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List words separated by comma and without duplicates

Hi all.

Suppose I have a file made by a list of names and surnames, e.g.:

Arvo Part
Harold Pinter
Lucio Battisti
Antonio Amurri
Eduardo De Filippo
Eduardo De Filippo

and that I want them listed all on one line, separated by a comma and without
duplicates, i.e.:

Arvo Part, Harold Pinter, Lucio Battisti, Antonio Amurri, Eduardo De Filippo

How can I do that with proper Unix commands?

Thanks for any help.