and French biotech company
have removed roughly half of the participants from their Phase 3 Lyme disease vaccine trial, citing violations of ethical and scientific quality standards by a third-party operator of some of the clinical trial sites.
The companies said the decision was not made due to safety issues.
(ticker: PFE) said it had learned of potential violations of “Good Clinical Practice,” a quality standard regulating human trials, and shut down the sites after investigating.
The Lyme vaccine is among the higher-profile projects in
‘s late-stage pipeline. Executives regularly mention it in presentations to investors, and last June Pfizer bought 8.1% of
‘s share capital for $95 million.
American depositary receipts of
(VALN) were down 8.9% early Friday. Pfizer shares were down 0.8%.
Pfizer and Valneva did not say which trial sites had been closed, but said the participants removed from the trial represented a “significant percentage” of U.S. participants.
“We are not publicly disclosing information on the third party, but the issues were related to study conduct,” a Pfizer spokesperson told Barron’s. “It is important to note that the discontinuation of these participants was not due to any safety concerns with the investigational vaccine and was not prompted by a participant-reported adverse event.”
Pfizer said that, before the discontinuations, the trial had enrolled 7,000 patients. Roughly half of those have now been discontinued. The trial aims to enroll 18,000 participants, according to a disclosure filing on the website clinicaltrials.gov, including children and adults.
The trial recruited patients across the northeastern U.S. and in Northern Europe.
The companies say they still aim to submit the vaccine to regulatory authorities for approval in 2025, assuming the trials are successful, and that regulators accept some changes to their clinical trial plan. They say the trial remains ongoing, and they are continuing to enroll new participants.
The vaccine the companies are testing, VLA15, is the only Lyme disease vaccine currently under development, according to Pfizer. As Barron’s reported in 2021, it is different in key ways from LYMErix, the Lyme disease vaccine that
(GSK) pulled from the market in 2002, for what GSK says were commercial reasons. Today there are no Lyme disease vaccines available for humans, though reported cases are rising.
VLA15 is administered as a three-dose vaccine, plus an additional booster dose.
Write to Josh Nathan-Kazis at firstname.lastname@example.org