Regex

Hey i am a tard at regex
How can I make a regex to match

GETTHISWORD1 i know what string is here GETTHISWORD2 blah blah blah discard

Currently I have

(.*) i know what string is here (.*)

but that matches the blah blah blah at the end
how do i make it only match the word i want

ah perfect. i kept trying to find something that 'symbolizes' whitespace, but i guess all i need is that. thanks!