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Juul Labs Inc. co-founder James Monsees plans to leave the e-cigarette maker, stepping down as an adviser and board member, the company said in an email to employees on Thursday.

Monsees and Adam Bowen created Juul after working together on their graduate thesis at Stanford University in 2005. The two designed what has become the most successful e-cigarette in the U.S., but it has generated controversy over the potential health risks of vaping and teen use of such products.

“Building this company alongside all of you has been the single most rewarding experience of my career and perhaps my life,” Monsees said in an email to Juul employees, adding that he was recently married and is looking forward to spending more time with his family and pursuing other interests.

Juul’s enormous popularity with young people has embroiled the San Francisco-based company in scrutiny from parents and lawmakers. The company is the target of lawsuits from school districts and state Attorneys General, as well as numerous federal investigations. Juul has said it never targeted minors in its marketing and is committed to gaining authorization from the U.S. Food and Drug Administration for its products.

The company in September hired K.C. Crosthwaite, a longtime executive at tobacco giant Altria Group Inc., to take over as chief executive officer. Altria made a $13 billion investment in Juul that it has subsequently marked down in value by roughly two-thirds.

Crosthwaite praised Monsees in an email to employees.

“As one of our founders, James was fundamental in the creation of this company and instrumental in building this company from the ground up,” Crosthwaite said.

Monsees, who had previously been Juul’s chief product officer, was moved to a newly formed founders office with Bowen in October. Bowen remains at the company.

Juul co-founder James Monsees steps down as adviser, board member

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