The head of the U.S. Food and Drug Administration’s vaccines and biologics unit, Dr. Vinay Prasad, will leave the agency at the end of April, a spokesperson for the U.S. Department of Health and Human Services said on Friday.

Prasad, an oncologist and outspoken critic of U.S. drug and vaccine policies before joining the agency, has drawn controversy over several regulatory decisions. He led the division responsible for approving vaccines and biotechnology products, and his tenure included a series of high‑profile disputes over product reviews.

He was appointed director of the FDA’s Center for Biologics Evaluation and Research in May last year. He briefly stepped down in July, with the Department of Health and Human Services saying he did not want to be a distraction, before returning to the role a little over two weeks later.

His tenure included contentious decisions involving Sarepta Therapeutics’ Duchenne muscular dystrophy gene therapy Elevidys.

The FDA has been mired in a back and forth with Dutch drugmaker UniQure over its gene therapy for Huntington’s disease.

The U.S. drug regulator called for a new study to support the approval of the company’s gene therapy for the rare brain disorder, but the company and patient advocates argued that what the study regulators were asking for was too lengthy and onerous on patients.

HHS has accused the company of misleading the public about what regulators were asking for.

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(Reporting by Christy Santhosh and Kamal Choudhury in Bengaluru; Editing by Sriraj Kalluvila and Shinjini Ganguli)