AstraZeneca PLC said Wednesday an independent committee is reviewing the potential safety concern that led to a pause in its clinical trials of an experimental Covid-19 vaccine, and the trials could restart depending on the outcome.
The company suspended testing of the vaccine, which it licensed from the University of Oxford, after a person in a U.K. study developed an unexplained illness.
It is unclear what happened to the trial subject, a woman from the U.K. who had received the experimental vaccine, according to a person familiar with the matter. Doctors are conducting tests to determine the cause, the person said.
Francis Collins, director of the National Institutes of Health, told Congress the trial was placed on hold because of a single adverse event involving a spinal cord problem.
The suspension threatens the progress of one of the most advanced Covid-19 vaccine candidates in development.
AstraZeneca had just started a large, late-stage trial in the U.S. that aims to enroll up to 30,000 people to test whether the vaccine safely protects people from Covid-19. AstraZeneca also had been testing the vaccine in countries including South Africa and Brazil.
The candidate vaccine was on track to be approved for use before year’s end if it proved to work safely in late-stage testing. Now, the timetable for its development is uncertain, though AstraZeneca expressed confidence the trials could resume.
The independent committee will guide AstraZeneca “as to when the trials could restart, so that we can continue our work at the earliest opportunity to provide this vaccine broadly, equitably and at no profit during this pandemic,” AstraZeneca Chief Executive Pascal Soriot said.
If the safety review determines the vaccine caused the subject’s illness, all the AstraZeneca doses already manufactured would be thrown away, Dr. Collins said. “We do not want to issue something that is not safe,” he said.
AstraZeneca’s American depositary receipts declined 2% Wednesday. Shares of other Covid-19 vaccine makers with shots in human testing rose on the news.
Many vaccines come with side effects, including injection-site soreness and low-grade fevers, according to the Centers for Disease Control and Prevention. Subjects in Covid-19 vaccine studies have had adverse events such as injection-site pain or flu-like symptoms.
Pauses in vaccine clinical trials aren’t uncommon, according to vaccine researchers. Many times, they said, further examination reveals that the vaccine candidate didn’t cause the safety event and the trial resumes.
“It’s quite common for serious adverse events to occur, most not relevant to the vaccine,” especially in a 30,000-person trial, said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. “It’s a reason why we do big trials, and a reason why we shouldn’t skip these important steps.”
Researchers conduct trials partly to look for safety issues, and studies like AstraZeneca’s are often overseen by committees of outside experts known as data safety monitoring boards, which look for any troubling signs.
To protect subjects, the boards can suspend trials to explore any serious safety signal and assess whether the drug or vaccine under study was the cause and whether the trial should restart or shut down.
“This is what happens in clinical trials. That’s why we do them,” said Naor Bar-Zeev, a pediatric infectious-diseases physician and epidemiologist at Johns Hopkins Bloomberg School of Public Health.
The U.K. study of the vaccine was paused once before, in July, according to an Oxford spokesman. The university declined to discuss specifics, other than that there were no ongoing concerns as a result of the event. Material sent to study subjects in July indicated the pause was triggered by symptoms in a volunteer of a neurological disorder known as transverse myelitis. But AstraZeneca said Wednesday the case turned out to be multiple sclerosis unrelated to the vaccine and the testing resumed.
The current suspension of AstraZeneca’s trials could prompt potential volunteers to seek out trials of other vaccines, Evercore ISI analyst Umer Raffat said on a webinar with investors discussing the suspension.
Moderna Inc. said it isn’t aware of any impact the AstraZeneca news might have on a large ongoing study of its coronavirus vaccine. Johnson & Johnson said studies of its vaccine continue and it still expects to start large, late-stage trials later this month.
Pfizer Inc. is tracking and evaluating safety of its two-dose vaccine, including review by an external, independent data-monitoring panel of vaccine experts, according to a Pfizer spokeswoman.
As the vaccine candidates move closer to use, health authorities, researchers and industry officials have begun trying to ease the safety and other concerns of sizable percentages of people who in polls and surveys express hesitance to take the shots when cleared for use.
This week, nine pharmaceutical companies developing Covid-19 vaccines issued a pledge promising not to file for regulatory approval or authorization of their experimental jabs until the shots have been shown to work safely through late-stage clinical testing.
Spokespeople for the Food and Drug Administration and the National Institute of Allergy and Infectious Diseases declined to comment on the AstraZeneca testing pause. NIAID is funding the U.S. trial of the AstraZeneca-Oxford vaccine, and the FDA monitors safety in clinical trials.
Also on Wednesday, Pfizer and partner BioNTech SE said they finished exploratory talks with the European Commission to supply 200 million doses of their experimental Covid-19 vaccine, with an option for the commission to purchase an additional 100 million doses. The companies said they expected to begin contract negotiations.
The amount of doses is the largest so far the companies have announced with governments and double the number the U.S. agreed to purchase. Financial details weren’t disclosed, although the separate U.S. agreement priced the shot at $19.50 per dose.
More than 25,000 volunteers have enrolled in a late-stage clinical trial testing the vaccine and seeking to enroll 30,000 people.
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