British drugmaker AstraZeneca has placed a late-stage Covid-19 vaccine study on hold due to a volunteer at one of the trial sites experiencing an adverse event.
News media reported Tuesday that the Phase III trial of AZD1222 – a vaccine against SARS-CoV-2 developed at the University of Oxford and originally known as ChAdOx1 nCoV-19 – had been paused due to what the company called in a subsequent emailed statement a “potentially unexplained illness” in a person who had received the vaccine.
Citing an unnamed person familiar with the situation, the New York Times reported that the participant was taking part in a Phase II/III U.K. trial and had been diagnosed with an inflammatory syndrome of the spinal cord known as transverse myelitis, though it remained unknown whether that was directly related to the vaccine.
“As part of the ongoing randomized, controlled global trials of the Oxford coronavirus vaccine, our standard review process was triggered and we voluntarily paused vaccination to allow review of safety data by an independent committee,” the emailed statement from AstraZeneca read, noting that such actions are routine in case of such unexplained illnesses. “In large trials illnesses will happen by chance but must be independently reviewed to check this carefully.”
Shares of AstraZeneca were down more than 1% on the New York and London stock exchanges Wednesday.
The company in-licensed the vaccine from the University of Oxford and is now planning a 30,000-participant Phase III trial in the U.S., though that study is still listed as not yet recruiting on ClinicalTrials.gov. Numerous other companies around the world, including in the U.S., are developing vaccines against SARS-CoV-2 as well and have already moved their candidates into Phase III testing.
“At the minimum, this reinforces the need for accumulating a large safety database before regulatory approvals are granted and removes the scenario of any Emergency Use Authorization (EUA) graned to AZD1222 prior to completion of the Ph. III trial, which to some extent was weighing on C-19 vaccine candidates such as Novavax’s NVX-CoV2373 as a disadvantage when it comes to speed to market despite being in the first wave, in our view,” wrote B. Riley FBR analyst Mayank Mamtani in a note to investors Wednesday.
The potential effect of the event on other vaccine-development programs remains unclear, Mamtani wrote. Another analyst, Morgan Stanley’s Matthew Harrison, wrote that the different technology used in other vaccine candidates – particularly the messenger RNA platforms of the Moderna and Pfizer-BioNTech vaccines – mean the event reported by AstraZeneca will likely not have any implications for them. He noted that the event appears to be acute rather than related to antibody-dependent enhancement, or ADE, a far more worrisome phenomenon in which a vaccine causes more severe Covid-19 disease when an individual is infected than if they had not been vaccinated.
Still, the event underscores growing concerns about the potential for a vaccine to be released to the public before completing Phase III trials, especially if that is done under political pressure, as some fear the Food and Drug Administration could do and as the government of Russia has already done. Also on Tuesday, AstraZeneca was among the nine biotechnology and pharmaceutical companies whose CEOs signed a pledge not to rush development of vaccines against Covid-19 and to rely on scientific data and ethical principles.
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