CRSP: Buy the dip or run away?

$CRISPR Therapeutics(CRSP.US)$
I've been waiting for an opportunity to take a position in this stock, the recent news about its cancer therapy seemed positive and I thought I might have lost my chance but the stock is down 10% AH.

Was this news not as positive as expected? Is this a buying opportunity or should I stay away for now and let it fall a bit more? Most medical stocks seem to fall hard for a few weeks to months after bad news.