from typing import List
import re


def _split_string_into_word_list(items_str: str) -> List[str]:
    """Preprocesses a string of one-word items delimited by ', ' into a sorted list of items.

    :param items_str: String of items delimited by comma, e.g. 'cat, dog, bird, ...'.
    :return: Sorted list of unique lowercase items.
    """
    items = re.sub(r'[^\w\s]', '', items_str.lower()).split()
    sorted_unique_items = sorted(set(items))
    return sorted_unique_items