Both had been with the show since the beginning and were known as the right-hand of creator/exec producer Tim Kring.
Heroes has struggled in the ratings its third season after a disasterous second season. It's rumored that Alexander and Loeb were let go because of NBC execs' frustration with the creative direction of the show (How surprising that, yet again, the non-creatives muck things up). The show is also said to have been overrunning their budget.
It looks like there will be no ressurrection. The show is dying a slow death.
<RANT> Did anyone else see this coming? The first season was good even though it was an obvious rip-off of X-Men, but right from the beginning, they didn't seem to have a plan after they "saved the cheerleader and the world" the first time. I kept asking myself, what are they gonna do the next season. Hmmmm? Maybe, save the world again? TV needs to take a clue from the successful movie franchises and turn it over to the comic book creatives and fans of the genre. Now they have dumped the two writers who could've brought it back. It's just typical. The suits have won again. </RANT>