From the document object, you obtain the SummaryInfo object, which has a LastSavedBy property. E.g.
I don't know how you'll get the creator, unless he's saved his name manually (File --> Drawing Properties), or through a custom lisp, to something like the Author property of the SummaryInfo object.
(setq doc (vla-get-ActiveDocument (vlax-get-acad-object))) ;Get the current drawing
(setq si (vla-get-SummaryInfo doc)) ;Get the summary info object
(princ "Last saved by: ")
(princ (vla-get-LastSavedBy si)) ;Prints login name of user last saved