In his resignation letter, provided to ABC News, Gottlieb says he will stay on in his job for another month but he does not cite a reason for his leaving.
Gottlieb handed in his resignation on Tuesday, after publically criticizing the drugstore chain Walgreens Monday for selling tobacco products to minors, "the company's stores have racked up nearly 1,800 violations across the country", he said in a statement.
Gottlieb joined the Trump Administration first as an advisor to the transition team in 2016 before being nominated as FDA Commissioner in March 2017. But Gottlieb said the agency could help spur competition and reshuffled its review procedures to speed up approvals of lower-cost generic drugs. "He and his talents will be greatly missed!"
Under Gottlieb, the FDA issued a ban on the sale of fruit- and candy-flavored electronic cigarettes in convenience stores and gas stations, meaning only tobacco, mint and menthol flavors can be sold at these outlets. He stressed that FDA "set in motion a historic modernization" of both the Office of New Drugs and of the Office of the Commissioner.
Deutsche Bank analysts said on Wednesday they expected Dr Gottlieb's agenda broadly to be continued.
Dr Gottlieb also announced that the Agency would explore the initiation of a rule making procedure on cannabidiol (CBD), with the goal of creating "an appropriately efficient and predictable regulatory framework for regulating CBD products". Although the agency worked to take one powerful addictive painkiller, Opana ER, off the market, it approved Dsuvia, a new form of an extremely potent opioid, for acute pain - which public health advocates feared would be just as risky.
Gottlieb made enemies out of e-cigarette companies like JUUL by cracking down on them in hopes of cutting down teen vaping, which he called an epidemic.
But Burr still praised Gottlieb upon news of his resignation, calling him "potentially one of the best commissioners we've ever had".
Gottlieb is also a cancer survivor, a venture capitalist and a government insider who long said he wanted to tear down the wall of FDA regulations that he believes is holding back innovation.
He also worked on the implementation of the Medicare drug benefit as a senior advisor to the Administrator of the Centers for Medicare and Medicaid Services, where he supported policy work on quality improvement and the agency's coverage process, particularly as it related to new medical technologies.
"There are many important efforts we undertook together, countless new policies we advanced, and laws we enforced with vigor to protect consumers", he wrote.