Now, assuming(and I think it is a bad assumption) that 6/9 reflects true SVR20 proportion, the real SVR20 that would playout with larger study numbers could be assumed to be 0.666*0.799 = 0.532 ie 53.2%
You are still missing the drop-out effect however. Most if not all drop-outs came much later. The better measure is the 70% SVR ITT measure at 12 weeks for the whole trial. Using 2/3 you 47%. Using 15% (feels more right to me), you get 60%. But I still think 12 + 24 SOC (12 being concurrently and 12 after stopping) will win out ultimately.