Adding books, need regex help

So, I'm getting ready to add some books and I'm working on my regex and it's almost there but not quite right. Book filename format is as follows:

Stephen King - [The Shining #2] - Doctor Sleep (2013) [9781476727660].azw3

This is my regex

(?P<author>[^_-]+) -?\s*\[(?P<series>[^_0-9-]*)(?P<series_index>[0-9]*)\] - (?P<title>[^_-]+) \((?P<published>[^_-]+)\) \[(?P<isbn>.+)\]

I'm getting matches on all my fields but I have one question.

My Series field shows: The Shining #

How can I remove that "#"? I feel like I did earlier but I forgot how.