John Ratliff resigned as chief executive officer of LabCorp Diagnostics on Nov. 1, the company announced Wednesday. Ratliff’s new role had been announced less than a month earlier and was set to take effect the day he stepped down.

Prior to serving as CEO of Diagnostics, Ratliff was CEO of Covance, a drug development business owned by LabCorp.

“We are grateful to John for his leadership of the Covance business, and we wish him well in his next endeavors,” Adam Schechter, CEO of LabCorp, said in a statement.

The company said in a press release that Ratliff left the company to “pursue another opportunity.”

Brian Caveney was named executive vice president and president of Diagnostics and Mark Schroeder was named executive vice president and president of Diagnostics laboratory operations and global supply chain.

“The board and I are pleased that Brian and Mark, two highly respected and strong leaders, will combine their unique skill sets for the continued growth of our Diagnostics business,” Schechter said in the statement.

LabCorp is a global life sciences company focused on clinical laboratory and drug development services.

Shares of LabCorp stock closed at $165.27 on Wednesday, up 13 cents.