Vascular Biogenics Ltd (VBLT)

[gr8db8]

Not a direct answer to your question, but a similar thing happened with DCVax:

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Discussing the DCVax-L phase III study, Liau said all enrolled brain tumor patients were living longer, which she described as a "good thing." But then Liau noted that patients living longer "was not really helping our study" because it hurts the chance of showing a difference in survival between the DCVax-L and placebo arms of the study. Without that difference, the study fails.

Liau, perhaps realizing she spoke too openly about the DCVax-L study, goes on to say that she doesn't have any data from the study because it's still ongoing and blinded.
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So it has happened before. In VB-111's case the data provided was good so I'll take that as we head into 2017.

Article:
https://www.thestreet.com/story/13452761/1/northwest-bio-blames-short-sellers-not-warning-from-expert-doctor-for-stock-plunge.html