A key U.S. Food and Drug Administration official who oversees vaccines and biotech treatments will step down from the agency following multiple decisions that raised concerns within the industry.

Vinay Prasad, director of the Center for Biologics Evaluation and Research, will leave the FDA at the end of April, an agency spokesperson confirmed on Friday. It is his second departure from the position: He briefly left the post in July following backlash over his regulatory decisions, and returned only two weeks later in August.

In a post on X, FDA Commissioner Marty Makary said the FDA will appoint a successor before Prasad returns next month to the University of California San Francisco, where he taught before taking the FDA position last year. Makary said Prasad “got a tremendous amount accomplished” during his tenure at the agency.

Prasad’s decision to step down comes after criticism of the FDA mounted within the biotech and pharmaceutical industry and among former health officials. In the past year, the agency has denied or discouraged the approval applications of at least eight drugs, according to RTW Investments, after taking issue with data the companies used to support their applications. The FDA also initially refused to review Moderna’s flu shot before it later reversed course.

All of those companies accused the FDA of reversing previous guidance about the evidence they could use to back their applications, sparking criticism within the industry that an unreliable regulatory process could stifle development of drugs for hard-to-treat diseases.

A former FDA official who spoke to CNBC on the condition of anonymity to speak freely on the issue called the reversals the worst kind of regulatory uncertainty because companies say they are being told one thing and then experience another.

In a statement earlier Friday, an FDA spokesperson said there was “no regulatory uncertainty,” adding the agency “makes decisions based on the evidence, but does not make assurances about outcomes.” The spokesperson said the FDA is “conducting rigorous, independent reviews and not rubber-stamping approvals.”

The most recent controversy came after the FDA discouraged UniQure from applying for expedited approval of its experimental treatment for Huntington’s disease.

The agency, which underwent staff cuts and an overhaul under Health and Human Services Secretary Robert F. Kennedy Jr., has faced broader backlash for its drug and vaccine approvals process. Critics have worried the agency could stifle the development of new treatments and risk the safety of patients.

The Wall Street Journal earlier reported Prasad’s departure.