Seems this may have been done, in an important 2nd line NSCLC trial run by Peregrine Pharma - CSM employee may have been compromised by outside sources, labels where swapped on vials - on purpose, only effected one of the arms. But the very good results of both arms could have led to early approval. When they discovered the tampering, stock PPS tanked!
In a sense they where stopped in their tracks for a few more years.