Pfizer Inc. and Valneva SE announced that Pfizer, as the study sponsor, has discontinued approximately half of the total recruited participants in the U.S. enrolled in the Vaccine Against Lyme for Outdoor Recreationists (VALOR) Phase 3 clinical trial investigating the efficacy, safety, and immunogenicity of Lyme disease vaccine candidate, VLA15. These study participants are being discontinued following violations of Good Clinical Practice (GCP) at certain clinical trial sites run by a third-party clinical trial site operator. The discontinuation of these participants was not related to safety concerns with the investigational vaccine and was not prompted by a participant-reported adverse event.

GCP is the international ethical and scientific quality standard for clinical trials that all clinical researchers need to follow. These standards are designed to put participants’ interests first and ensure high scientific integrity. 

The clinical trial remains ongoing with other sites not operated by the third party, and Pfizer continues to enroll new participants at those sites. The companies intend to work with regulatory authorities and aim for Pfizer to potentially submit a Biologics License Application (BLA) to the U.S. FDA and Marketing Authorization Application (MAA) to the European Medicines Agency (EMA) in 2025, pending successful completion of the Phase 3 studies and subject to the agreement of these regulatory agencies to proposed modifications of the clinical trial plan.

Integrity of data collected in clinical trials is critical to provide evidence and confidence in a potential vaccine or medicine’s safety and efficacy. Pfizer and Valneva are working to collect robust data needed for potential regulatory submission of VLA15. While VLA15 is still under investigation, to date the companies have been encouraged by the data from the Phase 2 studies, which demonstrated strong immunogenicity and acceptable safety and tolerability profiles.

VLA15 is the only Lyme disease vaccine candidate currently in clinical development. This investigational multivalent protein subunit vaccine uses an established mechanism of action for a Lyme disease vaccine that targets the outer surface protein A (OspA) of Borrelia burgdorferi, the bacteria that cause Lyme disease. Valneva and Pfizer entered into a collaboration agreement in April 2020 to co-develop VLA15, with updates to the terms within this agreement made in June 2022. VLA15 was granted Fast Track designation by the FDA in 2017.