Formula to remove last part of string

As the following example states, i need to remove the last part of a string, the "ref" part, to match rows that doesnt have this part to show under same header when used as a section.

As this string can be different from time to time it needs to locate the exact pattern "ref." to pinpoint where to cut the string.

Thank you a lot in advance,

Axel

example:

15651, SIG, Inst of TFA, ref.75100

needs to be exactly this (no comma)

15651, SIG, Inst of TFA