Maybe Genentech and Roche began to put pressure on BIIB. THis is only speculation of course, but the collaboration also has a humanized anti-CD20 (ocrelizumab) in ph 3 for MS and a follow-on anti_CD20 (GA101?) for oncology. Biib is involved in both of those.
Developing a biosimilar that would compete with the follow-ons seems like a conflict of interest to me. It wouldn't be the 1st time GNE has put pressure on BIIB to change their mind about something