Nginx proxy - limit request with regex - regex

Question

I've an Nginx 1.6.2, working as proxy. The backend HTTP server is an Apache.
I'ld like to control the number of connections certain URL, in some vhosts. The exact "location" form is works, but if I pass a regex to "location", it doesn't.
server {
listen 80;
server_name www.myhost.com;
location ~* ^/.*ABCD_promo.*$ {
limit_req zone=one burst=5;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
proxy_pass http://vm-apache4;
}
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
proxy_pass http://vm-apache4;
}
}
In nginx.conf, I've this directive:
limit_conn_zone $binary_remote_addr zone=addr:10m;
limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
before the config part(s) above.
When I change the "location ~* ^/.*ABCD..." to "location /ABCD_promo", then it works. What em I misses?