Why wouldn't a company that is interested in buying Amarin just load up on shares in the open market?
Imagine GSK was certain they had to have Amarin. So, they just start buying shares on the open market for $11 each. They buy millions of shares. Maybe tens of millions of shares.
Then, if they get to the point that they make the formal move to purchase Amarin, they have saved themselves tens of millions or hundreds of millions of dollars on the purchase price. If somehow they are outbid by some other company, they make tens of millions or hundreds of millions in profit from the sale of those shares.
Do we need to check each Big Pharma sec filings or can we tell by searching AMRN for major % shareholders?