Rats (2003)

When a journalist checks into a hospital for the criminally insane which also doubles as a rehab center for fallen celebrities, he's on the hunt for gossip but finds a different, scarier story. The institution is overrun by highly-intelligent and unusually powerful rats, the result of testing by one of the high-up doctors, William Winslow. As of late, however, the rats have been harnessed by the caretaker and former patient, Ernst, for some evil purposes.