What you are wanting to not capture is in the middle of your string/sample. Regex is a tool to find a pattern of text. Unfortunately it is not possible with just one pattern with one result.
Not unless @yoichi or @ppr know of something.
Now you have only provided 1 sample, the output and limited info, so we have to make assumptions.
Assuming all your samples are the same then you could try this workaround but it’s not the traditional/proper/best use of Regex.
Try this pattern
In a matches activity.
The use an assign activity (or write line) like this:
StringResult = MATCHESOUTPUT(0).tostring + MATCHESOUTPUT(1).tostring
*Replace capitals with Matches result variable.
This is an unusual workaround and is likely not endorsed by the likes of @ppr or @Yoichi
Either way, you are going to need a second step of sorts.
I am still unsure of why you are not wanting to use the replace method
2 simple robust steps are better than 1 complex one.