals, are being tested in patients around the world.

Celularity has also enthusiastically publicized the news of its early-stage trial for its treatment, known as Cynk-001. In an email Wednesday to a reporter, its public relations firm described a development as the “first F.D.A. approval for Covid-19 cell therapy.” The agency’s decision, however, merely gives a green light for its product to be used in a clinical trial, not widely prescribed to patients.