I may have misunderstood this, esp as it was the first 'live' cfs event I attended, but when Fluge spoke at Norwich early this year I understood him to say that the Stage 2 rutuximab trials included some participants who they knew were responders from previous treatment / Stage 1 trials. Clearly this could make a sense in a Phase 2 trial where the primary questions are about type & length of response, not proportion of responders. If only a sub-set of pwcfs respond, which is the expectation, it would have been terrible to spend the money on a Phase 2 trial which happened not to include any participants who respond to the treatment! But if I'm right about this, it could have artificially inflated the Phase 2 trial response rates.
Once they had Phase 2 data, the recruitment and all other aspects of the much larger Phase 3 blinded trial will have been constructed to give a more accurate assessment of the proportion of participants who respond, which participants respond, etc. etc.
Could this explain lower responder rates among a general population of pwcfs, and maybe expectations of lower responder rates for the Phase 3 trial?