The price for Dendreon Corp., the bankrupt developer of a drug to treat advanced prostate cancer, rose more than one-third to $400 million before an auction has even been held, Bloomberg News reported yesterday. To retain its place as the stalking-horse bid, Valeant Pharmaceuticals International Inc. boosted its initial offer from $296 million. A bankruptcy judge in Delaware approved Valeant as the stalking horse yesterday. Competing bids for the Feb. 12. auction are due Feb. 10. A sale-approval hearing is set for Feb. 20.