Therefore, first query fnd_user_resp_groups_direct to get the start_date for the existing assignment.
Then use the following API to end date it.
user_id => x.user_id,
responsibility_id => x.responsibility_id,
responsibility_application_id => x.RESPONSIBILITY_APPLICATION_ID,
start_date => x.start_date,
end_date => sysdate,
description => null);
One concern is the user could see the changes are not getting reflected immediately when queried on User Define Form.
These processes are deferred at the workflow level of processing. It should be no longer than a couple minutes before the changes are reflected in the define users (FNDSCAUS) form.