Do not even commit an escrow transaction until you have made a contract of agreement to legally bind the transaction even if you send them the domain name a year before they pay you.
DON'T approach the company. A pharmaceutical doesn't run this kind of transaction from the CEO hotseat. You aren't emailing the guy with the name on the golden plaque asking for the best offer. Instead, you deal with their legal department. The legal department also doesn't know anything about domain names and don't even deal directly with the owner in most cases so you can get a much higher offer than another seated individual would suggest.
But there's no way you can deal with the legal department alone. They speak in riddles and hide under ruthless legal terminology so you agree to untranscending bindings you didn't even know you were signing on. Get yourself a lawyer to broker the deal. Most lawyers will actually pay out of their anticipated-commision pocket to use a brokering agency while they deal with the legal side, so make that their expense.
Not really sure how to find a good lawyer in this field other than referrals like the one in this thread. I'm a business/law student but can't enter the field yet.
One day I'll be WF's go-to lawyer, but until then, I can't even compile a list of lawyers I
If you want any other advice, go ahead an PM me.