How to remove all data to the right of last instance of a seperator

Hello all,
Was wondering if any kind soul can solve my problem :

I have thousands of rows of data like this :
111,222222,333333,444
66666,555555,999,88888

Each row contains multiple instances of a seperator. All I want is a formula that will remove all data to the RIGHT of the last seperator
So now the above rows become :
111,222222,333333,444 becomes 111,222222,333333
66666,555555,999,88888 becomes 66666,555555,999

Thanks in advance for your help !!