Seriously, would Onyx allow bad "data" to be reviewed?
Of course not.
So the data is good, and ONXX knows it.
My speculation is that ONXX would not release this data to AMGN alone unless another very strong potential bidder was in the wings. Why? Because AMGN could screw ONXX after reviewing the data, even if it was good. They could withdraw their bid, which would suggest to the market place that the data was bad, thus killing the ONXX share price. It would probably plummet below pre-AMGN-offer prices. But releasing the data suggests to me that AMGN is NOT the only player, and there NOT capable of acting alone to screw ONXX. Someone else is out there and bidding.... If ONXX suggested that AMGN's bid "significantly undervalued" the company, why in the world would they kow-tow to AMGN's request to release data without a) a much higher bid from AMGN based on the data and /or 2) another bidder that will keep AMGN honest in this thing... Think about it... JMHO