Eminent domain would still require fair compensation to the company, so you'd have to pay them more or less what they'd lose from not having the patent anymore.
(Though I think the term you might be looking for is 'compulsory licensing' or so? Not sure.)
The drug companies are presumably pricing optimally for profit (but not for maximum public benefit, for which the optimum price is ~0). You could calculate the net present value of the drug companies' total profits attributable to the patent, add on 10% as a bonus, and pay them off. If the welfare gains of having cheap drugs are genuinely greater than the value of the patent to the holder, this would be win/win.
“If you invest hundreds of millions and it turns out to be life changing, we’re going to seize it”
The point is that you don't get to withhold the drug from people to maximize profits.
