Use the character class [:alpha:]

E.g. [[:alpha:]]+ to match one-or-more such characters.

C-hig (elisp)Char Classes says:

[:alpha:]

This matches any letter. For multibyte characters, it matches characters whose Unicode ‘general-category’ property (*note Character Properties::) indicates they are alphabetic characters.

Whereas you were using:

[:word:]

This matches any character that has word syntax (*note Syntax Class Table::).

Use the character class [:alpha:]

E.g. [[:alpha:]]+ to match one-or-more such characters.

C-hig (elisp)Char Classes says:

[:alpha:]

This matches any letter. For multibyte characters, it matches characters whose Unicode general-category property (*note Character Properties::) indicates they are alphabetic characters.

Whereas you were using:

[:word:]

This matches any character that has word syntax (*note Syntax Class Table::).