From AICN:

“Development was really starting to heat up, And it appears like I may be writing multiple pilots for NBC so that wasn’t leaving a ton of room for ‘Heroes,’ unfortunately,” the star writer-producer tells AICN exclusively. “We crafted some really great arcs for the season that I’m excited to see come to fruition. I love that cast dearly and am sad to go, but the plate — she was over-flowing.”

Fuller, of course, is the “Dead Like Me”/”Wonderfalls”/”Pushing Daisies” creator who wrote the best “Heroes” episodes, including “Company Man” and “Cold Snap.” He left “Heroes” near the end of its first season to create “Daisies,” then returned to “Heroes” near the end of last season.

Fuller is under contract with “Heroes” producer NBC Universal for another year and a half, and has been preparing new series pitches for the media giant since he left Warner Bros.’ “Daisies.” He’s also expressed an ambition to eventually create, or help create, a new Paramount TV series set in J.J. Abrams’ new “Star Trek” universe.