"ethical" reasons? No idea what that could even mean.
The only new info that was close to time of the hold lifting, and might be explanatory, is nwbo not enrolling beyond 331.
My reason for citing the risk note is that equivalency testing could take quite a bit of time. Perhaps fits the extended period that the hold was in place.
Like everyone else here, I don't know, and doubt we'll ever get a full explanation.
News 
Market Data 
Discover 
