Extracting numbers or removing text between delimeters

Hey there friends,

I have a column that lists topics with their ID and display name that are used in posts on my website.

It looks like this: 

I am trying to build a new column that would extract and list only the ID, seperated by a comma.

So for example if my column is: ID1/Diplay-name1,ID2/Diplay-name2,ID7/Diplay-name7, it would return this: ID1,ID2,ID7

So my guess would be to remove anything that is held between / ... ,

It seems simple but I am not sure where to start 😁