(AP) — Food and Drug Administration Commissioner Scott Gottlieb is stepping down after nearly two years leading the agency’s response to a host of public health challenges, including the opioid epidemic, rising drug prices and underage vaping.

Health and Human Services Secretary Alex Azar announced in a statement Tuesday that Gottlieb would leave in a month. In a note to FDA staffers announcing his departure, Gottlieb cited “the challenge of being apart from my family” in Connecticut.

President Donald Trump tapped Gottlieb in 2017 to “cut red tape” at the FDA. But Gottlieb bucked expectations by pushing the agency to expand its authorities in several key ways, including an unprecedented effort to make cigarettes less addictive by requiring lower nicotine levels.

The 46-year-old physician and former conservative pundit advanced his agenda while managing to maintain the support of the president, Republicans and key Democrats in Congress.

Still, he departs with his most sweeping plans unfinished, including the initiative to make cigarettes less addictive.

In recent months, he came under fire for not acting more quickly to address an explosion in teenage use of electronic cigarettes, especially those with candy and fruit flavors. Under Gottlieb, the FDA has emphasized vaping as a potential tool to wean adult smokers off traditional cigarettes. And in a widely criticized move, Gottlieb delayed key regulations on vaping devices until 2022, in part, to avoid over-regulating the industry.

Anti-smoking groups are now suing the agency to begin reviewing e-cigarettes immediately as the most recent federal data suggest that 1 in 5 high school students are using e-cigarettes. While the FDA has taken steps to keep e-cigarettes away from teenagers, including tightening restrictions on convenience store sales, it’s unclear whether they will be enough to reverse the trend.

The pushback against FDA’s approach to vaping threatens to overshadow what is by far Gottlieb’s most far-reaching plan. Gottlieb announced in May 2017 the FDA would seek to require tobacco companies to drastically cut nicotine in cigarettes, in a bid to help adult smokers quit. The agency has had the authority to regulate nicotine levels since 2009, though no previous FDA commissioner tried to use it. The agency is still in the early stages of writing regulations that would standardize nicotine in cigarettes.

Elsewhere, Gottlieb targeted drug industry tactics used to maintain sky-high prices on older drugs, calling them “shenanigans” and “deceptions.” For decades, FDA commissioners steered clear of the issue, noting that the FDA has no direct role in regulating U.S. medicine prices, which are set by drugmakers. But Gottlieb said the agency could help spur competition and reshuffled its review procedures to speed up approvals of lower-cost generic drugs.

Drug overdose deaths hit their highest level on record in 2017 — the most recent year for which federal data is available. Fatal overdoses are largely driven by illegal opioids including fentanyl and heroin, though the epidemic was trigged by legal prescription painkillers like OxyContin.

As FDA Commissioner, Gottlieb boosted the agency’s inspectors at U.S. mail facilities to try and intercept illegal opioid shipments from China and other nations. It’s not yet clear whether that effort has reduced drug abuse or overdose rates.

Trump tweeted that Gottlieb “has done an absolutely terrific job,” adding “he and his talents will be greatly missed.”

On FDA’s more day-to-day responsibilities, Gottlieb continued a multi-decade, bipartisan shift toward faster, more streamlined product reviews for drugs and medical devices. That issue has long been the top priority for the powerful pharmaceutical and device industries, which spend millions lobbying Congress and the federal government annually to ensure speedy market access for their products.

FDA approvals for first-of-a-kind drugs and devices hit all-time highs last year.

Gottlieb has long been a favorite of the medical industries, due to his focus on cutting unnecessary regulations and speeding product approvals. He spent nearly a decade as a conservative commentator at the American Enterprise Institute and industry consultant after serving in the FDA under George W. Bush.