Closed:regular expression on Notepad+++

Question

[newbiebio]

There are thousand regular expressions in my sheet like 'space2spaceABCC5', I want to replace it as 'ABCC5'. I tried to find the regular expression as ' (\d) ([A-Z0-9]+)' and replace it as '\2'. But the Notepad++ told me that 'Find:invalid regular expression'. Please help me out on this. Thank you very much.