From Meg Rosoff's blog:
There are four or five actors in the running for Edmond and three for Piper, and they’ll be workshopping with the director (Kevin MacDonald) and Saoirse Ronan for the final choice. As far as I know, these are all “unknowns”, ie, not Zac Efron or Taylor Lautner. Or Daniel Radcliffe or Robert Pattinson. Or Shia LaBeouf. Or Eddie Redmayne.