Contacted by seo brand middleman about a domain - need advice

I received an email out of the blue this week from a seo/brand expert company requesting to purchase a domain I have had for several years. The domain is a generic name of a potential medication. I was given an initial low X,XXX offer which lead me to investigate further, thinking it might be a high profile company who is interested. I found that a trademark for the term was filed and published in the last month by the company most likely to produce this medication. How do I determine a reasonable asking price for the domain? the company who is likely behind it probably has a pretty large bankroll. Anywhere you could recommend I seek guidance?

sorry if this isnt directly seo related.. this seemed like the most relevant sub for folks with knowledge in this area.

[–]BlackGuyOne

Maybe post in entrepreneur...there might be someone that has had this happen to them.

[–]BlackGuyOne

I would decide how much you are happy with, usually about 5k, and sell it. They don't have to use your name;they could use any variation.

[–]MAVERICK910 

is it Sildenafil citrate by any chance? ;)