Brooks Perlin and Katie Couric, in September 2011
Marion Curtis/Startraks
The couple were "at different stages in their careers," says a friend of Couric's, who adds, "the split was inevitable."
Couric, 54, and Perlin, 37, met at a 2006 fundraising event for cancer research. Couric's husband, Jay Monahan, died of colon cancer in 1998, at age 42.
After her breakup, Couric, who hosts ABC's The Year, a two-hour special collaboration with PEOPLE that airs Dec. 15 and looks back at the newsmakers of 2011, is "full of energy and just as active and engaged as always," says the friend.
"Brooks is a good guy," the friend continues, "but there is a time for each relationship – and the time is past for this one."
In May, Couric, whose new syndicated ABC daytime talk show will begin next September, told PEOPLE her relationship with Perlin was "complicated," and that much had been made of the fact that she was dating someone 17 years her junior.
"I'm in the process of figuring out the future, and so is he," she said at the time.
News of the breakup was first reported by the New York Post.
