(?:        ## Group, but do not store it into $1
[^,]*      ## Anything that is not a comma
,          ## Followed by a comma
\s*        ## Followed by possible whitespace
){3}       ## Find three of these (the first three)
(.*?)      ## Match any character, but don't be so greedy about it
\s*        ## Possible whitespace
,          ## Stops at first comma, because we are not being greedy