[SR-Users] Can Kamailio send an ACK to a final response?

Hello, I'm exploring using Kamailio as a dumb edge proxy, and as such I want to keep things as lean as possible. In some scenarios I would like the "core" proxies to signal to the edge that a request should be dropped without a response. This could be with a custom header in the reply or perhaps a 444 response ( nginx uses this internally to drop a request without responding ) I have discovered that if I drop the response in the reply_route, the edge proxy doesn't send an ACK and keeps retransmitting the request until it times out, at which point it sends a 408 back to the UA. Is there any way to ACK the response from the core and destroy the transaction? Thanks Matthew