AZN Astrazeneca Plc

By Thomas M. Burton 

Federal health regulators allowed the resumption of U.S. studies of a leading Covid-19 vaccine candidate from AstraZeneca PLC and the University of Oxford, according to a person familiar with the matter and materials reviewed by The Wall Street Journal.

The U.S. Food and Drug Administration wrapped up its examination of two cases of a possible neurological side effect that emerged in two people in clinical research testing the shot. The agency told AstraZeneca that the late-stage trial in the U.S. can resume, the company said Friday.

The decision, which was first reported by The Wall Street Journal, came after the FDA didn't find the vaccine was responsible for the two cases, though the agency couldn't rule out a link either, a person familiar with the matter said.

The agency plans to require researchers to inform study subjects of the cases and monitor them for any related neurological events, such as numbness, the person said.

The move "allows us to continue our efforts to develop this vaccine to help defeat this terrible pandemic. We should be reassured by the care taken by independent regulators to protect the public and ensure the vaccine is safe before it is approved for use," AstraZeneca Chief Executive Pascal Soriot said in a statement.

The vaccine is among the most advanced in development. If it proves to work safely, it could be one of the first, if not the first, greenlighted by regulators for widespread use.

The vaccine had been on track to be authorized for widespread use before year's end, if it proved to work safely in the late-stage testing.

Last month, however, AstraZeneca paused trials testing the shot around the world, including in the U.S., after a U.K. woman developed a mysterious neurological illness. A U.S. health official had said the event involved a spinal cord problem.

The illness followed a pause in testing, in July, after an unexplained illness of a trial subject. Researchers initially told subjects in the study the case involved a neurological disorder known as transverse myelitis. AstraZeneca later said the case turned out to be multiple sclerosis unrelated to the vaccine, and the testing resumed.

Studies testing the vaccine around the world later resumed after regulators outside the U.S. determined it was safe to do so, except a late-stage trial in the U.S. because the FDA was still investigating the two events.

The FDA has spent weeks exploring whether the two cases involved transverse myelitis and whether the vaccine was responsible for the illness, the person said.

An AstraZeneca spokesman has said the company was working with the FDA so it can evaluate whether the U.S. trial can resume. All the studies testing the shots are being closely watched for safety, including by health regulators in various countries, the spokesman said.

Reuters had earlier reported the U.S. trial could resume this week.

Transverse myelitis is a known side effect of vaccines but is rarely linked to the shots. Other times, it is an early symptom of the nerve-system disease multiple sclerosis, and unrelated to getting a shot.

The condition refers to inflammation of the spinal cord involving the destruction of a fatty white material, known as myelin, that insulates nerve cell fibers. It impedes the ability of nerves in the spinal cord to send messages to the rest of the body.

Cases are rare, with only about 1,400 diagnosed annually in the U.S. The cause is unknown. It can trigger a variety of symptoms, including weak arms and legs, along with sharp pains, numbness and tingling.

It can sometimes also lead to paraplegia that necessitates wheelchair use.

Experimental vaccines undergo study, in trials that progressively test the shots in increasing numbers of volunteers, both to test effectiveness and to look for any side effects that could harm people if regulators greenlighted the vaccines and they were then given widely.

To protect trial subjects, independent researchers who didn't play a role in the vaccine's development, or at the company that would sell it, look for any signs that the shot could be harmful. This data-safety monitoring board evaluates side effects in subjects.

Side effects often emerge in trials evaluating drugs and vaccines, and the studies are frequently paused for researchers and regulators to make sure it is safe to go on.

Since the trial for the vaccine from AstraZeneca and Oxford was put on hold, studies of Johnson & Johnson's Covid-19 vaccine candidate and of a combination of Eli Lilly & Co.'s antibody and Gilead Sciences Inc.'s antiviral remdesivir w ere paused.

AstraZeneca was among the drugmakers that pledged to not seek regulators' permission for widespread use of their Covid-19 vaccines until the shots proved to work safely in late-stage testing.

--Joseph Walker contributed to this article.

Write to Thomas M. Burton at tom.burton@wsj.com

(END) Dow Jones Newswires

October 23, 2020 16:26 ET (20:26 GMT)

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