Regarding the right of first refusal, seems my original comments...

Regarding the right of first refusal, seems my original comments were astray (wrong) so did more research with qualified people. FWIW below is my understanding.

ROFR and ROFO (offer) are fairly commonly used in joint venture type arrangements.

ROFR is usually structured so that, before you can offer to sell something, you have to allow the party with the benefit of the ROFR to make an Offer. (not the other way around)
You then have a window whereby you could accept a higher offer from a third party, but you aren't permitted to sell on equal or worse terms than the offer made. If you tried to do so the party with the ROFR benefit could injuct you.

In other words if the ROFR holder does not pitch a realistic offer/deal within the agreed time frame, there is nothing to stop a better offer from a third party succeeding. Would it come to that between MSB/Celgene, it's hard to imagine. And of course there's also all the fine print stuff between the two parties that we are not privy to.

ROFO (first offer) is different; we don't need to go there.

Opinion only. DYOR.