Pfizer cuts enrollment for Lyme disease trial after CRO debacle

After complications with the CRO behind Pfizer's Lyme disease shot, vaccine R&D chief Annaliesa Anderson, Ph.D., says that much fewer than the planned 18,000 participants will be recruited. 

“By moving just to the high endemic areas and taking out sites where we didn't think that people would really be at risk of getting Lyme disease, it meant that we could actually considerably reduce the number of participants that we enroll,” Anderson said in an interview with Fierce Biotech.

The new enrollment expectations for the phase 3 VLA15 program follow a dramatic back-and-forth between Pfizer and a contract research organization, Care Access—owned by Reify Health. Pfizer alleged in February that due to breaches of Good Clinical Practice half of the enrolled patients to-date would be removed. Care Access CEO Ahmad Namvargolian said in a LinkedIn post that his company disagreed with the decision. Endpoints News subsequently reported that Pfizer had ended work with Care Access. 

The trial originally got underway in August 2022 with an overall enrollment goal of 18,000 healthy people who live in areas with endemic Lyme disease and lead lifestyles that put them at increased risk of being bitten by ticks. An initial 6,000 people were supposed to be enrolled to ensure a read out by the second quarter of this year. 

Anderson noted that recruitment got moving again a couple of months ago. While she could not pin down exactly what the new expected enrollment figure is, the number will be “much less than 18,000.” The expected enrollment was revised down to 6,400 in the middle of July, according to the study’s page, before returning to 18,000 at the end of the month. 

Follow-up disclosures by Pfizer and partner Valneva suggest that the snag has delayed the trial by at least a year. The two companies originally expected to submit an approval application for VLA15 to regulators in 2025 but have pushed the timeline back to 2026. The study is expected to conclude at the end of 2025, according to the clinical trial record. 

Pfizer picked up the vaccine from Valneva for $130 million upfront in 2020 as it progressed through a couple midstage trials. A separate phase 3 trial that got underway late last year is testing the safety of the shot in children 5 to 17 years old, with an expected enrollment of roughly 3,500 kids. In July, the trial record updated to suggest that recruitment had concluded. 

The setback in Lyme disease has been an aberration in Pfizer's larger vaccine portfolio, which just today saw the approval of the RSV vaccine Abrysvo in pregnant people. The FDA nod follows an earlier approval for older adults.