The drama series, which focuses on five people with superhuman abilities, will premiere on Syfy on July 11.
"We started working on it and we sold it once to ABC," Penn told Collider. "But then the writers' strike came, and then we sold it again to Syfy."
The Incredible Hulk writer explained that he encountered "a lot more resistance" to the project's science fiction elements at ABC.
"At ABC, I felt like we were constantly trying to pretend that it wasn't a science fiction show while still writing a science fiction show," he revealed. "Once we got rid of that, it just freed us up a lot more to get into the stuff that we wanted to do. It was a relief, honestly."
Penn confirmed that Alphas had not progressed beyond the script stage at ABC.
"We were just about to cast at ABC," he said. "We had hired writers, but we hadn't yet cast the show when the writers' strike hit, so we never really got around to casting it."
Alphas begins on Monday at 10/9c on Syfy.
> Lost director for Syfy's Alphas
Watch a trailer for Alphas below: