As the green light alone in the interim... it is a futility analysis. His point was that since the interim will be so close to the end of the trial, passing futility means its working or having a biological effect, whereas if the interim was too early, the passing of futility is less meaningful.
Take a look at CLDX, it failed on the interim, showing the vaccine did not pass futility, i.e. both arms were equal. But, CLDX actually had a much earlier futility after relatively few events and it "passed" that futility endpoint leading investors to accept the bullish hypothesis. Dror's point, I believe is that the futility will be close to the end of the trial... when 50 % of patient have accrued 12 months of potential study time, and we know almost for a certainly that enrollment increased throughout the trial, leading to a potential read out for the interim in the Summer.
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