Need to remove numeric values from field to find top values

I have millions of values indexed that look like this

,A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_season_percent_stars_33097521 A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_season_percent_20709664 A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_586_user_by_outfit_32587030 A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_592_impression_33141624 ,A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_season_percent_stars_33952008 A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_new_33208512 A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_new_stars_32270501 ,A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_season_percent_stars_32635194 ,A}MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_season_percent_stars_32635194 A}USER_V2_ID_TO_CAREER_TIER_1417875 A}US_MC_USER_EVENTS_BY_UID_U_802735 A}USER_OUTFIT_LOOK_RATING_STARS_SAVED_KEY3_17481979 A}USEROUTFIT_32305379

There is many more variations. I need to create a field that grabs all the alpha characters and excludes all numbers to be able to see top patters/values IE

MCTEST1_SI_EVENTS_TEST1_SI_EVENTS_no_event_id_total_value_season_percent_stars_

MCTEST1_SI_EVENTS_TEST1_SI_EVENTS__impression_

MCTEST1_SI_EVENTS_TEST1_SI_EVENTS__user_by_outfit_

USER_V2_ID_TO_CAREER_TIER_

US_MC_USER_EVENTS_BY_UID_U_