The mere fact that Missling chose to announce the Biogen MTA (which simply is not done by others) created expectations. And no, Missling never said a word about it. I read EVERYTHING he says. He made no comments. Whatever happened with Biogen was buried. Why? What happened that Missling didn’t want to tell shareholders?
At the time Biogen was looking at 2-73 all testing had been in vitro with cell cultures. The research was at a preliminary stage. You assume it was an "unexplained failure". That is quite a leap to conclusion. Biogen could have had many reasons for not pursuing 2-73 for MS. Many of which may have had nothing to do with 2-73. Budgets cuts, staff changes, other research directions chosen, just to name a few. And yes, it is possible that 2-73 did not live up to Biogen's expectations.
In this context and considering the BIIB's past the two firms management are likely just culturally incompatible. (make you an offer you cannot refuse). I have also thought .."what if BIIB's influence on Instie's" to :stay away from" AVXL has impacted OUR SP over time?.