There are also 「その」and「どの」 and together they make up what's known as 「こそあど言葉」. But since those two are outside the scope of the question, let's just look at 「この」「これ」「ここ」「その」「それ」「そこ」.
この/これ/ここ：You use this when you have physical or emotional closeness to the thing or person at issue, and it also indicates you are closer to that thing/person than the other party in the conversation.
その/それ/そこ：You don't have that kind of attachment or affinity with the thing under discussion. The topic is closer to the listener.
I don't see a reason to choose 「この」in this sentence. You don't feel close to someone whom you just met and whom you have to refer to as "a person called 木村さん".
It's gone. You can't point to it and say "this place". Time separates you from that place in your memory.
You have either heard this from people or read this somewhere. You don't have any closeness to what's talked about. This sentence suggests the speaker isn't in アメリカ where the new medicine has been developed.