Dr. Scott Gottlieb made headlines in March with his resignation from his role at the FDA. “This has been a wonderful journey and parting is very hard,” he tweeted at the time.

Appointed in 2017, Gottlieb was outspoken about the need to address the surge in vaping by young people. His stance stood in stark opposition to that of Donald Trump, who pledged to limit e-cigarette regulation. “Teens are becoming regular users, and the proportion of regular users is increasing,” Gottlieb told USA Today in 2018. “We’re going to have to take action.”

Reducing the amount of nicotine in cigarettes was another hot-button issue for Gottlieb. The FDA has the authority to regulate nicotine levels and is currently in the early stages of writing regulations that would do so.

Under Gottlieb’s leadership, FDA approvals for first-of-a-kind drugs, generics and medical devices hit all-time highs last year. In addition, the agency boosted the ability of its inspectors at mail facilities to intercept illegal opioid shipments from abroad.