Sort posts by first letter in the title, not by first number

Question

This is a bit messy to do in MySQL, given the lack of a preg_replace – the following uses a nested REPLACE to strip all numbers from the title:

function wpse167989_posts_orderby( $orderby, $query ) {
    global $wpdb;
    // Strip all numbers from title, and trim any leading spaces.
    return $wpdb->prepare(
        'LTRIM(' . str_repeat( 'REPLACE(', 10 ) . $wpdb->posts . '.post_title'
        . str_repeat( ', %s, %s)', 10 ) . ') ' . $query->get( 'order' )
        , 0, '', 1, '', 2, '', 3, '', 4, '', 5, '', 6, '', 7, '', 8, '', 9, '' );
}

Then

add_filter( 'posts_orderby', 'wpse167989_posts_orderby', 10, 2 );
$loop = new WP_Query( $args );
remove_filter( 'posts_orderby', 'wpse167989_posts_orderby', 10 );

EDIT per comments: to remove hyphens in addition, the filter becomes

function wpse167989_posts_orderby( $orderby, $query ) {
    global $wpdb;
    // Strip all numbers & hyphens from title, and trim any leading spaces.
    return $wpdb->prepare(
        'LTRIM(' . str_repeat( 'REPLACE(', 11 ) . $wpdb->posts . '.post_title'
        . str_repeat( ', %s, %s)', 11 ) . ') ' . $query->get( 'order' )
        , 0, '', 1, '', 2, '', 3, '', 4, '', 5, '', 6, '', 7, '', 8, '', 9, '', '-', '' );
}