I'm not sure about seeing the word "encouraged" used prior to results being released, but I've seen it issued with the release of failed results.
Here's an example of a phase IIb trial where "no difference" was shown between the treatment and control arms, so it was a failure. But the company was "encouraged" by the secondary outcome:
This isn't a vaccine so it isn't relevant to DCVax's odds. Nonetheless it is interesting in that it reversed the IMUC experience: this study used PFS as the primary outcome and it failed. But had they used OS it might have succeeded.